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

[Shortround6]

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.

 

[Koopernic]

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.

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.

 

[Shortround6]

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.

 

[tomo pauk]

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):

 

[windswords]

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?

 

[pbehn]

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.

 

[tomo pauk]

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.

 

[pbehn]

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.

 

[Shortround6]

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?

 

[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.

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.

 

[InlineRanger]

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.

 

[wuzak]

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.

 

[parsifal]

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

 

[parsifal]

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.

 

[tomo pauk]

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

 

[mcoffee]

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.

 

[Shortround6]

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.

 

[drgondog]

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.

 

[drgondog]

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.

 

[tomo pauk]

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.