# I don't understand how some planes ended up being so fast



## grampi (Nov 2, 2017)

There were certain fighters that were extremely fast, but for the life of me, I can't figure out why. I can understand planes like the P-51, Spitfire, and Me 109 being fast, as they were relatively small and aerodynamically clean aircraft. But how in the world does a P-47 have any business having a top speed of 500+ MPH, or a Corsair being able to do in the high 400s? Both of these planes were big and heavy, and neither look to have anywhere near the clean aerodynamics of the 51, Spit, or 109. So how were they able to achieve such high top speeds with the planes?


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## tomo pauk (Nov 2, 2017)

Horsepower at altitude matters. P-47 that went close to 500 mph have had 2800 HP at 30000 ft. Weight plays almost no role in speed.


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## pbehn (Nov 2, 2017)

2000+ horsepower helps. In fact the corsair had some aspects that were aerodynamically "cleaner than the Spit and the 109. The gull wing joins the fuselage at 90 deg which is a better set up. The big air cooled radials had a higher frontal area but didn't have the radiators.


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## Shortround6 (Nov 2, 2017)

Speed without altitude given is almost meaningless.

Drag depends on the density of air while engine power, given good superchargers, does not.

Air at 20,000ft is 53.27% as dense as the air at sea level (on a 59 degree F day standard pressure) while the air at 30,000ft is 37.40% as dense as sea level air. 

An Allison P-51 using "cruise power" (2600rpm and wide open throttle) or about 1000hp at a bit over 12,000ft could keep up with if not slightly beat a P-47D using WEP with water injection. over double the power (2300hp) but at 31,000ft the P-47 could hit 435mph while the Allison Mustang would be down to under 340mph at that altitude due the engine haven fallen to under 600hp while the P-47 still had 2200hp. Amazing what over 3 times the power can do  

A Corsair, without water injection would be down to about 360-365mph at 31,000ft going by charts. Engine power might be around 1100HP?


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## Koopernic (Nov 3, 2017)

grampi said:


> There were certain fighters that were extremely fast, but for the life of me, I can't figure out why. I can understand planes like the P-51, Spitfire, and Me 109 being fast, as they were relatively small and aerodynamically clean aircraft. But how in the world does a P-47 have any business having a top speed of 500+ MPH, or a Corsair being able to do in the high 400s? Both of these planes were big and heavy, and neither look to have anywhere near the clean aerodynamics of the 51, Spit, or 109. So how were they able to achieve such high top speeds with the planes?




The equation for air resistance is
F=1/2 Cd A ρ V²

F is the force in Newton’s (about 100 grams)
Cd is the coefficient of drag
A is Frontal Area
ρ is the air density.
V² is velocity squared.

The P47 because of its turbosupercharger did not loose as much power at altitude as other designs and was fast there. It was not particularly fast at sea level, even the P47M on 150PN fuel. For instance at 25,000ft the air is only 0.4 times as dense as at sea level yet the P-47 has lost no power. It’s said the American turbo engines were all flat rated from seal level to 25,000ft. At sea level the P51 and Tempest did well because of laminar flow wings and because their non turbo charged engines didn’t have cost in terms of turbo weight.

The Corsair didn’t have a turbo but it had a two stage mechanical supercharger with an inter cooler so it’s high altitude power as quite good. This type of arrangement has significant exhaust thrust because of the high pressure.

Also the blunt nose is not as unaerodynamic as it seems. It’s more important to have a smoothly tapering fuselage so that the air remains attached (thereby not becoming turbulent)

The air flowing into the cowling also came out and there were probably some attempts to eject the now heated air at higher velocity to recover some thrust.

The 1930s Gee Bee racers were particularly fast despite their stocky bodies. Things climbed faster than a Griffon Spitfire.

I would say that the packaging that BMW did on their radial the 801 was particularly effective. They closed the nose of and ensured adequate airflow by using a geared fan. Don’t know if any American engines did this, perhaps only the R4360. Might have helped the R3350 during its struggles.


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## fastmongrel (Nov 3, 2017)

*Power*.

You could get a shopping mall up to 500mph if you had enough power


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## pbehn (Nov 3, 2017)

fastmongrel said:


> *Power*.
> 
> You could get a shopping mall up to 500mph if you had enough power


That was the principle behind the F-4.

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## DogMD11 (Nov 3, 2017)

The XP-47J had a fan-cooled R-2800 and the XP-72 and XF-12 Rainbow had fan-cooled R-4360's


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## Koopernic (Nov 4, 2017)

DogMD11 said:


> The XP-47J had a fan-cooled R-2800 and the XP-72 and XF-12 Rainbow had fan-cooled R-4360's


At around 500mph the XP-47J was an extremely impressive aircraft. I’m curious as to whether it could have gotten into service baring the fact it was decided to focus on the R-4360 engined XP-72 instead.


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## Shortround6 (Nov 4, 2017)

Koopernic said:


> At around 500mph the XP-47J was an extremely impressive aircraft. I’m curious as to whether it could have gotten into service baring the fact it was decided to focus on the R-4360 engined XP-72 instead.


According to one source:
"In addition, 70% of the P-47 production line needed to be re-tooled in order to produce the P-47J."

I don't know how true this was but they claim it used a "lightened wing". The "empty weight" is claimed to be 300-500lbs lighter than various D models.


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## drgondog (Nov 5, 2017)

tomo pauk said:


> Horsepower at altitude matters. P-47 that went close to 500 mph have had 2800 HP at 30000 ft. Weight plays almost no role in speed.


 Tomo - you are correct that Induced Drag, which is a function of CL is much less important at top speeds, but very important at Cruising speed. Near optimal cruising speed CDp=CDi


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## drgondog (Nov 5, 2017)

Koopernic said:


> The equation for air resistance is
> F=1/2 Cd A ρ V²
> 
> 
> ...



"F is the force in Newton’s (about 100 grams)
Cd is the coefficient of drag
A is Frontal Area
ρ is the air density.
V² is velocity squared."

*F=1/2 Cd*S*rho*V^^2 is correct for Aero when S=Wing Area and Cd = (CDp1+CDp2+CDp3)*CDc +Cdi
CDp1 is a function of Reynolds Number and the Parasite Drag build up of airframe components derived at a Specific RN during wind tunnel testing
CDp2 is composed of additional items such as guns, radio masts, leaks, surface roughness
CDp2 is increment of CDp due to angle of attack (profile drag)
CDp3 is increment of CDp due to cooling drag and items immersed in slipstream during climb - also important to derive Power Required calculations.
CDc mulitiplier for Compressibility - increasingly important at M>0.3 
CDc is a compressibility factor which includes drag rise of compressible flow 
CDi is the Induced Drag which is function of CL^^2, divided by AR*Pi*e
Actually the "e" factor is the reason that the P-47 elliptical wing offset Mustang advantage in WL and AR.*

The major reason the Mustang drag was so low was a.) the wing and b.) the extremely well designed 2nd order curve layout of the airframe. The latter was only slightly lower than the P-47 and FW 190.

Frontal area per se, was not a linear comparative factor


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## Todd Secrest (Nov 6, 2017)

grampi said:


> There were certain fighters that were extremely fast, but for the life of me, I can't figure out why. I can understand planes like the P-51, Spitfire, and Me 109 being fast, as they were relatively small and aerodynamically clean aircraft. But how in the world does a P-47 have any business having a top speed of 500+ MPH, or a Corsair being able to do in the high 400s? Both of these planes were big and heavy, and neither look to have anywhere near the clean aerodynamics of the 51, Spit, or 109. So how were they able to achieve such high top speeds with the planes?


I would assume the P-47 and Corsair had bigger propellers, then the P-51, Spitfire, Me-109.


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## mad_max (Nov 8, 2017)

Todd Secrest said:


> I would assume the P-47 and Corsair had bigger propellers, then the P-51, Spitfire, Me-109.



Size of the propeller was proportional to the power the engine produced, prop gearing and problem of the prop tips going supersonic. All the test results I've studied pointed to props that provided good climb and good speed. Some tests showed certain props had slightly better speed, but a lower climb rate, while others had slightly better climb with a slower speed. You want the best of both worlds, but compromising has to be done so you have a respectable climb and speed.

Propellers of all Nations at War were constantly changing as new data came forward and tested. All of them slowly changed to a wider chord on their props with prop gearing to keep the tips under mach 1. 

Take this for what it's worth. I'm not an engineer, just an aircraft junkie.

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## Todd Secrest (Nov 9, 2017)

mad_max said:


> Size of the propeller was proportional to the power the engine produced, prop gearing and problem of the prop tips going supersonic. All the test results I've studied pointed to props that provided good climb and good speed. Some tests showed certain props had slightly better speed, but a lower climb rate, while others had slightly better climb with a slower speed. You want the best of both worlds, but compromising has to be done so you have a respectable climb and speed.
> Propellers of all Nations at War were constantly changing as new data came forward and tested. All of them slowly changed to a wider chord on their props with prop gearing to keep the tips under mach 1.
> Take this for what it's worth. I'm not an engineer, just an aircraft junkie.


Did not the F4U Corsair and F6F use the same engine? (answer is yes)
And the Corsair still had a higher top speed and I'm assume because it had a bigger propeller (13ft 4in)?
The Corsair was designed with the gull wings, to accommodate the big propeller (and to shorten the landing gear).
The F6F Hellcats propeller was 13ft 1in, Could 3 inches make much of a difference?


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## tomo pauk (Nov 9, 2017)

mad_max said:


> ...
> Take this for what it's worth. I'm not an engineer, just an aircraft junkie.



I'm thinking about stealing that line for the signature; credited, of course 



Todd Secrest said:


> Did not the F4U Corsair and F6F use the same engine? (answer is yes)
> And the Corsair still had a higher top speed and I'm assume because it had a bigger propeller (13ft 4in)?
> The Corsair was designed with the gull wings, to accommodate the big propeller (and to shorten the landing gear).
> The F6F Hellcats propeller was 13ft 1in, Could 3 inches make much of a difference?



The F6F have had bigger Cd0 (C d zero, coefficient of drag at high speed), IIRC by some 10%, even though it used a thinner wing. Wing was also bigger on the Hellcat.


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## pbehn (Nov 9, 2017)

Top speed is not always the ultimate measure of high performance, it is just one of them. The most successful F1 cars are rarely the fastest through the speed trap.

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## fastmongrel (Nov 9, 2017)

pbehn said:


> Top speed is not always the ultimate measure of high performance, it is just one of them. The most successful F1 cars are rarely the fastest through the speed trap.



How often did a WW2 plane operate at maximum speed.

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## pbehn (Nov 9, 2017)

fastmongrel said:


> How often did a WW2 plane operate at maximum speed.


For carrier based planes there are many aspects of performance that are important, by 1945 enough was known about aircraft performance for me to say that the Bearcat was as fast as the designers wanted bearing in mind what they wanted in other areas like rate of climb, turn and take off/landing.

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## tomo pauk (Nov 9, 2017)

fastmongrel said:


> How often did a WW2 plane operate at maximum speed.



Time-wise rarely. 
But always when it was really important & possible.


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## Shortround6 (Nov 9, 2017)

The importance of top speed and rate of climb in addition to the obvious, is that they are _indicators _of an aircraft's potential.
The faster plane will have more _options_.

top speed is done flying straight and level. As soon as you begin to bank the speed falls off. Deflection of the control surfaces cause drag, flying with wings tilted/banked causes drag as in the loss of lift has to be countered by an increase in the angle of attack of the wing. 
Take two planes, one that can do 330mph and one that can do 360mph at the same height. The 2nd plane can actually be performing gentile maneuvers at 330mph, wide turn or gentile climb as opposed to just flying straight and level. 

Even if you are at 300mph the faster plane still has more options because it has more surplus power to accelerate with, or climb or compensate for a steeper bank angle/tighter turn. 

Nobody had enough power to compensate for a 5-6 G turn for very long even if the pilot didn't black out, without loosing altitude. 

The "faster" plane may not be using it's "speed" at all times but you can bet the pilot (if he is any good) is using the extra power that speed margin represents.

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## chuter (Nov 9, 2017)

Todd Secrest said:


> Did not the F4U Corsair and F6F use the same engine? (answer is yes)
> And the Corsair still had a higher top speed and I'm assume because it had a bigger propeller (13ft 4in)?
> The Corsair was designed with the gull wings, to accommodate the big propeller (and to shorten the landing gear).
> The F6F Hellcats propeller was 13ft 1in, Could 3 inches make much of a difference?





Actually, the 13' 1" paddle blade prop was adopted by the Corsair early in -1D production, and retrofit to earlier aircraft as available, meaning the Avenger, Corsair and Hellcat all wound up with the same prop. Climb and low speed acceleration was slightly improved (If my memory isn't sabotaged). My buddy Bruce (he has the 11th from the last FG-1D with some factory F2G mods) had some brand new bat-handle blades (13' 4") and briefly considered backdating the plane but traded them away for more relevant parts. 

(He also had a short tailwheel strut.)


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## YF12A (Nov 9, 2017)

On the topic of exhaust thrust, if you want to see an extreme example of the power of it, go to youtube and look up Jeff Diehl header break. These engines are now putting out over 11,000 HP out of an 8.4 Litre engine and I have been told that it takes roughly 1,000 HP to drive the supercharger alone!


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## fastmongrel (Nov 9, 2017)

YF12A said:


> On the topic of exhaust thrust, if you want to see an extreme example of the power of it, go to youtube and look up Jeff Diehl header break. These engines are now putting out over 11,000 HP out of an 8.4 Litre engine and I have been told that it takes roughly 1,000 HP to drive the supercharger alone!



Thats actually pretty efficent iirc a RR Merlin 60 series engine producing 1600hp was taking around 400hp to drive the supercharger.


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## Shortround6 (Nov 9, 2017)

YF12A said:


> On the topic of exhaust thrust, if you want to see an extreme example of the power of it, go to youtube and look up Jeff Diehl header break. These engines are now putting out over 11,000 HP out of an 8.4 Litre engine and I have been told that it takes roughly 1,000 HP to drive the supercharger alone!



Actually what you may be seeing is the exhaust gas collecting under the car vs venting out the side. It wouldn't take more than a few pounds per sq in of pressure under that body to lift the car off the ground. I am guessing that is what blew the hood off. 
Interesting that the car swung to the left, opposite the intact right side headers, Exhaust thrust from those pipes may have been what shoved the car to the left?

I would note that these racers don't seem to be using much of the exhaust thrust for propulsion. With the upcurve in the end of the pipes they may be using the "thrust" to help keep the car on the ground? 

I know I could practically clean street gutters with the exhaust from one of the fire trucks I drove. 

Exhaust thrust is both simple and complicated. It is mass time velocity, that is simple. Getting it pointed in the direction you want it, keeping it stream lined, and not using a long convoluted pipe that allows it to both cool (reduces pressure/velocity) and slow down due to friction in the pipe and turbulence in the bends is more difficult, keeping up the velocity of the exhaust stream while sending it through a turbine, collecting it and redirecting it through a rear facing outlet is a lot harder.


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## grampi (Nov 9, 2017)

pbehn said:


> For carrier based planes there are many aspects of performance that are important, by 1945 enough was known about aircraft performance for me to say that the Bearcat was as fast as the designers wanted bearing in mind what they wanted in other areas like rate of climb, turn and take off/landing.



The Bearcat is another good example. Considering its size, its extremely smooth outer surface, and considerably high amount of power, you'd think it would be much faster than any version of the P-47 or Corsair, but that just wasn't the case...


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## mad_max (Nov 9, 2017)

grampi said:


> The Bearcat is another good example. Considering its size, its extremely smooth outer surface, and considerably high amount of power, you'd think it would be much faster than any version of the P-47 or Corsair, but that just wasn't the case...



You can only go so fast using a prop. 500 MPH and you're up against the wall for speed; hence the move to the jet engine.


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## Shortround6 (Nov 9, 2017)

you have to compare speeds at the same altitudes, The Bearcat used a single stage supercharger so it's 2000 plus horsepower tended to disappear pretty quick. 

A clean F8F-1 using military power of 2100hp was good for 331knots (380.9mph) at sea level while a P-47D using water injection and 2210hp was good for 289.3 knots (333mph) at sea level. 
F8F-1 was almost 50mph faster while using just over 100hp less. 

P-47D could hit 435mph at 31,000ft where the engine was making 2220hp thanks to the turbo. The F8F-1 engine was good for just 1700hp at 16,000ft and had dropped over 30% (down to around 1200hp?) from that so by the time it got to 31,000 where it's speed was around 400mph? (405 at 30,000ft).

Corsair used a two stage supercharger so while not as good as the P-47 in had hundreds more horsepower at some altitudes compared to the F8F-1.


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## Carboncrank (Nov 9, 2017)

grampi said:


> There were certain fighters that were extremely fast, but for the life of me, I can't figure out why. I can understand planes like the P-51, Spitfire, and Me 109 being fast, as they were relatively small and aerodynamically clean aircraft. But how in the world does a P-47 have any business having a top speed of 500+ MPH, or a Corsair being able to do in the high 400s? Both of these planes were big and heavy, and neither look to have anywhere near the clean aerodynamics of the 51, Spit, or 109. So how were they able to achieve such high top speeds with the planes?




People here are doing a lot of jumping though hoops to prove your false premise. No combat jug would do 500 plus and the corsairs did not do high 400, not in any models that saw significant production anyway in WWII. At any lower altitudes the huge amount of air that a Jug had to push out of the way slowed it. Same with the corsair to a lessor degree. The Mustang's smaller air frame, narrow nose and laminar flow and low drag far outweighed having less HP. 

Why wouldn't you google before posting the question? 

F4U Corsair - WW2 US Navy Fighter Plane - History, Specs, Pictures

Republic P-47 Thunderbolt - The Seven Ton Milk Jug, WW2 Fighter Plane

The mustang was faster but it wasn't just about raw top speed because the jug would only fly it's top speed at very high altitude and both it and the corsair climbed like a school bus compared to the mustang. The Mustang had usable speed at every altitude. The mustang would fly an astounding 388 miles per hour at sea lever, 50 mph faster than a Jug. The jug's fastest speeds were at 38 to 40 thousand feet. That's not where dogfights happen. Loaded bomber didn't cruise or bomb anywhere near that high, more like 20 to 25 thousand feet so there is no practical advantage to the jug's 40 thousand foot speed. 

dogfights happened at the bomber altitude on down. That's where the huge difference in lower altitude speed of the mustang was a huge advantage. If a jug ends up with a German on his tail at 25 thousand feet and he can't out-turn him or out fly him but he can shove the stick forward and get a gap in a dive. He better get a big one though because if it's an FW190 that sticks close enough the FW will reel in the Jug. The mustang will motor away. Reverse the situation at mid to low altitude and make the mustang the pursuer he's going to close the gap on anything in the sky. Think about a 50 mph advantage on the deck. Say the mustang is chase from a mile behind. He's gaining about 50 or 60 feet per second. Or flipped around from low to mid altitude, where most fur balls end up the mustang will run away from anything he can't out turn. 


P-51 Mustang Performance
P-47 Performance Tests

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## mad_max (Nov 9, 2017)

"Carboncrank, posted:The Mustang's smaller air frame, narrow nose and laminar flow and low drag far outweighed having less HP.

Laminar Flow was never accomplished on the Pony.

Why wouldn't you google before posting the question?

I'm wondering why you haven't used google.

The mustang was faster but it wasn't just about raw top speed because the jug would only fly it's top speed at very high altitude and both it and the corsair climbed like a school bus compared to the mustang. The Mustang had usable speed at every altitude. The mustang would fly an astounding 388 miles per hour at sea lever, 50 mph faster than a Jug. The jug's fastest speeds were at 38 to 40 thousand feet. That's not where dogfights happen. Loaded bomber didn't cruise or bomb anywhere near that high, more like 20 to 25 thousand feet so there is no practical advantage to the jug's 40 thousand foot speed.

The Jug's top speed was approx. 32,000 ft on the D's 435 mph, M's - 473 mph (granted only 100 made), N's - 457 mph. As you can see it's not at 38-40,000 ft. Alt. is energy, energy is what you need to effectively fight in any aircraft; whether from high power, sleek design or Altitude. Better yet is to have all three in one aircraft.

dogfights happened at the bomber altitude on down. That's where the huge difference in lower altitude speed of the mustang was a huge advantage. If a jug ends up with a German on his tail at 25 thousand feet and he can't out-turn him or out fly him but he can shove the stick forward and get a gap in a dive. He better get a big one though because if it's an FW190 that sticks close enough the FW will reel in the Jug. The mustang will motor away. Reverse the situation at mid to low altitude and make the mustang the pursuer he's going to close the gap on anything in the sky. Think about a 50 mph advantage on the deck. Say the mustang is chase from a mile behind. He's gaining about 50 or 60 feet per second. Or flipped around from low to mid altitude, where most fur balls end up the mustang will run away from anything he can't out turn.

At 25,000 ft the FW 190 is struggling. The Jug will out turn it at 250 mph and out run it level speed at that alt. Even at 10,000 ft as long as the Jug's speed is over 250 it can out turn the 190; at least that's what the flight test against each other says.

The Mustang was a jack of all trades. It did all things good, but the only one excellent was range. That is what made the Mustang very good for the job that was required of it.

Oh and forgot to mention. The 109 had one of the least aerodynamically clean airframes of that time period for fighter aircraft. Of the different marks the F model was as clean as it would get; although the G-10 and K models were close.

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## pbehn (Nov 9, 2017)

Carboncrank, google can provide much useful information but will also tell me what the Holy Chalice looks like. The original post just asked a question, there are many possible answers.

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## taly01 (Nov 10, 2017)

The other side of the coin is why some planes don't get faster, for example the P-38 only improved from 400 -> 420mph, from a power increase of 2 x 1150 -> 2 x 1600hp!

The 1937 Ki-15 3 seat fixed landing gear recon plane is interesting that it got to 300mph from a 750hp radial and a 2400km range, must be close to best performance/$hp, and did set world endurance records back in its time!


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## tomo pauk (Nov 10, 2017)

Carboncrank said:


> <snip>



I usualy don't give 'dislike' marks on the posts, but in this case it was helped by less than friendly approach accompanied by handful of faulty numbers/figures/notions.


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## drgondog (Nov 10, 2017)

A couple of points?
First, Power Available vs Power Required are the two major factors, along with comparative W/L, which determine Climb and Turn Performance.

With respect to Power Required for Climb, the dominant Drag 'adds' over level flight are a.) Cooling Drag and b.) Pressure/Form Drag due both to high Angle of Attack CL, and incremental Drag of the airframe components immersed in the Prop Vortex.

For Power Available, in addition to the THP of the engine/prop combo, the Mustang also had a decided advantage in Exhaust thrust 

Relative to comments made earlier about the 'inescapability' of a P-47D from an FW 190A-7 or -8 above 25000 feet? The THp of the FW 190 was declining rapidly above 20,000 feet while the P-47 (and P-51B/C) were steady from 24000 through 29000 feet. The W/L of all three were about the same with combat tanks gone and some internal fuel consumed before combat engaged. The advantage in climb and turn was pronounced for both the P-47 and P-51B/C, over the FW 190A, at bomber altitudes and above.


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## pbehn (Nov 10, 2017)

The Hellcat had a much better view over the nose and probably better to the rear, there may have been a price considered worth paying in top speed for this. The Corsair could be landed on a carrier but was not so simple.

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## Carboncrank (Nov 10, 2017)

mad_max said:


> "Carboncrank, posted:The Mustang's smaller air frame, narrow nose and laminar flow and low drag far outweighed having less HP.
> 
> Laminar Flow was never accomplished on the Pony.
> 
> ...



you very obviously didn't look at the source material a gave. Show me where you get you "facts" otherwise it's just opinion. And I figured you go for numbers on models made in small numbers late in the war that are totally irrelevant.

The fact I errored in the top speed altitude of the Thunderbolt doesn't negate the point. The Mustang and the Jug are about same speed at that altitude, but still, dog fighting doesn't happen at that altitude. The lower you go the more glaring the speed difference between the 2 planes. So if at any point from see level up to 25k if you find yourself in a position where you need to accelerate away you are better of in a Mustang. With the exception of diving from high altitude, anything the Jug could do in air to air a Mustang could do better. Jugs became train killers while the Mustangs dominated the Luftwaffe. 

I wasn't comparing the Jug to an FW190, I was comparing it to a Mustang proving the Mustang was a better air plane in every aspect of dog-fighting. 

The mustang was obviously the best fighter of the war in all regards. It showed up in theater way later than the jugs and shot down a low-side estimate of 4,950 aircraft at a loss of 2500 while the jug shot down 3,662 and lost 3500. The only P47 squadrons that didn't replaced by the mustangs were the ones kept for short range ground attack missions, which it was very good at. 

The air war was decided in the spring of 44. "Big Week" operations with their massive deep penetration raids drew large numbers of German planes up to fight where they lost veteran combat pilots they could not replace. Through Feb and March the Jugs still far outnumbered the mustangs in raw numbers of planes in the big missions yet the mustangs the kill per sortie numbers for the Mustangs was multiples of the Jug, possibly because the Mustangs flew far into Germany where the Germans put up their best efforts to stop the bombers. Air superiority was achieved in about 8 weeks with near domination by June 44 or there would have been no D-day. Keep in mind also that the "Big Week" Mustangs were B models. 

We went from a near halt of Missions into Germany in October 43 for lack of long range support (the inadequacy of the P*47) to domination by June 44. Simply put, no P-51, no "big week". No "Big week" no June D-Day invasion, 

And don't sound like the range problem wasn't a major flaw. After the disastrous long range missions to Schweinfurt–Regensburg August 17, 1943 and second Schweinfurt October 14th the 8th severely scaled back the bombing for 5 months because of the inadequacies of the P-47, waiting for enough P-51s to replace them. 

Here is a daily from Dec 1st 1943 91st bombgroup 322nd squadron mission to bomb the chemical works of I. G. FarbenIndustrie A/C.(Bayer), Leverkusen, Germany. That's just 40 miles into Germany. They put 8 bombers up. 
------------
Time: Take Off 0755. Target 1202. Return 1434.
Bomb Load 8 x 500 G.P, 20 x 100 I.lB.'s
Bombing Altitude 26,000
Results: Unobserved 9/10 cloud

Fighter Opposition: 40-50 E/A mostly FW190's and Me-109's with a few
Me-100's and FW-189's. FW-190's were painted to look like out P-47's.
Rocket firing E/A were in evidence. Between 1140 and 1200 hours our
fighter support did not cover our formation. It was during this
period of time that our group suffered its losses (5 A/C M.I.A.) also
4 A/C landing elsewhere in England .

Remarks: The following A/C failed to return: A/C 794 piloted by Lt.
L. J. Anderson, A/C 511 piloted by Lt. J. T. Wennenberg, A/C 836
piloted by Lt. Charles L. Early. Major H. W. Weitzenfeld, C.O. of
the 401st, was group leader.
--------------

Notice the missed hand off between P-47 squadrons. 5 of the 8 bombers were shot down in that 20 minute screw up. 

Aircraft #511 was "Wheel n' Deal". The bombardier was 2nd Lt John W Temple, the husband of my mother's older sister. He spent 18 months in various POW camps. 

40 miles into Germany, 160 miles from the coast, 240 miles from England and yet the Jugs had to fly in relays to cover even that, and the result was a missed relay, 5 B-17's shot down, 50 men killed or captured. My uncle's plane was hit by FW190's before the bomb run. It also had an 88 round go up through the plane right behind the pilots a out the top without exploding. The Jugs finally arrived but only covered a few minutes before they had to go home because of the range problem. The force had no fighter escort for the bomb run but "Wheel n' Deal's" didn't make to the run because it was hit again in an engine in a FW190 pass, became a straggler and a sitting duck. Still they didn't go down and they found cloud cover but as soon as they came out of the cloud the 88's were all over them one round leaving a whole in a wing "big enough to drop a cow through". They bailed out, the pilot left it on auto pilot when he left an she flew on another 10 miles or more before belly landing, still on auto pilot, on the Rhine river. The German's fished it out but my uncle had destroyed the bombsite. 9 of the ten survived. 

This kind of story repeats itself over and over again until the arrival of the Mustang. 

So don't try to make the P-47 into something it was not, Read the 91st dailies, see the losses. 

The story of "Wheel N Deal", including it's final fight, is told here. If you don't want to read the whole page do a page search on "Wheel N Deal". BTW that page tells the story of "Memphis Belle" too as it was 91st bombgoup, 324th squadron. 

Chapter 4 - One Came Home. The Stories of Those Left Behind 



mad_max said:


> "Carboncrank, posted:The Mustang's smaller air frame, narrow nose and laminar flow and low drag far outweighed having less HP.
> 
> Laminar Flow was never accomplished on the Pony.
> 
> ...





mad_max said:


> "Carboncrank, posted:The Mustang's smaller air frame, narrow nose and laminar flow and low drag far outweighed having less HP.
> 
> Laminar Flow was never accomplished on the Pony.
> 
> ...



you very obviously didn't look at the source material a gave. Show me where you get you "facts" otherwise it's just opinion. And I figured you go for numbers on models made in small numbers late in the war that are totally irrelevant.

The fact I errored in the top speed altitude of the Thunderbolt doesn't negate the point. The Mustang and the Jug are about same speed at that altitude, but still, dog fighting doesn't happen at that altitude. The lower you go the more glaring the speed difference between the 2 planes. So if at any point from see level up to 25k if you find yourself in a position where you need to accelerate away you are better of in a Mustang. With the exception of diving from high altitude, anything the Jug could do in air to air a Mustang could do better. Jugs became train killers while the Mustangs dominated the Luftwaffe. 

I wasn't comparing the Jug to an FW190, I was comparing it to a Mustang proving the Mustang was a better air plane in every aspect of dog-fighting. 

The mustang was obviously the best fighter of the war in all regards. It showed up in theater way later than the jugs and shot down a low-side estimate of 4,950 aircraft at a loss of 2500 while the jug shot down 3,662 and lost 3500. The only P47 squadrons that didn't replaced by the mustangs were the ones kept for short range ground attack missions, which it was very good at. 

The air war was decided in the spring of 44. "Big Week" operations with their massive deep penetration raids drew large numbers of German planes up to fight where they lost veteran combat pilots they could not replace. Through Feb and March the Jugs still far outnumbered the mustangs in raw numbers of planes in the big missions yet the mustangs the kill per sortie numbers for the Mustangs was multiples of the Jug, possibly because the Mustangs flew far into Germany where the Germans put up their best efforts to stop the bombers. Air superiority was achieved in about 8 weeks with near domination by June 44 or there would have been no D-day. Keep in mind also that the "Big Week" Mustangs were B models. 

We went from a near halt of Missions into Germany in October 43 for lack of long range support (the inadequacy of the P*47) to domination by June 44. Simply put, no P-51, no "big week". No "Big week" no June D-Day invasion, 

And don't sound like the range problem wasn't a major flaw. After the disastrous long range missions to Schweinfurt–Regensburg August 17, 1943 and second Schweinfurt October 14th the 8th severely scaled back the bombing for 5 months because of the inadequacies of the P-47, waiting for enough P-51s to replace them. 

Here is a daily from Dec 1st 1943 91st bombgroup 322nd squadron mission to bomb the chemical works of I. G. FarbenIndustrie A/C.(Bayer), Leverkusen, Germany. That's just 40 miles into Germany. They put 8 bombers up. 
------------
Time: Take Off 0755. Target 1202. Return 1434.
Bomb Load 8 x 500 G.P, 20 x 100 I.lB.'s
Bombing Altitude 26,000
Results: Unobserved 9/10 cloud

Fighter Opposition: 40-50 E/A mostly FW190's and Me-109's with a few
Me-100's and FW-189's. FW-190's were painted to look like out P-47's.
Rocket firing E/A were in evidence. Between 1140 and 1200 hours our
fighter support did not cover our formation. It was during this
period of time that our group suffered its losses (5 A/C M.I.A.) also
4 A/C landing elsewhere in England .

Remarks: The following A/C failed to return: A/C 794 piloted by Lt.
L. J. Anderson, A/C 511 piloted by Lt. J. T. Wennenberg, A/C 836
piloted by Lt. Charles L. Early. Major H. W. Weitzenfeld, C.O. of
the 401st, was group leader.
--------------

Notice the missed hand off between P-47 squadrons. 5 of the 8 bombers were shot down in that 20 minute screw up. 

Aircraft #511 was "Wheel n' Deal". The bombardier was 2nd Lt John W Temple, the husband of my mother's older sister. He spent 18 months in various POW camps. 

40 miles into Germany, 160 miles from the coast, 240 miles from England and yet the Jugs had to fly in relays to cover even that, and the result was a missed relay, 5 B-17's shot down, 50 men killed or captured. My uncle's plane was hit by FW190's before the bomb run. It also had an 88 round go up through the plane right behind the pilots a out the top without exploding. The Jugs finally arrived but only covered a few minutes before they had to go home because of the range problem. The force had no fighter escort for the bomb run but "Wheel n' Deal's" didn't make to the run because it was hit again in an engine in a FW190 pass, became a straggler and a sitting duck. Still they didn't go down and they found cloud cover but as soon as they came out of the cloud the 88's were all over them one round leaving a whole in a wing "big enough to drop a cow through". They bailed out, the pilot left it on auto pilot when he left an she flew on another 10 miles or more before belly landing, still on auto pilot, on the Rhine river. The German's fished it out but my uncle had destroyed the bombsite. 9 of the ten survived. 

This kind of story repeats itself over and over again until the arrival of the Mustang. 

So don't try to make the P-47 into something it was not, Read the 91st dailies, see the losses. 

The story of "Wheel N Deal", including it's final fight, is told here. If you don't want to read the whole page do a page search on "Wheel N Deal". BTW that page tells the story of "Memphis Belle" too as it was 91st bombgoup, 324th squadron. 

Chapter 4 - One Came Home. The Stories of Those Left Behind


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## pbehn (Nov 10, 2017)

Carboncrank said:


> The mustang was obviously the best fighter of the war in all regards.


It quite obviously wasn't. It was no match for anything at altitude from 1939 to 1943. It was no match for a Griffon engined Spitfire or an Me 262 when they came in to service. What it did have was good performance at all altitudes, fantastic range and huge numbers. Those numbers were magnified by the use of P 47s P 38s and Spitfires. After D Day when combats were at lower altitude it was no match for a Tempest in performance nor a P 47 for firepower and durability.

Mistakes made in the early days of the bombing offensive were not the fault of the machines involved. It was a learning experience for the group and required many more re con planes and weather reports to solve.

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## Shortround6 (Nov 10, 2017)

I would be rather leery of using operational mistakes/mishaps in evaluating performance of aircraft. 
A missed rendezvous can happen to any aircraft unless it can be shown that due to excessive head winds or some other factor that a particular aircraft could not over come that another one could. 

I would also note that while the P-51 was a much superior escort fighter the P-47 was constantly evolving. Jan 1944 seeing the start of the equipping of the P-47 planes already in theater with under wing tanks in addition to the under fuselage tanks to extend range.
The under fuselage tank itself under going a series of changes and the 150 gal, under fuselage tank was introduced in Feb 1944 just in time for "Big week". it added 15 minutes of flying time (over the 108 gallon tank?) and extended radius to 350 miles. 
Big week escorts were mostly P-47s.
May of 1944 starts to see the P-47D-25 show up with another 65 gallons of internal fuel which really extends the radius, even though most are being sent to the 9th Air Force. And most in theater P-47s are being transferred to the 9th Air Force as quickly as deliveries of P-51s allow. 

There was a fair amount of overlap and things were happening very quickly. As of Dec 1st 1943 the Mustangs still had lots of bugs and were not yet operating with either rear fuselage tanks or under wing drop tanks. By March of 1944 all three US fighters were using under wing tanks and often larger than what what they were using in the fall of 1943 for the P-38. 
Please remember that it could take several months from when a particular serial number aircraft rolled out the door of it's factory in the US and when it flew it's first combat mission in Europe. 
A lot of decisions were made _without _the benefit of combat experience as there just wasn't time.
Fortunately they guessed correctly.

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## pbehn (Nov 10, 2017)

Carboncrank, why not do some clear eyed skeptical analysis instead of a few square miles of claptrap linking P 47 performance to the present state of the White House.

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## Shortround6 (Nov 10, 2017)

Whatever the merits or demerits of this thread it does not deserve to be closed/locked because one contributor brought in modern day politics which has no relevance to the discussion.

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## Carboncrank (Nov 10, 2017)

Shortround6 said:


> I would be rather leery of using operational mistakes/mishaps in evaluating performance of aircraft.
> A missed rendezvous can happen to any aircraft unless it can be shown that due to excessive head winds or some other factor that a particular aircraft could not over come that another one could.
> 
> I would also note that while the P-51 was a much superior escort fighter the P-47 was constantly evolving. Jan 1944 seeing the start of the equipping of the P-47 planes already in theater with under wing tanks in addition to the under fuselage tanks to extend range.
> ...



On dec 1st 1943 there were zero Mustang squadron supporting bombers and they had external tanks available from day 1. They are on all Packard/Melin Mustangs. There were no bugs to be worked out. With very little pilot familiarization they went straight into combat. Where do you get this stuff? A source every once in awhile would be nice. 

You're saying nobody thought to put a drop tank on a jug before Feb 44? It's true the jugs far outnumber the mustangs in big week, but a quick look at the numbers of planes and numbers of kills shows astoundingly higher kill per sortie number on the mustangs. I'll zero in on that more if I can but you can see it clearly here. Even without the long range considerations the Mustang was a superior air to air weapon. The best of the war. 

Big Week - Wikipedia

The first Mustang missions are flown Feb 11, 44 66th Fighter wing, 357th fighter group. 

357th Fighter Group - Wikipedia

They didn't augment Jug squadrons, they replaced them. I find no evidence that he D model jugs had any impact on the air to air campaign. 

I'm still hearing denial that range was the biggest problem of the jug. 

More corrections later. and I have more to say about that 20 minute gap. I know how difficult rendezvous are but planning is suppose to take that into account. Why do you think their had to be a last minute hand off in the first place? Because the second group flew a slightly different route using different fuel settings just to cover the last 20 minutes. This is the exact reason they stopped trying to fly into Germany for 5 months. This mission was the deepest I find in the dailies until Feb, and it was not very far into Germany. This mission was right on the edge of what was possible for the big fuel sucking Thunderbolt and the foul up was taken very seriously, heads rolled, because it was known exactly what would happen if they didn't hand off properly. 5 planes in 20 minutes and that was just from my uncles squadron alone. This was a mission not just military but intended to send a message to Hitler's economic and political backers as well. You'd have to research I. G. Farben Industrie to find it. It was the worlds largest chemical company. Actually, the largest company of any kind in the world at the time. Wall Street made a lot of money off them and been helping them set up field offices in Canada before the war. Why Canada? Because big money Nazi apologists were getting enough heat already without being tied to them. The largest American investors were pro nazi even after the blitz. The company and it's family were the main financial supporters of the Nazi party all through Hitlers rise to power. It wasn't just a military target, it was a political one and an economic one aimed to hit the Nazi party in the pocketbook and it was supposed to send a clear message that similar considerations would be on the table in targeting. I started out just being curious about the target my uncle was trying to bomb and it led a complicated shameful story. I found the details in 1946 congressional hearing on American financial ties to the Nazi party. It was an idea that had come from the top and the brass all the way down to the group level knew it was of particular interest to the white house. What happened was an embarrassment.


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## Carboncrank (Nov 10, 2017)

tomo pauk said:


> Horsepower at altitude matters. P-47 that went close to 500 mph have had 2800 HP at 30000 ft. Weight plays almost no role in speed.


it did not


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## Carboncrank (Nov 10, 2017)

mad_max said:


> "Carboncrank, posted:The Mustang's smaller air frame, narrow nose and laminar flow and low drag far outweighed having less HP.
> 
> Laminar Flow was never accomplished on the Pony.
> 
> ...


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## tomo pauk (Nov 10, 2017)

Carboncrank said:


> a lot easier to dis me than to make a counter argument isn't it?
> 
> There is no correct answer to a question with incorrect facts. There is no right answer to " how in the world does a P-47 have any business having a top speed of 500+ MPH" because P-47's did not fly 500+, yet posters were trying to answer it anyway.
> 
> ...



I'll humbly suggest taking another look at mad_max's post here, #30, that I completely agree with.
Local and/or today's politics are barely if ever discussed here, at least in this sub-forum. My take is that it is better that way.
Numbers/figures are sometimes hard to agree about, however the less-than-frinedly attitude can be spotted promptly. I did it a few times, looking back it didn't painted a nice picture about myself at the end. Still trying to improve on that.



> The emphasis on making everything a popularity contest is the facebook way of life. And THAT has the world up to it's neck in fact facts, fake news, and lies propagated by people that know how to manipulate algorithms. That is how the Russians got Donald Trump elected. Fake news, falsehood and propaganda shoved further and further up the rankings because someone hits the "like" button in a worlds where people care more about what their friend believe than they do the truth. The internet was invented for searching factual data. I use it all the time so I don't say stupid stuff. Social media is a perversion of that intent. People raised in a world where the internet has always been their have become astoundingly lazy about using it for what it was intended for. So I see more and more stupid stuff.
> 
> I don't know how the original poster got the 500mph plus notion, but I know where they didn't get it. They didn't get it through actual data on the craft. More likely they think they remember someone posting it online in some other discussion. Fact checking? Who needs it right?
> 
> ...



Nobody will try to prevent you posting whatever you think it is relevant, nor any of us here is bias-free. People that regualrly post here are from all generations, from 20 to 80 year old folks, many of them don't care much about facebook and similar novelties.
OP was perhaps thinking about this P-47 that supposedly made 505 mph: link

BTW - there is no clique here. I've verbaly clashed with some members before on this forum on some topics, and yet agreed with them on some other topics. Just like in real life.



Carboncrank said:


> it did not



Did not what?


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## Carboncrank (Nov 10, 2017)

Shortround6 said:


> Whatever the merits or demerits of this thread it does not deserve to be closed/locked because one contributor brought in modern day politics which has no relevance to the discussion.



My comments stemmed from someone going out of their way to make a personal comment about me. 

I do get the point though and will try and refrain from politics even though I was talking about a mindset more than a person regardless how I feel about people's behaivoir on the internet to be linked to the situation we find ourselves in now. 

And then there is the interconnectedness of things. Even when just trying to talk about a bombing target I end up finding out there were politics involved.


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## YF12A (Nov 10, 2017)

All I can add is what I was told from someone who flew 70 + missions from 1942 to 1945, from the first mission over Germany, led the 1st Air Division on the Schweinfurt massacre until the end of the war as a Group Co. He believed the P-51 made the long range missions possible. This coming from someone who had his own highly modified razorback P-47D to fly what became Ramrod missions when he wasn't flying a B-17.


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## Ivan1GFP (Nov 10, 2017)

Todd Secrest said:


> Did not the F4U Corsair and F6F use the same engine? (answer is yes)
> And the Corsair still had a higher top speed and I'm assume because it had a bigger propeller (13ft 4in)?
> The Corsair was designed with the gull wings, to accommodate the big propeller (and to shorten the landing gear).
> The F6F Hellcats propeller was 13ft 1in, Could 3 inches make much of a difference?



According to Corky Meyer, Grumman Test Pilot, the two were nearly identical for maximum speed and differences were mostly due to the way that the ASIs were driven.
I don't believe this was entirely accurate but the differences were probably not as high as one typically finds in the books.
The Corsair did have a speed advantage but it wasn't much and was probably due to the slightly smaller wing area and smaller frontal area and coefficient of drag.
Depending on your source, speeds for the two aeroplanes could be:
F4U-1 Corsair: 390 MPH - 417 MPH
F6F-5 Hellcat: 370 MPH - 409 MPH

Your note about the propeller differences is interesting because:
The Hellcat started with a 13 foot 1 inch propeller while the Corsair had a 13 foot 4 inch propeller.
During the Corsair's production run, it was found that the 13 foot 4 inch propeller was not optimal and the aircraft would actually go slightly faster if RPM was reduced from maximum (probably because of transonic effects on propeller tips).
It was then retrofitted with the 13 foot 1 inch propeller from the Hellcat.
I first found this in a British test report and found the retrofit propellers mentioned again in a comparative test conducted by the US Navy of a captured FW 190A-5/U4 against a Corsair and a Hellcat. (See attached document in last section above signatures.)

- Ivan.


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## Carboncrank (Nov 10, 2017)

pbehn said:


> Carboncrank, google can provide much useful information but will also tell me what the Holy Chalice looks like. The original post just asked a question, there are many possible answers.



There are no possible CORRECT answers to a question with a false premise.


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## Carboncrank (Nov 10, 2017)

pbehn said:


> It quite obviously wasn't. It was no match for anything at altitude from 1939 to 1943. It was no match for a Griffon engined Spitfire or an Me 262 when they came in to service. What it did have was good performance at all altitudes, fantastic range and huge numbers. Those numbers were magnified by the use of P 47s P 38s and Spitfires. After D Day when combats were at lower altitude it was no match for a Tempest in performance nor a P 47 for firepower and durability.
> 
> Mistakes made in the early days of the bombing offensive were not the fault of the machines involved. It was a learning experience for the group and required many more re con planes and weather reports to solve.





tomo pauk said:


> Horsepower at altitude matters. P-47 that went close to 500 mph have had 2800 HP at 30000 ft. Weight plays almost no role in speed.


 

Of course it does. The Mustang has less horsepower yet goes faster. Weight. It takes lift to lift. Along with lift comes drag. The more weight the more lift required to lift it into that thing called flying. The the more lift required the more drag. The more drag the harder it is to go fast. Not going to find a source for that because it's homework you should do yourself. Basic Newtonian physics. 

And NO the jug did NOT go close to 500 mph. No P-47 made in meaningful numbers could do close to 500. I don't think even the final X version would do that. 

That the false part of the question that started this whole thread. Stop repeating it.


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## Carboncrank (Nov 10, 2017)

tomo pauk said:


> I'll humbly suggest taking another look at mad_max's post here, #30, that I completely agree with.
> Local and/or today's politics are barely if ever discussed here, at least in this sub-forum. My take is that it is better that way.
> Numbers/figures are sometimes hard to agree about, however the less-than-frinedly attitude can be spotted promptly. I did it a few times, looking back it didn't painted a nice picture about myself at the end. Still trying to improve on that.
> 
> ...



it did not go near 500 mph.


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## Carboncrank (Nov 10, 2017)

Shortround6 said:


> The importance of top speed and rate of climb in addition to the obvious, is that they are _indicators _of an aircraft's potential.
> The faster plane will have more _options_.
> 
> top speed is done flying straight and level. As soon as you begin to bank the speed falls off. Deflection of the control surfaces cause drag, flying with wings tilted/banked causes drag as in the loss of lift has to be countered by an increase in the angle of attack of the wing.
> ...




How much speed is lost in climbing or in turns or any kind of maneuver depends on the plane. Nobody had enough power to compensate for a 5-6 g turn very long without running out of airspeed. That's one of the problems with the claim the jug would turn well. the jug loses speed in turns much faster than a smaller plane. Bigger wing area, more lift required to make the turn, more loss of momentum. That's what makes the Jugs top speed at 32k feet so irrelevant. if you have to put the jug into a tight turn you'd better not run out of ideas before you run out of airspeed. The size and weight come with a price tag. You'll find yourself quickly at a lower altitude in a plane that's not so fast anymore. The Jug loses speed at lower altitudes faster than smaller air frames do. 

It was best off strafing trains.


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## tomo pauk (Nov 10, 2017)

Carboncrank said:


> Of course it does. The Mustang has less horsepower yet goes faster. Weight. It takes lift to lift. Along with lift comes drag. The more weight the more lift required to lift it into that thing called flying. The the more lift required the more drag. The more drag the harder it is to go fast. Not going to find a source for that because it's homework you should do yourself. Basic Newtonian physics.
> 
> And NO the jug did NOT go close to 500 mph. No P-47 made in meaningful numbers could do close to 500. I don't think even the final X version would do that.
> 
> That the false part of the question that started this whole thread. Stop repeating it.





Carboncrank said:


> it did not go near 500 mph.



So you say. Other people say it did. I take orders from moderators here and from my wife at home.
P-47 vs. P-51 speed comparison includes drag vs. thrust. We know that eg. P-51B/D was faster than Spitfire IX with equivalent engine, despite the Spit being lighter. Drag is cruel, per Bill Marshall, and P-51 was both with lower coefficient of drag (any of the 3 kinds) and it was a smaller A/C that the P-47.
At pg. 125 of the 'America's Hundred thousand', it will take a 1000 lb weight increase on the P-51D in clean state to lose 3 mph. I'll reiterate that weight plays almost no role in max speed for ww2 aircraft as we know them.

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## pbehn (Nov 10, 2017)

Carboncrank said:


> There are no possible CORRECT answers to a question with a false premise.


 Well then you should have learned the danger of basing a conclusion on a false premise.

You claim for the P 51 was this "The mustang was obviously the best fighter of the war in all regards." In this you must be very precise about names. The Mustang was not an escort fighter, it was an Allison engined tactical recon plane, it had very good but limited performance because it could not perform at high altitude. The P 51 B/C and D were what made the legend and some of these were operated by the RAF and called Mustangs. When it comes to best fighter the only thing that is obvious is that it is an opinion not a fact. As a British citizen I place huge store on being there. The P-51, P 47, P 38, P39 were fine aeroplanes but they were not there in 1939/40 so you may as well discuss F-22s. Similarly, it is all very well to complain about the short range of the P 47 as your anecdotal post does, but where was the P 51? It wasn't there! When the P 51 B/C was introduced in numbers the USAAF had already learned a lot and it was this knowledge as well as the P 51 which led to success. Without the Spitfire and Hurricane the P 51 has no place to take off and land from in Europe, that is my opinion, it is a valid opinion so the P51 is not "OBVIOUSLY" anything, as great as it was.

Please Carboncrank have some respect. There are experts in aerodynamics post here and their posts will show in chapter and verse why laminar flow was not achieved on the P 51. There are veterans of the European bomber campaign still post here. There are people who have written histories and can quote chapter and verse on the subject you claim to be an expert. There is no conspiracy against your view, just put them in a more friendly way.

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## pbehn (Nov 10, 2017)

Carboncrank said:


> It takes lift to lift. Along with lift comes drag. The more weight the more lift required to lift it into that thing called flying. The the more lift required the more drag. The more drag the harder it is to go fast. .



But at very high speed most drag is not involved in providing lift is it? If you cannot say how much of the P 47 and P 51 drag was caused by providing lift, there are people here can help you.


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## Shortround6 (Nov 10, 2017)

Carboncrank said:


> On dec 1st 1943 there were zero Mustang squadron supporting bombers and they had external tanks available from day 1. They are on all Packard/Melin Mustangs. There were no bugs to be worked out. With very little pilot familiarization they went straight into combat. Where do you get this stuff? A source every once in awhile would be nice.



You want a source, fine. America's Hundred Thousand, page 333, right hand column, 6th entry.

"_Dec 1'43 _The P-51Bs of the 354th Ftr.Grp. are being 'de-bugged". They also are not yet operating with the extra fuselage fuel tank or with external tanks." 

and right below it,

"_Dec 1'43-_Twenty-four P-51Bs of the 354th Ftr.Grp. tanke their first fighter sweep over Belgium and France led by Lt.Col. Don Blakeslee of the 4th Ftr.Grp. There is no enemy action and they do some ground strafing."

The P-51s do a fighter sweep over Ameins on Dec 5th and 2 squadrons also escort B-17s from the French coast to Paix France (about 1/2 way from the coast to Paris) Where P-47s take over for the rest of the mission.

Dec 13 sees the first long range escort done by P-51s, they use 75 gallon drop tanks and help P-38s of the 55th Ftr.Grp. escort bombers to Kiel, Bremen and Hamburg. Total of 1462aircraft, 710 are bombers. 46 are P-51s. Majority of the escorts are probably P-47s seeing as how back on Oct 15th the 55th Ftr.Grp. was declared operational while there were 9 fighter groups operational on P-47s. 



> You're saying nobody thought to put a drop tank on a jug before Feb 44?



Please show me where I said or wrote that? As most of us know they had been putting drop tanks on P-47s since the summer of 1943.
However there were a lot of problems with the early tanks and the P-47 needed a lot of fuel to fly very far. A single 75-110 gallon tank wasn't going to come close to doing the job. They went though a lot of lash-ups and experiments while they sorted out a large combat capable belly tank* and *engineered, manufactured and fitted the fuel lines, valves, fittings for the under wing tanks, which I already said in this thread they _started _fitting to planes already in England (in theater) in Dec of 1943, it just takes time to refit hundreds of aircraft on active fighter bases. 



> I'm still hearing denial that range was the biggest problem of the jug.



Not from me, the Jug did have a range problem, however it was solved, somewhat, about the same time the P-51 was being issued to the fighter groups of the 8th Air Force so it is sort of moot. From an operational point of view the fact that the P-51 could fly 700 miles on 419 gallons of fuel compared to a P-47D-25 flying 600 miles on 670 gallons means it is much easier to supply hundreds of P-51s compared to a like number of P-47s. Now please note I have said nothing about or in no way implied that the P-47 was the equal of the P-51 in air to air combat in any of the above.

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## mad_max (Nov 10, 2017)

Carboncrank

You know I've learned much from the gents on here and I'm sure they've learned from my posts also. We don't always agree and I can be blunt at times. I don't like to speak verbal garbage, so I tend to tell it like it is. Some wrong facts were posted and all I did was post what I know. I don't just pull stuff out of the air when I post things. Maybe I have faulty data or such and then I get corrected. That's how things work here.

I've spent the better part of 35 years on studying WW2 aircraft, esp. fighters. I've been involved in data for sims since before the internet and am still involved with one today. I started doing this all the way back when Air Warrior was played on a BBS. Back then my state of the art computer was a Mac SE30 13" monochrome with a whopping 30 mhz processor.

Do I know everything? Not a chance. That's why I come here. Get off the horse you're riding and take a deep breath. The people here are great and you will learn more than you can ever believe.

I have never stated there were P-47's in service that could go 500mph. Sorry if I led you to believe I did. I also didn't say the Jug was the best fighter; although it did put many top notch German Fighter Pilots out of the picture before the P-51 B/C ever made a sortie in combat. My choices would be the P-47 for ground work, the P-51 for long distance escort and for pure fighter vs fighter a Spit IX or Spit XIV.

Since you want supporting evidence I googled P-51 laminar flow wing and this link was the second that came up. I have books and magazines that come to the same conclusion. I'll continue with the other corrections later if you so desire.

Here's some links for your perusal.

https://crgis.ndc.nasa.gov/historic/XP-51_Mustang
Laminar Flow Airfoil

For data you can't beat Mike's sight for loads of it.

WWII Aircraft Performance


Have a great day!

ABL

The North American P-51 "Mustang" is one of the best known fighter aircraft of the Second World War. Much has been written about the advantage in performance of the P-51 compared with other contemporary fighters by using a laminar flow airfoil. Its spectacular performance combined with excellent flying qualities and a very long range made it the best propeller driven fighter airplane of the war. The designer of the P-51 was Edgar Schmued, perfectionist and chief designer at North American Aviation. It was his intention to build an exceptionally clean aircraft showing the same aerodynamic characteristics like the smooth wind tunnel model. When in early 1940 the NACA first released information on the new laminar flow airfoil, Schmued decided to incorporate this new airfoil into the design of the P-51. The laminar flow airfoil promised about 20% less drag than conventional airfoils.

The introduction of the laminar flow airfoil into the P-51 design was observed with interest by the NACA. But NACA engineers expressed serious doubts concerning the performance of the laminar flow airfoil under real flight operations. Manufacturing irregulations, surface roughness and dirt would reduce the laminar flow to only a small region near the leading edge. The conditions of a highly polished windtunnel model could not be maintained on a real aircraft.

Nevertheless reports from England, where the NA-73 was flight tested, were very favourable with respect to the performance of the new fighter. RAF flight test engineers were convinced that the laminar flow had been achieved. But RAE scientists at Farnborough were very sceptical that the laminar flow airfoil was the key to its performance. They shared the doubts of their NACA colleagues. To find out what was that all about the US Material Command at Wright Field sent Dr. Edward P. Warner over to England. Warner's report was not conclusive with respect to the influence of the laminar flow airfoil on the performance of the NA-73. But he warned that the Germans could build aircraft of similar performance after a "Mustang" had got into German hands and the secrets of its laminar flow airfoil are disclosed.

But the fears of Dr. Warner were unjustified. At that time German scientists (Schlichting, Tollmien, Kawalki) had found a new way, to calculate the point of transition of the boundary layer from laminar to turbulent for compressible flow. This opened the way for the development of a new series of high-speed airfoils with superiour characteristics. First application was on the Messerschmitt Me 262 jet fighter.

In spite of that, the German aeronautical scientific community was interested in airfoils with laminar flow characteristics. Prof. Hermann Schlichting of the Technical Highschool Braunschweig did a lot of theoretical and experimental work to find laminar flow airfoils which would maintain its characteristics to very high Reynold Numbers. He investigated laminar flow airfoils of Russian and Japanese origin. It was the opinion of the scientific community that the laminar flow would disappear with increasing Reynold Numbers. The problem was that there existed no wind tunnel which could produce speeds high enough to come into the region of real flight Reynold Numbers (Re > 20 million) in order to prove the assumptions.

When the first P-51 Mustangs appeared over Germany in spring 1943, the good performance of this aircraft was well noticed. There were rumours that this aircraft had a laminar flow airfoil. Early in 1943 the German Air Ministry (RLM) provided an original P-51 wing in a good shape for further investigations. The AVA Göttingen measured pressure distributions at several wing sections and made drag measurements. The latter resulted in a surprising low profile drag. At this point Prof. Schlichting became interested. The same wing was put into the large 8 m wind tunnel A3 of the Luftfahrtforschungsanstalt Braunschweig-Völkenrode (LFA). It was Schlichting's intention to make boundary layer measurements and to estimate the point of transition on the airfoil where the air flow changes from laminar to turbulent. Measurements allowed Reynold Numbers up to 7,6 millions.The wing was carefully smoothed and a new coat of paint was applied. A problem was the position of the main spar where the wing surface had a small gap at ca. 25% depth.

The mesurements using a special probe which had to be moved very close to the surface were difficult. The slightest damage of the paint after the probe had touched the surface caused an immediate transition of the air flow from laminar to turbulent. The measurements were repeated for different Reynold Numbers and different lift coefficients. For the lowest Reynold Number (4 millions) the point of transition was measured at 50% depth on the upper surface. It moved to the leading edge with increasing Reynold Number, arriving at 20% for Re=7,5 millions. Measurements with different laminar flow airfoils including the Mustang airfoil were later continued in the large high-speed wind tunnel of the DVL, Berlin up to Reynold Numbers of 20 millions. These measurements clearly revealed the fact that the laminar flow effect completely disappeared at real flight Reynold Numbers. This was an expected but sobering result.

One important result of the wind tunnel investigations on the original Mustang wing was its low profile drag. This lead to a comparison of the Mustang wing with wings from different German aircraft. In 1944, rather late in a war, comparative wind tunnel measurements were made with original wings of the Fw 190, He 219, He 177, Ar 234, Me 109 F, Ju 288 and Martin B-26 "Marauder". Objective of these measurements was the estimation of the profile drag for different lift coefficients. These measurements revealed a clear advantage of the Mustang wing. Compared with the ideal smooth wing (wind tunnel model), the wings of the German aircraft had up to 60% higher drag than the ideal smooth wing. This reflects the poor manufacturing standards in Germany at that time. The Mustang wing had by far the lowest profile drag that could not be explained with the laminar effect alone, but to a large extent with the very good manufacturing standards at NAA.

Concluding you can say that the performance of the Mustang could not be attributed to its laminar flow airfoil. It was the overall low drag design of this aircraft with clean surfaces including the careful design of the radiator that was the key of its good performance. Edgar Schmued succeeded to build an aircraft as clean as the wind tunnel model - a remarkable aircraft and a remarkable designer.

*References*

Ray Wagner: Mustang Designer Edgar Schmued and the P-51. Smithsonian Institution Press: Washington D.C. / London 1990.
James R. Hansen: Engineer in Charge, A History of the Langley Aeronautical Laboratory 1917-1958. The NASA History Series. NASA: Washington D.C. 1987.
Breford / Müller: Messungen am Originalflügel des Baumusters P-51 "Mustang". AVA FB. Nr. 1724/2, 1943.
Kopfermann / Breford: Umschlagpunktmessungen am Originalflügel des Baumusters P-51 "Mustang". In: Deutsche Luftfahrtforschung, UM 2035, 1943.

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## DerAdlerIstGelandet (Nov 10, 2017)

Carboncrank said:


> a lot easier to dis me than to make a counter argument isn't it?
> 
> There is no correct answer to a question with incorrect facts. There is no right answer to " how in the world does a P-47 have any business having a top speed of 500+ MPH" because P-47's did not fly 500+, yet posters were trying to answer it anyway.
> 
> ...



And we do not allow any modern political discussion of any kind on this forum.

Go and read the forum rules. This will be the only warning on the topic of politics. 

Posting modern political discussion, regardless of what side of the fence you are on, can and will get either a thread closed or a poster removed (temporarily for a first offense) if they can not abide by the forum rules that are posted. Please respect the forum rules, especially regarding politics and civil discussion. I have posted links to two threads regarding forum rules. 

A few ground rules for the new folks

The Thread to end All Political Threads (Hopefully)



Carboncrank said:


> I do get the point though and will try and refrain from politics even though I was talking about a mindset more than a person regardless how I feel about people's behaivoir on the internet to be linked to the situation we find ourselves in now.



You will not try and refrain, you will refrain...

Not trying to be an asshole here, but modern politics has 0, zilch, nada, nothing to do with this topic, and this forum has a 0 modern politics rule in place anyhow.


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## DerAdlerIstGelandet (Nov 10, 2017)

And to all members posting in this thread. Please do so in a civil and respectful manner.


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## Shortround6 (Nov 11, 2017)

We may have some confusion as to what the "original premise" of this thread is. 

I could be wrong (it's happened plenty of times before), but I took it as a general question as to why some rather large, heavy aircraft were as fast or faster than some smaller, lighter and more streamline appearing aircraft. I believe that question has been answered by the replies concerning power and drag at altitudes. 

Now perhaps the examples given for the bulky fighters were not the best possible ones (may depend on your point of view) as they were either prototypes or late/post war versions built in limited numbers, but I don't believe that invalidates the basic question. 
The XP-47J is supposed to have flown at over 500mph. Perhaps only once or twice? Perhaps never? Depends on which stories you believe. However this prototype does show up along with the 500+ speed in practically every book or long article about the P-47 and so is widely known. 





And yes it is far, very far, from a standard P-47. However stuffing the same basic powerplant in a P-47D airframe did get you the P-47M version (100 built) and 470mph which I figure is close enough to ask how they did it compared to even a P-51H which was a bit faster on a lot less power. 

I don't believe anybody in this thread has been arguing that _normal_ production P-47s of 1943/44 could do 500mph or even 450mph. 

I do believe that people who want to argue about the technical aspects of aircraft would do well to use better sources than Acepilots.com. a nice "quicky" look at a plane but hardly detailed (like the common error of *not* giving the altitude at which the speed was achieved)

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## drgondog (Nov 11, 2017)

Couple of notes;

XP-47J flew 505mph at Republic
XP-51G flew 498mph at NAA
Neither flight tested by AAF, nor in any certified closed course.
First Operational P-51B mission was by 354FG led by Don Blakeslee on December 1, 1943. Standard 'Newbie break-in' Area Patrol over French Coastal area.
P-51B-1 and early P-51B-5 did not have factory pressure pump installed at factory and all were modified at Warton BAD2 until the mid P-51B-5 block 43-67XX (have to look up). Ditto P-47C and early P-47D. Haven't yet confirmed first 75 gallon auxiliary tank mission. Bremen on 12/10 is a possibility. Bordeaux on 12/31 is a certainty. The 200 gallon ferry tank was tested with first exhaust pump modified at 8th Svc Cmd in July 1943, but the 200 gallon tank was replaced with the 75 gallon, then 108 gallon C/L tanks in August, 1943.
P-51B-10 (#1 43-7113) first factory 85 gallon tank. P-51B-1 43-12112 was modified with steel fuselage fus tank (~92 gallons) and flown by Chilton on July 16, 1943. AAF Flight Tests in 43-12305 during first two weeks of August.
1200 85 Gallon Kits (complete) were shipped from NAA to both stateside Base Depots and BAD2 Warton. The first kits were applied to P-51B-1 in UK in December. The first 85 gallon kit installed on P-51B-5 in the States (as near as I can find) was 43-6382 at Buffalo Base Depot. All succeeding P-51B-5 through 43-7112 were modified in the US.

Not even NAA called the NACA/NAA 45-100 Laminar Flow. It's primary features were a.) very low drag and b.) delayed Mc by virtue of max T/C at 45% C and low velocity gradient from zero to 45% C when compared to NACA 23xxx (P-38, F4U, F6F, FW 190, etc)
Laminar Flow to Turbulent Flow transition is RN~ 500,000 (0.5x10^^6) (taxi speed). The key to the 45-100 is that the adverse pressure gradient due BL separation was delayed.

Induced Drag at top speed is about 0.75% of Total Drag for a P-51B, less for the P-47 due to higher Oswald efficiency of wing. CLARIFICATION - The % contribution of Induced Drag to Parasite Drag increases over baseline when weight is added. It is a function of CL and AoA which must increase when more weight is carried by the wing. The figures provided were for P-51D when weight was added over P-51B normal combat load.

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## Shortround6 (Nov 11, 2017)

A few comments if I may.
If memory serves the XP-47J 500mp flight and the XP-51G 490+ flights may have been within a few weeks (if not a few days?) of each other and there may have been a certain amount of one-upsmanship going on? No source in front of me at the moment though  
Maybe just a good story?

Thank you for the details on the P-51 fuel tank situation/time line. 

The P-38, P-47 and P-51 were all evolving of the summer/fall of 1943 and into the spring of 1944. 

There is quite a bit of confusion between what was called "laminar flow" in the popular press of the time (and got into later books/articles) and what the aerodynamicists working the wind tunnels/labs considered "laminar flow". I believe the Davis wing used on the B-24 was considered at one time by some people to be "laminar flow" for example. It did maintain non turbulent airflow further along the airfoil than most other airfoils of the time (and that is not saying much) but had some serious drag issues as the speed went up and certainly did NOT maintain that airflow over even 1/3 of the wing. 
The US went from about 13 wind tunnels ( and no full size high speed tunnels) in the country in 1939/40 to over 40 windtunnels by the end of 1945 so what was KNOWN vs what was theory also changed quite a bit.

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## Koopernic (Nov 12, 2017)

Carboncrank said:


> On dec 1st 1943 there were zero Mustang squadron supporting bombers and they had external tanks available from day 1. They are on all Packard/Melin Mustangs. There were no bugs to be worked out. With very little pilot familiarization they went straight into combat. Where do you get this stuff? A source every once in awhile would be nice.
> 
> You're saying nobody thought to put a drop tank on a jug before Feb 44? It's true the jugs far outnumber the mustangs in big week, but a quick look at the numbers of planes and numbers of kills shows astoundingly higher kill per sortie number on the mustangs. I'll zero in on that more if I can but you can see it clearly here. Even without the long range considerations the Mustang was a superior air to air weapon. The best of the war.
> 
> ...



It’s a really interesting take on the relative ineffectiveness of the P-47. I hope you post more information because relative loss and victory ratios would let us know a lot.

I don’t go for the story about IG Farben being bombed or rather not bombed on time. It’s a conspiracy theory. Nothing wrong with conspiracy theories, they must be created and examined because sometimes they are true. I love conspiracy theorists. In this case it doesn’t work for me.

How about instead of a conspiracy theory we assume I.G.Farben operated a coal to liquids synthetic fuel plant in the area and this was part of the carefully timed allied pre invasion oil campaign that was designed to disrupt German fuel supplies prior to D-day. Allied particularly US bombing had deliberately avoided attacks on the oil industry to avoid alerting the Germans. That’s what all the documents say and what the timing actually was. US bombing was directed against ball bearings, airframes, engines, shipyards where it caused long term damage to plant and tooling that was in many cases irreplaceable. Then before the invasion, before the Germans can take measures, you disrupt their fuel supplies so that their transport problems support the invasion.

The P47 fighter pilots and bomber pilots and their respective planners who didn’t rendezvous for a successful escort mission to various I.G.Farben synthetic fuel plants didn’t fail because nazi sympathising shareholders had a secretly organised a conspiracy via their network in the USAAF. There wasn’t a lot of computerized tracking and navigation or experience in this.

There were no significant nazi sympathisers in the USA and non had any power or access to media control. Control of banking had long passed from WASPs. It’s just a label people use to demonise or dehumanise people arguing against them. In this case Isolationists. I won’t be part of it. What there were was people that wanted their country to stay neutral because they knew what terminal harm it would do to our civilisation and that when big powerful country gets talked into supporting a little country that little country becomes more pugilistic and intransigent and war is more likely. There was ample evidence of this to the American public from WW1 because the British actually apologized for it in parliament. (Refreshing, no one does that anymore). All the really nasty stuff in a war happens years after it starts so avoiding it is a noble thing.

The house committee on unamerican activities was of course looking for nazis. Finding shareholders is not finding nazis. The Congress Committee always gets confused with Senator Joseph McCarthy (lawyer, judge, USMC intelligence officer and 13 mission tail gunner (for photo recon purposes) because they both exposed communist activities as well. Having a business or a corporation doing business in Japan or Germany between the wars is also not wrong. Free trade agreements would have given the Germans and Japanese what they wanted (materials) and this almost succeeded with elements in both countries. 

There is another spin on this conspiracy. This one is that Standard Oil (ie Exxon) gave the “Nazis” the technology to make tetra ethyle lead to boost octane ratings.

If we assume that German chemists were too dumb to figure out how to make tetra ethyle lead and simply ignore international patent law when war came about then maybe this was a bad thing. But of course German Chemists could make TEL and in fact they had first developed other effective anti knock agents such as iron pentacarbonyl (marketed as Motalin by Farben in 1927)

But what actually happened is that IG Farben and Standard Oil swapped patents. The Germans got the right to use TEL and the US got the right to use BUNA synthetic rubber. That was in 1934 when Hitler was only just elected Chancellor.

It was a profitable deal for the Americans because the Germans couldn’t make money out of synthetic rubber since they lacked the cheap raw material required.

In fact the raw material needed to make both octane and synthetic rubber is a gas called butylene. Butyl rubber. That’s the real reason the Luftwaffe lacked 100 octane. Apparently those idiots thought the German Army and population having tires was more important than fighters flying around with a 100kg of butylene derived octane.


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## Shortround6 (Nov 12, 2017)

On the P-47s effectiveness, I would note that some P-47 groups did rack up some decent scores. Not as good as some Mustang groups in similar periods of time but that hardly means the P-47 was ineffective. Also please note that the P-47s changed their performance considerably in a matter of months. Initial water injection kits (raising boost from 52in to 56in) being fitted in the fall of 1943, the paddle blade props being fitted over the late fall and winter and new water injection kits being fitted in spring of 1944 allowed 64/65in of boost. 
The old props with the first water injection really didn't show a lot of improvement but the the new props and water injection added around 600fp to the climb at most lower altitudes (below bomber stream.)
All of these changes could be and were retrofitted to planes in the field. 

Again, I am not saying the P-47 was the equal of the Mustang but that the P-47s capability changed a lot in a short period of time which overlapped the introduction of the Mustang.

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## tomo pauk (Nov 12, 2017)

Even before the w-i kits and paddle bade props were installed, the LW interceptors disliked to go anywhere close to them (thanks stona/Steve for pointing me to this some time ago):

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## windswords (Nov 14, 2017)

This may not be true (and if not I'm sure someone will correct the record), but I heard that the first American fighters flying escort over Berlin were P-47 Thunderbolts - and that the Mustangs got lost and did not make the party. Whether true or not the P-47's range was extended so that they could fly to Berlin. Yes, I realize the range was not as good as the 51 and the loiter time was probably shorter. But the points made by Shortround6 about the continual improvement in both the 47 and the 38 (let's not forget they were improving the B-17 and B-24 all the time as well) are well taken.

If the Mustang had not come along, the Thunderbolts and Lightnings would have been improved to the point where they could do the job (the P-47N escorting B-29's to Japan comes to mind). Maybe it would have delayed the inevitable, but not for long. D-Day would have taken place. Everywhere I've read that the top speed tested for the P-47M was 473 mph, but I have seen lower numbers in this thread. Does anyone have sources for those lower numbers?


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## pbehn (Nov 14, 2017)

Frequently lost in this discussion is that until 1943 many of those involved in the US bombing offensive were adamant that a long range escort fighter was either not needed or was impossible to make. The breakneck development of the range of all these fighters came from the realisation that an escort fighter was absolutely essential and so had to be constructed no matter what the cost.

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## tomo pauk (Nov 14, 2017)

Before the German declaration of war, USA probably can be excused for not embracing the escort fighter - after all they were trying to came out with inter-continetal bombers. After that, there were fast ways to create long range escort force for 1943, however the doctrine was again much slower than technology.

Japanese were doing LR escort before the advent of Zero or Oscar.


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## pbehn (Nov 14, 2017)

tomo pauk said:


> Before the German declaration of war, USA probably can be excused for not embracing the escort fighter - after all they were trying to came out with inter-continetal bombers. After that, there were fast ways to create long range escort force for 1943, however the doctrine was again much slower than technology.
> 
> Japanese were doing LR escort before the advent of Zero or Oscar.


A complex discussion, in 1940 the Merlin produced 1000 BHP, it couldn't possibly power any S/E fighter aircraft to Berlin and back. Just over two years later it could and three/four years later it did.


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## Shortround6 (Nov 14, 2017)

Part of the long range escort problem when comparing countries is the difference in defense.
Tomo is correct, for the US long over water flights were planed with only brief periods of combat.
For the Japanese, they were doing either long flights over China (or Manchuria) or long flights over water.
Low transit speeds and low altitudes could be used by both bombers and escorting fighters as there are few AA batteries in mid ocean/sea and neither China or any other areas of Japanese interest had much in the way of AA guns. A large amount of the Chinese air force in the 1930s being biplanes of limited power/range defensive fighters were pretty much found only near the target cities. 
When trying to bomb Germany, especially raids several hundred miles into Germany proper and not just a hundred miles from the coast and into occupied territory, it was _possible_ to run into enemy fighters almost anywhere along the route. It might not be likely in some areas but it was possible so escorts had to be provided along the entire route. Since there was no "safe zone" the escorts also had to cruise at higher speeds to avoid being at too great a disadvantage IF the enemy fighters showed up. Cruising altitudes also had to be higher to feep out of the worst of the flak. 

Please note what even the bombers of 1940 were _capable _of. Extreme example being the Whitley raid against Genoa Italy. Granted the vast majority of raids were much shorter but escort fighters in 1940/41 would have been doing good to manage a radius of action that included the Ruhr valley. If the Germans realize the British/Americans aren't flying east of the Ruhr what can they do with the deployment of their AA guns?


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## InlineRanger (Nov 14, 2017)

Here's my understanding of the topic:

*Maximum speed = thrust - drag*. Thrust is engine power x propeller efficiency. At maximum speed, drag is almost entirely parasitic. The larger the difference between thrust and drag, the higher the maximum speed.

You maximize engine power by increasing the oxygen mass flow rate, increasing compression ratio and reducing parasitic losses. You increase propeller efficiency by reducing span loading (_low disk loading, high aspect ratio blades_), maximize lift distribution (_elliptical loading_), and keeping wave drag to a minimum (_tip speed below critical mach, thin airfoil/sweep to increase critical mach_).

Parasitic drag is defined by the well known equation *drag = zero lift cd * .5 * air density * velocity^2 * wing area*. In reality, this is just an approximation that assumes all aircraft share similar fuselage to wing proportions. A more relevant metric would be the wetted area drag coefficient and wetted area. So drag can be reduced by flying higher and/or in hotter temperatures (_reduce air density_), reducing the wetted area, and streamlining.

Flying higher reduces thrust (_reduced oxygen mass flow rate, lower propeller efficiency due to decreased critical mach_) and also reduces critical mach (_drag divergence occurs at a lower TAS_). Supercharging (_mechanical, turbine_) and oxygen injection (_compressed/liquid O2, nitrous oxide_) help restore mass flow rate. Larger, slower turning propellers and/or increased blade count mitigate propeller efficiency losses at altitude.

The wetted area can be reduced by increasing thrust/weight ratio, increasing wing loading, using a low moment coefficient airfoil (_reduce tailplane size_), decrease cg range (_reduce tailplane size_), reduce area forward of wing quarter chord (_reduce tailplane size_), and reducing protuberances (_canopy, antennas, lights_).

The wetted drag coefficient can be reduced by using a long chord wing (_higher reynolds number_), reducing pressure gradients (_laminar flow wings, long shallow canopy, generous radii at stagnation points_), reducing interference drag (_area ruling fuselage/wing/tailplane intersections_), removing protuberances (_antennas, lights_), reducing surface roughness, decreasing cooling drag.

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## InlineRanger (Nov 14, 2017)

So why is Rare Bear, a stubby radial engine F8F Bearcat the fastest piston engine aircraft in the world?

While the original Bearcat has a higher zero lift drag coefficient than a v12 fighter, it has a comparatively smaller wetted area. Radial engines package a lot of displacement in very little depth, so they have less area forward of the quarter chord and can utilize shorter fuselage lengths for their frontal area. These short, squat fuselages have lower surface to volume ratios than long, sleek aircraft. So while their frontal area is larger and drag coefficient higher, their total drag area (_Cd X Wetted Area_) is still competitively low.

Rare Bear mainly improved the design by increasing thrust. Oxygen mass flow rate was increase by using a higher displacement engine (_R-3350 in lieu of R-2800_), increasing engine speed (_>3000rpm_), increasing boost (_many Reno racers reduce static compression to run higher boost_) and using nitrous oxide. Google seems to say power output is ~4500+hp. The propeller disc loading was decreased by using a large diameter propeller (_3-point landings only_) with a wider chord.

Drag was reduced by dropping weight (_increasing thrust/weight_) by cutting unneeded systems. As an example, Darryl Greenamyer, the previous record holder also flying a Bearcat, retracted the landing gear via a compressed gas cylinder and relied on gravity to get them locked down. The wingspan was reduced to increase wing loading (_reduce wing/wetted area_). The cooling system drag was reduced by installing a spinner to reduce intake area and using a methanol boil-off system for the oil cooler. Trim drag was reduced by setting tail surfaces to 0 degrees angle of attack. The canopy was also reduced in size and streamlined.


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## wuzak (Nov 14, 2017)

InlineRanger said:


> So why is Rare Bear, a stubby radial engine F8F Bearcat the fastest piston engine aircraft in the world?



Brute force.

Voodoo holds the record now, with maybe 1000hp less.

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## parsifal (Nov 15, 2017)

Ive read this thread through quickly, and to be honest, Im not getting the overall arguments and counterarguments.

To my mind, the P-47, the P-51 and the P-38, along the F6f and F4U were the war winning combination of US fighters that collectively turned the fortunes of the air war in the west and in the pacific around and were major contributors to the allied victory. All of them were fast and effective fighters that outclassed the opposition by a combination of performance and numbers……being there at the right time, ready to fight and able to take that fight to the enemy and win.

You don’t get better than that.

As for the speed issue, some types did go faster than others, and some seemed to benefit from the increases in power more than others. So what. We are having this rather ridiculous argument about whether one type could do 500mph or not. Who cares? They were fast enough and heavily enough armed to be dangerous, very dangerous to their enemies anytime and anywhere

Proof of this is that the p-47 and P-51 were still flying in front line service across the world well into the 1950’s

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## parsifal (Nov 15, 2017)

The fastest prop driven a/c to enter production was the Soviet Tu114., With four massive turboprop engines, it has a maximum speed of 870 km/h (540 mph, Mach 0.73). Its 15,000 hp NK-12 turboprop engines are the most powerful turboprops ever built and drive large contra rotating props.. This engine-propeller combination gives the Tu-114 the official distinction of being the fastest propeller-driven aircraft in the world, a record it has held since 1960.

This is not the fastest prop driven aircraft however. 

This distinction is probably the property of the McDonnell XF-88 experimental fighter which was made by installing an Allison T38 engine in the nose of a pure jet-powered Voodoo. This unusual aircraft was intended to explore the use of high-speed propellers and achieved supersonic speeds. This aircraft is not considered to be propeller-driven since most of the thrust was provided by two jet engines. 

An oft-cited contender for the fastest propeller-driven aircraft is the XF-84. This aircraft is named in the guiness world records, as the fastest in this category with a speed of 623 mph, achieved in 1997. While it may have been _designed_ as the fastest propeller-driven aircraft, this goal was not realized due to its inherent instability. This record speed is inconsistent with data from the National Museum of the USAF, which gives a top speed of 520 mph, slower than the Tu-114. 

Rare Bear is still credited as the fastest conventional piston engine aircraft, though there are serious disputes about this, with some unconfirmed reports of modified P-51Cs which I vaguely recall as being slightly faster . These claims don't appear in the records books as official speed however.


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## tomo pauk (Nov 15, 2017)

pbehn said:


> A complex discussion, in 1940 the Merlin produced 1000 BHP, it couldn't possibly power any S/E fighter aircraft to Berlin and back. Just over two years later it could and three/four years later it did.



Merlin was producing 1300 BHP already in 1939.
As for the fighter that can do Kent to Berlin and back on budget (= one engine of 1000-1100 HP at altitude) while still being compettitive in the air, see Ki-61 and Zero. (link) Both used much draggier wings than Spitfire, and weaker engines.
BTW - in 1940, Ruhr can be attacked from France, 300 miles away. So can Berlin.

I'll stick to what I've said before - long range fighter was was much more restricted because of doctrine and politics/policy, than because of technology

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## mcoffee (Nov 15, 2017)

windswords said:


> This may not be true (and if not I'm sure someone will correct the record), but I heard that the first American fighters flying escort over Berlin were P-47 Thunderbolts -



The first US fighters over Berlin on an escort mission were P-38's of the 55th Fighter Group on 3 March 1944. The bombers aborted due to weather short of reaching Berlin, but the 55th continued over the city.

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## Shortround6 (Nov 15, 2017)

tomo pauk said:


> Merlin was producing 1300 BHP already in 1939.
> As for the fighter that can do Kent to Berlin and back on budget (= one engine of 1000-1100 HP at altitude) while still being compettitive in the air, see Ki-61 and Zero. (link) Both used much draggier wings than Spitfire, and weaker engines.
> BTW - in 1940, Ruhr can be attacked from France, 300 miles away. So can Berlin.
> 
> I'll stick to what I've said before - long range fighter was was much more restricted because of doctrine and politics/policy, than because of technology



Sorry Tomo, I am on the other side for 1940/41
France is out of it, 860-910hp Hispano V-12s have enough trouble powering local interceptors even though they stuck big fuel tanks in the D.520. 
Italy is out of it, the Fiat Radial doesn't make enough power and has too much drag.

The Japanese fighters are out of it also. Please note the conditions of cruise for everything except the Zeke 32, cruise is at 1500 ft, not 15,000ft. Unless it is a misprint. Just what are you escorting flying at 1500ft? Please look at the average speeds. speeds for max range are barely above minimum controlled airspeed. Any plane operating in enemy airspace at such a speed is little more than a target. 
The radius figures are a bit more believable but speeds are unknown and suddenly the Zeke 52 fails on the Berlin mission.
Zeke 52s were also not avialable in 1940/41. 
The Ki-61 is suspect due to the amount of fuel on board. the behind the pilot fuselage tank tended to disappear in later models did it not? 
Was it a combat tank or a ferry tank? trying to fight with the rear tank full or near full may have presented problems. 

Please note that the behind the seat tank on the P-36 was a ferry tank and the plane was not supposed to do combat maneuvers with the tank full or even part full. P-40s varied as to what they were supposed to do with the behind the seat tank according to model. 
I would note that you could probably fly a P-40 from England to Berlin and back (engage in combat is another story) by using around a 75 gallon drop tank? maybe not 
A P-40E was supposed to be able to fly 700 miles on 120 US gallons of fuel (after using an astonishing 28 gallons to warm up and take off with) Does anybody really believe a P-40C could have successfully been used as even a decent escort into western Germany in 1941 using 52 gallon drop tanks? It simply doesn't have the performance. and it was a pretty slick airplane.


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## drgondog (Nov 15, 2017)

windswords said:


> This may not be true (and if not I'm sure someone will correct the record), but I heard that the first American fighters flying escort over Berlin were P-47 Thunderbolts - and that the Mustangs got lost and did not make the party. Whether true or not the P-47's range was extended so that they could fly to Berlin. Yes, I realize the range was not as good as the 51 and the loiter time was probably shorter. But the points made by Shortround6 about the continual improvement in both the 47 and the 38 (let's not forget they were improving the B-17 and B-24 all the time as well) are well taken.
> 
> If the Mustang had not come along, the Thunderbolts and Lightnings would have been improved to the point where they could do the job (the P-47N escorting B-29's to Japan comes to mind). Maybe it would have delayed the inevitable, but for long. D-Day would have taken place. Everywhere I've read that the top speed tested for the P-47M was 473 mph, but I have seen lower numbers in this thread. Does anyone have sources for those lower numbers?


No to the P-47D. At the Time, Mar3, 1944 the max combat radius of the P-47D series, with external tanks and 305 gallons internal fuel was Stuttgart/Brunswick radius. It was not until the P-47D-25 w/bubble canopy and 370 gal of internal fuel was combat operational in June 1944 that the P-47 could get to Leipzig/Magdeburg/Schweinfurt radius for target escort. By that time the P-51B/C and early D had populated 50% of 8th AF FG, with three more P-38 FG on-line for July conversion. and there was no need to change the role (Penetration/Withdrawal escort) for the P-47D.

The Prime Issue with 'necessary improvements' to the P-47D is that zero were in process to support POINTBLANK objectives to destroy Germany's a/c industry and achieve air superiority prior to D-Day. It is Not certain that D-Day would have occurred in 1944 had SHAEF determined that maintaining air superiority over the Beach was not guaranteed. 

The P-38J was capable of Berlin but only 3 FGs were in ops in March of 1944 - not nearly enough to perform target escort for 3 Bomb divisions of 10-13 BG's each. The day losses would have reduced but the P-38 was barely achieving 1.5:1 air victory credits per loss and the operational losses due to the intercooler/engine/turbo issues only slowed down.

To the first point. The 55th FG did go to Berlin on March 3rd. That said, elements of the 4th FG and 354th FG Mustangs escorted as far as Oranienburg (the actual target 12m N of Berlin). All of the P-47 FGs turned back from Hannover to Brunswick.


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## drgondog (Nov 15, 2017)

QUOTE="InlineRanger, Here's my understanding of the topic:

*Maximum speed = thrust - drag*. Thrust is engine power x propeller efficiency. At maximum speed, drag is almost entirely parasitic. The larger the difference between thrust and drag, the higher the maximum speed.

*Your equation is for Force, not velocity. 

When Thrust=Drag, acceleration =0. At that 'point' (for that altitude, MP, RPM), Vmax is attained. That said, deriving actual Thrust Hp is very complicated, particularly when Ram air and exhaust Thrust for the engine is required to solve. Total Drag is reasonably straightforward for level flight in incompressible flow range <0.3M. As flight speeds approach Mcr the drag rise factor is a Major delta. Incremental Drag factors over Zero Lift drag for say, climb or turn, must take into account RN, Form Drag due to AoA, pressure Drag due to airframe components immersed in prop vortex, Cooling drag, etc. *

*The determinant for achieving max velocity (and increase climb and Turn) is Power achieved - Power Required = T*V-D*V and is quite a bit more complicated analysis with Conventional aircraft. *

You maximize engine power by increasing the oxygen mass flow rate, increasing compression ratio and reducing parasitic losses. You increase propeller efficiency by reducing span loading (_low disk loading, high aspect ratio blades_), maximize lift distribution (_elliptical loading_), and keeping wave drag to a minimum (_tip speed below critical mach, thin airfoil/sweep to increase critical mach_).

Parasitic drag is defined by the well known equation *drag = zero lift cd * .5 * air density * velocity^2 * wing area*. In reality, this is just an approximation that assumes all aircraft share similar fuselage to wing proportions. A more relevant metric would be the wetted area drag coefficient and wetted area. So drag can be reduced by flying higher and/or in hotter temperatures (_reduce air density_), reducing the wetted area, and streamlining.

*CD= (CDp1+DeltaCDp1+DeltaCDp2)*CD/CDinc + Cdi where CDp1 is a f(RN) and will decrease with Velocity and density
CDp1 is minimum Parasite Drag Coefficient of the aircraft in zero lift at a particular RN and is comprised of wind tunnel measured component characteristics of the airframe (wing, fuselage, empennage, cockpit enclosure, carb duct, radiator duct and exhaust stacks for P-51)
'Delta' CDp1 are CD of individual components such as external antenna, machine gun ports or fairings, leaks and surface roughness)
Delta CDP2 are increments due to Angle of Attack and expressed as CL. Included are Cooling Drag/Net internal Flow losses during climb, external load items such as fuel tank/bombs, and Immersed items in slipstream (fuselage/empennage/cockpit, etc plus 1/3 of the wing) --------> for the latter, wind tunnel data are power off. Calculations of Power Required mandate accounting for the free stream dynamic head in the increased velocity slipstream behind the prop. The usual method is to apply increased drag for increased velocity over those components assuming velocity is constant throughout the slipstream. This calculation is extrapolated for RN in same fashion as CDp1

CDi is the Induced Drag component due to lifting surfaces, including Wing, H.Stab/Elevator and slats if ya got em'. There is also a small delta component due to washout of leading edge which changes the chordwise Lift distribution.

For Power Required calcs, the momentum loss in Carb air is also considered a loss in Power Available.*

*CD/CDinc is the compressibility factor over CD for incompressible flow.*

*For your THp data, you need to correct Static Hp with following:
Adiabatic temp rise
Friction Hp of Engine
Manifold Temp
Aircraft True air speed.*

*The Jet Thrust is a factor of;
Outside air pressure
Total Stack exhaust area
Engine charge consumption, slugs/sec
Ratio outside static air pressure to manifold pressure*

*With these data in hand the next step is to calculate prop efficiency - normally taken from Manufacturer's data*

*Then, make corrections to Power Available by deriving Power losses due to Slipstream, engine air momentum loss and corrections to Thrust Hp prop efficiencies

During the analysis phase, particularly for a two stage/two speed supercharged engine - the Power Available and Power Required for each desired Weight and stores condition and altitude are calculated to point to achievable Velocity and climb and range performance as function of MP and RPM.*

Flying higher reduces thrust (_reduced oxygen mass flow rate, lower propeller efficiency due to decreased critical mach_) and also reduces critical mach (_drag divergence occurs at a lower TAS_). Supercharging (_mechanical, turbine_) and oxygen injection (_compressed/liquid O2, nitrous oxide_) help restore mass flow rate. Larger, slower turning propellers and/or increased blade count mitigate propeller efficiency losses at altitude.

The wetted area can be reduced by increasing thrust/weight ratio, increasing wing loading, using a low moment coefficient airfoil (_reduce tailplane size_), decrease cg range (_reduce tailplane size_), reduce area forward of wing quarter chord (_reduce tailplane size_), and reducing protuberances (_canopy, antennas, lights_).

Wetted area is what the term implies ---------> the total surface area top to bottom, side to side, of the airframe. The Wetted Area Drag coefficient is simply based on Total Drag divided by wetted area while the conventional CD is derived by dividing Total Drag by Wing Area.



The wetted drag coefficient can be reduced by using a long chord wing (_higher reynolds number_), reducing pressure gradients (_laminar flow wings, long shallow canopy, generous radii at stagnation points_), reducing interference drag (_area ruling fuselage/wing/tailplane intersections_), removing protuberances (_antennas, lights_), reducing surface roughness, decreasing cooling drag.

To the extent that Total Drag of the studied airframe can be reduced by any/all of your proposed changes will alter Wetted Surface Area, the Wetted Drag Coefficient will also change but;
1.) increasing chord without changing wing area will move the needle on RN but not change Wetted Area or Wetted Drag Coefficient unless the Wing change to alter chord also changes the CDp1 of the wing. This is true for P-51H wing in contrast to P-51/A/B/C/D/K
2.) All of your cited factors are functions of Parasite Drag (Form drag, interference drag, friction drag, etc) - independent of Wetted area. If you maintain Wetted Area but say, change the Parasite Drag CDp1 by making an airfoil change that achieves lower Drag as function of CL, then Wetted Area is same but Total Drag is reduced so both Total Drag and Wetted Drag reduce. If you change aspect Ratio while maintaining Oswald Efficiency but make no change to Wing Area - you may or may not change parasite drag but will reduce Induced drag - so possible change Wetted Area Drag to same extent Total Drag is altered. 

All this is memory driven and of all the things I miss, I miss my mind the most.

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## tomo pauk (Nov 15, 2017)

Shortround6 said:


> Sorry Tomo, I am on the other side for 1940/41
> France is out of it, 860-910hp Hispano V-12s have enough trouble powering local interceptors even though they stuck big fuel tanks in the D.520.
> Italy is out of it, the Fiat Radial doesn't make enough power and has too much drag.



Dang, I've reckoned you're part of the clique. Oh, well 
Piaggio radial makes better power at higher altitude than the Fiat radial. The Re.2000 carried 460 kg (~600 L) of fuel, the LR version of the Re.2000 carried even more for it's range of 2000 km @430 km/h cruise. If 320-330 mph is too slow for 1940, the Re.2001 (~350 mph) or it's equivalent was well within the state of the art of Germany and UK and USA in 1939, let alone in 1940.
RAF fighters can do escort job from France to Germany in Spring of 1940.



> The Japanese fighters are out of it also. Please note the conditions of cruise for everything except the Zeke 32, cruise is at 1500 ft, not 15,000ft. Unless it is a misprint. Just what are you escorting flying at 1500ft? Please look at the average speeds. speeds for max range are barely above minimum controlled airspeed. Any plane operating in enemy airspace at such a speed is little more than a target.
> The radius figures are a bit more believable but speeds are unknown and suddenly the Zeke 52 fails on the Berlin mission.
> Zeke 52s were also not avialable in 1940/41.
> The Ki-61 is suspect due to the amount of fuel on board. the behind the pilot fuselage tank tended to disappear in later models did it not?
> Was it a combat tank or a ferry tank? trying to fight with the rear tank full or near full may have presented problems.



Zero carried 140-160 gals of fuel internaly, plus ~ 90 gal drop tank for it's 950-1150 HP engine, thus great range. Again everything within state of the art of many Western countries.
Ki-100 carried on with rear fuel tank from the Ki-61 (schematics). Rear tank carried about 50 gals of fuel, fuel system also comprised from two drop tanks, 2 x 50 gals per US data.



> Please note that the behind the seat tank on the P-36 was a ferry tank and the plane was not supposed to do combat maneuvers with the tank full or even part full. P-40s varied as to what they were supposed to do with the behind the seat tank according to model.
> I would note that you could probably fly a P-40 from England to Berlin and back (engage in combat is another story) by using around a 75 gallon drop tank? maybe not
> A P-40E was supposed to be able to fly 700 miles on 120 US gallons of fuel (after using an astonishing 28 gallons to warm up and take off with) Does anybody really believe a P-40C could have successfully been used as even a decent escort into western Germany in 1941 using 52 gallon drop tanks? It simply doesn't have the performance. and it was a pretty slick airplane.



P-40C + Merlin 45 + two 75 gal drop tanks. Perhaps not Berlin and back, but has performance and range.


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## pbehn (Nov 15, 2017)

I don't join cliques Tomo. My argument is based purely on the P51. It needed all the fuel that could be put inside and outside to do the job as a long range escort and it needed a 1750BHP Merlin engine to get it all off the ground and up to altitude. An airframe with more drag needs more fuel and power The P51 was already heavier as an airframe than a Spitfire with a 1940 Merlin it just wouldn't have been a practical proposition.


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## pbehn (Nov 15, 2017)

drgondog said:


> QUOTE="InlineRanger, Here's my understanding of the topic:
> 
> *Maximum speed = thrust - drag*. Thrust is engine power x propeller efficiency. At maximum speed, drag is almost entirely parasitic. The larger the difference between thrust and drag, the higher the maximum speed.
> 
> ...



AAAHHHHHHRRGGGG 

Like a fool I googled Oswald efficiency number, then Reynolds number. Within minutes I am thinking about viscous flow in closed channels. After five minutes I have more coefficients and ratios than I can wave a stick at and stuff too complicated to copy and paste.



You are not fooling me Drgondog, it is black magic and witchcraft because I now know less than I did before I switched my computer on.

Great post, I will read it a few times to get my head around it.

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## tomo pauk (Nov 15, 2017)

pbehn said:


> I don't join cliques Tomo. My argument is based purely on the P51. It needed all the fuel that could be put inside and outside to do the job as a long range escort and it needed a 1750BHP Merlin engine to get it all off the ground and up to altitude. An airframe with more drag needs more fuel and power The P51 was already heavier as an airframe than a Spitfire with a 1940 Merlin it just wouldn't have been a practical proposition.



Sorry if you feel called out, it was an attempt of a joke in no way directed at you.
I was trying to name a few real aircraft that possesed long range combined with useful performance, while using just one engine of modest power. The engines actually being lower power than weakest Merlin. Neither of the aircraft I've listed was using the ground-breaking aerodynamics, either.
P-51 with 1940 Merlin would've been even better than P-51 or P-51A.

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## pbehn (Nov 15, 2017)

tomo pauk said:


> Sorry if you feel called out, it was an attempt of a joke in no way directed at you.
> I was trying to name a few real aircraft that possesed long range combined with useful performance, while using just one engine of modest power. The engines actually being lower power than weakest Merlin. Neither of the aircraft I've listed was using the ground-breaking aerodynamics, either.
> P-51 with 1940 Merlin would've been even better than P-51 or P-51A.


I thought you were joking. The first Mustang 1 was powered by a 1220 BHP Allison, well above the 1940 Merlin which was 1030-1100.


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## tomo pauk (Nov 15, 2017)

pbehn said:


> The first Mustang 1 was powered by a 1220 BHP Allison, well above the 1940 Merlin which was 1030-1100.



I'm afraid you're wrong here. 

On 100 oct fuel, in 1939, the Merlin III was rated for 1300 HP at 9000 ft, 5 min limit. At rated altitude of 16250 ft it was making 1030 HP. There is 48 total of V-1710s delivered in 1939, on 100 oct fuel they do 1040 HP at 14300 ft. There is no overboost ike the Merlin was rated, per factory. There is also no Merlin X (2-speed S/C) equivalent of the V-1710.
In 1940, slightly improved Merln XII (1-speed S/C) and much improved Merlin XX* are in production and in service. 1280-1400 HP.
V-1710, power-wise, remains at 1939 figures at altitude. Still no overboost - no factory-approved nor otherwise. Prototypes of the V-1710-39 are installed on the NAA-73 and P-40, power is 1150 HP at 12000 ft, altitude power over 15000 ft is in the ballpark of the older V-1710-33 of 1940. The -33 is rated 1090 HP at ~13200 ft.

Power charts: 
Merlin III (and Merlin 60)
V-1710-39 (a.k.a. V-1710 F3R, on the Mustang I/Ia/(X)P-51 and P-40s; taken from manual)
Merlin 20 series (includes Mk.XX)
Interestingly enough, the V-1710-33 gives a tad more power at altitude than DB-601A in 1940.

*The advent of the Merlin XX will not go unnoticed by the USAAC/AAF brass in the USA, where Packard got a license production deal after the deal with Ford went thorugh the floor.


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## Shortround6 (Nov 15, 2017)

We seem to suffering from thread drift.........

There are a number of fighters that could possibly fly the distances we are talking about, the problem comes in with either escorting bombers or simply surviving in enemy airspace at the speeds and altitudes required to get the long ranges specified. 

Numbers are all over the place for the Zero. However from "Zero" by Motorbooks International and authored by Robert Mikesh

We have some figures, since they are copies of US translations of captured wartime documents they may or may not be accurate  
BTW I would note in the link you gave that US intelligence on the Zero is a little off. Like they have the wrong engine in the Model 32. 

Anyway fuel consumption figures for the Sakae 12 are given as (after the US converted liters to gallons and KPH to Knots)
16.4 US gallons per hour at 180 knots
24.0 US gallons per hour at 190 knots
26.15 US gallons per hour at 200 knots
91.14 US gallons per hour at max rated power. 

Unfortunately altitude is not given. Now if you can survive and/or perform escort duties while flying at 180 knots (207mph/334kph) all well and good. However if you need to fly much faster the range goes to hell in a handbasket. As does the range if you are forced to use max rated power for very long. 
Flying range with combat time.
after 10 minutes 1025NM
after 20 minutes 900NM
after 30 minutes 774NM
so 10 minutes of combat was worth 125NM (144 statute miles/ 213KM)
Please note that flying at 190kts or above will shorten the range by about 1/3. roughly 10% increase in speed needs 50% more fuel per hour. 
Also note that the British found that Spitfire II & Vs needed to cruise about 300mph (260kts) to improve survivability even on fighter sweeps over the low countries and France. It taking about 2 minutes to accelerate from a speed in the low 200mph range to full speed at which point the German attackers have pretty much done whatever they were going to do and left the area. 
How good the A6M2 model 21 with it's single speed supercharger would have been over Europe in 1940/41 is questionable even if not restricted to low cruise speeds. 
For the Sakae 21 the fuel figures change to:
21.98 US gallons per hour at 180 knots
24.43 US gallons per hour at 190 knots
26.97 US gallons per hour at 200 knots
114.92 US gallons per hour at max rated power. 

Forget escorting B-17s, could any of these 1940/41 planes (or low tech 1942/43 planes) actually succeed in escorting even Whitley's/Wellingtons or on the other side He 111s in daylight on long range missions? 
Granted tactics evolved and pre war or 1939/40 thinking may have been that cruising alongside or just over the bombers at the same speed was good enough. Actual combat might soon consign that thinking to the rubbish bin but then the escort "range" of these early fighters plummets if they adopt higher cruise speeds and "S"ing over the bombers.

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## Shortround6 (Nov 15, 2017)

tomo pauk said:


> I'm afraid you're wrong here.
> 
> On 100 oct fuel, in 1939, the Merlin III was rated for 1300 HP at 9000 ft, 5 min limit. At rated altitude of 16250 ft it was making 1030 HP. There is 48 total of V-1710s delivered in 1939, on 100 oct fuel they do 1040 HP at 14300 ft.



You are correct but then so is Pbehn, in the sense that the early Merlins were NOT rated at the higher powers for take-off and if trying to fly top cover for a bomber group/formation flying at 15-18,000ft the Merlin's power was pretty much down to 1030-1100hp.


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## tomo pauk (Nov 15, 2017)

Shortround6 said:


> You are correct but then so is Pbehn, in the sense that the early Merlins were NOT rated at the higher powers for take-off and if trying to fly top cover for a bomber group/formation flying at 15-18,000ft the Merlin's power was pretty much down to 1030-1100hp.



I'm not sure if my point came through. Basically - in each year we pick, and currently our interest is 1940 and 41, Merlin has more power than V-1710 at any altitude. Best Merlin also beats best DB 601 in 1939-41.
During several years when the early Merlins were in service, there was no in-service V-1710.


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## Shortround6 (Nov 15, 2017)

That may be true, however the real question is does the Merlin have the power to lug around the extra weight of the "escort" fighter and remain competitive with the "local" interceptor even if the "local" interceptor uses a lower powered engine? 

Part of this is theory as some of the actual aircraft suffered from some problems. Like being able to beat 109Es might not be a good benchmark as the 109E seems to be flying around with a small parachute attached in regards to drag. 
If you can build 350mph+ Spitfires or 350mph P-40s with their large wings using 1000-1100hp engines then what could you get from a small fighter (short ranged) using the same engines? 
Granted 109Fs were not much as bomber busters but Spitfire Is, IIs and Vs trying to play escort with several hundred more pounds of fuel and fuel tank aboard against early 109Fs might be biting off more than they can chew. 
Designing and building escort fighters that depend on your opponent screwing up his defensive fighters is not very good planning or strategy.

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## drgondog (Nov 15, 2017)

As all of you know, the discussion of Range compared to Combat Radius for operational planning purposes is far apart on just basic assumptions. The Range is the optimal, controlled, performance data for which the conditions of STP, zero winds aloft, minimal warm up and taxi time, perfect climb out to the stated altitude for which the test was designed, perfect throttle and altitude and RPM management including changes as fuel burned and a/c became lighter. Never happened except in extreme Ferry role.

'Book' Combat Radius for planning purposes presented a set of assumptions for warm, take off, climb, cruise, fight, cruise and RTB with 30 minute reserve.

Real Combat Radius "Depends'. For AAF the SOP for Fighter Operations differed significantly between ETO and CBI, for example in specific parameters as: Altitude, External Load, type of mission (Sweep, Close escort - Penetration, Target Escort, etc, etc.)

So, to clarify for decomposing a frag order from 8th AF HQ to Bomb Division to Fighter Wing to Fighter Group the general Plan breaks down to Group/Squadron assignments for that mission. When the Fighter Group receives the Frag Order, the information presented is a.) type of mission i.e. Ramrod bomber escort - Target, Map Co-ordinates for R/V, time of R/V, Position in Bomber stream for assigned Box/Boxes.

The Group Ops, Weather and Intelligence staff co-ordinate the flight path, winds aloft and waypoints, taking into consideration various flak concentrations desired to avoid. Based on the PLAN to arrive at the Rendezvous point at same time as the Bomb Wings, then the entire route timings are backed out based on the Cruise Speed and mission Load and Performance Charts right to the time of Start Engines for the Entire Group of three squadrons plus spares back in Jolly Old.

As an aside - from SE time is the project plan to back out times for a.) get line crews up for breakfast and out to line, b.) wake up pilots, feed them, brief them, draw equipment, catch ride to parked a/c, perform pre-flight - and hop in to perform cockpit/panel check, Battery/Generator On- bring the systems to life and watch the instruments as crew chief looks over your shoulder, adjust the seat, hook up oxygen, etc - then Start Engine.

The Engine warm up time, taxi and form up like gaggles of Geese from the squadron revetments to position on Transient position, element or flight take offs, circling the airfield as individual elements form into flights form into Flight position behind squadron lead, circling as number tow and three squadrons assemble and start climb to cruise altitude. Once cruise altitude is reached the guys with least fuel consumption is Squadron/Group CO. The other bastards behind him have to jocky throttle to maintain wing/formation integrity and usually use more than 5% greater fuel during the cruise process. Combat is accounted for but entirely depends on dropping externals to clean up, engage at Military Power for 15 minues, WEP for 5 - and have enough fuel for straight line cruise at a specific altitude - to RTB with a 20-30 minute reserve.

What really happens is that every pilot pretty well knows how much internal fuel he needs to return Radius "X" based on the winds experienced - plus reserve. He knows how much internal fuel he used to get to Cruise altitude, and how much he has when he punches his tanks.

The Story of 8th AF would have been different if the tactical thesis was to perform bomber escort at 15,000 feet rather than 25K

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## tomo pauk (Nov 15, 2017)

Shortround6 said:


> ...
> 
> Part of this is theory as some of the actual aircraft suffered from some problems. Like being able to beat 109Es might not be a good benchmark as the 109E seems to be flying around with a small parachute attached in regards to drag.
> If you can build 350mph+ Spitfires or 350mph P-40s with their large wings using 1000-1100hp engines then what could you get from a small fighter (short ranged) using the same engines?
> ...



1st half of 1941 will mean historically Merlin 45 for the UK and DB 601N for the Germans. At the rated alt of 18000 ft (5.5 km) and +9 psi boost, Merlin 45 has 1210 HP, vs. 1100 PS for the 601N (one minute rating for the DB!). Spitfire V acting as LR fighter does not need to absolutely have several hundreds pounds worth of cannons & ammo installed.
Short range fighter is a disadvantage for Germany in 1941 if the RAF deploys LR fighters. Defending fighters in different parts of the occupied Western Europe can't support each other, situation is much worse than with different Groups of the RAF FC during the BoB. So the attacker has numerical advantage, plus it is already at altitude and speed, plus there are actual bombers than needed to be killed.


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## pbehn (Nov 15, 2017)

We are at cross purposes in the discussion. The engine development went pretty much in parallel with the Alison and Merlin. When the Mustang Mk 1 first flew The Spitfire had the MkV in production with a 1450BHP engine. My point was that in 1940/41 there was nothing to base a long range escort fighter on. By the time of Pearl Harbour in Dec 1941 less than 100 Mustangs had been manufactured. It is a massive leap of faith to base a strategy on what this airframe may do, with a better engine and better fuels which are still on the drawing board or in the lab.

When discussing a raid to Berlin as an example, it is stated elsewhere that forming up of bombers took hours not minutes. The escorts therefore have to meet the bombers and escort for a set period then hand over to another group. The mission is therefore a complex calculation of take off, climb, cruise to rendezvous, escort, combat and cruise home. Six hour missions were not uncommon, the issue is therefore a plane that can stay in the air for 6 hours and be competitive with the enemy between hours 2 and 5 (or similar).

My contention is that with a 1940 Merlin a P51 would not be a plane to base a strategy on. Those who saw the promise of the Mustang /P51 saw it as a prospect worth looking at not a certainty.


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## tomo pauk (Nov 15, 2017)

pbehn said:


> We are at cross purposes in the discussion. The engine development went pretty much in parallel with the Alison and Merlin. When the Mustang Mk 1 first flew The Spitfire had the MkV in production with a 1450BHP engine. My point was that in 1940/41 there was nothing to base a long range escort fighter on. By the time of Pearl Harbour in Dec 1941 less than 100 Mustangs had been manufactured. It is a massive leap of faith to base a strategy on what this airframe may do, with a better engine and better fuels which are still on the drawing board or in the lab.



Non-turbo V-1710 was lagging at least two years behind the Merlin. For a short war the ww2 was (technology-wise; it was endless war for people at the receiving end), that is big chunk of time. What Merlin offered in 1937, V-1710 offered in 1939. It was 1942 when V-1710 went better than Merlin III in altitude power - 5 years to beat it, (while the Merlin started being manufactured in the excellent 2-stage supercharged variant). And it still was not as good as Merlin XX or 45. As per 'it was nothing to base a long escort fighter on in 1940/41' - it was, in Japan, Italy, USA, Germany and the UK.



> When discussing a raid to Berlin as an example, it is stated elsewhere that forming up of bombers took hours not minutes. The escorts therefore have to meet the bombers and escort for a set period then hand over to another group. The mission is therefore a complex calculation of take off, climb, cruise to rendezvous, escort, combat and cruise home. Six hour missions were not uncommon, the issue is therefore a plane that can stay in the air for 6 hours and be competitive with the enemy between hours 2 and 5 (or similar).
> 
> My contention is that with a 1940 Merlin a P51 would not be a plane to base a strategy on. Those who saw the promise of the Mustang /P51 saw it as a prospect worth looking at not a certainty.



As before - P-51 with Merlin from 1939 would've been a great fighter. See the P-51 and P-51A - 390-410+ mph on 1150-1125 HP. linky


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## pbehn (Nov 15, 2017)

tomo pauk said:


> 1st half of 1941 will mean historically QUOTE].


Tomo, not to take your post out of context but please bear in mind in the first half of 1941 Roosevelt was having difficulty getting the USA engaged in another European war, Germany had a non aggression pact with Russia, London was still enduring the Blitz and Pearl harbour hadn't yet happened. With Pearl Harbour and the declarations of war between the Axis and Allies discussion of strategic bombing went from theoretical to logistical almost overnight, but that is December 1941. Only a year before the USA was looking at the possibility of the UK falling to Germany and launching bombing raids across the Atlantic. The term long range escort is a convenient construct for what was actually possible, if the British Isles were a hundred miles from France not twenty one then the whole thing would have been impossible


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## pbehn (Nov 15, 2017)

tomo pauk said:


> As before - P-51 with Merlin from 1939 would've been a great fighter. See the P-51 and P-51A - 390-410+ mph on 1150-1125 HP. linky


I am not talking about just a fighter but one that hauls full fuel tanks additional rear tank and external tanks up to 25,000 ft.


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## InlineRanger (Nov 15, 2017)

wuzak said:


> Brute force.
> 
> Voodoo holds the record now, with maybe 1000hp less.



Brute force ignores exponential drag rise. You can't get 500mph putting 4500hp on a Cessna... but yes, brute force. 

Is Voodoo's record unofficial? What mph? I thought Rare Bear still holds the FAI piston speed record?



drgondog said:


> *Your equation is for Force, not velocity.*



Ah, I agree. Power Available - Power Required is the relevant metric.
*



That said, deriving actual Thrust Hp is very complicated, particularly when Ram air and exhaust Thrust for the engine is required to solve.

Click to expand...

*Good points, especially about the exhaust thrust/carb momentum changes.

*



Total Drag is reasonably straightforward for level flight in incompressible flow range <0.3M. As flight speeds approach Mcr the drag rise factor is a Major delta.

Click to expand...

*
Other than the propeller tips, the critical mach of WWII airfoils seems to be ~.72 to .74 mach, with drag divergence occurring a few tenths of a mach later. So we're talking ~530-550mph at Reno race density altitudes. I can see drag divergence happening at lower speeds during maneuver/climb, but does incompressible flow have any other relevant effects I'm not thinking of during maximum speed flight?

*



With these data in hand the next step is to calculate prop efficiency - normally taken from Manufacturer's data

Click to expand...

*
Wouldn't it be ideal to analyze the propeller as the wing it is rather than rely on a third party? Most commercial/old military propellers seem inefficient with wide tips/non elliptic loading.



> *To the extent that Total Drag of the studied airframe can be reduced by any/all of your proposed changes will alter Wetted Surface Area, the Wetted Drag Coefficient will also change but;
> 1.) increasing chord without changing wing area will move the needle on RN but not change Wetted Area or Wetted Drag Coefficient unless the Wing change to alter chord also changes the CDp1 of the wing. This is true for P-51H wing in contrast to P-51/A/B/C/D/K*



Increasing the wing chord increases reynolds number, which decreases the airfoil's parasitic drag coefficient, right? I should have said a low aspect ratio has a lower parasitic drag coefficient than high aspect ratio due to reynolds effects.



> 2.) All of your cited factors are functions of Parasite Drag (Form drag, interference drag, friction drag, etc) - independent of Wetted area. If you maintain Wetted Area but say, change the Parasite Drag CDp1 by making an airfoil change that achieves lower Drag as function of CL, then Wetted Area is same but Total Drag is reduced so both Total Drag and Wetted Drag reduce. If you change aspect Ratio while maintaining Oswald Efficiency but make no change to Wing Area - you may or may not change parasite drag but will reduce Induced drag - so possible change Wetted Area Drag to same extent Total Drag is altered.



This is just semantics, though isn't it? The parasite drag coefficient is in reference to some area, usually the wing. My understanding is that it can also be expressed in terms of wetted area, which is more difficult to calculate but more relevant.



> All this is memory driven and of all the things I miss, I miss my mind the most.



Thanks for making me think.


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## drgondog (Nov 16, 2017)

Is Voodoo's record unofficial? What mph? I thought Rare Bear still holds the FAI piston speed record?
*Simple answer Yes, official, but for the FAI piston speed record, Voodoo had to average 1% over Rare Bear for the 'book' The last run was a slow 510 (IIRC). The first was 550 IIRC the 6 run average was 531+ to Rare Bear 528. *

Other than the propeller tips, the critical mach of WWII airfoils seems to be ~.72 to .74 mach, with drag divergence occurring a few tenths of a mach later. So we're talking ~530-550mph at Reno race density altitudes. I can see drag divergence happening at lower speeds during maneuver/climb, but does incompressible flow have any other relevant effects I'm not thinking of during maximum speed flight?

*If we take Mcr as that region in which Cd (total) increases by 0.002 above low speed CD, but Drag Divergence dCD/dM= 0.10, then most WWII airfoils stepped into Mcr near .6-.62, with full blown Drag Divergence at ~ .65 for similar T/C of 14-16%. It is only in this discussion that Incompressible flow has much meaning for practical aero. At Reno speeds all of the 500 mph racers are in full blown Drag Divergence well before 500mph - the Mustang wing was the lucky accidence of max T/C at 45% which delayed the drag rise region due to the reduced velocity gradient from nose to Max T/C (when compared to conventional 23-25% max T/C) and 'disturbeth not' the CMac compared to the others - so no violent Mach Tuck when CP moved aft with shock wave.*

*
*
Wouldn't it be ideal to analyze the propeller as the wing it is rather than rely on a third party? Most commercial/old military propellers seem inefficient with wide tips/non elliptic loading.

*I would think not - For the same reason I would be inclined to rely on NAA for Mustang Aero analysis, I would as an NAA aero rely on HamStd for their prop analysis, unless I wished to set up my design team with prop specialists and subcontract development and production? The Military props are migrating more and more to swept paddle blade with pointed tips to address the balance between delaying transonic drag divergence while stlll generating the desired performance - but take this comment with appropriate salt dose. I was never a 'prop' guy.*

Increasing the wing chord increases reynolds number, which decreases the airfoil's parasitic drag coefficient, right? I should have said a low aspect ratio has a lower parasitic drag coefficient than high aspect ratio due to reynolds effects.
*Yes to increasing Reynold's number for same velocity and density altitude. The P-51H wing compared to P-51A/B/C/D/K and earlier Mustangs is an example of slightly larger chord. As to increasing Parasite Drag? If the Wing Are is maintained by shortening span proportionately, with the same airfoil, the only Drag difference should be Induced drag due to slightly smaller AR and perhaps tip effects due to change in Tip/Root Chord ratio. The friction drag should be same, form drag would be examined in wind tunnel. I can confirm that P-51H Parasite Drag was slightly lower at Same RN but it also had a newer NACA 66,2-18155 airfoil so the extrapolation of cause and effect is not clear. It also a straight LE wing with constant washout, whereas the Early Mustangs through P-51B/C had a cranked LE with one washout to WS 61, the D/K had a greater crank and different washout from C/L to WS 61. 

Now, all that said, the effect of RN is not an effect - it is a non scalar value used to compare CDs for comparable RN as well as to plot CD as function of Velocity. So, all I can tell you is that RN was only important to me to extrapolate more information from wind tunnel results for drag on a scale model.*

This is just semantics, though isn't it? The parasite drag coefficient is in reference to some area, usually the wing. My understanding is that it can also be expressed in terms of wetted area, which is more difficult to calculate but more relevant.

*The Cd, Cl and CMac are all a function of Wing Area. Wetted Drag coefficient is a function of total area. The latter is useful when comparing against another airframe, for Kentucky windage of design efficiency. An example of that would be Mustang vs Bf 109. The P-51 was huge compared to 109 but much lower drag, including wetted area drag which pointed out why the meticulous high quality manufacturing process and airframe design - smooth surface, flush rivets, tight gaps between sheet metal, no protubrances, second order curves, windshield/canopy design, etc - of the Mustang was so novel at the time. NAA does not get near as much credit as they deserve for the high quality/high quantity production techniques. *

Thanks for making me think. 

*Unfortunately you made me think, also - hate when that happens.*

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## wuzak (Nov 16, 2017)

drgondog said:


> Is Voodoo's record unofficial? What mph? I thought Rare Bear still holds the FAI piston speed record?
> *Simple answer Yes, official, but for the FAI piston speed record, Voodoo had to average 1% over Rare Bear for the 'book' The last run was a slow 510 (IIRC). The first was 550 IIRC the 6 run average was 531+ to Rare Bear 528.*



The numbers show they didn't have enough to officially beat Rare Bear's record, but I understand the categories were redone, so Voodoo hold the record for its category now.


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## tomo pauk (Nov 16, 2017)

pbehn said:


> Tomo, not to take your post out of context but please bear in mind in the first half of 1941 Roosevelt was having difficulty getting the USA engaged in another European war, Germany had a non aggression pact with Russia, London was still enduring the Blitz and Pearl harbour hadn't yet happened. With Pearl Harbour and the declarations of war between the Axis and Allies discussion of strategic bombing went from theoretical to logistical almost overnight, but that is December 1941. Only a year before the USA was looking at the possibility of the UK falling to Germany and launching bombing raids across the Atlantic. The term long range escort is a convenient construct for what was actually possible, if the British Isles were a hundred miles from France not twenty one then the whole thing would have been impossible



No quarrels with this quoted post. IMO it points into political realities, not technical ones.



pbehn said:


> I am not talking about just a fighter but one that hauls full fuel tanks additional rear tank and external tanks up to 25,000 ft.



I was talking about both existing and feasible long range fighters - with plenty of both internal and external fuel.


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## Shortround6 (Nov 16, 2017)

We have pointed out the large increase in power the Merlin got for a small increase in weight due to better supercharges and fuel that helped make the "escort fighter" possible.

Part of our trouble is not having a good definition of "escort fighter" for the beginning of the war. We don't need P-51B performance in 1940/41 because A, the enemy fighters aren't that good, and B, the bombers aren't B-17s, they can't fly as high or as far carrying 4-5000lbs of bombs. 

The US is sort of a special case as they had some of the longest distances to deal with and the most practice in designing long range aircraft in the 30s. Just getting around the US was major problem. In 1939 the US only had 17 air bases and 4 air depots in the entire country. This is one reason for the overload tank in the P-36, just getting from base to base required longer ranges than the European air forces needed. 
Then look at what the US was buying for bombers _and what they were planning. _
Even a B-18A Bolo was supposed to fly 1150 miles with 2496lbs of bombs, granted at around 167mph. and it wasn't what the Army wanted, it was what they could afford. 
The Army also _wanted _7000ft paved runways for it's bombers. It couldn't afford many of them either in 1938-40. 
The B-15 and B-19 showed where the Army _wanted _to go and no single engine fighter of the time could hope to get anywhere near their range. Granted this is an extreme. 

For the British things are both a bit simpler and bit more complicated. Their bombing force, as it existed in 1939-41 was somewhat shorter ranged. Leaving the Whitley out of it as it was almost always considered a night bomber, you have the Wellington and Hampden as the main bombers with the Blenheim and Battle hanging around the edges. Since even the last two could operate (in theory) over a 400 mile radius (1000 mile range - 1 hour at cruising speed reserve/allowance and then divide by two for radius) you are trying to design a 400 mile radius fighter in 1938-40. that or tell the air staff and the politicians doling out the money that "Yes we have bombers that can strike 400-500 miles from base but our escort fighters can only cover them to a 300 mile radius." Hardly a good answer. 
British have tiny airfields and are several years behind in adopting constant speed propellers so while in theory it may be possible to design an escort fighter with good performance from a technical point of view, in practice it was much harder. 

Please remember up until the shooting started there were all manner of restrictions on what were allowable landing speeds and even how many pounds per square in the tires were allowed to put on the turf/sod airfields. The Whirlwind had to get special dispensation for being 10% over the limit. 
Please note that even a P-39 had a higher approach and landing speed than the Whirlwind which was much criticized for it's landing speed and the feared restriction on number of fields it could operate from. 
any pre war work on a British escort fighter would have to take all this into account in initial design stages even if a lot got thrown out by the time it entered service.


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## Zipper730 (Nov 16, 2017)

pbehn said:


> Frequently lost in this discussion is that until 1943 many of those involved in the US bombing offensive were adamant that a long range escort fighter was either not needed or was impossible to make.


The idea of escort fighters was actually around for some time.

The problem that seems to have appeared with escort fighters had to do with the following

They didn't think they were necessary: They saw them as inherently useful, but not a requirement for a successful bombing mission by in large (Billy Mitchell felt that they'd be essential, unless they could subdue the enemy Air Force on the ground).
They were adamantly against external tanks: If they could not be jettisoned, they would be a source of drag after they served their purpose; if they were jettisonable, they would be punched off at the first sight of enemy fighters, and largely be a waste of perfectly good gasoline. So they wanted the plane to fly the range on internal fuel only, which required either a heavier plane, or a higher fuel-fraction.
Advice of fighter pilots were not listened to: The bomber-guys had an agenda, and that often ran contrary to the fighter-pilots; they often were butting heads against each other, rather than working together for a common good. The fighter-guys had proposed both methods for shooting down bombers, as well as providing escorts, but they went unheeded.

They wanted fighters with rear guns: Sounds insane, but the idea was kind of like using destroyers to protect a larger ship. It's not necessary because a bomber has defensive armament because they're not maneuverable enough to just fight it out on their own (and are more likely to be attacked from every single angle at once because of the grief they can cause). From a performance standpoint, it tends to either cut into fuel, or require a larger and heavier aircraft; from the issue of practical: Several fighters were built with such a configuration (the gunners were useless). If they listened to the fighter-tactic guys, they might very well have learned effective ways to cover bomber formations.
There was a predilection with turbochargers: High altitude performance was favored for bombers, so the fighters had to have the ability too. The problem was that they seemed to focus very little on twin-stage superchargers (which provided less bulk), nor did they pay much attention to the idea of liquid-to-air intercoolers (they are more compact).
They were largely unwilling to use a twin-engined fighter: It would overcome the issue with engine power...
They were more expensive: They had to do all the things that fighters could do, except they also needed long range, and high-altitude capability (not to mention a rear-gunner). That costs more to develop, and to procure, and they were spending shitloads on bombers, so it had to wait.
Some might have viewed such a design as impossible: The combination of small, fast, and agile, with long-range (and rear-gunners), and altitude would have been seen as quite a challenge.



tomo pauk said:


> Before the German declaration of war, USA probably can be excused for not embracing the escort fighter - after all they were trying to came out with inter-continetal bombers. After that, there were fast ways to create long range escort force for 1943, however the doctrine was again much slower than technology.


Often that's a problem -- the technology comes out faster than anybody can figure out what to do with it. This is actually more of a problem today than then...


> Japanese were doing LR escort before the advent of Zero or Oscar.


Really?



InlineRanger said:


> So why is Rare Bear, a stubby radial engine F8F Bearcat the fastest piston engine aircraft in the world?
> 
> While the original Bearcat has a higher zero lift drag coefficient than a v12 fighter, it has a comparatively smaller wetted area. Radial engines package a lot of displacement in very little depth


You mean a lot of engine power in a small space?


> they have less area forward of the quarter chord and can utilize shorter fuselage lengths for their frontal area.


But doesn't fineness area affect speed?


> These short, squat fuselages have lower surface to volume ratios than long, sleek aircraft. So while their frontal area is larger and drag coefficient higher, their total drag area (_Cd X Wetted Area_) is still competitively low.


Somehow I'm drawing a blank...


> Rare Bear mainly improved the design by increasing thrust. Oxygen mass flow rate was increase by using a higher displacement engine (_R-3350 in lieu of R-2800_), increasing engine speed (_>3000rpm_), increasing boost (_many Reno racers reduce static compression to run higher boost_) and using nitrous oxide.


Static compression? Do you mean like compression ratio?


> Google seems to say power output is ~4500+hp. The propeller disc loading was decreased by using a large diameter propeller (_3-point landings only_) with a wider chord.


Tough to land



wuzak said:


> Voodoo holds the record now, with maybe 1000hp less.


What's Voodoo?


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## drgondog (Nov 16, 2017)

"Zipper730, post: 1365230, member: 67843"]The idea of escort fighters was actually around for some time.

The problem that seems to have appeared with escort fighters had to do with the following

They didn't think they were necessary: They saw them as inherently useful, but not a requirement for a successful bombing mission by in large (Billy Mitchell felt that they'd be essential, unless they could subdue the enemy Air Force on the ground).
They were adamantly against external tanks: If they could not be jettisoned, they would be a source of drag after they served their purpose; if they were jettisonable, they would be punched off at the first sight of enemy fighters, and largely be a waste of perfectly good gasoline. So they wanted the plane to fly the range on internal fuel only, which required either a heavier plane, or a higher fuel-fraction.
Advice of fighter pilots were not listened to: The bomber-guys had an agenda, and that often ran contrary to the fighter-pilots; they often were butting heads against each other, rather than working together for a common good. The fighter-guys had proposed both methods for shooting down bombers, as well as providing escorts, but they went unheeded.

They wanted fighters with rear guns: Sounds insane, but the idea was kind of like using destroyers to protect a larger ship. It's not necessary because a bomber has defensive armament because they're not maneuverable enough to just fight it out on their own (and are more likely to be attacked from every single angle at once because of the grief they can cause). From a performance standpoint, it tends to either cut into fuel, or require a larger and heavier aircraft; from the issue of practical: Several fighters were built with such a configuration (the gunners were useless). If they listened to the fighter-tactic guys, they might very well have learned effective ways to cover bomber formations.
There was a predilection with turbochargers: High altitude performance was favored for bombers, so the fighters had to have the ability too. The problem was that they seemed to focus very little on twin-stage superchargers (which provided less bulk), nor did they pay much attention to the idea of liquid-to-air intercoolers (they are more compact).
They were largely unwilling to use a twin-engined fighter: It would overcome the issue with engine power...
They were more expensive: They had to do all the things that fighters could do, except they also needed long range, and high-altitude capability (not to mention a rear-gunner). That costs more to develop, and to procure, and they were spending shitloads on bombers, so it had to wait.
Some might have viewed such a design as impossible: The combination of small, fast, and agile, with long-range (and rear-gunners), and altitude would have been seen as quite a challenge.
*Too simplistic. The 'future' AAF leaders were struggling to raise the role of armed aircraft from Pursuit to Attack role, and secure a place at the Joint Chief's table as an equal. Billy Mitchell (and Doughet) provided to inspiration in the mid-30's to position Bombers as Coastal Defense, which aroused animosity from the Naval mafia as well as traditional Army senior staff.*

*The B-17 changed everything with the combination of high altitude performance, payload and range - then shocked USN with the successful intercept of the Rex (Lemay navigator) 600 miles offshore. At that time, and through 1939-1940, there were really no interceptors save the P-38 capable of catching and attacking a B-17C at 30,000 feet.

Pursuit Aviation advocates who were perceived as 'nay sayers' to the Bomber Will Always Get Through, such as Chennault were moved aside or retired early - while Eaker, Spaatz, Arnold closed ranks and controlled allocation of aircraft technology funds.*

*Limited funds and evolving mission, combined with only one choice of in-line engine w/single stage supercharger and gas sucking,air cooled piston R2800 about to come on line. The specs generated after never really cited range as one of the most important attributes for successful bid, but speed was dominant. Bomber interception and attack aircraft were the focus.

Short sightedness regarding future combat ops let unprotected useful fuel capacity be designed into the P-38, P-39, & P-40. The RAF Purchasing commission intercepted the P-51 proposal and required 180 gallons in Protected fuel cells. The P-39 scaled from 200 to 120 gal, the P-38 from 400 to 300 gal, P-40 from 180 to 148/157 gal. 

At no time during the spec process developed and released by Material Command, was a range capability to even closely approximate to the B-17.*

*Both Eaker and Spaatz were in UK during BoB and Blitz at different times, heard the skepticism from RAF regarding AAF strategic daylight mission planning - and Nobody on either side of the Atlantic foresaw the single or twin engine fighter with ability to escort our bombers at the Target. The P-61 proposal and contract was the first attempt at looking at long range fighter role with range potential equal or greater than P-38 with 646 gal internal fuel capacity - w/projected range 20% greater than P-47 and P-38, 60% greater than P-39 and P-40 - and the same as P-51 (Allison).

Eaker actually flew (and liked) the P-51 very much in 1942, but like all the rest of the AAF hierarchy, dismissed any thought of Escort fighter as the only engine on the horizon was the Allison and Merlin XX with poor performance at B-17 altitudes.*

*The drive for external tanks was officially noted as an outcome of Arnold's fighter Conference in Jan-Feb, 1942. Ferry tanks, unprotected, were verboten by AAF MC as being 'too hazardous'. Kelsey/Lockheed were first to take the initiative and mounted 160 ferry tank on P-38F/G to ferry to UK for 8th AF FC start up. But, neither that tank nor the 200 gal ferry tank for P-47 represented a rational approach to combat ops until summer/fall 1943 when Cass Hough at 8th Services Command and Pappy Gun 5th AF, modified P-47 and P-38 to bleed exhaust air to pressurize external fuel tanks - just as 8th AF experienced losses of Blitz Week, Tidal Wave, Schweinfurt-Regensburg.

The most important barriers to a successful Escort fighter was that AAF did not have either a.) a production engine or one with promise, in 1941, that had 1200+ HP at 25,000 feet, unless integrated with a turbo, and b.) internal fuel capacity mated to the specific fuel consumption of either the P&W R2800 or Allison V-1710, with Turbo, to achieve a combat radius of the B-17 at the same altitudes.

The additional complication was 'not invented here' syndrome that afflicted so many key AAF leaders that prevented embracing the full range of licensing for British in-line engines, as well as corporate officers at GM (owned Allison and NAA) that prevented NAA from dumping Allison altogether in late 1941 due to major issues between NAA/Allison. So, rather than have a Brit/US Commission evaluating 'Best of Breed' technical developments, successful outcomes like Merlin Mustang arose from 'middle manager' advocates like Hitchcock - with connections to Winant and Roosevelt - to go around the bureaucracy.*

*Thank God for Barney Giles who effectively led AAF when Arnold was recovering from Heart attack on US side, and Tommy Hitchcock/Winant on UK side.*

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## tomo pauk (Nov 16, 2017)

drgondog said:


> ...
> *The additional complication was 'not invented here' syndrome that afflicted so many key AAF leaders that prevented embracing the full range of licensing for British in-line engines, as well as corporate officers at GM (owned Allison and NAA) that prevented NAA from dumping Allison altogether in late 1941 due to major issues between NAA/Allison.*
> ...



Bill, care to ellaborate about major issues between NAA and Allison (IIRC GM owned 30% of NAA; not whole company)?


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## wuzak (Nov 16, 2017)

tomo pauk said:


> Bill, care to ellaborate about major issues between NAA and Allison (IIRC GM owned 30% of NAA; not whole company)?



Maybe it started when NAA rolled out the NA-73X without an engine because it hadn't yet arrived?

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## drgondog (Nov 16, 2017)

tomo pauk said:


> Bill, care to ellaborate about major issues between NAA and Allison (IIRC GM owned 30% of NAA; not whole company)?


Allison was doing a very poor job in two specific areas - 1.) delivery schedules, slowing down completion of Mustang I's to RAF, 2.) making significant changes to the delivered engines without communicating the changes to NAA, placing NAA in awkward position of having to modify airframe to properly install the engines.

NAA went so far as to get Mossie engine mount drawings and contact Packard to get necessary information in had for Kindleberger to meet with GM Board - allegedly it was quite a Board Meeting with GM, Allison and NAA CEO in same room. NAA was turned down, but apparently the meeting resulted in much better communication between Allison/NAA. That feud continued for years and IMO affected the fix to the Two Stage/Speed supercharged -119 replacement for Merlin after the XP-82/82B which never solved detonation issues at high MP

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## pbehn (Nov 16, 2017)

An objection to external tanks only seems a bit strange with hind sight. It is a historical fact that the LW dropped back in the face of large daylight raids waiting for the escorts to turn back. However whoever was in charge of strategy must consider that their planes entering enemy air space would be met by fighters, if the LW could have met the escorts and made them drop their tanks, things could or would have been much different.


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## tomo pauk (Nov 16, 2017)

drgondog said:


> ..
> *
> The most important barriers to a successful Escort fighter was that AAF did not have either a.) a production engine or one with promise, in 1941, that had 1200+ HP at 25,000 feet, unless integrated with a turbo, and b.) internal fuel capacity mated to the specific fuel consumption of either the P&W R2800 or Allison V-1710, with Turbo, to achieve a combat radius of the B-17 at the same altitudes.*
> ...



Thanks for the feedback at post #105.

A few things about the quoted part. Nobody in the world in 1941 have had an non-turbo engine in production, let alone in service, that was making 1200+ HP at 25000 ft. Only UK and USA were making such engines in 1942, others did not.
However, there was prototype 2-stage R-2800 that fits the bill already in 1940. Unfortunately, USAAC was blind for that engine as a powerplant for 1-engined fighters.
There were enough of companies in the USA that could've designed a long range fighter around one turboed V-1710, or around one 2-stage supercharged R-2800 for the needs of the USAAAC/AAF before 1941. Yet they did not, and I'd bet that USAAC not wanting/specifying such a thing was much more of a hurdle than companies (in)ability.

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## Zipper730 (Nov 16, 2017)

drgondog said:


> "Zipper730, post: 1365230, member: 67843"]Too simplistic.


I was trying to bottom-line it...


> The 'future' AAF leaders were struggling to raise the role of armed aircraft from Pursuit to Attack role, and secure a place at the Joint Chief's table as an equal.


I think you mean develop a strategic bombing capability, instead of the current pursuit & attack category, as part of a goal of an independent Air-Force like the RAF?


> Billy Mitchell (and Doughet) provided to inspiration in the mid-30's to position Bombers as Coastal Defense, which aroused animosity from the Naval mafia as well as traditional Army senior staff.


Mitchell wanted to use bombers to hammer airfields, harbors, and cities predominantly: He focused on bombing ships because it seemed more acceptable to the public than what he really wanted (Many people subscribe to the notion that when the cause is just, the methods don't matter); the idea of using them for maritime patrol was simply an excuse to build a fleet of heavy bombers, though I think they started to believe their own narrative (the pit-fall of creating an echo-chamber where no opposing view is allowed), and the unerring accuracy of the Norden (which erred many times).


> The B-17 changed everything with the combination of high altitude performance, payload and range


Actually, it started with the Martin B-10, which was able to outrun the fighters that were in service at the time (mostly due to having a monoplane, and retractible gear, though eventually the aircraft would have an enclosed canopy, turrets, NACA cowlings, and variable pitch props, etc.), a fighter with similar features would probably be able to outrun it.
As for the B-17, the prototype (Model 299) didn't actually have a turbocharger (that was added later), though it produced a critical altitude of around 25000 feet, and got the top speed over 300 miles an hour. It wasn't uncommon to see cruising altitudes around 32000 feet in some variants, though over Europe, altitudes were often around 22000 to 27000 feet it seemed.


> At that time, and through 1939-1940, there were really no interceptors save the P-38 capable of catching and attacking a B-17C at 30,000 feet.


That sounds about right.


> Pursuit Aviation advocates who were perceived as 'nay sayers' to the Bomber Will Always Get Through, such as Chennault were moved aside or retired early


Which basically is what I said about the bomber guys not listening to them: This wasn't something unique to the US, the RAF's Bomber Barons largely thought the same way until they suffered high losses over Germany (ironically at least some of it had to do with the altitude they were attacking at, owing to the change in target systems).

Regardless, it was clearly true: Provided a fighter had sufficient speed and high altitude capability, the bombers would be in major trouble. In the US, we did favor high altitude capability, but found it a crap-shoot in both fighters and bombers

There was a B-10 fitted with a turbo: Increased speed to 236 mph. It was unreliable and dropped.
The P-30 was based on the P-24 with aerodynamic refinement and a turbo: It worked after some work
The P-37 was able to achieve 340 mph at 25000 feet but had an excessively long nose
The B-17 worked
The P-38 worked
The P-39 didn't seem to have enough internal volume to pack in everything it was supposed to carry, and it's aerodynamics (propulsion wise) seemed to be a bit shoddy
The B-24 worked



> Eaker, Spaatz, Arnold closed ranks and controlled allocation of aircraft technology funds.


Which basically meant that bombers got priority...


> Limited funds and evolving mission, combined with only one choice of in-line engine w/single stage supercharger and gas sucking,air cooled piston R2800 about to come on line.


The inline-engine issue had to do with the following

Too Many Designs: They had numerous engine designs being drawn up, but basically had a limited demand for them after the great-depression, and the development of the NACA cowling. With limited resources, it is best to focus on the engines with the best potential, and pour the bulk of the resources into those (this problem is not entirely dissimilar from the Luftwaffe during WWII: They produced loads of designs, some of them brilliant, but few in numbers large enough to make a difference).

Continental Engines: They were owned by the US Army, which basically drew up the designs for a hyper-engine that they wanted (O-1430, later I-1430); then told them to build it. It doesn't appear that they really listened much to the engine designers insights and knowledge, and fixated on the opposed-cylinder layout long after common sense showed that it was not needed.
Conflict of Interest: The Lycoming O-1230 seemed actually to be a better design, but with the Army owning Continental, who's going to be picked?
As for the radials, there were was at least the R-2600 available since the mid/late 1930's.


> The drive for external tanks was officially noted as an outcome of Arnold's fighter Conference in Jan-Feb, 1942. Ferry tanks, unprotected, were verboten by AAF MC as being 'too hazardous'.


Yet the RAF adopted drop-tanks of various sorts


> Kelsey/Lockheed were first to take the initiative and mounted 160 ferry tank on P-38F/G to ferry to UK for 8th AF FC start up. But, neither that tank nor the 200 gal ferry tank for P-47 represented a rational approach to combat ops until summer/fall 1943 when Cass Hough at 8th Services Command and Pappy Gun 5th AF, modified P-47 and P-38 to bleed exhaust air to pressurize external fuel tanks - just as 8th AF experienced losses of Blitz Week, Tidal Wave, Schweinfurt-Regensburg.


Wait, the P-38's weren't pressurized at first? I know the P-47's weren't...


> The most important barriers to a successful Escort fighter was that AAF did not have either a.) a production engine or one with promise, in 1941, that had 1200+ HP at 25,000 feet, unless integrated with a turbo, and b.) internal fuel capacity mated to the specific fuel consumption of either the P&W R2800 or Allison V-1710, with Turbo, to achieve a combat radius of the B-17 at the same altitudes.


Yup...


> The additional complication was 'not invented here' syndrome that afflicted so many key AAF leaders that prevented embracing the full range of licensing for British in-line engines, as well as corporate officers at GM (owned Allison and NAA) that prevented NAA from dumping Allison altogether in late 1941 due to major issues between NAA/Allison.


Firstly what engines would have been practical to license other than the Merlin, and what problems existed between Allison and NAA?[/quote][/quote]


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## mad_max (Nov 16, 2017)

There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.

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## pbehn (Nov 16, 2017)

mad_max said:


> There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.


That is a question of resources, you have to take account of the worst case scenario. To meet US escorts in equal numbers all around the airspace Germany had to defend results in fantasy numbers, but there are scenarios where the LW could have "got lucky" and inflicted devastating losses.


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## Shortround6 (Nov 16, 2017)

You also had the Americans using relays of fighter, one (or more) groups escorted the bombers in to a certain point, flying at over 300mph and doing "S" turns above the bombers in order to not get ahead of them. At some point a fresh group of fighters would show up having flown directly form their bases and thus having much more fuel still in the tanks. Perhaps this group is present over the target,perhaps it is relieved by a third group of fighters right before the target?
There will be other groups of fighters waiting to meet the bombers on their way out and escort them into save airspace. Forcing the 1st or 2nd group to drop tanks does NOT leave the bombers exposed for the majority of the mission.

External tanks had been used during the early 30s, but I have never read any reports on how they worked, either good or bad. Perhaps there were accidents that prejudiced the officers against them?

AS far as long range fighters vs bombers goes, A Vickers Wellington IC with Pegasus engines could go 28,500lbs at take-off which is a wing loading of 34lbs per sq ft at a time when the Spitfire was around 28.8lbs per sq ft (late MK V), a B-17 at 54,000lbs around 38lbs per sq ft.

Nobody expected bombers to fly like fighters (mostly) and they loaded them accordingly. lots of fuel to go with the bombs.
A late B-17 could hold 2780 gallons in the wings or around 10 times what a Mustang could hold including rear tank. An early B-17 could hold around 1700 gallons in the inner wing tanks, or about 10 times what a P-36 would hold including the Ferry tank. About 425 gallons per engine. Granted the B-17 has more drag but you are going to have cram a LOT of fuel into a P-36 to come close to the range of a B-17.
Heck , stick a 100 gallon drop tank under it and see how far you get? A B-17F running light (under 50,000lbs) could fly at about 200mph at around 10,000ft getting about 1 mile per gallon or about 1600miles on the inner wing tanks after using up 132 gallons in warm up, taxi and take-off The older ones might do a bit better, A P-36 was good for about 6.5 miles per gallon at the same speed/altitude under best conditions, soooo.... you need 246 gallons *after *warming up, taxing, take-off and climb to several thousand feet, I would add that even 15 minutes at 88% power will suck up 45 minutes worth of this low speed cruise or 150 miles of range.

SO you either limit the range of your bombers to that of a compromise fighter or you admit that the single engine escort fighter isn't viable until the Merlin 61 comes along. (or perhaps cramming a P-47 full of fuel).

The Navy 2 stage R-2800 isn't the answer for turbo charged B-17s. the power was only rated at about 1460hp at 23,500ft (including RAM) in the fall of 1941. Given the weight and drag (and thirst) of the R-2800 this isn't good enough to plan an escort fighter around. Production engines got a bit better and the production F4U-1 used a "B" series engine that gave 1650hp at 23,000ft with ram. Again, given the weight/drag and thirst of the R-2800 this isn't good enough.

I have said this before, a number of air staffs believed the only way to get performance and range was by using twin engined fighters.
Japanese Army built Ki-45s in addition to the Ki-43. Germans had the Bf 110.
The thinking behind the Ki-45 started in 1936, the requirement was issued to the manufacturers in March of 1937, many of these programs took years.

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## Zipper730 (Nov 16, 2017)

mad_max said:


> There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.


That has to do with logistics: Because they never planned to use escorts with drop-tanks, they never procured enough.

The 5th Air Force interestingly was manufacturing their own: And people say government can't do anything right...



Shortround6 said:


> External tanks had been used during the early 30s, but I have never read any reports on how they worked, either good or bad. Perhaps there were accidents that prejudiced the officers against them?


No idea...


> I have said this before, a number of air staffs believed the only way to get performance and range was by using twin engined fighters.
> Japanese Army built Ki-45s in addition to the Ki-43. Germans had the Bf 110.


It's a simpler way to do it. We also developed the YFM-1 Airacuda (It was predominantly a long range patrol interceptor, that could also double as a bomber escort) which despite its interesting looks was a turd with wings.


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## drgondog (Nov 17, 2017)

mad_max said:


> There were days when they did send out a small unit to do just that pbehn just after the start of using drop tanks. What ended up happening is that within little time there were so many fighters inbound that they couldn't make enough of them drop tanks anymore, plus needing them to help the bomber hunters get to their quarry.



You are dead right. The strategy was to force en masse drop with a bounce, but the leadership of 8th FC were already responding appropriately - namely sending a flight instead of a squadron when a few attacking fighters were encountered.


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## tomo pauk (Nov 17, 2017)

Shortround6 said:


> ...
> SO you either limit the range of your bombers to that of a compromise fighter or you admit that the single engine escort fighter isn't viable until the Merlin 61 comes along. (or perhaps cramming a P-47 full of fuel).
> 
> The Navy 2 stage R-2800 isn't the answer for turbo charged B-17s. the power was only rated at about 1460hp at 23,500ft (including RAM) in the fall of 1941. Given the weight and drag (and thirst) of the R-2800 this isn't good enough to plan an escort fighter around. Production engines got a bit better and the production F4U-1 used a "B" series engine that gave 1650hp at 23,000ft with ram. Again, given the weight/drag and thirst of the R-2800 this isn't good enough.



In 1941, the BMW 801C was making ~1100 HP (~1120 PS) there, weighting 2325 lbs dry (+ armored oil coooler + oil). 
The Navy's R-2800 was making the power you stated in the fall of 1940, not 1941. Weight 2495 lbs dry. Excellent engine to plan an escort fighter for tasks well above 20000 ft, it pushed big, heavy and thick-winged XF4U-1 at 380 mph at 23500 ft in 1940. 
As for the Army's escort fighter around it - 350 gals of fuel + drop tanks, 300 sq ft wing of perhaps NACA 23015 profile at root. Engine is thirsty, but so are two V-1710s on a single airframe.

The P-47 with 350 gal of fuel also works, so does a fighter with 220-230 gals of fuel based around one turboed V-1710 from 1941 on.


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## grampi (Nov 21, 2017)

Zipper730 said:


> What's Voodoo?



A highly modified P-51...


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## Shortround6 (Nov 21, 2017)

tomo pauk said:


> The P-47 with 350 gal of fuel also works, so does a fighter with 220-230 gals of fuel based around one turboed V-1710 from 1941 on.


for the last part





A Mustang it ain't 
one source says 200 gallons internal.

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## Zipper730 (Nov 23, 2017)

Shortround6 said:


> Nobody expected bombers to fly like fighters (mostly) and they loaded them accordingly. lots of fuel to go with the bombs.


There's probably more to it than that.

When it comes to voluminousness: It favors the large. If you double in length, width and height (2 x 2 x 2), you get an increase of 8, so basically, many large aircraft could carry substantial amounts of fuel. The only exception came with structural members that had to hold together the bigger machine.

When it comes to strength to weight: It favors the small. This is offset through creative design features, and lower g-load requirements (bombers); the same applies to power to weight ratio, which is also why you'll see a high power to weight ratio on a fighter, a smaller amount on a bomber.


> A late B-17 could hold 2780 gallons in the wings or around 10 times what a Mustang could hold including rear tank.


True, but you're not factoring in fuel fraction. Fuel fraction is more important for performance than actual weight.


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## pbehn (Nov 23, 2017)

Zipper730 said:


> There's probably more to it than that.
> 
> When it comes to voluminousness: It favors the large. If you double in length, width and height (2 x 2 x 2), you get an increase of 8, so basically, many large aircraft could carry substantial amounts of fuel. The only exception came with structural members that had to hold together the bigger machine.
> 
> ...


Zipper, I love some of your posts, have you considered patenting the flying cube? I can see some issues in drag and lift but in terms of bomb load and fuel capacity it is a winner.

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## Shortround6 (Nov 24, 2017)

Zipper730 said:


> There's probably more to it than that.
> 
> When it comes to voluminousness: It favors the large. If you double in length, width and height (2 x 2 x 2), you get an increase of 8, so basically, many large aircraft could carry substantial amounts of fuel. The only exception came with structural members that had to hold together the bigger machine.
> 
> ...



I really have no idea what you are talking about here.
I could be mistaken but Fuel fraction has very little to do performance _except _for range. For example take two hypothetical fighters, both 8,000lbs gross and both with 1500hp engines, Plane "A" holds 180 gallons (fuel fraction 13.5%?) and plane "B" holds 150 gallons (fuel fraction 11. 25%?). this tells us very little except that plane "A" _might _be expected to have longer range/endurance than plane "B". Assuming equal payloads (guns/ammo for a fighter) it may tell us that the designer of Plane "A" managed to design a lighter weight structure (or used lighter engine). It sure doesn't tell us anything about speed, climb or turn. Please note that Plane "B" _might _have used 180lbs of weight up in either heavier armament or in better protection on essentially the same weight airframe. but without knowing the payload fuel fraction really doesn't tell us much. 

Please note that every plane built in the 1930s and early 40s had unused volume somewhere in the structure. The engines simply weren't powerful enough to allow all the "space" to be filled up. Unlike modern jets were even the vertical stabilizer is sometimes used for fuel storage the old planes were rather restricted as to where you could put things. 

The B-17 started as the Boeing 299 in 1934 and the first one used P & W Hornet (R-1690) engines rated at 750hp at 7000ft and 850-875hp for take-off. Empty weight was 21,657 pounds max loaded was 38,053 pounds. While they changed the rear fuselage/tail the wing stayed the same shape and area. The last of the B-17Gs weighed 32,720 pounds empty and 72,000 pounds maximum although even 65,000lbs called for restricted take-offs and very restricted maneuvers when flying. Obviously they filled up some of the empty volume over the years but trying to fly 65,000lb bombers with 800 hp engine wasn't going to get very far. See XB-15 or Boeing model *294 *for what it took for a long range bomber with small engines. The Boeing 299/B-17 was Boeing's 2nd shot at a 4 engine bomber. 

I would note that while we are arguing about escort fighters the Boeing 299 prototype flew 2100 miles nonstop on it's Delivery flight from the Boeing factory to Wright Field, granted it was very likely it was aided by a tail wind but NOBODY had single engine fighters that could fly anywhere near 2000 miles no matter what you did to them in the summer of 1935. 

I would note that sometimes size has a strength of it's own. As in a thick wing section is harder to bend than a thin wing section of the size (span and area) due to the upper surface having to be compressed more and the bottom surface having to be stretched more for the same amount of "bend".


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## pbehn (Nov 24, 2017)

S/R I was thinking along the same lines this afternoon, looking at cut away drawings of the P-51 there isn't much unused space. I wonder what the engineers at FAA thought when told "hey that's a great plane, can you put another 300 gallons of fuel and oil in or on it and a couple of extra guns would be nice too"


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## Carboncrank (Nov 25, 2017)

DerAdlerIstGelandet said:


> And we do not allow any modern political discussion of any kind on this forum.
> 
> Go and read the forum rules. This will be the only warning on the topic of politics.
> 
> ...


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## Carboncrank (Nov 25, 2017)

DerAdlerIstGelandet said:


> And we do not allow any modern political discussion of any kind on this forum.
> 
> Go and read the forum rules. This will be the only warning on the topic of politics.
> 
> ...




Sorry it's too late. you were an asshole about it. boot me at will but I won't be talked to like that. if you want be so petty as to boot the son of a hellcat and skyraider pilot, and the nephew of a b-17 bombardier who spent 18 months as a prisoner, and who grew up on airbases and has a life long connection to wwII aircraft over the use of the word "try" feel free, I don't grovel, I don't beg forgiveness. 

I don't do well with assumed authority and I will always speak truth to power, and I don't mean politics in this case, I mean the bullying tone in your reply.

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## Carboncrank (Nov 25, 2017)

Shortround6 said:


> We may have some confusion as to what the "original premise" of this thread is.
> 
> I could be wrong (it's happened plenty of times before), but I took it as a general question as to why some rather large, heavy aircraft were as fast or faster than some smaller, lighter and more streamline appearing aircraft. I believe that question has been answered by the replies concerning power and drag at altitudes.
> 
> ...



or course the premise matters. the original post made no distinction about a normal p47. it should have been pointed out as an extraordinary claim with no extraordinary proof. In what world should anybody begin a discussion of anything on a false premise.


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## Carboncrank (Nov 25, 2017)

Shortround6 said:


> We may have some confusion as to what the "original premise" of this thread is.
> 
> I could be wrong (it's happened plenty of times before), but I took it as a general question as to why some rather large, heavy aircraft were as fast or faster than some smaller, lighter and more streamline appearing aircraft. I believe that question has been answered by the replies concerning power and drag at altitudes.
> 
> ...



I thought this forum was about WWII aircraft as in aircraft used in the war. 


mad_max said:


> Carboncrank
> 
> 
> 
> ...



I don't think I said you said 500mph, it was the original premise. 

But thanks for an excellent thoughtful post.


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## Carboncrank (Nov 25, 2017)

Shortround6 said:


> You want a source, fine. America's Hundred Thousand, page 333, right hand column, 6th entry.
> 
> 
> 
> ...



I'm fortunate that the 91st bomb group kept its dailes and posted them on their website. I details every mission flown. I've found that there is very little of that kind of information available in such detail. I've not only looked for dailes of other bomb groups tried to find what p47 squadron it was that missed the hand off Dec 1st 43 that got my uncle shot down. I cant find anything. 

So when you mention a specific mustang squadron that flew a combat mission dec 1st I thought cool let me check and see what I can find about that squadron, especially since I'd seen no evidence of the merlin mustangs arriving that early. 

One little problem. The 354th has a website and it directly contradicts what you quote from that book that so many people think is the most reliable book on the topic

"The first Merlin-engine Mustangs were delivered to the 354th Fighter Group of the 9th Air Force in Great Britain on December 1, 1943. The P-51B first went into action as a fighter on December 17, 1943". 

354th Fighter Group During WWII


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## Carboncrank (Nov 25, 2017)

pbehn said:


> Well then you should have learned the danger of basing a conclusion on a false premise.
> 
> You claim for the P 51 was this "The mustang was obviously the best fighter of the war in all regards." In this you must be very precise about names. The Mustang was not an escort fighter, it was an Allison engined tactical recon plane, it had very good but limited performance because it could not perform at high altitude. The P 51 B/C and D were what made the legend and some of these were operated by the RAF and called Mustangs. When it comes to best fighter the only thing that is obvious is that it is an opinion not a fact. As a British citizen I place huge store on being there. The P-51, P 47, P 38, P39 were fine aeroplanes but they were not there in 1939/40 so you may as well discuss F-22s. Similarly, it is all very well to complain about the short range of the P 47 as your anecdotal post does, but where was the P 51? It wasn't there! When the P 51 B/C was introduced in numbers the USAAF had already learned a lot and it was this knowledge as well as the P 51 which led to success. Without the Spitfire and Hurricane the P 51 has no place to take off and land from in Europe, that is my opinion, it is a valid opinion so the P51 is not "OBVIOUSLY" anything, as great as it was.
> 
> Please Carboncrank have some respect. There are experts in aerodynamics post here and their posts will show in chapter and verse why laminar flow was not achieved on the P 51. There are veterans of the European bomber campaign still post here. There are people who have written histories and can quote chapter and verse on the subject you claim to be an expert. There is no conspiracy against your view, just put them in a more friendly way.



the mustang isn't the mustang until it has the merlin. I'm perfectly aware of what model i was referring too. i would assume you were too. So the premise is not false

I see there are some aerodynamicist on here and I'm reading what they say with interest. I think you're aware of the popular belief that it was a laminar flow wing and I quoted a document backing that claim. That's all I did. I see they've got way better math skills than I do.


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## Carboncrank (Nov 25, 2017)

Koopernic said:


> It’s a really interesting take on the relative ineffectiveness of the P-47. I hope you post more information because relative loss and victory ratios would let us know a lot.
> 
> I don’t go for the story about IG Farben being bombed or rather not bombed on time. It’s a conspiracy theory. Nothing wrong with conspiracy theories, they must be created and examined because sometimes they are true. I love conspiracy theorists. In this case it doesn’t work for me.



It's not a story and it's not a conspiracy theory. If you want me to look up The Daily Report from The 91st Bomb Group 322nd Squadron mission on December 1st 1943 I will. That was the target and just the other day I found a photo reconnaissance photograph showing the damage they did. Problem is my uncle didn't make it to the Target because of the Missed P-47 hand off.

I'm not totally sure that was the damage from the December 1st strike but I know they came back to that Target repeatedly. Please don't ask me to try to find the 1946 Congressional hearing I was talking about where they said that company was a political Target as well as a military one. I know what I read. It was eye-opening. I'll try to come back tomorrow and address the rest of what you said in that post. Hearings I'm talking about had nothing to do with the McCarthy hearings. 
You must have read some of them many books about the relationship between Wall Street and Nazi Germany. I started out with just a question about where the money had come from to support the Nazi war machine. It's a stunning story and wall Street's ended up to their eyeballs. Profit over the well-being of country or the world continues to this day. American investors we're trying to help I G farben set up offices in Canada when the Japanese attacked Pearl Harbor.

I'll be back.


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## pbehn (Nov 25, 2017)

Carboncrank said:


> the mustang isn't the mustang until it has the merlin. I'm perfectly aware of what model i was referring too. i would assume you were too. So the premise is not false
> 
> I see there are some aerodynamicist on here and I'm reading what they say with interest. I think you're aware of the popular belief that it was a laminar flow wing and I quoted a document backing that claim. That's all I did. I see they've got way better math skills than I do.


Mustang was the RAF name for the machine they ordered , P 51 was the number of the machine the USA ordered. The MKI Mustang had an Allison engine as did the P51A they were generally the same with small differences like specified armament. Over time the two designations have become synonyms when in fact they were actually slightly different.


North American P-51 Mustang variants - Wikipedia

Popular belief is not fact, the P51 has a wing that is popularly referred to as laminar flow but in fact never achieved that as you are now aware.


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## rochie (Nov 25, 2017)

being an ex para, and the son of a para who was the son of a para and also being the grandson of a Royal Navy Veteran does that mean my dick is bigger than yours and i can adopt an aggressive and confrontational tone in nearly all of my posts because being from a family of brave veterans means i am always right ?

just wondering

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## drgondog (Nov 25, 2017)

Carboncrank - a couple of misconceptions from your research may be useful to point out. First it was sad that you were free to criticize the fighter escort as the blame for your uncle being shot down. Really?

First, R/V between bomber boxes and assigned fighter escort occurred for multiple reasons.

Bad weather was the number one cause and bad weather, including icing was prevalent on December 1, 1943. The situation that day was near complete undercast with heavy layered overcast to 30,000 feet. The cover was so bad that the Leverkusen target was deselected due to weather and the first BD bombed on alternate Solingen via PFF.

The 3rd Division turned back. All three bomb divisions struggled to form up over England because of the crappy weather. Ditto fighters but they had the advantage of increasing speed to make up time to R/V

Other reasons for missed escort were a.) bad navigation on part of either bomber or fighter, b.) delayed forming of the bomber force causing late arrival at R/V, c.) change of frag order re; times for R/V making it impossible for fighters to get there, d.) bomber task force off course.

Figure out the Fighter mission - some insight may be gained, Dig deeper into the FG histories to figure out who had Target escort. Get the MACR of your Uncle's B-17 to see where and how they were shot down? Clue - of the 5 91st BG losses, 4 were flak, 1 fighter. Get Encounter reports for the FG's mentioned below to get an idea of time and location of claimed German fighters

The LW fighter shoot down was B-17 42-39836, 322BS/91st BG, Pilot Charles Early, 2 KIA 8 POW MACR 1320 Location - Koblenz. The 20th FG P-38s engaged LW at Coblenz and the 4th, 56th, 78th, 352nd, 353rd, 355th and 356th FG P-47s all scored in Cologne/Coblenz/Aachen/Solingen area.

Point - the 4th FG led a Ramrod Target escort and reported that R/V at 1123 and that the 1st BD was late to R/V. They also reported that instead of taking the lead box, they dropped back to second box as the another P-47 FG plus P-38 FG was already in place - i.e. Penetration support probably for the P-47 group and Target escort for the P-38 group. 

The 354th FG flew its first mission, led by Don Blakeslee (4FG Gp Ops Officer) on a sweep. It was not a bomber escort mission but a sweep over Knocke/St.Omer/Calais as standard first mission familiarization. The next mission was Penetration escort on the 5th - to Paris. The first Germany mission was the 11th to Emden.

Also, as stated before - the NACA/NAA 45-100 airfoil was Never named Laminar by the engineers. It was always Low Drag.

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## drgondog (Nov 25, 2017)

Carboncrank said:


> the mustang isn't the mustang until it has the merlin. I'm perfectly aware of what model i was referring too. i would assume you were too. So the premise is not false
> 
> I see there are some aerodynamicist on here and I'm reading what they say with interest. I think you're aware of the popular belief that it was a laminar flow wing and I quoted a document backing that claim. That's all I did. I see they've got way better math skills than I do.



No, actually the AAF Material Command cleared that all up and issued a memo, to wit:
For the following aircraft, the official designation is Mustang
P-51
A-36
P-51A
P-51B/C
P-51D
P-51K

The first three are Allison powered, with variations on the engine supercharger gear ratios, max power FTH, and Hp. As a point of interest, the P-51A w/WI was always faster than Merlin P-51B/C/D/K until 150 Octane fuel and 75" Boost - below 15,000 feet. As another point of possible interest, the key distinction between the A/B was the ability of the B/C to carry the excellent aerodynamics and airframe to much better performance at 30,000 feet than the P-51A at 20,000. 

Had the 8th AF changed bombing altitude doctrine from 25,000 to 15,000 - more like RAF, they would have lost more to flak, but would have had a.) much more effective reliability from P-38, b.) effective escort from P-51A and P-47 much earlier than the introduction of the P-51B. That said, Berlin was still not possible until addition of 85 gallon tank into P-51A and 55 Gallon LE tanks in P-38, so that issue would stall Berlin attacks by a modified P-51A to the same timeframe as P-51B

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## pbehn (Nov 25, 2017)

drgondog said:


> No, actually the AAF Material Command cleared that all up and issued a memo, to wit:
> For the following aircraft, the official designation is Mustang
> P-51
> A-36
> ...



The RAF did use Mustang Mk Is to escort Wellingtons to Germany but these were not plumbed for drop tanks.
Do you know when that memo was dd? I thought the A36 was known as the Apache.


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## DerAdlerIstGelandet (Nov 25, 2017)

Carboncrank said:


> Sorry it's too late. you were an asshole about it. boot me at will but I won't be talked to like that. if you want be so petty as to boot the son of a hellcat and skyraider pilot, and the nephew of a b-17 bombardier who spent 18 months as a prisoner, and who grew up on airbases and has a life long connection to wwII aircraft over the use of the word "try" feel free, I don't grovel, I don't beg forgiveness.
> 
> I don't do well with assumed authority and I will always speak truth to power, and I don't mean politics in this case, I mean the bullying tone in your reply.



First of all I thank your father for his service. My family served on both sides of the conflict, and in every major conflict since. I’m a combat veteran myself. None of that makes me above the forum rules, or better than anyone else here.

Second of all, it was not bullying. It was telling you the forum ground rules. Everyone, include myself has to abide by them. Maybe you should not be so sensative. You broke the forum rules, and were informed of it. All you had to do was apologize, and say you wont do it again. All would be forgotten, and we would not even be discussibg this.

You should have read them, when you joined the forum.

Third. This forum has many actual combat veterans, sons of combat veterans, and everyone has a life long passion for aviation. So please don’t attempt to put yourself on a higher pedastal.

Fourth. Those who live in glass houses should not throw stones. From day one, you have exhibited a holier than thou, above everyone else attitude. My parents taught me to treat others as you would like to be treated. Try it sometime...

When people come in with the “I know it all attitude”, everyone else becomes very stand offish. 

Now the ball is in your court. You can stop pretending to be above the forum rules, stop pretending to be above everyone else, and be a productive member of this forum, which I think everyone would prefer, or you can leave.


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## DerAdlerIstGelandet (Nov 25, 2017)

rochie said:


> being an ex para, and the son of a para who was the son of a para and also being the grandson of a Royal Navy Veteran does that mean my dick is bigger than yours and i can adopt an aggressive and confrontational tone in nearly all of my posts because being from a family of brave veterans means i am always right ?
> 
> just wondering



Thank you so much for saying what I wanted to say...

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## rochie (Nov 25, 2017)

DerAdlerIstGelandet said:


> Thank you so much for saying what I wanted to say...


No worries, whenever childish sarcasm is needed just pm me

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## drgondog (Nov 25, 2017)

pbehn said:


> The RAF did use Mustang Mk Is to escort Wellingtons to Germany but these were not plumbed for drop tanks.
> Do you know when that memo was dd? I thought the A36 was known as the Apache.


The name Apache was a short term designation from AAF in 1942, Invader was an informal nomenclature for the A-36 in MTO. Never used by NAA. I'll have to dig up the memo


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## drgondog (Nov 25, 2017)

Carboncrank said:


> One little problem. The 354th has a website and it directly contradicts what you quote from that book that so many people think is the most reliable book on the topic
> 
> "The first Merlin-engine Mustangs were delivered to the 354th Fighter Group of the 9th Air Force in Great Britain on December 1, 1943. The P-51B first went into action as a fighter on December 17, 1943".
> 
> 354th Fighter Group During WWII



The 354th arrived in England Nov 1, 1943. The first P-51B-1-NA (5) arrived on 11 November but several pilots got time in 67th Tactical Recon P-51A Mustangs. The total reached 54 P-51B-1s plus three new P-51B-5 by November 30. Blakeslee led the first mission on December 1 with 354FG CO Martin flying #2 on a sweep along France/Belgian coastal area. That date is the first operational date. If you want first victory date -> Glen Eagleston shot down a Me 110 on 13 December, 1944 

The info is clearly stated in the 'history' section of the posted website. You just didn't read closely enough.

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## DerAdlerIstGelandet (Nov 25, 2017)

Hey Bill, what squadron did your dad fly P-51’s in again?

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## drgondog (Nov 25, 2017)

DerAdlerIstGelandet said:


> Hey Bill, what squadron did your dad fly P-51’s in again?


354FS/355FG then 355FG HQ (as contrast with our recent subject 354FG). Also 35th FBW CO flying P-51s out of Johnson AFB near Tokyo. I think he had nearly 1000 hours in P-51B/C/D/K and H. Nothing compared to warbird community but very high with USAF 

They were sister Groups relative to Org date and assignment of FS and FG number. The 354Fg has 353, 355 and 356FS. The 355FG had 354,357 and 358. Both groups still very prominent in USAF today. During Vietnam, they both flew F-105s and when 354TFW transitioned to A-7 with 355TFW, the 354FS was TDY to Korat under 354TFW.

IIRC the 354FS just returned from their 7th A-10 deployment from Sandbox, Afghanistan and now Syria. AFAIK they have lost nobody but some A-10s never flew again.

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## Carboncrank (Nov 25, 2017)

pbehn said:


> Mustang was the RAF name for the machine they ordered , P 51 was the number of the machine the USA ordered. The MKI Mustang had an Allison engine as did the P51A they were generally the same with small differences like specified armament. Over time the two designations have become synonyms when in fact they were actually slightly different.
> 
> 
> North American P-51 Mustang variants - Wikipedia
> ...



Would you say it created less drag than any wing before it?


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## pbehn (Nov 25, 2017)

Carboncrank said:


> Would you say it created less drag than any wing before it?


I am not qualified to say, in terms of WW2 and pre war fighters I believe so from what I have read here, but it wasn't laminar flow(that I can say quite definitely), it just had more laminar flow than others, at the time of its introduction it certainly had the lowest drag at high speed, it may even have had laminar flow at taxi speed but at that speed it isn't an aircraft.


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## Carboncrank (Nov 25, 2017)

Koopernic said:


> It’s a really interesting take on the relative ineffectiveness of the P-47. I hope you post more information because relative loss and victory ratios would let us know a lot.
> 
> I don’t go for the story about IG Farben being bombed or rather not bombed on time. It’s a conspiracy theory. Nothing wrong with conspiracy theories, they must be created and examined because sometimes they are true. I love conspiracy theorists. In this case it doesn’t work for me.
> 
> ...





Koopernic said:


> It’s a really interesting take on the relative ineffectiveness of the P-47. I hope you post more information because relative loss and victory ratios would let us know a lot.
> 
> I don’t go for the story about IG Farben being bombed or rather not bombed on time. It’s a conspiracy theory. Nothing wrong with conspiracy theories, they must be created and examined because sometimes they are true. I love conspiracy theorists. In this case it doesn’t work for me.
> 
> ...


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## Carboncrank (Nov 25, 2017)

rochie said:


> being an ex para, and the son of a para who was the son of a para and also being the grandson of a Royal Navy Veteran does that mean my dick is bigger than yours and i can adopt an aggressive and confrontational tone in nearly all of my posts because being from a family of brave veterans means i am always right ?
> 
> just wondering



kick me out if you want. I don't really give a damn. I was just saying I have value whether you like my manner or not. and not liking my manner is another thing I don't really give a damn about.

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## rochie (Nov 26, 2017)

Carboncrank said:


> kick me out if you want. I don't really give a damn. I was just saying I have value whether you like my manner or not. and not liking my manner is another thing I don't really give a damn about.


How to win friends and influence people !
I just love internet tough guys.

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## Wayne Little (Nov 26, 2017)

Mmmm......some interesting reading.....


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## Kryten (Nov 26, 2017)

In another life I was Alexander the Greats chief Eunuch!

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## ChrisMcD (Nov 26, 2017)

Zipper730 said:


> Firstly what engines would have been practical to license other than the Merlin



Hope I got the right "quoter"!

The obvious choice was the Napier Sabre, but it was considered too different in technology for anyone to be really keen. But bear in mind that P&W got bitten by the sleeve valve bug in the late 30's and even persuaded the Navy to fund a water cooled XH-3130 before sanity was restored and they got on with the R-4360.

Pratt & Whitney XH-3130 - Wikipedia

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## pbehn (Nov 26, 2017)

Sleeve valves have a theoretical advantage on radial engines because they don't have the valve gear on the head, meaning a narrower engine for a given piston stroke.

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## drgondog (Nov 26, 2017)

Carboncrank said:


> Would you say it created less drag than any wing before it?


Yes. Proven to develop 30=% less profile drag than comparable NACA 23015 wing

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## pbehn (Nov 26, 2017)

drgondog said:


> Yes. Proven to develop 30=% less profile drag than comparable NACA 23015 wing


I was hesitant to say because I have no idea about earlier wings on say an Eindecker, which may or may not have had less drag but the wing is of no use to a WW2 fighter, no room for weapons fuel, no control surfaces or strength for turning.


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## Shortround6 (Nov 26, 2017)

pbehn said:


> Sleeve valves have a theoretical advantage on radial engines because they don't have the valve gear on the head, meaning a narrower engine for a given piston stroke.


Unfortunately the theory didn't work out in practice. The Hercules being larger in diameter the Gnome-Rhone 14N/R (and the 14K derivatives ) that used the same bore and stroke. Difference in diameter compared to the Wright R-2600 was also minor although the Wright used a 4.8mm shorter stroke (but bigger bore) 
This was pretty much the story of the sleeve valve. Most of it's promised advantages were measured against mid/late 1920s engines. Many of the problems with those engines had been solved by other means by the time the sleeve valve engine became a mass produced article.

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## pbehn (Nov 26, 2017)

Shortround6 said:


> Unfortunately the theory didn't work out in practice. The Hercules being larger in diameter the Gnome-Rhone 14N/R (and the 14K derivatives ) that used the same bore and stroke. Difference in diameter compared to the Wright R-2600 was also minor although the Wright used a 4.8mm shorter stroke (but bigger bore)
> This was pretty much the story of the sleeve valve. Most of it's promised advantages were measured against mid/late 1920s engines. Many of the problems with those engines had been solved by other means by the time the sleeve valve engine became a mass produced article.


I was careful to add theoretical as a "rider" as a motorcyclist in the 1970s there were all sorts of developments that promised the theoretical earth. Stepped pistons, rotary valves, desmodromic valves, disc valves, exhaust power valves, reed valves....some worked some were complete fantasy.


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## Shortround6 (Nov 26, 2017)

Sorry I wasn't more careful with my wording, I wasn't trying to "correct" you but to expand on the _theoretical_

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## pbehn (Nov 26, 2017)

Shortround6 said:


> Sorry I wasn't more careful with my wording, I wasn't trying to "correct" you but to expand on the _theoretical_


I didn't take it that way at all SR, there are all sorts of suspension systems on motorcycles that offer a theoretical advantage, but in practice they havnt changed on the front or rear for years, they have just had refinements added.


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## Koopernic (Nov 26, 2017)

pbehn said:


> Sleeve valves have a theoretical advantage on radial engines because they don't have the valve gear on the head, meaning a narrower engine for a given piston stroke.



The sleeve valve was a response to a problem Sir Harry Ricardo himself had noted which was that poppet exhaust valves were getting so hot they would start causing pre-ignition as engine performance grew. This stimulated the development of sleeve valves in Britain some with one and some with two sleeves. There were even several automobiles in production that used them.

Sodium cooled exhaust valves, better springs and a myriad of refinements overcame the issue of the poppet valves.

At one point US researchers promoted the idea of installing a sleeve in a poppet engine to reduce fuel consumption, piston wear and pollution. Apparently the motion of the sleeve at top and bottom dead centre maintains the hydrodynamic oil film which reduces friction and prevents stiction. Oddly poppet valves had developed to the point that the idea of cutting a port into the sleeve to aspirate the engine via the anti-friction sleeve was not seen as an advantage.

The Sleeve valved Bristol Hercules and Centaurus offered no diameter advantage over the contemporary R-2600, R2800, R-3350, BMW801.

Looking at a cutaway of the Sabre shows that an enormous amount of space was allocated to the cylinder head, so much I question whether it even reduced the height of the cylinder and head assembly over a poppet valve system. The Sabres advantage may have come from the balance its horizontally opposed design offered and the high RPM this allowed.

I suspect the 3000hp Sabre probably would have given tempest a speed of around 430mph at sea level because the 2600hp version got to 410 on 150 PN fuel.

Fw 190D with plane old Jumo 213A (an engine the same weight as the Sabre were running at 2 ATA boost (about 2310hp over the 1.75 ATA 2100hp engines) so the Sabre was winning but 2.2 ATA must have been around the corner for the advanced versions of the Jumo engine which were expected to achieve 2700hp and that with a refined intercooled two stage 3 speed supercharger. 

By that time jets were offering 520 mph at sea level and by the end of 1945 had exceeded 600mph. So the Sabre won a technical war it was maybe by 10%-15% over similar sized engines with single stage supercharger but that the margin would be less when inter cooling was added.

Obviously the money went to the jet.


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## tomo pauk (Nov 27, 2017)

Shortround6 said:


> Unfortunately the theory didn't work out in practice. The Hercules being larger in diameter the Gnome-Rhone 14N/R (and the 14K derivatives ) that used the same bore and stroke. Difference in diameter compared to the Wright R-2600 was also minor although the Wright used a 4.8mm shorter stroke (but bigger bore)
> ...





Koopernic said:


> ...
> The Sleeve valved Bristol Hercules and Centaurus offered no diameter advantage over the contemporary R-2600, R2800, R-3350, BMW801.
> ...



Hercules was with 3 in smaller diameter than the R-2600 - 52 vs. 55 in. It was lighter than BMW 801, by some 15%.


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## Koopernic (Nov 27, 2017)

tomo pauk said:


> Hercules was with 3 in smaller diameter than the R-2600 - 52 vs. 55 in. It was lighter than BMW 801, by some 15%.



BMW801 weight is always confounded by the incorporation of gearbox, integral fan gearbox and the often armoured tank cooler.

Double check your sources, the Hercules has the largest diameter.

I've spot checked 3 sources and all give the Bristol Hercules and Curtiss Wright R-2600 as 55 inches diamter . The R-2800 the biggest displacement and most powerful of the engines is actually the smallest at 52.8.

The BMW801 is also significantly more powerfull than the Hercules. The BMW801 ended the war at about 2000hp for the 801D and 801TS at 1.62 ATA with the 801TS being able to operate at 1.82 ATA and 2350hp for emergencies. The 801 competed with the centaurus. The 801F version could have produced 2600hp.

The BMW 801 was 51 inches in diameter as opposed to the Hercules's 55 inches. The small diameter as well as the tight fan cooled cowling is what made it suitable for use on a fighter.

The diameter of the Bristol Centaurus was 55.3 inches, the same as the Hercules and the R-3350.

Conclusion, no advantage in diameter for the sleeve valve.

This credible source, they actually have one, says the 801 weighed 880kg, which would make it quite a light engine. Same as the 875kg of the Hercules.
BMW 801, Radial 14 Engine


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## tomo pauk (Nov 27, 2017)

Koopernic said:


> BMW801 weight is always confounded by the incorporation of gearbox, integral fan gearbox and the often armoured tank cooler.
> 
> Double check your sources, the Hercules has the largest diameter.
> 
> ...



52 in diameter for Herucles, per contemporary source: link
BMW 801 weight starts from 1010-1012 kg. link



> The BMW801 is also significantly more powerfull than the Hercules. The BMW801 ended the war at about 2000hp for the 801D and 801TS at 1.62 ATA with the 801TS being able to operate at 1.82 ATA and 2350hp for emergencies. The 801 competed with the centaurus. The 801F version could have produced 2600hp.



The BMW 801S was supposed to make 2200 PS for emergency, minus what fan consumed (70 PS max) = 2100 HP? Hercules 100 was making 1800 HP at 10000 ft, but also 1630 HP at 20000 ft - no worse than 801S. link Later versions went above 2000 HP.
Centaurus went above 2500 HP in service use early on, later version went to 2740 HP, with water injection above 3000 HP. Military versions, Mk.XV and XVIII (for Sea Fury and Tempest II) were making 2100 HP at 20000 ft, 400-450 HP more than 801S there.
801F was making 2600 PS on test bench, that is not service figure.

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## Shortround6 (Nov 27, 2017)

Diameter of the Hercules is often confounded by the same factor as the BMW 801, many sources give the diameter of the cowl and not the bare engine as the Hercules was often supplied as a "power egg". 
Bare engine was usually given as 52in. Weights on the Hercules are going to be all over the place as there were quite a few versions. Be very careful the source is NOT using numbers from post war engines which used a new crankshaft and crank case in addition to new cylinder heads. Also note the weights for the Hercules, like the BMW 801, sometimes include the cowl/exhaust and sometimes are for the "dry" (or bare) engine. 

Can we please stop with the experimental or limited production German engines being compared to bog standard Allied engines?
By the end of the war the Hercules 100 series was well in hand but British development was going it a bit different direction When introduced in 1944 the Hercules 100 was said to be approaching 2000 hours overhaul life. While rated at 1675HP for takeoff it was good for 1625HP at 19,500ft. in high gear. (1800hp at 9,000ft). In 1944/45 I have no idea how far along the Hercules 120 was (it shows up in the 1946 edition of AIrcraft engines of the World) and it offered 1330hp at 27,500ft from it's single stage, two speed supercharger. 


I left out the P & W R-2800 as it used 18 cylinders which of course are smaller (6.0 in stroke) and would tend to cloud the comparison/claim that sleeve valves would allow a smaller diameter on the same (pr similar) stroke engine 

Sources on diameter of the Hercules are Lumsden and several editions of Aircraft Engines of the World


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## Koopernic (Nov 27, 2017)

tomo pauk said:


> 52 in diameter for Herucles, per contemporary source: link
> BMW 801 weight starts from 1010-1012 kg. link
> 
> 
> ...



The service figures you quote are for engine service ratings achieved well after WW2. In 1945 they were bench figures just like the BMW801F.

Quite interesting data. The claims that the Hetcules had a diameter of 55 occurs multiple times as does that it was 52, perhaps an indication that different things are being measured.

Note the exhaust manifolds that increase diameter.













Either way the difference is marginal. Sleeves thicken a cylinder.

http://www.enginehistory.org/members/articles/Sleeve.pdf
14. Conclusions 14.1. Weight and Size

Both air and liquid-cooled sleeve-valve engines were heavier per unit of displacement than their poppet-valve counterparts. The Bristol air-cooled engines were competi- tive on a weight per take-off horsepower basis while only the Napier Sabre in its VII A version was competitive with the liquid-cooled poppet-valve engines on the same basis.

The frontal area of the radial sleeve-valve engine was comparable to the poppet-valve radials, while the liquid- cooled sleeve-valve engines were somewhat larger than the poppet-valve engines. The latter comparison is somewhat subjective since both of the liquid-cooled sleeve-valve engines were of an H configuration while the poppet-valve engines were all V-12s. There were no poppet-valve H con- figurations with which to compare the sleeve-valve engines, so one cannot state definitively that the difference in the frontal area was due solely to the presence of the sleeve- valve.

------

German engines often are quoted at their sea level power. At about 1500m their rated power will be greater than the sea level power. This is inevitable in engines that choke of the supercharger pressure. Im thinking the 801TS produced 2200 at sea level and a little higher at rated altitude.


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## tomo pauk (Nov 27, 2017)

Koopernic said:


> The service figures you quote are for engine service ratings achieved well after WW2. In 1945 they were bench figures just like the BMW801F.
> ...
> Either way the difference is marginal. Sleeves thicken a cylinder.



5th May 1945 - Centaurus V making 2650 HP: link. If you believe that a 2560 cu in engine running at 2700 rpm will equal a 3270 cu in running at same RPM, in same year, on same reliability, I have Brooklyn bridge on sale. 
Cylinder thickness has next to ne bearing on engine diameter.



> German engines often are quoted at their sea level power. At about 1500m their rated power will be greater than the sea level power. This is inevitable in engines that choke of the supercharger pressure. Im thinking the 801TS produced 2200 at sea level and a little higher at rated altitude.



Minus the power to drive the fan, minus the difference of PS vs. HP. BTW - there is yet to emerge a test where the BMW 801S makes more than 1.7 ata (< 2000 PS) in service trim.

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## Shortround6 (Nov 27, 2017)

Koopernic said:


> The service figures you quote are for engine service ratings achieved well after WW2. In 1945 they were bench figures just like the BMW801F.



well after WW II (1948?) you got the 230-260 series Hercules around 2000hp for take-off. One of them with a two speed supercharger (most had single speed) was rated at 1840hp at 13,250ft military power. 
The 100-120 were pretty much end of war engines (1945-46)

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## pbehn (Nov 27, 2017)

Koopernic said:


> The sleeve valve was a response to a problem Sir Harry Ricardo himself had noted which was that poppet exhaust valves were getting so hot they would start causing pre-ignition as engine performance grew. This stimulated the development of sleeve valves in Britain some with one and some with two sleeves. There were even several automobiles in production that used them.
> 
> Sodium cooled exhaust valves, better springs and a myriad of refinements overcame the issue of the poppet valves.
> 
> ...


Great post Koopernic, there are all sorts of theoretical advantages to a sleeve valve and also disadvantages. Theoretically it could be made more powerful and more economical due to better gas flow and scavenging. In the seventies I read a sort of "what if" article which speculated that if engines had started off as sleeve valve and had been producing and researching them for twenty to thirty years all over the world they could well have been much better than poppet valve engines. If jets had not existed or succeeded then Rolls Royce were looking at two stroke designs with reciprocal sleeve valves. 
Rolls-Royce Crecy - Wikipedia

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## grampi (Nov 27, 2017)

Carboncrank said:


> or course the premise matters. the original post made no distinction about a normal p47. it should have been pointed out as an extraordinary claim with no extraordinary proof. In what world should anybody begin a discussion of anything on a false premise.


So you don't believe ANY version of the P-47 did 500 mph?


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## Koopernic (Nov 27, 2017)

pbehn said:


> Great post Koopernic, there are all sorts of theoretical advantages to a sleeve valve and also disadvantages. Theoretically it could be made more powerful and more economical due to better gas flow and scavenging. In the seventies I read a sort of "what if" article which speculated that if engines had started off as sleeve valve and had been producing and researching them for twenty to thirty years all over the world they could well have been much better than poppet valve engines. If jets had not existed or succeeded then Rolls Royce were looking at two stroke designs with reciprocal sleeve valves.
> Rolls-Royce Crecy - Wikipedia



If turbojets hadn't been possible giant airliners would be winging their way across the ocean probably as 2 stroke diesels or possibly petrol engined. The usual problem with two strokes is the fuel mixture loss during scavenging. This can be overcome with direct injection. One then has the problem of determining the air fuel ratio because some of the charge is mixed with exhaust air. Using a pre chamber relaxes both octane requirements and the stoichiometric limits for reliable ignition. The pre-chamber can initiate reliable ignition while any pre-ignition or knocking is soon snuffed by oxygen starvation. 

It is possible to use exhaust gas measurements to determine the airfuel ratio. I think the Merlin relied on engine RPM, exhaust temperature and ambient pressure to determine fuel rates. There was no intake flow measurement.

History of the sleeve

https://www.newcomen.com/wp-content/uploads/2012/12/Chapter-6-Hassell.pdf

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## pbehn (Nov 27, 2017)

Koopernic said:


> If turbojets hadn't been possible giant airliners would be winging their way across the ocean probably as 2 stroke diesels or possibly petrol engined. The usual problem with two strokes is the fuel mixture loss during scavenging. This can be overcome with direct injection. One then has the problem of determining the air fuel ratio because some of the charge is mixed with exhaust air. Using a pre chamber relaxes both octane requirements and the stoichiometric limits for reliable ignition. The pre-chamber can initiate reliable ignition while any pre-ignition or knocking is soon snuffed by oxygen starvation.
> 
> It is possible to use exhaust gas measurements to determine the airfuel ratio. I think the Merlin relied on engine RPM, exhaust temperature and ambient pressure to determine fuel rates. There was no intake flow measurement.
> https://www.newcomen.com/wp-content/uploads/2012/12/Chapter-6-Hassell.pdf


Good post and attachment Koopernic, I must confess when I was involved in tuning two strokes I didnt give a monkeys toss about fuel efficiency or economy By some strange twist of fate I ended up with one of the fastest Suzuki X7s ever raced in UK in production clases, many good racers who had switched to Yamaha RD250s asked me what I had done to it, so I asked the tuner (Terry Becket) what he did and he said "same as all the others". Even in the 1980s two strokes were still in some ways a black art. However that was just top speed, my X7 lost ten yards at least coming out of every corner, even in lower capacity classes torque across a broad range rules the roost.

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## wuzak (Nov 27, 2017)

Koopernic said:


> It is possible to use exhaust gas measurements to determine the airfuel ratio. I think the Merlin relied on engine RPM, exhaust temperature and ambient pressure to determine fuel rates. There was no intake flow measurement.



Doubtful.

Early Merlins used a carburetor which uses the air flow to determine the air:fuel ratio. Later versions used an injection carburetor - which also used the air flow to determine the air:fuel ratio.

Pressure Injection Carburetors – Typical Injection Carburetor

Also, modern engines that use the exhaust to determine air fuel ratios use a sensor which detects excess oxygen in the exhaust. This can be used to adjust the air:fuel ratio. 

And, if you look at a typical Merlin exhaust installation you would notice that there are no feedback mechanisms for exhaust temperature.


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## wuzak (Nov 27, 2017)

Koopernic said:


> The BMW801 is also significantly more powerfull than the Hercules. The BMW801 ended the war at about 2000hp for the 801D and 801TS at 1.62 ATA with the 801TS being able to operate at 1.82 ATA and 2350hp for emergencies. The 801 competed with the centaurus. The 801F version could have produced 2600hp.



The Rolls-Royce Vulture could have made 2500hp+ and had a diameter of 48". Well, it did on test in 1941.

The Daimler Benz DB 604 was rated at >2600hp, diameter I am not sure, but probably less than the Vulture.

The Merlin could have produced 2600hp also. The RM.17SM did just that in 1944. During tests it also ran over 2300hp (less boost, more rpm). The RM.17SM was type rated at 2200hp MS and 2100hp FS in 1945. Without ADI (which the V-1650-9 used to achieve similar numbers).


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## Koopernic (Nov 28, 2017)

wuzak said:


> The Rolls-Royce Vulture could have made 2500hp+ and had a diameter of 48". Well, it did on test in 1941.
> 
> The Daimler Benz DB 604 was rated at >2600hp, diameter I am not sure, but probably less than the Vulture.
> 
> The Merlin could have produced 2600hp also. The RM.17SM did just that in 1944. During tests it also ran over 2300hp (less boost, more rpm). The RM.17SM was type rated at 2200hp MS and 2100hp FS in 1945. Without ADI (which the V-1650-9 used to achieve similar numbers).



Cynic?

The BMW 801F was delayed but scheduled for production in April 1945, BMW was forced to supply the BMW 801TS instead as an interim. It had promised the 801F or "similar" engine. Because the 801TS was lighter than the 801F and the Fw 190A9 had its centre of gravity built around the BMW 801F the Fw 190A9 had weights applied to the propeller to balance the aircraft. It got that close to production it effected the airframe.

The 2580hp was intended as a service rating. It wasn’t a test stand experiment to detect vibration or heat load.

The 801F remained somewhat as an abstract engine in which new strengthened components were developed that then turned up in production in interim engines. A specific power of 2600hp out of 2600 cubic inches was not exceptional for an engine running on 100/130 + Water Injection. The R2800 achieved 2800hp on 100/130 plus water. The BMW801 was also a highly developed engine, with much modification based on experience.

Production of the engine was supposedly held up by tooling issues since everything was highly modified.

There was also a BMW801TH supplied at the same time as the TS. The TH had provision for Nitous Oxide.

I doubt that the BMW801F had it been produced in 1945 would have been put into Fw 190 airframes. The Jumo 213 reduced drag over the total airframe by 13%, promised more power and had a fully developed two stage supercharger with intercooler. It gave the speed at all altitudes the Luftwaffe needed to take on Griffon Spitfires, Tempest V, P51H and P47N on an equal level.

The core of the of the 801F engine would have turned up in the turbo charged BMW801TQ on Ju 388 etc and maybe Ju 88G1 night fighters,

The 801 was reaching the end of its development potential but 2600hp was realistic. It just couldn’t make the Fw 190 airframe competitive. The Jumo 213 and DB603L could.


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## Koopernic (Nov 28, 2017)

wuzak said:


> Doubtful.
> 
> Early Merlins used a carburetor which uses the air flow to determine the air:fuel ratio. Later versions used an injection carburetor - which also used the air flow to determine the air:fuel ratio.
> 
> ...



My description was a little off but in essence correct. They didn’t measure air mass flow but computed it from pressure ratios of the inlet to exhaust pressure and inlet temperature. That’s all the data you need if you have the correct physical laws.

Read the section on the SU “Skinners Union” carburettor which was really an injection system.
Aircraft Carburetors and Fuel Systems: A Brief History - 09

In essence they use an engine map the way some motorcycles do only they used levers, cams and hydraulic fuel pressures to do the computations.

“*Skinners Union (SU) and Rolls-Royce Speed-Density System*

A speed-density carburetor system does away with the carburetor venturi, replacing it with an engine driven fuel pump that delivers the fuel to either the intake eye of the supercharger or divides it into individual fuel charges that are injected directly into the engine cylinder. Atmospheric pressure and the mass of air passing through the unit combine to control the fuel pump.

Rolls-Royce wanted to use the speed-density method of controlling the fuel-air ratio. It found that the Skinners Union carburetor division of the Morris group had already manufactured a reciprocating swash-plate pump, although it was much too small for the purpose. Rolls-Royce then invited SU to produce a larger pump of the same design, and to develop a control system for it with Rolls-Royce. SU engineers came to the Rolls-Royce plant, and received engine specific data of what the fuel supply produce under all operating conditions. The volume of fuel pumped with the SU swash plate pump can vary from no fuel to full fuel by changing the angle of the swash plate, similar to the method used to control the pitch of a helicopter's rotor blades. In the case of the fuel pump, intake and exhaust manifold pressure, intake manifold temperature and engine speed combine to control the swash plate angle.

Rolls-Royce later developed its own speed-density system that was mechanically simpler than the SU device. In the Rolls-Royce system, the feed pump supplied fuel at a constant pressure to two jets in parallel. A tapered needle valve operated by a pressure capsule measuring the pressure difference between the intake and exhaust manifolds controlled the size of one jet. The other jet was controlled a tapered needle valve connected to a temperature-sensitive device in the intake manifold. The fuel pressure drop across the pair of jets acted on one side of a flexible diaphragm that was loaded by the action of an engine-driven centrifugal governor on the other; the diaphragm operated a valve regulating fuel flow as the two forces balanced against one another on the diaphragm. Rolls-Royce was much more involved in the development of these speed-density systems than it had been in the development of float-type carburetors it used before.”

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## Koopernic (Nov 28, 2017)

pbehn said:


> Good post and attachment Koopernic, I must confess when I was involved in tuning two strokes I didnt give a monkeys toss about fuel efficiency or economy By some strange twist of fate I ended up with one of the fastest Suzuki X7s ever raced in UK in production clases, many good racers who had switched to Yamaha RD250s asked me what I had done to it, so I asked the tuner (Terry Becket) what he did and he said "same as all the others". Even in the 1980s two strokes were still in some ways a black art. However that was just top speed, my X7 lost ten yards at least coming out of every corner, even in lower capacity classes torque across a broad range rules the roost.



Never ridde nmotor cycles much except for a few 50cc step throughs while on holiday. They still give you that "born to be wild" song in the head. Might take up Segway racing.


In the 1990s Ralph Sarich developed a compressed air direct fuel injection system that could develop a stratified charge that was rich across the spark plus but lean elsewhere. This system could make a 2 stroke superior to 4 strokes though it is applicable to all cycles. It was perfect for two-stroke cars but entrenched conservatism prevented an uptake. It in essence worked like the crecy.

Ralph Sarich -- Fuel injector

It was taken up by Evinrude for their outboard motors, a maritime environment is not a place for valve gear. The patent may have gone to a motorcycle manufacturer.

They do use oxygen sensors and fuel sensors in the exhaust but these are required for catalytic converters anyway.


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## pbehn (Nov 28, 2017)

Koopernic said:


> Never ridde nmotor cycles much except for a few 50cc step throughs while on holiday. They still give you that "born to be wild" song in the head. Might take up Segway racing.
> 
> 
> In the 1990s Ralph Sarich developed a compressed air direct fuel injection system that could develop a stratified charge that was rich across the spark plus but lean elsewhere. This system could make a 2 stroke superior to 4 strokes though it is applicable to all cycles. It was perfect for two-stroke cars but entrenched conservatism prevented an uptake. It in essence worked like the crecy.
> ...


Two strokes were running in to problems of safety, noise and emissions even before economy and power output became an issue.


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## Denniss (Nov 28, 2017)

BMW 801TH contains the 801F engine
BMW 801TS contains the 801S engine
BMW 801TU contains the 801Q-2 engine = a D-2 with larger/better armored oil tank/cooler and provision for injection systems
The T designation is for "Triebwerksanlage", an engine complete will all parts to simply attach to an airframe using quick change mounts.
Never heard of the Fw 190 A-9 designed around/for the F-engine or requiring additional ballast at prop, this was an A-8 with a similar-weight but more-powerful engine. Later A-8 already got nose-heavier due to switching D-2 for slightly heavier Q-2 engine

EDIT: typo fixed - TU with Q-2 engine, not TQ with Q-2 engine, matching numbers of engine and M/T types was rare

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## fastmongrel (Nov 28, 2017)

Shortround6 said:


> Unfortunately the theory didn't work out in practice. The Hercules being larger in diameter the Gnome-Rhone 14N/R (and the 14K derivatives ) that used the same bore and stroke. Difference in diameter compared to the Wright R-2600 was also minor although the Wright used a 4.8mm shorter stroke (but bigger bore)




The 14N was a very light engine compared to other 14 cyl radials, the postwar Snecma R developments gained a lot of weight and got a little bit bigger in diameter.


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## Shortround6 (Nov 28, 2017)

Thank you. The reason for bringing in the Gr 14N was that it used the same bore and stroke as the Hercules and would be a good comparison for the claim that a sleeve valve would offer a smaller diameter. 
The BMW used a 6.15in stroke (156mm) vs the 6.5 in (165mm) stroke of the Gr 14N and Hercules. This isn't the 100% explanation of the difference in diameters, the R-2600 used a 6.3215 (160mm) stroke. However I believe it shows my point that this "theoretical" advantage of the sleeve valve didn't work out in practice. 

The Snecma R started pre-war as the Gr 14R but they didn't have enough time to get it into production although it powered one or more prototypes, most famous being the Bloch 157.

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## fastmongrel (Nov 28, 2017)

The reason for the Bristol sleeve valve engines diameter being bigger than expected originally was that the Junk Head needed a lot of extra finning as power increased.





You can see the depth of the Junk Head from the above wikipedia picture. From the Junk Head sealing rings to the top of the fins is about the same as a normal push rod and poppet valve system from head gasket to rocker cover.

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## Shortround6 (Nov 28, 2017)

Also please note that the sleeve rises several inches above the the "head" surface. The ports, when closed are above the combustion chamber.


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## tomo pauk (Nov 28, 2017)

Koopernic said:


> ...
> The BMW 801F was delayed but scheduled for production in April 1945, BMW was forced to supply the BMW 801TS instead as an interim. It had promised the 801F or "similar" engine. Because the 801TS was lighter than the 801F and the Fw 190A9 had its centre of gravity built around the BMW 801F the Fw 190A9 had weights applied to the propeller to balance the aircraft. It got that close to production it effected the airframe.
> 
> The 2580hp was intended as a service rating. It wasn’t a test stand experiment to detect vibration or heat load.
> ...



I'd kindly ask for sources for the statements quoted.


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## Koopernic (Nov 29, 2017)

Denniss said:


> BMW 801TH contains the 801F engine
> BMW 801TS contains the 801S engine
> BMW 801TQ contains the 801Q-2 engine = a D-2 with larger/better armored oil tank/cooler and provision for injection systems
> The T designation is for "Triebwerksanlage", an engine complete will all parts to simply attach to an airframe using quick change mounts.
> Never heard of the Fw 190 A-9 designed around/for the F-engine or requiring additional ballast at prop, this was an A-8 with a similar-weight but more-powerful engine. Later A-8 already got nose-heavier due to switching D-2 for slightly heavier Q-2 engine



I've added two scans from a pair of of my reference Books. The first is The excellent Creek & Smith Book Fw 190 Volume 2, the second from Ju 388 by Christof Vernalken and Martin Handif because of its information on the 801E engine which is a bomber analog of the 801F AFAIKT. 

Unfortunately I had taken some bad information from Wikipedia (calling the 801TJ-1 the 801TQ and confusing the TH and TU)

801C-2 1600hp at 900m
801D-2 1700hp at sea level (D series increased to around 1950hp shp around 1943 with C3 intake injection for emergencies)
801F*(TH)* 2400hp at sea level
801R*(TR)* 2000hp at sea level, 1950hp @ 5200m/17060ft, 1760hp @ 8600m/28220ft. Two Stage 4 speed inter-cooled engine for Ta 152C etc
801S*(TS)* 2000hp at sea level. Improved supercharger, altered SC gear ratios, straightened components.
801U*(TU) *1730hp at sea level but significantly improved altitude performance over the D2 as it could maintain 1710hp to 18700ft

*There are plenty of photos of Fw 190A9, their distinguishing feature is two air intakes, left and right.*

The above are the military and takeoff power ratings not the higher ratings possible with WEP.

801E appears to be a bomber analog of the 801F and was also to be capable of 2400hp with either 150kg/hour of MW0 (pure water) or 250kg/hour of MW50.

801TJ-0 Turbo-Charged Intercooled engine used on Ju 388
801TJ-1 Turbo-Charged Intercooled engine but with improved turbo charger and 801E core.


***************
Notes
1 The 801F ie 801TH was flown in the Fw 190 V34 on 9 August 1943.
2 Focke Wulf Documents of August 1943 note that *production series delivery of the 801TH* probably won't commence till May 1945.
3 Focke-Wulf BMW will supply the improved BMW801TU and 801TS in the interim. 
4* Increased emergency power (ie WEP) is not possible due to the weakness of the propeller gearbox
*
In regards to the 801E (bomber engine) which can be regarded as having the same issues in reaching 2400hp (2600hp WEP) AS THE 801F (fighter engine)

1 Gearbox not strong enough to handle increased power
2 Con rods not strong enough to handle increased power
3 Drive Shaft not strong enough to handle bigger propeller to handle increased power.
4 Electrical motor for pitch change mechanism needs more power to handle bigger and greater number of blades.

Id say the 801F and 801E were complete redesigns with stronger gearbox, con rods, stronger pistons, precision vacuum caste heads and likely bigger bearings. It sounds like everything needed strengthening and everything was "new production". I can't see the Fw 190A8 propeller absorbing 2600hp

Also noteworthy in the Ju388/Vernalen/Handig book is that production of the Jumo 213EB was beginning as production of modified inlet guide vanes for the Jumo 213EB had been made. The new vanes solved a surge problem at altitude.

BMW gave the Junker Ju 388 program priority for new stronger connecting rods. This means the Fw 190A would have lower priority, an indication the Fw 190A was being phased out.

Its clear the future for the Fw 190 lay with liquid cooled engines, they were already producing more power.

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## Koopernic (Nov 29, 2017)

tomo pauk said:


> I'd kindly ask for sources for the statements quoted.



See my response to Deniss. The BMW801F(TH) was flown in the Fw 190V34 as early as Aug 1943.

The 801F can be regarded as analogous to the R-2800-57 which had a power rating of 1hp per cubic inch and was in essence completely engineered.

There was nothing wrong with the 801F, the Germans just couldn't set up production at that stage of the war, just a few of the more important components were transfered into the TS and TU


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## Shortround6 (Nov 29, 2017)

The 2800hp R-2800 engine _installation_ was far from trouble free in service at the 2800hp rating. Apparently the pressure inside the ducts (both exhaust and intake) was more than the duct work could really handle and the ducts needed constant attention (almost every time WEP was used?) to keep "air tight". 
Little mention is made of the need to actually work on the engine and the basic power section was rated at 2400hp with water injection (56in MAP) using a single stage supercharger in commercial service by 1946. 

Even more than the BMW 801 the "C" series R-2800 was ALL NEW, with no parts shared with the older engines. 

Nobody else really got an *air-cooled aircraft *engine up to 1 hp per cubic in in the 1940s. A few may have made claims/advertised in the 1950s but I am not sure they actually panned out. For instance "Aircraft Engines of the World 1956" lists a Hercules 811 engine at 2250hp at 3,000ft wet but Lumsden doesn't list any 800 series engines. Likewise a Centaurus 373 is listed at 3220hp (3270 cu in) but Lumsden doesn't list any 300 series Centaurus engines.

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## tomo pauk (Nov 29, 2017)

Koopernic said:


> See my response to Deniss. The BMW801F(TH) was flown in the Fw 190V34 as early as Aug 1943.
> 
> The 801F can be regarded as analogous to the R-2800-57 which had a power rating of 1hp per cubic inch and was in essence completely engineered.
> 
> There was nothing wrong with the 801F, the Germans just couldn't set up production at that stage of the war, just a few of the more important components were transfered into the TS and TU



There seem to be a problem in nomenclature - the power-egg based on the BMW 801E engine was supposed to be called 801TH and TG (that one was with flame dampers), per 'Flugmotoren und Strahltriebwerke' by von Ghersdorff et al. Several chapters of that book are actually transcribbed in Russian language here, google translation is here. (with a grain of salt, some things will not add up due to 3 translations)
Most of the schematics are also taken from that book, the drawings of the BMW 800 line are interesting.

That book does list that 801E passed serveral 100 hr endurance runs at the test bench during July and Augus 1942, up to 2300 PS was achieved during the tests. Since the 801E required too much of chage in production tooling, it never went in mass production stage, some parts of it (heads, supercharger & inlet) were added to the 801D engine to create 801S.
The 801F was also to incorporate external, but streamlined intakes, new crankcase, valves, crankshaft with vibration dampers, increased S/C drive ratio, improver 'internal and external aerodynamics' - almost a new engine. BTW, the R-2800-57 was with turbo.
801F was discussed for the Ta-152, the engine was to be 'pushed' forward by 250mm to cancel out the CoG chages due to switch from the long V12 engine to the short radial. Power egg based on the 801F was to be called 801TF.

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## Peter Gunn (Nov 29, 2017)

Shortround6 said:


> Also please note that the sleeve rises several inches above the the "head" surface. The ports, when closed are above the combustion chamber.




I don't think there are enough moving parts in this design...

Holy Cow! Did a watchmaker design this thing?


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## BiffF15 (Nov 29, 2017)

Peter Gunn said:


> I don't think there are enough moving parts in this design...
> 
> Holy Cow! Did a watchmaker design this thing?




Concur!

Does anyone know if there are less moving parts to this set up than the "standard" valve layout? Also, it seems to have a weakness if hit in the "watch" mechanism it could take out the entire motor (sort of like liquid cooled engines and their ever so required liquid coolant).

Cheers,
Biff

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## Koopernic (Nov 29, 2017)

Vernaleken/Handig in their massive Ju 388 book recall minutes from a meetings between Junkers and BMW on the BMW 801TJ-0 and the BMW801TJ-1. The meeting was held in 20 October 1944 where they anticipate production in January/February 1945 and they thought they could achieve a functioning installation at 2400hp with C3 fuel plus Water Injection and then achieve this in series engines with B4 Water Injection. It may have been ambitious but they were already at 2200hp.

The BMW engines within the 801TJ maintained their mechanical superchargers underneethn the turbo chargers.

Most of the problems uncovered during testing were pedestrian. Blocked or burst oil lines as a result of poor manufacturing, cracks in poor castings in the fan. New high altitude spark plugs from Siemens were required to resolve a problem that BMW was forced to admit had already occurred on the 801D2. Production problems meant they had to make do with a propeller that was inefficient due to tips going supersonic. They wanted a 6 bladed propeller.

2600hp was a special emergency power target of the 801F ie special (water injection). 

The Simulations Junkers and BMW conducted indicated they could get 2400hp WEP for 15 minutes at sea level and 30 minutes at high altitude. There would be a marginal overstep of the cylinder temperature by 13C during climb at combat/military power also requiring MW50. They abandoned the ignition advance used in the 801TS and this helped keep the cylinders cooler.

So even though 2600 was not an immediate target 2400hp looked likely in a series engine even if it was the turbocharged version. By Feb 1945, the scheduled manufacturing date, Germany was split in two by the advancing enemies so it wasn't a situation conducive to logistics for a highly modified engine.

BMW's single seat fighter market for its radial was likely to disappear, the Jumo 213 and DB603 offered less drag, more power and had developed two stage superchargers and inter-coolers.

So if the 801E (within the 801TJ-1) could achieve 2400hp it so could the 801F and from 2400hp to 2600hp there is a smaller step. The 801TJ-1 never flew but it did run in an altitude test chamber and the slightly 701TJ-0 did fly

The bottleneck to increasing Jumo 213E power to 2500hp turned out to be the surprisingly low coolant flow of 9.5L/sec and too small radiators.


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## pbehn (Nov 29, 2017)

Peter Gunn said:


> I don't think there are enough moving parts in this design...
> 
> Holy Cow! Did a watchmaker design this thing?


The theory is that they are moving but not reciprocating like a valve against a spring, howver I would say the friction between the surfaces, even with oil lubrication probably means very little gain.

_View: https://www.youtube.com/watch?v=lfS7XJZR2Ok

bristol photo centaurus engine - Google Search:
_


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## tomo pauk (Nov 29, 2017)

Koopernic said:


> Vernaleken/Handig in their massive Ju 388 book recall minutes from a meetings between Junkers and BMW on the BMW 801TJ-0 and the BMW801TJ-1. The meeting was held in 20 October 1944 where they anticipate production in January/February 1945 and they thought they could achieve a functioning installation at 2400hp with C3 fuel plus Water Injection and then achieve this in series engines with B4 Water Injection. It may have been ambitious but they were already at 2200hp.
> 
> The BMW engines within the 801TJ maintained their mechanical superchargers underneethn the turbo chargers.



US turboed engines engines also retained gear-driven superchargers.
The feature I like at German and Japanese turbo engines, admitedly there was just a small number produced of them, was that they also retained 2-speed gear change. That was a feature that enabled the 801J to acheive more than 1250 PS at 11800 m (rated altitude for 2nd gear; 1200 PS at 12000 m) at just 2400 rpm, while with just 1st speed engaged in the engine stage S/C it would've make just ~800 PS there. The BMW 801E-based turbo engine was supposed to make almost 1400 PS at 12000 m at 2500 rpm. Obviously, at 2700 both engines will make significantly more. Allied post-war data gives 1500 PS at 40000 ft for the 800(T)J.
Another feature is the use of hollow turbine blades, that saves plenty on size of fuselage, meaning also other 'knock-on' effects/benefits. The problem with all of this stuff is that it came too late to matter.
The 1st US service engine with hollow-bladed turbine was the R-1830 installed on the Curtiss SC Seahawk. Unfortunately, today there is no surviving aircraft of that type.

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## Denniss (Nov 29, 2017)

801 TJ isn't an engine but a Triebwerksanlage with the turbocharged 801 J
the 801Q-2 in the Triebwerksanlage TU did no have a vastly improved supercharger but it may have achieved that power with C3 injection. It had a slight better take-off power than (early?) 801 D-2 (~20-30PS)
Most of the power ratings in the book are actually wrong due to the 1:1 PS/hp conversion
801 S power ratings are wrong because this is pure engine power without reduction for fan, 11/44 data from BMW has it at 2000/1930 PS with 1.65 ata.
The 11/44 BMW data has the 801F-1 at 2000/1940 PS with 1.65 ata
Both 801S/F were to achieve higher power ratings with more boost in 1945, the 801F probably with more rpm too. 801S was supposed to go to 2200PS (-fan)

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## ChrisMcD (Nov 29, 2017)

fastmongrel said:


> The reason for the Bristol sleeve valve engines diameter being bigger than expected originally was that the Junk Head needed a lot of extra finning as power increased.
> View attachment 473777
> 
> 
> You can see the depth of the Junk Head from the above wikipedia picture. From the Junk Head sealing rings to the top of the fins is about the same as a normal push rod and poppet valve system from head gasket to rocker cover.



Roy Fedden really did try and do it the hard way with an air-cooled sleeve valve. 

Whatever it's other faults the liquid-cooled Sabre did not have major cooling problems.

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## ChrisMcD (Nov 29, 2017)

fastmongrel said:


> The 14N was a very light engine compared to other 14 cyl radials, the postwar Snecma R developments gained a lot of weight and got a little bit bigger in diameter.



According to Herschel Smith the 14M was the most compact, powerful radial ever made.

But I have a feeling that it was a bit too compact - it's war record was nothing special and it did not have a great reputation for reliability


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## fastmongrel (Nov 29, 2017)

ChrisMcD said:


> Roy Fedden really did try and do it the hard way with an air-cooled sleeve valve.
> 
> Whatever it's other faults the liquid-cooled Sabre did not have major cooling problems.



In the 1920s and 30s the sleeve valve looked to be the technology of the future to many experts. Problem for Fedden was the goalposts kept moving with things like Sodium cooled exhaust valves, anti friction coatings like Stellite, better spark plugs and oils eroding the theoretical advantage of the sleeve valve.

Bristols poppet valve engines were good, light and reliable but lacking in raw power. A 14 cylinder twin row radial with Mercury size cylinders might have been a cheaper quicker route to Hercules type power. A 18 cylinder twin row with Pegasus size cylinders could have been a good heavy bomber engine.


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## fastmongrel (Nov 29, 2017)

ChrisMcD said:


> According to Herschel Smith the 14M was the most compact, powerful radial ever made.



Powerful ? I dont think so unless you are comparing power to weight

Compact ? I think some of the Japanese radials of similar power made the GR engine look huge


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## tomo pauk (Nov 29, 2017)

G&R 14M was light and small, 410 kg and 950 mm diameter. 14N was bigger brother - 590-630 kg, 1280 mm diameter.

Re. sleeve valve engines, the RR Eagle 46 (IIRC that meant 4 banks of 6 cylinders) was making 3500 HP from 2800 cu in, in service trim.


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## KiwiBiggles (Nov 29, 2017)

tomo pauk said:


> G&R 14M was light and small, 410 kg and 950 mm diameter. 14N was bigger brother - 590-630 kg, 1280 mm diameter.
> 
> Re. sleeve valve engines, the RR Eagle 46 (IIRC that meant 4 banks of 6 cylinders) was making 3500 HP from 2800 cu in, in service trim.


RR Eagle = yet another copy of a Sabre.


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## Zipper730 (Nov 29, 2017)

ChrisMcD said:


> Hope I got the right "quoter"!


You did


> The obvious choice was the Napier Sabre, but it was considered too different in technology for anyone to be really keen.


The sleeve-valve reason was too different?


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## Juha2 (Nov 29, 2017)

Koopernic said:


> ... By Feb 1945, the scheduled manufacturing date, Germany was split in two by the advancing enemies so it wasn't a situation conducive to logistics for a highly modified engine....



In fact Germany wasn't split in two by advancing enemis by Feb. 1945, the Soviet operation from Oder began on 16 April 1945 and even the Western Allies attack from Rhein had begun not until 22 March. München area, where the main BMW factories lay was occupied in late April 1945.


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## Zipper730 (Nov 29, 2017)

pbehn said:


> Zipper, I love some of your posts, have you considered patenting the flying cube?


No, I don't think it'd fly too good.



Shortround6 said:


> I really have no idea what you are talking about here.


I was talking about power to weight ratios, and also structural strength to weight.

A good example would be the following

An ant can lift 100 times its weight, and a flee can jump with the force of 50g (50 times its weight).: Nonetheless the amount of force the ant can lift is fairly little and the force a flee can produce during a jump is tiny compared to a human being.
There was a female figure skater who was 92 pounds and could squat over 200; there was a power-clean record (male) that was around 2.7 times his weight. Either figures are much heavier than an ant or flee can produce, but are proportionately only 2.17 to 2.7 times their respective weights
There are power-lifters who can lift more than the light human being, but it's a smaller proportion.
Understand?


> I could be mistaken but Fuel fraction has very little to do performance _except _for range.


As a general rule that's right: However provided the following criteria are met

At least two aircraft are involved, and for the sake of the argument: There will be two aircraft
Both aircraft have the same armament: Say 4 x 20mm with 150 rpg
Both aircraft have the same weight when armed, full fuel and oil: For some reason, I'll pick 10,000 pounds
Both designs have the same wing-area (310 ft^2), same aspect ratio (6), same L/D ratio (13.5%)
Both designs have the exact same horsepower engine (1875 hp) same critical altitude (24000 feet with ram)
Design A has a fuel fraction of 11.1% (185 gallons) and Design-B has a fuel fraction of 16.68% (278 gallons)
Both aircraft are stressed for a g-load of 9g ultimate when fully loaded at takeoff.
The following will be the case: 

Aircraft 1 & 2 will perform exactly the same when on 100% internal fuel
Aircraft 2 will have a longer range providing the same basic cruise settings, and combat settings & limits will be used even if both use drop-tanks of the same size and capacity.
Aircraft 1 & 2's performance will more radically diverge as fuel load goes from 100% to 80%, and from 80% to 50% as the different percentages of fuel will correspond to a different amount of fuel relative to the plane's weight: At 100% weight, Aircraft & 2 have no difference; at 80% weight, Aircraft 2 will weigh 98.85% the weight of Aircraft 1; at 50%, is 97% the weight of Aircraft 1.
Aircraft 1 & 2's power-loading, maximum g-load capability, and corner velocities will all more radically diverge.



> Please note that every plane built in the 1930s and early 40s had unused volume somewhere in the structure. The engines simply weren't powerful enough to allow all the "space" to be filled up.


Of course


> The B-17 started as the Boeing 299 in 1934 and the first one used P & W Hornet (R-1690) engines rated at 750hp at 7000ft and 850-875hp for take-off. Empty weight was 21,657 pounds max loaded was 38,053 pounds. While they changed the rear fuselage/tail the wing stayed the same shape and area. The last of the B-17Gs weighed 32,720 pounds empty and 72,000 pounds maximum although even 65,000lbs called for restricted take-offs and very restricted maneuvers when flying. Obviously they filled up some of the empty volume over the years but trying to fly 65,000lb bombers with 800 hp engine wasn't going to get very far.


But horsepower went up considerably in that time...


> See XB-15 or Boeing model *294 *for what it took for a long range bomber with small engines. The Boeing 299/B-17 was Boeing's 2nd shot at a 4 engine bomber.


Honestly, I'm surprised they never thought of fitting the R-2600 to it.


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## Koopernic (Nov 30, 2017)

Denniss said:


> 801 TJ isn't an engine but a Triebwerksanlage with the turbocharged 801 J
> the 801Q-2 in the Triebwerksanlage TU did no have a vastly improved supercharger but it may have achieved that power with C3 injection. It had a slight better take-off power than (early?) 801 D-2 (~20-30PS)
> Most of the power ratings in the book are actually wrong due to the 1:1 PS/hp conversion
> 801 S power ratings are wrong because this is pure engine power without reduction for fan, 11/44 data from BMW has it at 2000/1930 PS with 1.65 ata.
> ...




Could you provide a "table" of core engine versus the "power egg" they were used on with a note on the nature of the engine as well as the sources you have used? This whole area is very confusing with a lot of contradictory data out theremand you seem to have sources.

Vernaleken & Handig clearly refer to the core engine within the BMW 801-TJ-1 as the 801E. It may be that 801J is a German Air Ministry designation.

I don't imagine that the book in its orginal German had a problem with the 1.6% error between Imperial and Continental Horse power.

The deduction of fan power is essential from the point of view of propellor calculations, however in comparison with other engines I don't think it needs to be accounted for because
1 Normal Propeller wastes power and thrust with blade area and cuffs of the roots being used to blow air on the engine as well.
2 The fan is producing some thrust. It doesn't just allow a more streamlined cowling, it is removing air from the front of the aircraft so that this air never has to pass over the air-frame. The air is then heated in the engine and likely ejected at higher velocity than it entered thus providing some modest thrust.
3 Its possible that at high speed the fan is wind milling rather than absorbing power.

Also what is the nature of the 801TU power egg, the power of 1730hp at 5700m (19000ft) that Smith and Creek quote is extremely good.

I had thought this might be a GM-1 rating. But this power level would be possible I think on a single stage supercharger. Air density at 5700m/19000ft is about 0.55 of sea level. If the 801D2 achieved 1710hp at 1.42 ata at sea level then the 801TU would need to achieve about 1.65 ata at 19000ft to provide 1730hp at the shaft since additional power (about 100kW) is required to drive the super charger and account for the slightly hotter air. This requires a pressure ratio of 3:1 and an ability to compress about 1000L of air per second.


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## Denniss (Nov 30, 2017)

801A engine = 801MA (Motorenanlage)
801L engine = 801ML (Motorenanlage)
801D-2 or G-2 (not sure on this) = 801MG (Motorenanlage) = 801TC (Triebwerksanlage)
801TZ was also used for early/testbed Ju 188E, containing 801MA/ML engines
first 2 from 801 engine manual, latter two from Ju 188E Triebwersanlage

801Q = 801TU
801F = 801TH
801S = 801TS

the deduction for fan is always done by BMW and is the difference between Motorleistung (engine power) and Triebwerksleistung (shaft power, power delivered to prop)
data from BMW charts/graphs of 11/44 - may alo be available here in Technical section

The 801TU was supposed to replace the 801D-2 in the Fw 190A by ~7/44 and be equipped with erhöhte Notleistung system (1.58 ata at first SC gear, 1.65 ata in second gear). Fw 190 A-8 was ~30 kg heavier with TU engine due to oil system armor increase.

WWII Aircraft Performance has some additional docs with further confusing info, having both 801F/TH and 801F/TS.
It's possible the 801F project was split into smaller changes to become the 801S and larger changes to stay as 801F.

And yes, the Motoren-/Triebwerksanlage designations are confusing and terribly documented or docs not available/lost. Some designations of experimental engines may have been re-used, adding further confusion.
Ju 388 data points to 801J = TJ combination

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## tomo pauk (Nov 30, 2017)

Pictures taken from the 'Motoren und Strahltriebwerke' book. The 801R was supposed to be outfitted with 2-stage, 4-speed S/C. The 801Q was, IMO, close sibling to the 801E. 801J is noted as 801D-2 with turbocharger.
The graph notes that 801E was to be core for the P. 8035 engine project. Please note the gear speed change at 8.5 km for the 801J, the turbo engine. 
'Luftschraubenwelle + Luefter' = 'prop shaft + fan'.

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## Koopernic (Nov 30, 2017)

ChrisMcD said:


> Roy Fedden really did try and do it the hard way with an air-cooled sleeve valve.
> 
> Whatever it's other faults the liquid-cooled Sabre did not have major cooling problems.



Fedden was related to Ricardo by blood and they discused the issue which is one reason Fedden had Bristol go that way. My understanding is that Fedden was eased out of Bristol by 1943 over conflicts with the family that owned Bristol.

I don't think there was anything wrong with the Sabre by the time the Tempest entered service. Napiers quality control and poor manufacturing had been the cause of half the problems rather than the design. I believe it did end the war as the worlds fastest piston engines fighter at low altitude. It went the way of the P-51H, P-47N etc.

Bristol Poppet valve engines were pretty good. Siemens-Bramo which was merged into BMW turned Feddens 1918 developed Juiper into a 1200hp machine, the Bramo 323 *Displacement:* 26.82 litres (1,636.8 in³) that powered the Fw 200 Condor.

A straight H block engine with poppet valves may have done much better.


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## fastmongrel (Nov 30, 2017)

Koopernic said:


> A straight H block engine with poppet valves may have done much better.



I believe with big capacity poppet valve H engines you would run into problems with the inlet and exhaust passages being too cramped for good breathing.

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## Shortround6 (Nov 30, 2017)

Zipper730 said:


> As a general rule that's right: However provided the following criteria are met
> 
> At least two aircraft are involved, and for the sake of the argument: There will be two aircraft
> Both aircraft have the same armament: Say 4 x 20mm with 150 rpg
> ...




Diverging by single digit percents, especially very low single digits makes very little difference in some aspects aircraft performance. You could vary the weight of a clean Mustang for example by hundreds of pounds (source claims 1000) and only vary the top speed at altitude by 3mph. Difference between a good paint job and a poor one is more than that. A change of 3% in wing loading while turning would be undetectable to a pilot while flying. You would need a very accurate recording "G" meter to find the difference. 
I would note that in tests of a Hawker Hurricane adding 434lbs internally to it's 6316lb weight (6.9%) slowed it down from 316mph to 309mph at 20,000ft. Unfortunately they had to change the engine between tests on the same airframe so it's not 100% accurate.

Probably in climb you could tell the difference but probably not at any reasonable fighting altitude.

The wings, fuselage and tail of a P-51B/C went around 2000lbs. doesn't include landing gear or fuel tanks. 



> But horsepower went up considerably in that time....


It did but they still weren't using all the volume. ANd there were a number of restrictions on how the plane was to be loaded,flown and even taxied at those high weights. A biggie was that at high weights you HAD to fill the outer wing tanks (they didn't exist on the early planes) to spread out the span loading, you couldn't fill the bombbay with AP bombs, hang a pair of 4000lbs under the plane and just fill the inner wing tanks, you had a good chance of bending/breaking the wing even if the gross weights were the same. 



> Honestly, I'm surprised they never thought of fitting the R-2600 to it.



If you are referring to the B-15 I am sure some bright spark thought of it. It just wasn't worth the effort. There was only one plane, they were never going to build anymore. They had learned a lot about structural design and aerodynamics in the meantime. 
Look at the B-19, took so long to build (Douglas didn't even want to finish it) that it was obsolete on the day it first flew. Army wanted it for analyzing/evaluating structural design. Not because they thought it was a viable warplane.


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## Koopernic (Nov 30, 2017)

Tye


tomo pauk said:


> Pictures taken from the 'Motoren und Strahltriebwerke' book. The 801R was supposed to be outfitted with 2-stage, 4-speed S/C. The 801Q was, IMO, close sibling to the 801E. 801J is noted as 801D-2 with turbocharger.
> The graph notes that 801E was to be core for the P. 8035 engine project. Please note the gear speed change at 8.5 km for the 801J, the turbo engine.
> 'Luftschraubenwelle + Luefter' = 'prop shaft + fan'.
> 
> ...



The Data quoted in Gersdorf looks like R+D data. Almost all of those engines look like minor variations of the
BMW801D except for the BMW 801E or F, the others were changes in the superchargers, accessories, propeller or gearbox.

The BMW801R had a 2 stage supercharger with 4 speeds. In fact each stage had independent drive so it was more like a 2 x 2 speed supercharger.
It also had a massive integral inter cooler. It was actually a little longer than the Jumo 213 and DB603 engine without their radiator.

The BMW factory testing and developing the 801R was bombed and the damage set back the project so far it could not be recovered in a sensible time.

It was intended for a version of the Ta 152C and obviously could have incorporated 801F technology to work its way to 2400/2600hp but its key characteristic was its high power at high altitude. It could maintain sea level power to 5200m/17,060 and 1760hp to 8600m/28220ft.

Noteworthy the length of these units
801D and 801S = 2006mm
801F = 2256mm
801R = 2550mm

So what was the F doing with the extra 250mm length? I have read on other forums that it was supposed to have a 3 speed supercharger? Could they have introduced a moderate amount of inter-cooling.

To achieve 2400hp or 2600hp requires 2.0 ata so this engine would have substantial jet thrust. It would also do well with good supercharger matching.

For fun Ive attached the airflow paths of the BMW 801TJ

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## Koopernic (Nov 30, 2017)

fastmongrel said:


> I believe with big capacity poppet valve H engines you would run into problems with the inlet and exhaust passages being too cramped for good breathing.



The Fairy Monarch was a H block engine. One problem was that the intake passages had been cast into the block making it difficult to improve its performance without changing castings. I don't know if this was a critical thing but it did restrict its development.

Argus made a H Block called the AS412 and there was an AS413 H24 project that used Jumo 213 pistons. Don't know how they planed to get around the problem of cramped gas flow passages.

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## fastmongrel (Nov 30, 2017)

Koopernic said:


> Don't know how they planed to get around the problem of cramped gas flow passages.



Possibly run a higher boost and a lot more valve overlap than a V or X of the same size would need.

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## Koopernic (Nov 30, 2017)

BiffF15 said:


> Concur!
> 
> Does anyone know if there are less moving parts to this set up than the "standard" valve layout? Also, it seems to have a weakness if hit in the "watch" mechanism it could take out the entire motor (sort of like liquid cooled engines and their ever so required liquid coolant).
> 
> ...



There is a cutaway
https://www.youtube.com/watch?v=EyPvpdy4dggt away of a R-2800 working on this you tube video. If you go to 1.30 you can see the cam pushrod mechanism working.

I'd suspect the Sleeve Valve radials valve drive mechanism would be deeply buried behind the gearbox and parts of the crankcase thereby being heavily protected.

Some WW2 aircraft had cutoff valves to isolate a leaking coolant flow to a radiator, I imagine it would be more useful in a twin radiator design but as the oil cooler was still keeping the the temperature down it might be quite useful to have coolant flow without a radiator just to even out heat in the engine.

Isolation valves were fitted to the Me 109F and Me 109K but skipped most of the Me 109G series, they were well regarded and maintenance crews would race to crash sites to recover the precious valves before salvage crews or even other maintenance teams could get there.

It wouldn’t be too hard to make a coolant flow 'fuse'. You would have two flow meters: one measuring outward flow of coolant and ther other the return flow. If there was a major difference the radiator could be bypassed. Several ways of doing it. A simple orifice plate that produces a pressure differential or maybe a vane type flow meter that was subtracted by a differential gear mechanism.

I don't know how coolant loss was detected. It apparently looked white (steam?)

I would have thought a good 'limp home mode' would have simply blocked of fuel to one bank of cylinders for a few seconds alternately so that it cooled. The engine would be running at 50% power but it would get the pilot home.

Coolant flow on a Jumo 213E was 9.5L/second so on a Merlin there must be about 2 US gallons coolant flow per second. That's why I suggested an coolant leak fuse, one would have to react quickly.

The problem with water cooled engines is that a single bullet could end the mission. Not so bad over your own country because you could get back to base. The engines didn't stop straight away.

Russian and German troops didn't dive for cover when aircraft came, they started shooting. The smaller 10-12 man squads the Germans were organised into at the end of the war could probably get 8 rifles firing of which 2 might be semiautomatic Gw 43. The Machine gunner might get his MG42 into operation if he had a stand for it. The Corporal, NCO or Sargent that ran things would have had a sub machine gun.

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## Shortround6 (Nov 30, 2017)

Simply space the cylinder blocks a decent width apart.














more photos and story/data here: Arsenal 24H and 24H Tandem Aircraft Engines

engine went about 4000lbs so you need a good sized plane to carry it

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## Shortround6 (Nov 30, 2017)

There is another thread here that I don't want to look for at the moment is which I took 3-4 posts to cover all the supposed advantages for the sleeve valve engine as listed by Roy Fedden in a talk given in England.
Not trying to take away anything from Fedden but he was comparing his sleeve valve engines to his own poppet valve engines which were 10-20 years older in basic design. He was NOT comparing his sleeve valve engines to P &W or Wright radial engines. Maybe he didn't consider the upstart Americans to be competition?
For instance he claimed the Sleeve valve was more oil tight and didn't leak as much oil into the engine compartment or onto the airplane. I am not claiming the American engines were oil tight but the Bristol poppet valve radial's valve gear was lubricated by grease gun and the valve springs, rockers and pivots were all flapping around in the breeze. NOT enclosed.
Photos were published of all the parts needed for ONE cylinder of both types of engine. Of course Bristol poppet valve cylinders used four valves so there are a lot more parts than a 2 valve cylinder would show. The photo also doesn't show all the gears in the crankcase vs the gears and cam ring/s needed for a single row radial.




The Mercury and Pegasus didn't get a whole lot of development during the 30s as most of the R&D was going into the sleeve valve engines.

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## Koopernic (Nov 30, 2017)

Shortround6 said:


> Simply space the cylinder blocks a decent width apart.
> View attachment 474135
> 
> View attachment 474136
> ...



The dimensions of the Sabre according to Wikipedia were

*Width:* 40 in (1,016 mm)
*Height:* 46 in (1,168 mm)
The dimensions of the Arsenal H24 were
3.94 ft (1.20 m) wide, 4.92 ft (1.50 m) tall,


*Width:* 47.5 in (1.2m)
*Height:* 59 in (1,5m)
The Sabre had 1/2 the swept volume so taking the cube root to scale the engine to the size of the Sabre


*Width:* 1.067m
*Height:* 1.144m
The dimensions are almost exactly the same though the Sabre is horizontal and the Arsenal H24 vertical.

The Sabre's pistons are over square whereas the Arsenal H24 like the Jumo 213 it was based on under-square. The horizontal arrangment should have some advantages in increasing RPM.

The Arsenal H24 like the Jumo 213 it was based on ran at 3250 rpm. The Jumo 213J was supposed to reach 3700 RPM. It was on the bench in Jan 1945 so the Arsenal H24 could probably have been pushed to 3700RPM and its boost level from 1.7 bar to 2.0 bar as Jumo were doing this.


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## Peter Gunn (Nov 30, 2017)

pbehn said:


> The theory is that they are moving but not reciprocating like a valve against a spring, *howver I would say the friction between the surfaces, even with oil lubrication probably means very little gain.*



Watched a couple more videos and I agree, there's a lot of metal on metal friction there.


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## pbehn (Nov 30, 2017)

Peter Gunn said:


> Watched a couple more videos and I agree, there's a lot of metal on metal friction there.


There is a motorised cutaway at the Yorkshire Air museum, it makes your brain hurt watching it. Since it runs very slowly but dry you can see the effect of the constant movement, nothing is able to "bed in" against anything else, and the scoring is visible.. Also for a brief period the block machined surface is exposed to the exhaust gas through the sleeve port, this must have seriously roasted the oil.

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## Juha2 (Nov 30, 2017)

Koopernic said:


> ...Russian and German troops didn't dive for cover when aircraft came, they started shooting. The smaller 10-12 man squads the Germans were organised into could probably get 8 rifles firing of which 2 might be semiautomatic Gw 43. The Machine gunner might get his MG42 into operation if he had a stand for it. The NCO or Sargent that ran things would have had a sub machine gun...



I doubt that, I would say sometimes they fired back but usually they took cover, based on Allied gun camera films and by the fact that He 111s attacked Soviet troops with their nose mg even during winter 41/42.
When I did my military service with the Finnish Army in mid-70s, inspirated by the NVPA experiences during the Vietnam War, we were trained for anti-a/c and anti-helicopter firing but even with 7 assault-rifles and one LMG per squad it was stressed to us squad leaders never to open up against incoming planes only against those attacking your neighbours. Odds were heavily against you if you engaged incoming plane. And never disturb Mi-24 Hinds!

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## Denniss (Nov 30, 2017)

Tomo, really sad this book use improper engine power and not proper shaft power as per BMW's documentation. Several power levels are wrong as a fair comparison is only given at sea level, not max power at various alts depending on SC setup.
The 801Q description is wrong unless this was a project code later reused (as 801Q-2). FW docs clearly state the Q-2 as D-2 with the mentioned oil system/amor changes which are in the 801S too.
Per BMW/Fw docs the U = TU is wrong as it contained the Q-2 engine
The 801J had the D-2 as base engine, this is correct. The further description is wrong as it was used in the Ju 388 (as TJ-1)
The 801S had a slightly improved supercharger for better alt performance, the 801F may have gotten an even further improved one taking more space + the external air intakes, stronger fan and probably larger oil tank/cooler may have caused a length increase

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## tomo pauk (Nov 30, 2017)

The biggest quarrel I have with book is it's jet engine half - I'm not interested in those  German engines of ww2 deserve far better books of greater number of pages. Unfortunately, the book about Junkers engines is too pricy for me. Hoperfully, Calum, our member, will have his book soon in print.


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## pbehn (Nov 30, 2017)

Shortround6 said:


> There is another thread here that I don't want to look for at the moment is which I took 3-4 posts to cover all the supposed advantages for the sleeve valve engine as listed by Roy Fedden in a talk given in England.
> *Not trying to take away anything from Fedden but he was comparing his sleeve valve engines to his own poppet valve engines which were 10-20 years older in basic design. He was NOT comparing his sleeve valve engines to P &W or Wright radial engines. Maybe he didn't consider the upstart Americans to be competition?
> For instance he claimed the Sleeve valve was more oil tight and didn't leak as much oil into the engine compartment or onto the airplane. I am not claiming the American engines were oil tight but the Bristol poppet valve radial's valve gear was lubricated by grease gun and the valve springs, rockers and pivots were all flapping around in the breeze. NOT enclosed.
> Photos were published of all the parts needed for ONE cylinder of both types of engine. Of course Bristol poppet valve cylinders used four valves so there are a lot more parts than a 2 valve cylinder would show. The photo also doesn't show all the gears in the crankcase vs the gears and cam ring/s needed for a single row radial.*
> ...



In my working life I met some very highly qualified and experienced people. On their professional subject they were masters of the subject. One man in particular was fundamental in getting his company as one of the world leaders in two products. If you asked him any question on metallurgy he would give you an answer but if the answer affected how his product was viewed he would omit, evade and at times tell outrageous lies, and he was not alone. Some of these lies were not only put in writing they were actually put in the company publicity brochure and prospectus.

When it comes to engines, when I was racing, all the tuners were completely disparaging about all the other tuners efforts. Some would allege cheating (over bored cylinders, bored out carbs, doped fuels etc). but only for favoured riders inmplying that other tuners were not selling what they advertised, on the other side there were dark mutterings about pistons collapsing. As a racer using one tuner racing against guys using all the others it was complete borrocks, there was only one guy I knew who cheated with a 350cc engine in the 250cc class. The man who won the national championship, that year in my class (Mick Crick) had a bike slower than mine and most other competitors, the rider makes the difference.

In the early 1980s there was a guy called Joe Ehrlich who was famous for engine tuning, he had some success in the 1950s and made a "come back" winning some races with his machines like the Junior TT. He was interviewed as Heddon was, and he declared that he was working on a new engine, a variation on the stepped piston which was so revolutionary it would make normal two strokes obsolete. He was so persuasive I you could imagine people buying one off the drawing board. The engine and the bike never materialised and probably never existed.

I cant say that Heddon was being dismissive of upstart Americans or not but to me he was just being like any other corporate engineer. From what I have read about the intrigues of the USA motor and defence industries they are pretty much the same, I hold up Curtiss and its War Hawk ads as evidence.


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## tomo pauk (Nov 30, 2017)

pbehn said:


> From what I have read about the intrigues of the USA motor and defence industries they are pretty much the same, I hold up Curtiss and its War Hawk ads as evidence.



Hmm - what was so wrong about the Warhawk?


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## pbehn (Nov 30, 2017)

tomo pauk said:


> Hmm - what was so wrong about the Warhawk?


Nothing wrong with it as a plane but it was no longer the world beater they continued to say it was until production stopped.


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## Shortround6 (Nov 30, 2017)

According to some sources (which could very well be wrong) Fedden came close to bankrupting Bristol in the quest to get the sleeve valve into large scale production (both basic engine development and production engineering).
Bristol had been, at the end of the 20s *THE *premier aircraft engine maker in Britain if not the world. Bristol engines (mainly the Jupiter) had powered over 260 types of aircraft world wide (many of them prototypes to be sure) and was being produced under licence in 16 countries. With the coming of the Great Depression of 1929 world wide demand for aircraft engines fell sharply, and then Fedden took off on the sleeve valve tangent. The Mercury and Pegasus (a modernized Jupiter) did get some improvements but it seems the Sleeve Valve projects sucked up most of the research and development. 
Wright during the same time period (roughly) introduced the R-1750 in 1927 (with forged tungsten steel intake valves and hollow exhaust valves of forged tungsten-cobalt-chrome steel with metal salts inside for cooling) at 525hp. Introduced the R-1820E (0.125in larger bore) in July 1930, moved to the "F" in 1932, followed by the F50 (with a new crankshaft) and while production continued, the G series was introduced in April of 1935 with 2800 sq in of cooling fin per cylinder, automatic valve gear lubrication with no external tubes, stellite faced exhaust valves and stainless steel exhaust valve seats and more.
Jan 1937 sees the introduction of the G-100 with forged steel crankcase among other major changes and in March of 1939 the G-200 shows up with a new different forged steel crankcase. Wright continued on but that gives the idea. The Cyclone went from 525hp at 1900rpm in 1927 to 1200hp in 1939 at 2500rpm. 

There were _many_ more changes than the ones listed above. 

While Bristol may have gone through lean times in the early 30s due to the world financial situation the market had changed in mid to late 30s with Both Wright and P&W intruding on the world stage. R-1830 Twin Wasps going into commercial service at the end of 1936 and the older Hornet making enough of an impression than BMW was building them under Licence since about 1928. 
Development of the Sleeve valve engines dragged on and on and..........on. After spending so much time and money on the project could Fedde admit (even to himself?) that it _might_ have been a mistake? 
There is no doubt that the final model/series Hercules and Centaurus engines were very fine engines indeed, very long lasting and reliable while putting out competitive power. But the world wide market had disappeared.

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## pbehn (Nov 30, 2017)

Heddon may or may not have been correct we will never know, if Bristol had made the investment then who knows what would have panned out. It is a bit like the Betamax and VHS debate or early AppleMac v Windows, in both cases the most popular VHS and Windows have people saying the other product was technically superior. I remember when Honda decided to take on the two strokes in 500cc motorcycles, they produced a 4 cylinder eight valve per cylinder oval piston engine, it didn't win but earned some points in races, with enough investment almost anything can be forced to work somehow but as you say the market had gone. By the end of WW2 big poppet radials had a huge track record on American bombers and the early passenger planes were based on them, a big consideration when people board a plane.


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## Koopernic (Nov 30, 2017)

Readers interested in the friction a sleeve valve might produce might be interested in this patent which asserts that a rotating sleeve in a poppet valve engine will eliminate engine wear through friction and increase efficiency.

Note also, I believe if used in a two stroke the sleeve only requires to rotate rather than to travel in an orbiting motion. Furthermore it can uncover intake and exhaust ports bottom and top of cylinder of to ensure purging.

Patent US6289872 - Rotating sleeve engine

Rotating sleeve engine
US 6289872 B1
ABSTRACT
An internal combustion engine is provided including at least one cylinder having a conventional valvetrain. The valvetrain consists of at least one camshaft, at least one intake poppet valve per cylinder activated by the camshaft and at least one exhaust valve per cylinder activated by the camshaft as well. Rotably disposed within the engine block is a rotatable cylinder liner which is supported from the block with at least two journal bearings. A piston is mounted in each liner for reciprocating movement therein. A connecting rod connects each piston to a crankshaft converting the reciprocating motion to crank rotation. The sleeve rotates with the objective of improving the lubrication conditions of the piston rings and piston. The reduction in friction coefficient between the piston rings and liner at certain portions of the cycle will result in significant frictional benefits. The motion of the liner will result in continuous fluid lubrication which results in severe reduction of piston ring and liner wear.

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## Zipper730 (Dec 1, 2017)

Post #203


Shortround6 said:


> Diverging by single digit percents, especially very low single digits makes very little difference in some aspects aircraft performance.


True enough, but I was just trying to make a point, and explain what I was trying to say.


> You could vary the weight of a clean Mustang for example by hundreds of pounds (source claims 1000) and only vary the top speed at altitude by 3mph.


Didn't know that, but I'm surprised it'd be so little...


> Difference between a good paint job and a poor one is more than that.


I could believe that, after all the whole premise of laminar flow was reducing drag through smooth airflow over the skin...


> It did but they still weren't using all the volume. ANd there were a number of restrictions on how the plane was to be loaded,flown and even taxied at those high weights. A biggie was that at high weights you HAD to fill the outer wing tanks (they didn't exist on the early planes) to spread out the span loading, you couldn't fill the bombbay with AP bombs, hang a pair of 4000lbs under the plane and just fill the inner wing tanks, you had a good chance of bending/breaking the wing even if the gross weights were the same.


Didn't know that...


> If you are referring to the B-15 I am sure some bright spark thought of it. It just wasn't worth the effort.


I'm not so sure, just as a basic estimate using the k-constant formula, bumping the horsepower up from 1000 (T/O), 850 (Normal) to 1500 (T/O) 1350 (Normal) seems to show an increase in speed to 233 mph; if one was to add a turbocharger (or a twin-stage supercharger) to the design and increase the critical altitude to 25000 feet (or 21500 feet), that seems to suggest a considerable top-speed if the weight stayed the same.


> There was only one plane, they were never going to build anymore.


Actually, if I recall the primary goal was experimentation, but they did consider potentially ordering up to 200 if I recall right.


> Look at the B-19, took so long to build (Douglas didn't even want to finish it) that it was obsolete on the day it first flew. Army wanted it for analyzing/evaluating structural design. Not because they thought it was a viable warplane.


Seems quite a strange reason to build a plane, but who knows, maybe something good came out of it.


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## Shortround6 (Dec 3, 2017)

Zipper730 said:


> Post #203
> True enough, but I was just trying to make a point, and explain what I was trying to say.


you can find all kinds of interesting, but somewhat useless statistics, like the output of an engine per square inch of valve area. Interesting to a designer bu of no practical value to the users. Fuel fraction is somewhat the same, It may show how clever the designer was but doesn't actually tell you anything about the actual performance of the aircraft as too many other things are different. 



> I could believe that, after all the whole premise of laminar flow was reducing drag through smooth airflow over the skin...


You could find differences of 5-10mph due to paint (or higher)on non laminar (so called) flow aircraft 



> I'm not so sure, just as a basic estimate using the k-constant formula, bumping the horsepower up from 1000 (T/O), 850 (Normal) to 1500 (T/O) 1350 (Normal) seems to show an increase in speed to 233 mph; if one was to add a turbocharger (or a twin-stage supercharger) to the design and increase the critical altitude to 25000 feet (or 21500 feet), that seems to suggest a considerable top-speed if the weight stayed the same.



Trouble is the weight either won't stay the same or the difference in power plant weight comes out of the payload. AN R-2600 is roughly 500lbs heavier than an R-1830 so four of them add a ton to the empty weight of the aircraft, and this is without the larger, heavier propellers and any trick superchargers. BTW before the war P &W had the patents on two stage supercharging so Wright would be starting from scratch to to try to get around them. For some reason the R-2600 never took to turbo charging very well, the R-1820 did pretty well in the B-17s but the R-3350 (used R-2600 cylinders) had a multitude of problems, but this is all well after the decision or not proceed with the XB-15 was made. If the Army decided to go with B-18s instead of B-17s because of price the chances of large scale (even by 1930s standards) of the B-15 was basically non-existent. 




> Seems quite a strange reason to build a plane, but who knows, maybe something good came out of it.



In the 1930s and 40s IF the Army (or Navy) paid for a design study or prototype aircraft then the Army or Navy became not only the owner of the aircraft but the owner of the data used to design and build the aircraft and was free to share such data with whatever companies and agencies they saw fit to share with. How much of the design data the Army got from the B-19 was shared with Boeing, Consolidated, Martin, Lockheed and others I don't know but please remember that designing and building very large aircraft was much more complicated than just scaling up smaller aircraft.


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## Zipper730 (Dec 3, 2017)

Shortround6 said:


> you can find all kinds of interesting, but somewhat useless statistics, like the output of an engine per square inch of valve area.


In the old days there was a tendency to try and maximize horsepower by displacement (hence the hyper-engine).


> Fuel fraction is somewhat the same, It may show how clever the designer was but doesn't actually tell you anything about the actual performance of the aircraft as too many other things are different.


It does tend to show a consistent benefit to range though...


> You could find differences of 5-10mph due to paint (or higher)on non laminar (so called) flow aircraft


That's rather significant...


> Trouble is the weight either won't stay the same or the difference in power plant weight comes out of the payload. AN R-2600 is roughly 500lbs heavier than an R-1830 so four of them add a ton to the empty weight of the aircraft, and this is without the larger, heavier propellers and any trick superchargers.


What size propeller was used on the XB-15, and what was used on the B-314?


> BTW before the war P &W had the patents on two stage supercharging so Wright would be starting from scratch to to try to get around them.


They'd have to re-invent something that somebody else already had mastered, and if the patent is still in force, they'd have to pay royalties...

I suggest twin-stage supercharging because the XB-15 had a rather poor climb rate and from what I remember based on the B-29: If the climb rate is sufficiently slow, you burn up so much fuel climbing to altitude that the energy saved while cruising up there stops being practical unless you can fly halfway around the world... climbing to 21,500 would be less fuel consuming than climbing to 25,200 (the B-17E/F's figures).


> For some reason the R-2600 never took to turbo charging very well


I know this might sound silly to ask, but do you have any idea why?


> If the Army decided to go with B-18s instead of B-17s because of price the chances of large scale (even by 1930s standards) of the B-15 was basically non-existent.


So the cost was the reason for some favoring the B-18? (I'm honestly surprised nobody considered issuing specifications for a four-engined bomber earlier... since the V/1500 and XNBL-1, the US or UK didn't seem to develop anything with 4 engines until the mid/late-1930's).


> In the 1930s and 40s IF the Army (or Navy) paid for a design study or prototype aircraft then the Army or Navy became not only the owner of the aircraft but the owner of the data used to design and build the aircraft and was free to share such data with whatever companies and agencies they saw fit to share with.


When did that change?


> How much of the design data the Army got from the B-19 was shared with Boeing, Consolidated, Martin, Lockheed and others I don't know


I would imagine it would be a lot. While I'm not fully aware of the effects of scaling factors, I am aware that they are significant.


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## Snowygrouch (Dec 30, 2017)

Koopernic said:


> The Jumo 213J was supposed to reach 2750 RPM. .



3700... not 2750. Sure you just made a typo.... 

If you want to read the original report - you can find it at Udvar-Hazy - if you dont mind
trawling through microfilm all day....haha

NASM-HAZY-MF-8184-1361_001 (_001 is my designation, meaning page number)

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## tomo pauk (Dec 30, 2017)

Snowygrouch said:


> <snip>



BTW, Calum - when we can expect the book?


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## Snowygrouch (Dec 30, 2017)

Hi Tomo !

I have set a printing date of August 2018. I hit 275 pages (US letter/A4) last week and expect to hit something close to 400 when its ready. A lot depends on the final copyright bill to the various archives. A full page print of photos costs an absolute fortune in rights-usage....this will determine the page count really.

I`ve just finished reviewing all of the Ernest Hives (@ Rolls-Royce) letters to the Ministry of Aircraft Production, so got that to write up next. He really spoke his mind I can tell you !!! Some of his letters would have caused an international diplomatic incident, if they had got out at the time.  I think you need a man like that calling the shots to be successful in times like that.

I`m trying to raise about $35,000 USD to have the surviving UK collection of German and Japanese captured docs. microfilms digitised (4000 reels of 35mm film). Thats my long-term project to safeguard all this data. So if you know any rich aviation philanthropists, do let me know ! 

If we were clever - could maybe organize it such that all this data could be got to online one day...and not need a plane ticket to England and 6months of spare time to rifle through 50,000 index cards....

C.

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## tomo pauk (Dec 30, 2017)

Paul Allen might be your man...

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## drgondog (Apr 26, 2021)

Carboncrank said:


> Would you say it created less drag than any wing before it?


 Same airfoil from NA-73X through P-51B/C/D/K. Same manufacturing processes for NAA at both Inglewood and Dallas. The Parasite Drag for the Mustang airframe from NA-73X through P-51K Essentially the same. That said, the Meredith system drag recovery was better in the Merlin Mustang for high temp/high speed envelope.

For same Hp ratings, the P-51A with V-1710-81 was slightly faster than P-51B/D at same GW though 10,000 ft with crossover between 11-15K in low blower for 1650-3 and-7. Ditto for climb.

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## Peter Gunn (Apr 26, 2021)

I think people forget or never really knew how fast (and capable) an Allison powered Mustang really was. Too much literature has it overshadowed by it's Merlin powered "big" brother and dismisses it as only a stopgap until the "real" Mustang arrives.

If only someone would write a definitive book regarding the development of the Mustangs early marques. "Sigh"... one can hope.

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