# P-38 vs P-51: Full internal fuel dogfighting



## gjs238 (Feb 6, 2013)

Which was the better dog-fighter with a full load of internal fuel?
I understand the P-51 had issues with the fuselage tank.


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## bobbysocks (Feb 6, 2013)

if they didnt burn down the fuse tank the center of gravity was off and they were limited on some of the maneuvers. that is why they ran it down to 25-30 gallons right after take-off.


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## GregP (Feb 6, 2013)

With the fuselage tank full, you could not dogfight the P-51 at all. You could run and you could hose somebody in front of you, but a rearward CG is not conducive to hard maneuvering. The P-38 had no such issues. However, they P-51's in the ETO and elsewhere that used the fuselage tank used the fuel in it first as stated above and were pretty much OK by the time they got to enemy territory.

The P-51 would no doubt out-turn the P-38 by a margin once the CG was OK and was slightly faster, but the P-38 could easily outclimb and out accelerate the P-51. Plus it had all the armament on centerline. I'd take a P-38, the mount of our top two aces in the war ... but therre is nothing whatsoever wrong with the P-51. The Mustang shot down more enemy planes as a type than did the P-38, but both are very good.

In the Pacific, the P-38's second engine would ease the pilot's mind somewhat about engine trouble I'm sure, but the single engine planes didn't suffer huge losses due to engine issues, so maybe its an overblown fear. I see no downside to either pick. They would, of course, be employed somewhat differently from one another. Against each other they never fought, so that is a what if that can be debated. I choose not to since it never happened and there is no definitive answer, just opinions ... and everybody has one.


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## tomo pauk (Feb 6, 2013)

Fine post.
One thing: would the P-51 really out-turn the P-38?


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## davebender (Feb 6, 2013)

I don't think either aircraft was particularly good for dog fighting. Neither was P-47. These aircraft need to escort bombers @ 25,000+ feet.


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## GregP (Feb 6, 2013)

I have the VN diagram for a P-51 but not for a P-38, so I can't say for sure right now. I think the P-51 would out-turn the P-38 but could well be wrong since I really have only one side of the question to evaluate. 

If anyone has the VN diagram for a P-38 ... would you post it?

Thanks!


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## drgondog (Feb 7, 2013)

The formulas for the factory manuals are the same as in the Aero books.

From another forum

_*From Report on Joint Fighter Conference NAS Patuxent River MD 16-23 October 1944 - the source for Dean's "America's One Hundred Thousad" 

Best Rudder = P-51 and P-38 tied at 6% in 6th place with twice as many favorable comments as the P-47 at 3% - (pg 318 ). This was the P-38's second Highest relative ranking in the Appemdix. Fighter exhibiting greatest All around Stability F6F 1st at 33%, P-47 4th at 11%t, F8F/P-51 tied for 5th at 6%, P-63 at 3%,P-38 1%, Best All Around Fighter Above 25K -P-47 1st at 45%, P-51 2nd at 39%, F4U-1 3rd at 7%, P-38 dead last. Best All Around Fighter below 25K - F8F 1st at 30%, P-51 second at 29%, F4U-1 at 27%, P-38 less than 2% with Mosquito, F6F, F4U-4, F2G ranked at 2% (pg 319); Worst Cockpit -P38 1st at 55% (pg 316)55%, Best All Around Visibility P-51 1st at 35%, P-47 2nd at 27%, F8F at 22%(p 317); Nicest Harmonization of Control Forces - F4U-1 1st at 26%, P-51 2nd at 20%. F6F at 14%; Best Ailerons at 100mph- F6F 1st at 36% F4U-1 2nd at 18%, P-47 4th at 6%, P-51 at 5% and P-38 at 3%; Best ailerons at 350 P-51 1st 33%, F4U-1 2nd 20%, P-38 3rd 19%, F6F 4th 9%, F8F 5th 6%, P-47 6th 4%
*_

The assmebled USN, USAAF, RAF and Contractor pilots weren't impressed by the P-38L-5 versus the P-51 or the Navy fighters..

The answer regarding turning is 'it depends'. The P-38 manuever flap worked better with fowler concept than the 51 hinged flap - so advantage to P-38 at low speed/high G and high AoA... but so would a 109 with LE Slats in the hands of a pro.

As to full fuel load, the only time a Mustang would (should) have more than 25 gallons in the fuel tank is after engine warm up, taxi, take off and climb to altitude. SOP was to burn it down before switching to externals.

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## Milosh (Feb 7, 2013)

Didn't some P-51s take off with a full load of fuel when under attack and make some 'kills' during Bodenplatte?


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## drgondog (Feb 7, 2013)

Yes, specifically J.C. Meyer. It was basically rotate, shoot, gear up and go look for the next one.

The 190 that he shot down had a choice of shooting Meyer or the C-47 on the side of the runway - and it chose the C-47 giving Meyer time to turn slightly for an 1145 head on slight deflection shot. This was at Asch Y-29.

Based on the narrative he probably did not have full internal tanks - the 352nd was flying CAP for 9th AF P-47s attacking near St. Vith so they also did not have drop tanks.


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## davparlr (Feb 7, 2013)

Milosh said:


> Didn't some P-51s take off with a full load of fuel when under attack and make some 'kills' during Bodenplatte?


Some of the P-51s like those at Asch were on combat patrol standby. I think it is highly unlikely that they had the extended range tanks full. Others, I don't know.


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## cherry blossom (Feb 8, 2013)

I am very hesitant in telling this as I may have been the victim of a tall story but ....

My relative Jim Rattray commanded a squadron of RAF Mustangs just after the end of the war in Europe and he told me that an aircraft had taken off for combat practise with the fuselage tank inadvertently filled. Another Mustang made a pass at this aircraft which turned into the attack. The attacking aircraft could not follow the very tight turn and broke off. The Mustang with the filled tank continued to turn and then broke up with the wings folding at the centre section so that the pilot fell out of aircraft, having lost consciousness due to the high G. Somehow, his parachute opened and he apparently survived.

When I was told this in about 1960-5, my young mind believed it completely. However, writing now, I feel very suspicious but unfortunately, I cannot ask Jim.


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## drgondog (Feb 8, 2013)

cherry blossom said:


> I am very hesitant in telling this as I may have been the victim of a tall story but ....
> 
> My relative Jim Ratray commanded a squadron of RAF Mustangs just after the end of the war in Europe and he told me that an aircraft had taken off for combat practise with the fuselage tank inadvertently filled. Another Mustang made a pass at this aircraft which turned into the attack. The attacking aircraft could not follow the very tight turn and broke off. The Mustang with the filled tank continued to turn and then broke up with the wings folding at the centre section so that the pilot fell out of aircraft, having lost consciousness due to the high G. Somehow, his parachute opened and he apparently survived.
> 
> When I was told this in about 1960-5, my young mind believed it completely. However, writing now, I feel very suspicious but unfortunately, I cannot ask Jim.



It is entirely possible. If the 51 with a full load of fuel in a high G turn 'departed' and snap rolled with a full load of fuel he could have a.) snapped the fuselage aft of the wing or b) lost one, then the other wing - all due to exceeding the ultimate load limit for the heavily loaded fighter.

It is Not likely that the turn itself caused the failure but it is possible. Far more likely would be a sudden violent stall and subsequent snap roll into an inverted spin. Somewhere between the stall and inverted spin is probably where the airplane failed in wing or epennage.


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## davparlr (Feb 8, 2013)

Heavy loaded fighters need to be flown as bombers. Even the F-4, when it came out, was notorious for departure when maneuvering with certain loads, IIRC.


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## syscom3 (Feb 8, 2013)

The P38 was never designed for dog fighting. It was an interceptor. Of course it would be at a disadvantage in that type of fight against a single engine fighter.

As for the general dislike of the P38 by the pilots at that conference; I wonder what their feelings would be if they were over the vast stretches of the Pacific in a single engine fighter, and they heard their engine start to cut out. Every single one of them would praise the P38 for being THE best fighter we had in the PTO.


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## MikeGazdik (Feb 8, 2013)

This is just my opinion, and how my knowledge has evolved over many years. Many things which I had firm believe in has changed over the few years I have been on this forum, learning. 

Somewhere back in time, if you cared to search, you would see on some thread about 'best fighter" or something. I said I would take a P-38L on against all comers. Knowledge has changed my opinion. I still love the plane, but my opinions have changed. I know prior to learning so much here, my opinion on how awesome the P-38 was borne of reading about its exploits against Japanese aircraft. I now know the Lightning held a huge speed and power advantage over those aircraft which gave it the advantage. 

As much as I love the old Lockheed, I feel now that I would not want to face a P-51, or several other top tier WWII single engine fighters in a one on one situation.

That doesn't mean if I play arm-chair General I wouldn't want a boat-load of them in my air force, because I would. They are a fantastic weapon capable of many missions.

But it is still the sexiest thing with wings ever to take to the sky!!


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## drgondog (Feb 9, 2013)

Mike - you know that I like the Mustang for a variety of reasons. Having said that the P-38L was a very good fighter with a lot of performance features that a good pilot could use to defeat any contemporary fighter depending on the tactical position and skill of the pilot. Ditto for the F4U, P-47, Bf 109, Fw 190, Spit, Ki 84, Yak 3, etc etc. The general theory of "he who has altitude and sees the other guy first" is a high probability winner.

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## Tante Ju (Feb 9, 2013)

Is there turn time available for these two fighters perhaps available?


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## drgondog (Feb 9, 2013)

Interesting question. The Soviets seemed most interested in obtaining actual minimum turn times and had access to P-51B's in very limited quantity. AFAIK they never had either a P-38L or P-38J-25 to perform tests on.

Even doing the calcs for the P-38 with manuevering flaps to raise the CL in high G turns is suspect because the Fowler Flaps also had high drag values as a function of deployment - I haven't seen those values in a reliable format.

Calculations for both are feasible with a range of error based on difficulty in plugging combination of increased Profile drag due to high Angle of Attack as well as carefully looking at prop efficiencies at high power/low speed profiles.

Modern computer modelling is very sophisticated and should be capable of doing such calculations but I haven't seen any results.


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## davparlr (Feb 9, 2013)

syscom3 said:


> As for the general dislike of the P38 by the pilots at that conference; I wonder what their feelings would be if they were over the vast stretches of the Pacific in a single engine fighter, and they heard their engine start to cut out. Every single one of them would praise the P38 for being THE best fighter we had in the PTO.


 
I am sure that most of those pilots were single engine drivers and the large and admittedly more complex twin engine aircraft would require more training to be able to get the best out of it.


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## Tante Ju (Feb 9, 2013)

I find it amusing because US report are generally the most through... and almost everyone produced some sort of estimate or measurements of the turn time of fighters. So, I find it difficult to believe that the USAAF never had an interest for such solid turn time figures, and would put up with with 'well we flew his pursuit plane against that pursuit plane, and pilots say the latter was a bit better in turns.'

Surely such figures must exist somewhere.. the Soviets did some tests with Allison Mustang (23 secs) and an early P-47D (26 secs), which does not seem unreasonable, but there is alway a way of error with foreign planes tested... also it difficult to extrapolate turn times from that to the Merlin Mustang, which was different in too many ways.


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## drgondog (Feb 9, 2013)

Don't disagree with your comments. The only tabular comparison I have seen is Chapter 5 Fighters Compared, pg 602-3 of America's Hundred Thousand.

They did not present actual turn times or radius, but expressed the turns as a Percent greater than the best ranked turner - the FM-2. They did not have either the P-40 or the P-39 which would have been a good comparison against Soviet data.

The ranking of the P-63 (@8780 pounds and 3G stall speed of 132mph) was 124% of the FM-2(@3G Stall 118.5), The P-61B-1(@27000 pounds 3G stall of 137mph) was 133%, F6F-5 (12500 w/3G stall of 139mph) was 138%, P-51D-15 (9500 w/3G stall at 159mph) was 179%, P-38L (@17488 w/3G stall of 170mph) was 205%, P-47D-25 (@14300 w/3G stall at 170mph) was 206% and the F4U-1D (@11,803 and 3G stall at 172 mph) was 206%.

What was interesting to me was that the max CL for the laminar flow P-63A-9 wing was 2.38 - the same as the FM-2. The Mustang had the lowest Stall CL max of 1.89. The F4U-1D had the worst Stall CL @3G with 1.48 - probably because of the spoiler under the right wing. 

The P-61 and P-38 both had stall speed Max CL of 2.38. the P47 was 1.93 and the P-38 was 2.17.

The W/L of each for these tests were (FM-2) 28.5 , (P-63A) 35.4 , (P-61B) 40.7 , (F6F-5) 37.4 , (P-51D) 40.7, (P-38L) 53.4 , (P-47D) 47.7 , (F4U-1D) 37.6 .


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## Kryten (Feb 9, 2013)

Tante Ju said:


> I find it amusing because US report are generally the most through... and almost everyone produced some sort of estimate or measurements of the turn time of fighters. So, I find it difficult to believe that the USAAF never had an interest for such solid turn time figures, and would put up with with 'well we flew his pursuit plane against that pursuit plane, and pilots say the latter was a bit better in turns.'
> 
> Surely such figures must exist somewhere.. the Soviets did some tests with Allison Mustang (23 secs) and an early P-47D (26 secs), which does not seem unreasonable, but there is alway a way of error with foreign planes tested... also it difficult to extrapolate turn times from that to the Merlin Mustang, which was different in too many ways.



Even if they existed unless they are compared in exactly the same way they again become meaningless, what altitude, speed, weight, power settings, conditions on the day etc etc!

you would then need to take several of each type and work off the average peformance, otherwise you may simply be testing a exceptional/sub standard model!

I have seen many reports of aircraft etsted that were declared not representative of type!


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## fastmongrel (Feb 9, 2013)

A P38 driver who gets into a turning battle is doing it wrong.


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## gjs238 (Feb 9, 2013)

fastmongrel said:


> A P38 driver who gets into a turning battle is doing it wrong.


AVG learned that with P-40's.


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## FLYBOYJ (Feb 9, 2013)

fastmongrel said:


> A P38 driver who gets into a turning battle is doing it wrong.



Or extremely skilled...

_"I was able to stay inside this maneuverable little rascal's left turn for 360 degrees while doing about 90MPH, and at less than 1000' above the water. That P-38J was bucking and shuddering all the way around in what was nothing more nor less than a controlled stall. I was so close to the Oscar that his engine oil covered my windshield. For the last half of the turn I was shooting at a dark blur that finally burst into-flames. When I saw the Oscar explode I pulled up and started calling for someone to lead me home cause I couldn't see through the oil on my windshield."_

Secrets of a P-38 Ace. John Tilley's electrifying story

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## MikeGazdik (Feb 9, 2013)

What amazes me in Drgondog's post is the turning radius of the P-61 ! I have read some on that bird and love it. That turn would have to have been using the full span flaps I surpose. Could you imagine looking over your shoulder and seeing that big black evil looking twin hanging on your tail in a turn???!!!!!!

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## tomo pauk (Feb 10, 2013)

Unlike most of the fighters, the Fowler flaps of the P-38 were enabling tight turns. The Japanese fighters were also using the 'butterfly flaps', so I can agree that the best thing got the P-38 driver would be to make a slashing pass vs. Japanese opponent. 
A pro could use the differential enigine power setting, too, to increase it's turning abilities.


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## fastmongrel (Feb 10, 2013)

FLYBOYJ said:


> Or extremely skilled...
> 
> _"I was able to stay inside this maneuverable little rascal's left turn for 360 degrees while doing about 90MPH, and at less than 1000' above the water. That P-38J was bucking and shuddering all the way around in what was nothing more nor less than a controlled stall. I was so close to the Oscar that his engine oil covered my windshield. For the last half of the turn I was shooting at a dark blur that finally burst into-flames. When I saw the Oscar explode I pulled up and started calling for someone to lead me home cause I couldn't see through the oil on my windshield."_
> 
> ...



Very skilfull but how many P38 drivers could do this without getting it wrong. Close to a terminal stall at less than 1,000 ft there is zero margin for error if the pilot so much as hiccuped he would have been in the drink. What the best 1% can do is not what the other 99% should even think of attempting. 

I am a very green microlight pilot and there is a member of my flying club who can do astonishing things, I watched him land into a strong breeze once vertically light as a feather by blipping the throttle and balancing on the edge of stalling. If I tried it I know the laws of gravity would kill me I simply am not one of those rare breed.

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## FLYBOYJ (Feb 10, 2013)

fastmongrel said:


> Very skilfull but how many P38 drivers could do this without getting it wrong. Close to a terminal stall at less than 1,000 ft there is zero margin for error if the pilot so much as hiccuped he would have been in the drink. What the best 1% can do is not what the other 99% should even think of attempting.
> 
> I am a very green microlight pilot and there is a member of my flying club who can do astonishing things, I watched him land into a strong breeze once vertically light as a feather by blipping the throttle and balancing on the edge of stalling. If I tried it I know the laws of gravity would kill me I simply am not one of those rare breed.



Actually I think there were more pilots in the PTO that could have done this. "Training and experience." Once a pilot is given the time to master their aircraft, they could push the envelope to the absolute limit, unfortunately during WW2, this was not always the case.

As you have the opportunity to fly more and learn your aircraft, you too will find that as time goes on, you'll learn to do maneuvers that you thought you were not capable of doing

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## GregP (Feb 12, 2013)

All too true. And if you are a wingman, how often do you get to practice your skills? What you must as a wingman do is fly good formation and keep your eyes on a pivot.

So my take is you must make flight leader before you can play around and learn the maneuvering skills you need in combat.

Sometimes they never made it that far. Many P-38 pilots got into combat with very little time in the aircraft ... not a good combination.


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## stug3 (Feb 17, 2013)

I thought P-51 fuselage tank center of gravity problems only arose with the bubble top D model, and was the main reason many pilots preferred the P-51B?


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## drgondog (Feb 17, 2013)

stug3 said:


> I thought P-51 fuselage tank center of gravity problems only arose with the bubble top D model, and was the main reason many pilots preferred the P-51B?



No. The P-51B-5 line block was changed to P-51B-7 block when the 85 gallon tank was installed at NAA. The P-51B-1 and -5's in the ETO were modified in March 1944 to install the 85 Gallon Tank and a "+" symbol was placed on the fuselage near the CG. The P-51B-10 43-7113 (#1) was the first factory installed 85 gallon tank in production series.

EDIT: The AAF so designated the P-51B-5 to -7, and C-1 to C-3 following each Depot modification but the practice of changing the data block and IARC's and Engineering records was very inconsistent.

All subsequent Mustangs had the 85 gallon tank until the P-51H - which carried a 50 gallon tank, and had increased fuselage length and re-designed tail to eliminate the stability issues inherent in the Merlin powered Mustang combined with increased gross weight and 85 gallons/500+ pounds aft of the CG on take off.

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## stug3 (Feb 17, 2013)

nm


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## Frank Stewart (Aug 13, 2016)

davebender said:


> I don't think either aircraft was particularly good for dog fighting. Neither was P-47. These aircraft need to escort bombers @ 25,000+ feet.


The P-51 could out roll the P-38 but the P-38 could out turn the smaller plane once established in the turn. This trick was a compliment6 of the maneuvering flaps, and, or the twin engines blowing over most of the wing at very low speeds WO prop torque causing the plane to stall.
The later models of the P-38 with the chin inter-coolers were also faster than the P-51D. (If the pilot broke the wire across the throttle gate to restrict use of WEP) It's a long story, but a good read if you look it up.
However niether plane was a great "Dog Fighter" and like all mono-plane fighters of the time should be used in the Zoom and Boom mode tactics exclusively!!!!


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## Frank Stewart (Aug 13, 2016)

Tante Ju said:


> I find it amusing because US report are generally the most through... and almost everyone produced some sort of estimate or measurements of the turn time of fighters. So, I find it difficult to believe that the USAAF never had an interest for such solid turn time figures, and would put up with with 'well we flew his pursuit plane against that pursuit plane, and pilots say the latter was a bit better in turns.'
> 
> Surely such figures must exist somewhere.. the Soviets did some tests with Allison Mustang (23 secs) and an early P-47D (26 secs), which does not seem unreasonable, but there is alway a way of error with foreign planes tested... also it difficult to extrapolate turn times from that to the Merlin Mustang, which was different in too many ways.


The best turn times and degrees per second figures will all be had at the slowest speed that the plane will pull the maximum G load the Pilot can stand! At that point in time few pilots could pull much more that four Gs for more than 5 seconds. The 1%ers could pull 6 or more Gs for as long as the plane could. That made dog fighting them irrational! No plane in the second world war could pull as much as TWO Gs with out slowing down drastically because of the large increase in "Induced Drag"! So pilots traded attitude for more speed to maintain the rate of turn until they were brush hopping at about 2/3 to 3/4 G!
The slower your plane could go and pull a certain level of G load, the tighter you could Dog Fight! At very low speeds the twin engined and contra-propped P-38 could out turn any other mono-plane fighter of the war! Not that I would recommend that tactic as low and slow just gives some other guy the opportunity to shoot you down.
This also leads to large errors in test numbers of foreign air craft flown by pilots who are not intimately familiar with said planes. The resulting conundrum of German "Experten" flatly stating their LE Slated Me-109s could out turn the Spitfire and British testers who stated just as vehemently that the opposite was true! When the facts show that they were both right at the right part of the Flight Envelope!


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## wuzak (Aug 13, 2016)

The Bf 109 could only out-turn a Spitfire if the 109 pilot was an experten and the Spitfire pilot a novice.



Frank Stewart said:


> At very low speeds the twin engined and contra-propped P-38 could out turn any other mono-plane fighter of the war!



I also doubt very much the claim that the P-38 could out turn _any_ monoplane fighter of WW2.

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## Greyman (Aug 13, 2016)

Sorry - I must break out my well-worn *ULTIMATE TURN PERFORMANCE/MANEUVERABILITY ANECDOTE*



> I've got a great anecdote that, for me, put the somewhat nebulous 'turn performance' quality in perspective for all time.
> 
> From (then Flight Lieutenant) Wing Commander Hugh Godefroy DSO, DFC and Bar, Croix de Guerre with Gold Star (Fr), shortly before Dieppe.
> 
> ...

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## drgondog (Aug 13, 2016)

Frank Stewart said:


> The best turn times and degrees per second figures will all be had at the slowest speed that the plane will pull the maximum G load the Pilot can stand! At that point in time few pilots could pull much more that four Gs for more than 5 seconds. The 1%ers could pull 6 or more Gs for as long as the plane could. That made dog fighting them irrational! No plane in the second world war could pull as much as TWO Gs with out slowing down drastically because of the large increase in "Induced Drag"! So pilots traded attitude for more speed to maintain the rate of turn until they were brush hopping at about 2/3 to 3/4 G!
> The slower your plane could go and pull a certain level of G load, the tighter you could Dog Fight! At very low speeds the twin engined and contra-propped P-38 could out turn any other mono-plane fighter of the war! Not that I would recommend that tactic as low and slow just gives some other guy the opportunity to shoot you down.
> This also leads to large errors in test numbers of foreign air craft flown by pilots who are not intimately familiar with said planes. The resulting conundrum of German "Experten" flatly stating their LE Slated Me-109s could out turn the Spitfire and British testers who stated just as vehemently that the opposite was true! When the facts show that they were both right at the right part of the Flight Envelope!



While I largely agree with your post I would modify some of the comments.

The key to sustained turn performance is the state of equilibrium of Thrust (at max power) to Drag where Power Available matches Power Required. Power Available is reduced from straight flight power in turns and climb where the incremental Form Drag due to Angle of Attack (CL increase) plus major Cooling Drag increases occur plus Trim Drag plus Induced Drag increases - all due to CL increases from level flight. 

The Max SUSTAINED Rate of turn while maintaining altitude, in Radians per second, is as you say - in the 2.0 to 2.7 range for most WWII fighters,

That said the Corner Velocity expressed in the V-n diagrams is based on Max N (G) attainable at CLmax for Design Stress Limit It is proportional to the Square Root of n, and W/L, and inversely proportional to Square Root of density and CL. This is maximum Initial Turn Velocity and Turn Rate based on structural limit.

This has nothing to do with calculations leading to maximum Sustained rates of turn which must take into consideration T=D.


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## grampi (Aug 24, 2016)

wuzak said:


> The Bf 109 could only out-turn a Spitfire if the 109 pilot was an experten and the Spitfire pilot a novice.
> 
> 
> 
> I also doubt very much the claim that the P-38 could out turn _any_ monoplane fighter of WW2.




I do too...


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## FLYBOYJ (Aug 24, 2016)

wuzak said:


> The Bf 109 could only out-turn a Spitfire if the 109 pilot was an experten and the Spitfire pilot a novice.
> 
> 
> 
> I also doubt very much the claim that the P-38 could out turn _any_ monoplane fighter of WW2.



The P-38 can and has out turned "monoplane fighters" for the same reasons you give for the BF 109 vs the Spitfire. I posted this on another thread...

_"on my 3rd mission while in a P-38H model. The 2nd was an Oscar while I was flying in a J model. I was particularly proud of this one 'cause I was able to stay inside this maneuverable little rascal's left turn for 360 degrees while doing about 90MPH, and at less than 1000' above the water. That P-38J was bucking and shuddering all the way around in what was nothing more nor less than a controlled stall. I was so close to the Oscar that his engine oil covered my windshield. For the last half of the turn I was shooting at a dark blur that finally burst into-flames. When I saw the Oscar explode I pulled up and started calling for someone to lead me home cause I couldn't see through the oil on my windshield. "Pete" Madison was kind enough to oblige. When we got back to base, I had to crank down the side window and wipe a clear spot on the windshield so I could see enough to land the bird."_

1st Lt. John Tilley, 431st Fighter Squadron, 475th Fighter Group

Secrets of a P-38 Ace. John Tilley's electrifying story

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## wuzak (Aug 24, 2016)

FLYBOYJ said:


> The P-38 can and has out turned "monoplane fighters" for the same reasons you give for the BF 109 vs the Spitfire.



Given an expert flyer against a novice I guess any fighter could out-turn any opposition fighter.

The implication of the use of the word _any_ is that the P-38 could out-turn all contemporary single engine fighters. Which I very much doubt, given pilots of equal ability.


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## FLYBOYJ (Aug 24, 2016)

wuzak said:


> Given an expert flyer against a novice I guess any fighter could out-turn any opposition fighter.
> 
> The implication of the use of the word _any_ is that the P-38 could out-turn all contemporary single engine fighters. Which I very much doubt, given pilots of equal ability.



OK


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## BiffF15 (Aug 25, 2016)

I would think there are regimes / envelopes where the P-38 would have an advantage due to little to no adverse yaw / torque with it's unique arrangement. IIRC didn't McGuire have a habit of getting slow with his opponents? I also think it contributed to his demise due to not jettisoning his belly tanks while getting slow.

Cheers,
Biff

PS Switched Lynch with McGuire!


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## fastmongrel (Aug 25, 2016)

Isnt getting into a low and slow turning battle in a P38 throwing away all its advantages of speed and climb, a P38 in that position is very vulnerable to being bounced. Obviously it could be done by experts but really the Sqdn leader should have put anyone who did this on a charge for being stupid.

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## FLYBOYJ (Aug 25, 2016)

fastmongrel said:


> Isnt getting into a low and slow turning battle in a P38 throwing away all its advantages of speed and climb, a P38 in that position is very vulnerable to being bounced. Obviously it could be done by experts but really the Sqdn leader should have put anyone who did this on a charge for being stupid.



Absolutely!


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## bobbysocks (Aug 28, 2016)

According to this the 38 with boost could hold its own...very good rate of roll and could out turn a 47 and 51B

http://www.wwiiaircraftperformance.org/mustang/Performance_Data_on_Fighter_Aircraft.pdf


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## drgondog (Aug 29, 2016)

bobbysocks said:


> According to this the 38 with boost could hold its own...very good rate of roll and could out turn a 47 and 51B
> 
> http://www.wwiiaircraftperformance.org/mustang/Performance_Data_on_Fighter_Aircraft.pdf



A couple of observations - the P-38J tested at 15000 pounds is 2699 pounds under full internal combat load. -------> 85% of full internal GW. If you 'grow' the P-38J GW to Normal full combat load you divide the recorded turn radius of 838 ft by 0.85 ------------>985 ft

The P-51B at 9000 pounds GW is 611 pounds under full internal combat load - the equivalent of flying without 85 gallon tank fuel ----------> 93% of full internal GW. If you then divide the presented turn radius of 883 ft by 0.93 -------> 949 feet, less than the comparably loaded P-38.

Calculated turn radius is directly proportional to Wing Loading (W/S).

Calculated rate of turn is inversely proportional to the Square Root of [k*CLmax/(W/S)]

Second Observation - rate of roll with boosted ailerons for the P-38J was outstanding. That said, the P-38J had a notable 'delayed' reaction between control movement and the Roll initiation (noticeable)., particularly when the 55 gallon LE tanks were full. That comment prevailed with nearly every pilot that flew the P-38J/L at the Patuxent Fighter Conference in October 1944. It is further documented in Dean's "America's Hundred Thousand". He also documents the turn performance of the P-38J/L as less than the P-51D - and the P-51B outperforms the P-51D.

Without tweaking CLmax or density or G - the test is skewed (unintentionally?) to favor the P-38J

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## BiffF15 (Aug 29, 2016)

I've wondered a bit about the comments made regarding initiating the roll in the P-38 (delayed action, pulling an engine, etc.). Obviously the engines outside the roll axis of the plane will require more "aileron / leverage" to cause roll, however it must be very noticeable for the amount of comments garnered at the Fighter Conference. 

I found this video called, "Flying the P-38 With Chris Fahey", and interestingly enough there are a few cockpit shots showing him turning the yoke and what is to me a rather lethargic response from the plane. Take that last comment with a grain of salt as I have not flown any WW2 type fighters to compare with, only that it seems slow for what appears to be a large amount of deflection as compared to a T-37 or OV-10. The Bronco being fairly slow itself.

Cheers,
Biff


_View: https://www.youtube.com/watch?v=P8ZkZu_pbWM_

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## drgondog (Aug 29, 2016)

Chris is a good guy and has a lot of time in most of the POF warbirds. So far Steve Hinton won't check him out in the A6M but I think he has flown all the other fighters there. Check out his Facebook page.

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## GregP (Aug 29, 2016)

Chris IS a very good guy. In fact, I can't think of a POF pilot who isn't. All are friendly and will interact with the public, volunteers, etc, and all show up for volunteer work on many Saturdays. Nobody flies a POF aircraft who doesn't work on it with their own tools. I have seen Chris removing and re-installing an Allison on several occasions when one engine or the other needed some work best done out of the aircraft. It doesn't happen often, but is a major pain when one needs to come out. The Allisons are practically built into the nacelle. Ours is a J-20-model without boosted ailerons, and engine removal is easier than the F and earlier models by an order of magnitude. When I mention the earlier models, I'm thinking of Glacier Girl. The other flying P-38 at Chino is an L-model with boosted ailerons.

Also keep in mind this was an airshow pass at reduced power. He was probably no faster than 180 - 200 mph or very slightly faster. Nobody in the racetrack pattern flies very fast since they circle around and make repeated passes for photo opportunities.

I have worked the last ten POF airshows and they do a racetrack pattern at slow cruise speeds, and also usually have maybe 8 - 15 airplanes in the circle at any one time, with a mix of things like our Tora, Tora, Tora "Val" (BT-15), T-6's dressed up like Zero as movie planes, and other slower aircraft. There are usually 2 circles, an inner one with the slow movers, and an outer one with the faster planes. Sometimes they pick up some speed on the last pass or two before breaking for landing. The passes are all in a line astern manner with maybe a 45° roll into a turn at the runway intersection and no aerobatics. The box is usually active and open only during the airshow itself and these passes are usually in the morning, before the show officially opens.

As far as I know, the only people now authorized to fly the Zero are Steve Hinton, John Maloney, and Kevin Eldridge ... could be mistaken, but that's what I have heard around the museum. That may change going forward, it's Steve's call. The Zero is looking very good since the recent complete, except for engine, overhaul.

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## Old Wizard (Aug 29, 2016)




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## bobbysocks (Aug 29, 2016)

what model 38 is he flying in the video...the older one or one with boost?


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## GregP (Aug 29, 2016)

Our P-38J-20 without boosted ailerons. The power in our "power ailerons is "armstrong" ... however hard you can twist the control wheel. I have seen Steve Hinton in our airshows do a breakaway that is exactly as fast as Kevin Eldridge flying the P-38L with the boosted ailerons.

My supposition is that the slower roll response comes at a higher airspeed since, again, we were in airshow mode, not high-speed combat. Add to that the fact that it was my impression of the relative quickness of initial roll (which I was actually looking for), not a quantitative comparative measurement of same. Also, I doubt they were deliberately trying to see who was quicker, but it was definitely a quicker initial roll than the other fighters doing the breakaway.

Might have also been that Steve flies a lot of big, smooth warbird aerobatics in formation (with the horsemen) and relishes the freedom to be able to horse (excuse the pun) it into a roll without synchronized formation considerations. I didn't ask and really don't anymore for internet posting. Almost every time I have done so and posted it, it generates more misunderstanding than clarification, and takes up more time and effort than it is worth.

But we are lucky as Biff is a member in here and will supply his own words! There are some warbird pilots in our membership, and we know who some of them are ... and there may be more we don't know about yet.


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## Kryten (Aug 30, 2016)

Does anyone know the reasoning behind the yoke in the P38 rather than a conventional stick?

Is it due to cockpit space?


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## BiffF15 (Aug 30, 2016)

fastmongrel said:


> Isnt getting into a low and slow turning battle in a P38 throwing away all its advantages of speed and climb, a P38 in that position is very vulnerable to being bounced. Obviously it could be done by experts but really the Sqdn leader should have put anyone who did this on a charge for being stupid.



FM,

Getting low and slow in ANY airplane makes it vulnerable to a bounce (you are pined between two adversaries, the ground and the shooter, of which both can kill you, and without airspeed your options are few). 

If two street fighters are in a brawl and one has a reach advantage, then the second guy will if able probably try to get the first guy on the ground (negate his advantage). However if the second fighter is faster, then he might go toe to toe, and in essence surprise the first fighter. My point is if you have found a corner of the flight envelope that gives you an advantage, then use it when appropriate. McGuire was obviously good enough to figure out the appropriate time to use a given maneuver the majority of the time. 

Cheers,
Biff

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## FLYBOYJ (Aug 30, 2016)

Kryten said:


> Does anyone know the reasoning behind the yoke in the P38 rather than a conventional stick?
> 
> Is it due to cockpit space?



From what I understand it was a design standard used by the USAAC when the P-38 was being developed, this because the P-38 was a twin engine aircraft. During the 1980s I attended a Lockheed Management Club meeting (I worked there for 11 years) and Kelly Johnson was the guest speaker. He spoke about many of his designs but when on the subject of the P-38, he mentioned it was his desire to put a stick in the aircraft, something that didn't go over well with the Air Corp officials at the time.

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## Kryten (Aug 30, 2016)

Thanks flyboy, I often wondered this as creating enough leverage with a yoke to roll at high speed must have required some kind of gearbox or chain like affair the Spit/Hurricane used, is it correct it was only the later aircraft had assisted ailerons, that and the response delay must have made aiming a seriously skilled affair?


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## bobbysocks (Aug 30, 2016)

biff...how much free play or dead space was there in the stick of the stuff you flew? there would have to be some sort of buffering built in I would think or the plane would be too twitchy...


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## BiffF15 (Aug 31, 2016)

bobbysocks said:


> biff...how much free play or dead space was there in the stick of the stuff you flew? there would have to be some sort of buffering built in I would think or the plane would be too twitchy...



BobbySocks,

The T37 was not as sensitive as the T38. The T38 was more sensitive than the Bronco, and none were as nice as the Eagle (not surprising)!

I should caveat "sensitivity" as well. The cable flight controls, T-37, and OV-10, can get stretch in the cables post rigging. That causes, particularly in the Bronco, each plane to fly different. The Bronco being most notable. I would notice differences in the Eagle but those would be CG factors for the most part.

I have 9 rides in F-16s, 1 in the Hornet, and 1.5k plus in the Eagle. The side stick / fly by wire is the best set up by far. The Hornet was the easiest of the three to fly. That is opine, most likely biased on the Hornet being more similar to the Eagle (my baseline) than the Viper. The Viper cockpit, side stick and canopy being the best without a doubt. Also realize in modern flight controls there is a little dead spot that occurs when the plane is trimmed up. The Thunderbirds fly with full nose down trim, while the Blues have a bungee cord arrangement to pull the stick forward, giving the feel of nose down trim. Allows more precise formation flying with a bit of practice.

In maneuvering harmonization is important with modern fighters, and having auto trim (this is a large spectrum) designed to help the pilot. Full aft stick deflection in the Eagle is about 45lbs, and when you enter a fight trimmed up at high Mach and end up groveling at the floor it's quite handy. I would often run the trim once slow to lighten the stick additionally (helps feel what the plane is telegraphing). The fly by wire jets don't buffet much or any depending on which one, so pilots fly with one eye on the airspeed indicator to know how much energy they have.

Cheers,
Biff

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## grampi (Jan 18, 2017)

GregP said:


> The P-51 would no doubt out-turn the P-38 by a margin once the CG was OK and was slightly faster, but the P-38 could easily outclimb and out accelerate the P-51.



That depends on which model of each aircraft you're comparing. If you're comparing a P-38L model to a P-51D model, then I agree. However, I doubt any model P-38 could out perform a P-51H in any performance category...


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## GregP (Jan 18, 2017)

You could be right. But, there were no P-51Hs in combat in WWII, unlike the thousands of P-38s that did see combat. I was speaking of wartime birds. 

In point of fact, I have never seen comparisons of post-war birds that were in the last generation of big pistons, like the Sea Fury, P-51H, Seafang. I have also never seen an evaluation of the last German planes like the Ta-152 (and it makes a difference whether the Ta is a C or an H) versus any other aircraft. I have seen only one opinion on the Lavochkin La-9, and that was from Ray Hana, who liked it VERY much and said the power and acceleration was second to no other warbird he had flown to date.

It would be great to see comparisons of the last of the big pistons. But if they haven't surfaced to date, I seriously doubt we're going to get to read them due to the fact that any survivors, if they are flyable, are very carewfully taken care of and would not be available for "flogging" in a performance comparison test. Should they actually BE available, they almost 100% are NOT in military stock configuration and are quite a bit lighter than combat-ready airplanes.

But I'd still love to find comparisons ...

I'll make a statement that I can't prove. I'd assume the last of the big piston fighters are probably the best of the breed in most categories. I have never sought to prove that, but it makes sense that new models would be improvements. If not, why build a new model?


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## parsifal (Jan 18, 2017)

would either type gain advantage as the altitude increases. ive played wargames that suggest the P-51 was superior in horizontal manouver over the p-38. im curious if these rough summaries contained in games have any basis at all.

Games are about as close as ill ever get to the real thing.


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## GregP (Jan 18, 2017)

I have my doubts that a flight simulator not specifically-designed for realism faithfully replicates the flight characteristics of a real aircraft. I have flown a T-38 simulator, but never a real T-38. Perhaps Biff could tell us if the T-38 and the T-38 simulator, or F-15 sim/plane are faithful simulations.

I watched a programmer one day change the flight chrracteristics in a sim, and he did it because he wanted it to fly better, not because it was "real." I have NO idea if the commercial game sims are good aerodynamic replications or not, but one Cessna 172 sim I used flew quite similarly to the real thing except for being easier to fly and having unlimited fuel and oil. When I say easier to fly, I mean I did some really bad landings on purpose and got away with it, apparently without damage.

The C-182 was also not easy to damage, even when landing nose gear first, unlike the real airplane.

I never DID take one to Sedona, Arizona on a warm summer day and see if it flew like the ones I used to land there, but I really doubt it.

On your question above, both had good altitude capability, and I'm not sure which one would retain better feel at, say, 25,000 feet. The P-38L had a service ceiling of about 44,000 feet and the P-51D was about 41,900 feet, so you can say the P-38 was probably better at 42,500 feet and be on solid ground. But both were flying on the razor edge up there and anything like a hard turn would probably see both falling for thousands of feet.

I'd think the P-38 would be better way up high, if only due to higher aspect ratio, which comes into effect at high altitudes, but I also wouldn't be surprised to find out the P-51 was better in the real world. We know the Mustang was faster.

In the end, I don't know for sure. Good thing they were on the same side!

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## wuzak (Jan 18, 2017)

GregP said:


> I have my doubts that a flight simulator not specifically-designed for realism faithfully replicates the flight characteristics of a real aircraft. I have flown a T-38 simulator, but never a real T-38. Perhaps Biff could tell us if the T-38 and the T-38 simulator, or F-15 sim/plane are faithful simulations.



I would suggest training simulators are a lot closer to reality than computer game simulators.

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## wuzak (Jan 18, 2017)

GregP said:


> On your question above, both had good altitude capability, and I'm not sure which one would retain better feel at, say, 25,000 feet. The P-38L had a service ceiling of about 44,000 feet and the P-51D was about 41,900 feet, so you can say the P-38 was probably better at 42,500 feet and be on solid ground. But both were flying on the razor edge up there and anything like a hard turn would probably see both falling for thousands of feet.
> 
> I'd think the P-38 would be better way up high, if only due to higher aspect ratio, which comes into effect at high altitudes, but I also wouldn't be surprised to find out the P-51 was better in the real world. We know the Mustang was faster.



We also know that the P-38 had a lower critical Mach number - I wonder if that would have any influence on the high altitude comparison.

In terms of performance, it looks like both were capable of ~300mph @ 40,000ft.

http://www.wwiiaircraftperformance.org/mustang/p-51h-64182-fig16a.jpg

http://www.wwiiaircraftperformance.org/p-38/p-38l-25092-level.jpg

The Spitfire XIV appears to be superior in speed to both - at least to 38,000ft.

http://www.spitfireperformance.com/JF319-level-speeds.jpg

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## GregP (Jan 18, 2017)

I think you'd want a P-51 if you were planning on a high-speed dive, for sure. I'd also bet that even if you tried to stay in the horizontal, any fight up near 40,000 feet would work its way downward in the course of the fight. no matter which aircraft you were in. I really like the P-38, but would personally choose a P-51 if I had to choose.

It is pretty good everywhere and the P-38 is pretty good except for a few glaring weaknesses. I wouldn't want to try to fight a P-51 when it was heavy with fuel in the 85-gal fuselage tank. And I wouldn't want to try fighting in a P-38 when a half-roll into a steep dive is the order of the day.

Overall, the P-51 was and is the better fighter, but specifically at 35,000 feet, I don't know. I'd lean toward the P-51, but that's purely from personal knowledge of them seen through eyes with no flying experience in either as pilot in command.

I know this, though. The video above with Chris Fahey is typical of WWII fighter responses. That is, if you were expecting them to do snap rolls like a Sukhoi-31, then you'll be disappointed with ALL of them. They all have slower roll response than sport aerobatic aircraft. At 280 mph, most are in the 40° - 80° per second category of roll, with more being on the slower side than you might imagine of you haven't studied it. It wsn't a handicap when most were siomilar in roll response, but very few are serious rollers like the Fw 190 series were supposed to be.

The roll response in a Cessna 310 looks like the P-38 respponse when the 310 tip tanks are full. That is, you put the wheel over and nothing much happens for a moment, then it starts to roll, and you have to lead the roll with active stop, or you will over-roll. They're MUCH more friendly when the tip tanks are empty. In the P-38, the Allisons don't go away, so it probably hesitates all the time. Probably less at higher speed, but with slower response as the speed increases. It would be good to see an in-cockpit view of an aerobatic display in the P-38. 

The strangest characteristic I have heard about the P-38 is that it has very little down elevator, so if you stop a roll inverted and more or less level, you can't really push forward to stop the descent. You have to come out by rolling out or pull through with elevator. That doesn't work very well if you are 100 feet. At least that is what has been told to me by people who should know. 

If you want to know and ever come to our airshow, you could always ask Chris Fahey yourself. He's very friendly and approachable unless he is getting ready to fly. Then he has to concentrate on that. He flies a few of our planes including the MiG-15 and F-86, and was an F-16 pilot before coming to the Planes of Fame. Good guy.

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## Peter Gunn (Jan 19, 2017)

BiffF15 said:


> I would think there are regimes / envelopes where the P-38 would have an advantage due to little to no adverse yaw / torque with it's unique arrangement. IIRC didn't Lynch have a habit of getting slow with his opponents? I also think it contributed to his demise due to not jettisoning his belly tanks while getting slow.
> 
> Cheers,
> Biff



I'm not sure if it was Lynch or Mcguire <sp?> that got slow with his opponents, could be both. Lynch was killed in a strafing attack but Mcguire did keep his tanks (Supposedly) in a low and slow dogfight, which is said to have contributed to his end.

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## drgondog (Jan 19, 2017)

Simply stated, McGuire chose not to drop his external tanks (presumably less than half full to near empty) and engage on the deck. The eyewitness report stated that he appeared to stall out trying to stay with the Japanese fighter.

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## drgondog (Jan 19, 2017)

I just edited the above post due to latent and lingering brain fart. Lynch IIRC got mad at a flak tower and the flak gunner won.

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## BiffF15 (Jan 19, 2017)

GregP said:


> I have my doubts that a flight simulator not specifically-designed for realism faithfully replicates the flight characteristics of a real aircraft. I have flown a T-38 simulator, but never a real T-38. Perhaps Biff could tell us if the T-38 and the T-38 simulator, or F-15 sim/plane are faithful simulations.
> 
> I watched a programmer one day change the flight chrracteristics in a sim, and he did it because he wanted it to fly better, not because it was "real." I have NO idea if the commercial game sims are good aerodynamic replications or not, but one Cessna 172 sim I used flew quite similarly to the real thing except for being easier to fly and having unlimited fuel and oil. When I say easier to fly, I mean I did some really bad landings on purpose and got away with it, apparently without damage.
> 
> ...




Greg,

The T-38 sim flew fairly close to the jet IIRC. The Eagle sim is fixed base, or doesn't move, so doesn't compare. The 757 / 767 / A320 / A319 sims I have flown are very close. The FAA allows you to get a type rating in them without ever having flown the jet.

Cheers,
Biff

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## soulezoo (Jan 19, 2017)

While I have not flown the C-5, I did fly the sim. Very realistic to me and confirmed by pilots.

I can tell you it's hell trying to land a Galaxy in 30kt cross winds and heavy rain at McChord AFB... with an inboard engine out!!

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## Glider (Jan 19, 2017)

wuzak said:


> I would suggest training simulators are a lot closer to reality than computer game simulators.


I should damn well hope so

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## drgondog (Jan 20, 2017)

Just a couple of thoughts on high altitude flight (from theoretical POV of course). First, the cruise speed for level flight narrows to a 'stall speed' the higher you climb and you are changing angle of attack to increase CL (density being critical factor in the Lift equation) - until you can't. For the same reason, the higher you go the faster you reach CLmax of Any turn.- same reason.

Long ago and far away I had a friend that was a retired USAF U-2 driver. Listening to him talk about the U-2 was an eye opener (before I got my Aero education) to understand how little margin of error the U-2 (or any vehicle requiring Lift in the fluid we name 'air') had for level flight and even more so for a turn at max altitude. Literally had to descend to be able to turn.

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## GregP (Jan 21, 2017)

I read that the original Learjet that got certified for flight at 51,000 feet was seriously in the "cofin corner," with some 4 knots higher to critical Mach numbers asome 4 lower to stall. So, if the pilot wasn't REALY on his airshpeed, he could stall or "lawn dart" when he exceeded critical Mach.

I never carefully checked out those claims because I never expected to be flying in one, but the newer jets, such as the Gulfstram 650, have a LOT of wing area, and have somegthing like a ±30 - 35 knot range before getting into trouble at either extreme.

I've read stories from U-2 pilots who said they were really AT the corner, with 1 - 2 kts before being too fast or slow, but never have confirmed it, and have no way to do so as I don't know any U-2 pilots. If I did, I seriously doubt they'd reveal anything they shouldn't. I worked on proximity fuzes for the Navy Standard Missile and would get VERY suspicious if anyone started asking about exact frequencys or specific test points. General curiosity is one thing, but technical detail questions rasie hackles when someone specifically asks about them.

I've always thought the U-2 / TR-2 flight specifics were "classified," but you can find a 1959 Pilot's Operating Handbook online. Scary to think it is a +2.5, -1 g airplane! A Cessna 172 is stronger than that!

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## BLine22 (Jan 22, 2017)

GregP said:


> I rad that the original Learjet thath got certified for flight at 51,000 feet was seriously in the "cofin corner," with some 4 knots higher to critical Mach numbers asome 4 lower to stall. So, if the pilot wasn't REALY on his airshpeed, he could stall or "lawn dart" when he exceeded critical Mach.



The Lear 31 that I currently fly is certified up to FL510. You would have to be so light to get that high that you would have almost no fuel left. Its a 3.5hr airplane. I've never been above 430 and usually cruise around FL400. By contrast the GIV is certified to 450 and you can usually get there after a couple of hours, but its a 9.5hr airplane.

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## grampi (Jan 23, 2017)

How did we go from P-51s to U2s and Lear jets?


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## Shortround6 (Jan 23, 2017)

the almost standard forum thread drift


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## drgondog (Jan 23, 2017)

The discussion focused on ceiling performance - and the various reasons for differences, including examples.


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## GregP (Jan 24, 2017)

The P-38L had a service ceiling of 44,000 feet, but I wonder how may ever actually GOT that high. The bombers in the ETO started out high and, when bombing accuracy was bad, went lower. After that, I wonder how many missions were actually flown way up high, other than perhaps recon missions. Likewise the P-51D had capability for over 40,000 feet. I doubt they spent a lot of time even at 35,000 feet, but could easily be wrong. I'm thinking mid 20s mostly after the initial high-altitude forays.

I would think that the P-38s in the PTO maybe started out up and 30,000 feet with the B-29s, but wound up down at 20,000 or below later in the war as the B-29s started coming down for better bombing accuracy and higher speeds over the target. That is, shallow dives at higher power levels after bombing the target.

So, once the ETO was won, I am thinking high-altitude missions for all the fighters virtually came to a halt sometime in 1945, but had been trending that way for some time.

Anyone know for sure? Bill Marshall? Did they start to drop a bit, or did they stay high?

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## Peter Gunn (Jan 24, 2017)

Not to nitpick but more a question, I thought PTO B-29 escort was the domain of the Mustang and maybe the N model Thunderbolt. Did the 38 ever get tasked shepherding Supefortress's over Japan?


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## drgondog (Jan 24, 2017)

I'm 99.9% sure that B-29 missions from the Marianas were escorted only by P-51s attached to 20th AF.

P-47Ns based at Okinawa and Ie Shima flew escort missions over Japan and Formosa but not for B-29s.


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## Conslaw (Jan 24, 2017)

The "N" Thunderbolt flew very few B-29 escort missions. I think I have read one group's unit history that recorded one escort mission. Of course there may have been others by the few other groups. The P-47N was still a hell of a plane and if the US had invaded Japan, the "N" would have been a true star. 

Going off on another tangent, I spoke to a veteran once who worked on the ground crew for a B-17 unit in Italy. He said late in the war they stripped their B-17s down so they could fly bombing missions from 30,000, like the early (Pre-E) B-17s. I have never read any unit histories or confirmations on this. If anybody has any info please post. I wish I knew the number of the bomb group.


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## drgondog (Jan 24, 2017)

Greg - the mission tasking in the ETO was not dogmatic in that bomber altitudes were primarily based on weather/flak considerations later in the war. That said, the 2nd BD B-24s were always flying lower when the B-17s were at 25000 feet (average). Early in the ETO experience the relative high altitude handling characteristics of the B-24, combined with best cruise speed advantage of the B-24 dictated an average formation altitude of 21-22000 feet.

When using radar for 10/10 cloud cover expectations the formations dropped as low as 18,000 feet for several missions.

As to fighter cover, the high squadrons frequently were as high as 5,000 feet above the high boxes of B-17s and so came to target as high as 30-32,000. I have not read every 8th AF mission Summary so can't comment if any fighter cover went as high as 35,000 but have read encounter reports where flights climbed to engage 109s observed at 35,000 feet. I doubt that very many P-51s or 47s or 38s bothered to climb that high with a full load of fuel.

The CBI/PTO/SWP bombing altitudes for B-24s was more often at 15-18,000 feet and frequently escorted by a range of fighters including P-40, F4U, P-38. I would be curious to know what missions, if any, ever flown by B-24 (or B-32) were at ETO/MTO altitudes.

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## drgondog (Jan 24, 2017)

Conslaw said:


> The "N" Thunderbolt flew very few B-29 escort missions. I think I have read one group's unit history that recorded one escort mission. Of course there may have been others by the few other groups. The P-47N was still a hell of a plane and if the US had invaded Japan, the "N" would have been a true star.
> 
> Going off on another tangent, I spoke to a veteran once who worked on the ground crew for a B-17 unit in Italy. He said late in the war they stripped their B-17s down so they could fly bombing missions from 30,000, like the early (Pre-E) B-17s. I have never read any unit histories or confirmations on this. If anybody has any info please post. I wish I knew the number of the bomb group.



Conslaw - in the waning months of ETO/MTO flak was the primary threat and several tactical mods were made to improve high altitude performance, including having the Navigator or Engineer toggle on lead crew and leav the bombardier home. including removing the ball turret and finally, cutting in half the ammo load of common practice during 1943.

It could have the effect of increasing effective cruise altitude for equivalent load of bombs, but late in the war the mission planners would have increased bomb loads more frequently for lower altitudes to improve % of bombs on target.

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## GregP (Jan 25, 2017)

I'll buy that, Bill.

The B-29 mission I never did investigate since the Navy war was what I was following. I assumed they used P-47Ns, P-51Ds, and P-38s just because all were avialable, and chose whatever fighter was suitable for the mission at the time, but didn't consider that perhaps ALL the B-29 missions were a bit long for the P-38s.

They chose the P-38 for the Yamamoto mission specificvally because the P-38 had the range ... so I never really thought about it as I was mostly a "fighter guy."


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## drgondog (Jan 25, 2017)

Greg - I think it was a combination of three factors, maybe more. The first was organizational. Only Mustang groups were assigned to 20th AF. The second reason, perhaps linked to the first is that every drop of fuel was 'imported' via shipping and the B-29s used a lot more fuel than comparable B-17/B-24 fleet. The P-51D was far more economical than the P-38 and 2/3 cost of P-47N to operate - That combined with proven track record of escort (for Lemay) made a choice, if he had to make one, a no brainer.

Logistics with respect to single type versus multiple type (say P-38 and P-47 along with P-51) IMO also contributed to the decision.

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## Zipper730 (Jan 28, 2017)

bobbysocks said:


> if they didnt burn down the fuse tank the center of gravity was off and they were limited on some of the maneuvers. that is why they ran it down to 25-30 gallons right after take-off.


Oh, I thought one would want to burn out the whole tank; then switch to the drop-tanks until you had to punch 'em off?

Regardless from what I remember the P-38J you had to burn off a little bit of the wing tanks first before switching to drp-tanks



drgondog said:


> All subsequent Mustangs had the 85 gallon tank until the P-51H - which carried a 50 gallon tank, and had increased fuselage length and re-designed tail to eliminate the stability issues inherent in the Merlin powered Mustang combined with increased gross weight and 85 gallons/500+ pounds aft of the CG on take off.


I though the center tank was had the CG just on the aft limit...


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## BiffF15 (Jan 28, 2017)

Zipper730 said:


> Oh, I thought one would want to burn out the whole tank; then switch to the drop-tanks until you had to punch 'em off?
> 
> Regardless from what I remember the P-38J you had to burn off a little bit of the wing tanks first before switching to drp-tanks
> 
> I though the center tank was had the CG just on the aft limit...



Zipper,

In the Eagle we would burn out the external wings first, external centerline, then internal. The plane would do that automatically (bleed air pressure to the wings was higher than to the center bag) so that when you jettisoned external tanks the internals where as full as they could be. In the Mustang, and I'm guessing here, the mentality was the same except for the CG problem. Get the CG under control, keep as much gas internally as possible until the situation drives you to jettison the external tanks, then fights on. Your burn rate in combat is so high, even in a Mustang, that you want to start a fight with as much fuel on board as possible (long ride home). This is a consideration that the Bf-109s / Fw-190s did not have which in turn is a serious performance advantage. Like Colin Chapman said, "Add lightness".

I also flew the OV-10 Bronco. We usually flew with a centerline bag (1500lbs) and could carry 1500lbs internal. Engine out climb performance in the summer was so anemic we would adjust fuel loads to compensate. In the morning "go" (bank) we would fly the planes with both internal and external full. The pilots would then burn most of the internal fuel out, then sip from the external. They would land with about 300-400lbs internal, and about 1k in the external. The next flight was in the heat of the day with the previously poor engine out performance, and should the pilot lose and engine he could jettison almost all his fuel (excess weight) to increase his odds of a safe recovery. 

The big picture I'm trying to convey is some planes in certain conditions require unusual operational considerations.

Cheers,
Biff

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## drgondog (Jan 29, 2017)

Zipper - find one of the texts I recommended earlier. Look up Neutral Point, Static and Dynamic Stability and Static Margin. I'm not going to dive into this but here is a simple concept in context of the issues arising from the addition of the 85 gallon fuselage tank. The center of mass for a full tank is well aft of the CG and in fact, very near the Neutral point, Note that the Tank is an addition to all the other masses contained in the Design for the Mustang - all of which contribute to the Center of Gravity and in fact establish the Neutral Point..

The CG MOVES depending upon the load out. When Dry, the CG is at a 'forward location'. When fully loaded, the 'new' CG moves aft but hopefully short of the Neutral Point. When fully loaded with 85 gallons the CG has moved very close to the Neutral Point (a well defined term that you need to research) rendering the aircraft Statically unstable.

One of the major design changes for the P-51H was to design it with a Neutral Point aft (relative to P-51 through P-51K) as well as increase the tail areas to address the stability issues the earlier Mustang experienced even prior to the 85 gallon fuselage tank introduced into the Merlin Mustang.

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## Zipper730 (Jan 29, 2017)

drgondog said:


> Zipper - find one of the texts I recommended earlier. Look up Neutral Point, Static and Dynamic Stability and Static Margin.


Dynamic stability has to do with oscillations like phugoids, Static stability is what most people think of with stability (i.e. if I pull back on the stick, g-load goes up to 1.5 fro 1.0 it should return back to 1.0 if the stick is centered), and neutral point I just checked... its the point where stability becomes neutral.


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## KiwiBiggles (Jan 30, 2017)

drgondog said:


> One of the major design changes for the P-51H was to design it with a Neutral Point aft (relative to P-51 through P-51K) as well as increase the tail areas to address the stability issues the earlier Mustang experienced even prior to the 85 gallon fuselage tank introduced into the Merlin Mustang.



Do you (or anyone else) know if giving the P-51H a larger static margin like this caused it to be slower on the controls than the D/K etc? My understanding has always been that stability and responsiveness are each other's inverse; that increasing static stability by providing a larger static margin leads to slower responses to pilot input.


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## GregP (Jan 30, 2017)

Are the control surfaces the same size on the D/K and H? I haven't checked. But it might make a difference.


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## drgondog (Jan 31, 2017)

Two factors - difference between the P-51B thru K had adjustable aileron throw from 10, 12 to 15 degrees, whereas the P-51H was 12 degrees max. The P-51H ailerons (and tail surfaces) were also larger. The Roll rates were approximately the same in flight tests but rigging data is not available for the tests that I have looked at, nor in NAA Performance Calculations.

As to static margin. I don't have the data on the stated aft cg location as percent of MAC for either. What Was different is that the center of mass for the 50 gallon fuselage fuel tank was closer to the normal take off CG AND within the static margin (and neutral point) for All load outs - contrast with all 85 gallon fuel tank installations.


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## Zipper730 (Jan 31, 2017)

drgondog said:


> As to static margin. I don't have the data on the stated aft cg location as percent of MAC for either. What Was different is that the center of mass for the 50 gallon fuselage fuel tank was closer to the normal take off CG AND within the static margin (and neutral point) for All load outs - contrast with all 85 gallon fuel tank installations.


So the P-51H was more docile for long-range operations


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## BiffF15 (Jan 31, 2017)

Zipper,
I think you could say long range or full internal fuel load ops. I imagine (Drgondog please correct me if I'm assuming incorrectly) that carrying either external tanks or bombs along with a full fuselage tank in the P-51H was safer due to the changes from the B/C/D models.
Cheers,
Biff


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## tomo pauk (Feb 1, 2017)

GregP said:


> Are the control surfaces the same size on the D/K and H? I haven't checked. But it might make a difference.





drgondog said:


> Two factors - difference between the P-51B thru K had adjustable aileron throw from 10, 12 to 15 degrees, whereas the P-51H was 12 degrees max. The P-51H ailerons (and tail surfaces) were also larger. The Roll rates were approximately the same in flight tests but rigging data is not available for the tests that I have looked at, nor in NAA Performance Calculations.
> 
> As to static margin. I don't have the data on the stated aft cg location as percent of MAC for either. What Was different is that the center of mass for the 50 gallon fuselage fuel tank was closer to the normal take off CG AND within the static margin (and neutral point) for All load outs - contrast with all 85 gallon fuel tank installations.



Looking at Gruenhagen's book, pg. 176, the -H have had smaller ailerons - 6.35 sq ft vs. 6.7 sq ft on previous in-service variants; both values include tab. Travel was also incresed to 15 deg both up and down, being 10 deg up and down previously (greater travel + greater area = greater rate of roll?). AIleron tabs were movable 10 deg up and down in all versions.
P-51H was with horizontal stabilizer of greater area, but of smaller span; however the area of the elevators was reduced a bit. Vertical tail was with greater area on the P-51H, too.


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## wuzak (Feb 1, 2017)

The P-51H was also longer by about a foot.

Increased leverage for the elevators?


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## drgondog (Feb 1, 2017)

Tomo - I think Bob transposed the D/H data on ailerons and Elevator data. The NAA data has 10-12-15 degree throw for all P-51B/C/D and P-51H at 10 for ailerons and the areas Bob presented are also 'opposite' for Elevator data.

Warbird Tech Series posts AN-60-60JE-2 Three View extracted from NAA top drawing three view. I will check my drawing package.


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## bobbysocks (Feb 1, 2017)

Zipper730 said:


> Oh, I thought one would want to burn out the whole tank; then switch to the drop-tanks until you had to punch 'em off?
> 
> Regardless from what I remember the P-38J you had to burn off a little bit of the wing tanks first before switching to drp-tanks
> 
> I though the center tank was had the CG just on the aft limit...



I think ( and only my opinion ) was they were hedging their bets. when they dropped their tanks they were on internal fuel and sometimes ( depending on the mission ) a LONG way from home. as missions started to go to berlin and points beyond, having enough fuel so they didn't have to ditch or bail out in enemy would be a concern. I have read several accounts where the plane's engine died due to fuel starvation almost as soon as the pilot plopped her on the runway. on a mission to Munich my dad and his wingman ran out of fuel before they hit the channel. by that time there were 9th AF and RAF bases in France and Belgium so it was no big deal...had that happened before D-day they would have had to break off the engagement they were in earlier or would have become POWs. that extra 30+ gallons might mean the difference between sleeping in your own bed or floating in a dingy in the north sea OR an all inclusive vacation to stalag luft ???...

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## Zipper730 (Feb 1, 2017)

syscom3 said:


> The P38 was never designed for dog fighting. It was an interceptor.


It was called an interceptor to circumvent armament restrictions that the USAAC put on pursuit planes, as well as possibly allow two engines.

It was intended to climb and accelerate fast, fly quickly, and at high altitudes, but it was intended to be able to fly as a traditional interceptor and a fighter.



drgondog said:


> A couple of observations - the P-38J tested at 15000 pounds is 2699 pounds under full internal combat load. -------> 85% of full internal GW. If you 'grow' the P-38J GW to Normal full combat load you divide the recorded turn radius of 838 ft by 0.85 ------------>985 ft
> 
> The P-51B at 9000 pounds GW is 611 pounds under full internal combat load - the equivalent of flying without 85 gallon tank fuel ----------> 93% of full internal GW. If you then divide the presented turn radius of 883 ft by 0.93 -------> 949 feet, less than the comparably loaded P-38.


Wait, I thought the P-51D was listed?


> It is further documented in Dean's "America's Hundred Thousand". He also documents the turn performance of the P-38J/L as less than the P-51D - and the P-51B outperforms the P-51D.


The B was a little cleaner with the razorback and had a slightly different wing; the P-51B was lighter also.



Conslaw said:


> The "N" Thunderbolt flew very few B-29 escort missions. I think I have read one group's unit history that recorded one escort mission. Of course there may have been others by the few other groups.


Why did it fly so little?


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## drgondog (Feb 2, 2017)

The P-51B at 5% less GW had less induced drag for the same throttle settings, altitude and load out. It was not 'cleaner'. In fact the windscreen canopy enclosure was slightly 'draggier' than the P-51D bubble canopy.

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## drgondog (Feb 3, 2017)

Tomo - I just checked 106-00001 P-51D Three View and 117-00001 P-51H Three View. The elevator and aileron data I presented is correct. Gruenhagen did transpose the P-51D and P-51H elevator and aileron deflection data and I just sent him an email just in case somebody else hasn't noted this before.

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## tomo pauk (Feb 3, 2017)

Thank you


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## drgondog (Feb 3, 2017)

I just pulled 102-00001 P-51B 3 View and found more data different from Bob's page 176 posting. He lumped B/C/D/K in one column and there were several differences such as 50 degree flap for B and 47 for D/K, Vertical Stab area of 20.02 sq ft versus Bob's 20.68 sq ft for B/C/D/K... there are a few more that I pointed out to him in an email.

In Gruenhagen's defense it could have simply been an editor error in transcribing from type written to editor copy and Bob missed it on revue.. It happened to me on my last corrections with (Schiffer) Our Might Always.


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## tomo pauk (Feb 3, 2017)

I guess I could've looked it myself, at least for the P-51B:


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## Zipper730 (Feb 3, 2017)

BiffF15 said:


> Zipper,
> 
> In the Eagle we would burn out the external wings first, external centerline, then internal. The plane would do that automatically (bleed air pressure to the wings was higher than to the center bag) so that when you jettisoned external tanks the internals where as full as they could be.


That's fascinating, I didn't know the F-15 used engine bleed air to pressurize the tanks. I know the F-106 used some kind of engine-driven bleed-air system to move fuel around in the tanks though (there was a concern that a single round could incapacitate the whole thing).


> In the Mustang, and I'm guessing here, the mentality was the same except for the CG problem. Get the CG under control, keep as much gas internally as possible until the situation drives you to jettison the external tanks, then fights on.


Makes enough sense


> Your burn rate in combat is so high, even in a Mustang, that you want to start a fight with as much fuel on board as possible (long ride home). This is a consideration that the Bf-109s / Fw-190s did not have which in turn is a serious performance advantage.


For the Me-109 and Fw-190's...


> Like Colin Chapman said, "Add lightness".


I never even knew who he was, but I know about one sports-car he built.


> I also flew the OV-10 Bronco.


Now that's pretty cool: I guess you flew during the Vietnam War era into the 1980's right?


> We usually flew with a centerline bag (1500lbs) and could carry 1500lbs internal. Engine out climb performance in the summer was so anemic we would adjust fuel loads to compensate. In the morning "go" (bank) we would fly the planes with both internal and external full. The pilots would then burn most of the internal fuel out, then sip from the external. They would land with about 300-400lbs internal, and about 1k in the external. The next flight was in the heat of the day with the previously poor engine out performance, and should the pilot lose and engine he could jettison almost all his fuel (excess weight) to increase his odds of a safe recovery.
> 
> The big picture I'm trying to convey is some planes in certain conditions require unusual operational considerations.





drgondog said:


> The P-51B at 5% less GW had less induced drag for the same throttle settings, altitude and load out. It was not 'cleaner'. In fact the windscreen canopy enclosure was slightly 'draggier' than the P-51D bubble canopy.


You mean the P-51D had 5% less gross weight and less induced drag? Because if I read what you said right, the P-51B was 5% lighter and had less induced drag, and was draggier than the P-51D...

I am puzzled regardless how the P-51D was less maneuverable than the P-51B and thus at low-speeds was less maneuverable at lower speeds than the Me-109, and at higher speeds, more so (if I recall altitude provided a disadvantage for the Me-109 due to having less power up there).


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## drgondog (Feb 4, 2017)

"
_You mean the P-51D had 5% less gross weight and less induced drag? Because if I read what you said right, the P-51B was 5% lighter and had less induced drag, and was draggier than the P-51D...

I am puzzled regardless how the P-51D was less maneuverable than the P-51B and thus at low-speeds was less maneuverable at lower speeds than the Me-109, and at higher speeds, more so (if I recall altitude provided a disadvantage for the Me-109 due to having less power up there).
_
*No. The P51B w/85 gallon tank, at full load out, with the same 1650-7 engine as the P-51D also at full load out is 4-5% lighter than the P-51D. Induced drag is related to Lift and proportional to the square of CL.

Another point which should be made is that all the references to '440mph' points to the P-51B-1 and -5 with no 85 gallon tank and having the 1650-3 for best performance at 29,000 feet. For that condition the weight differences are closer to 10% from the fully loaded P-51D.

The P-51B and D with 1650-7 's both have FTH at 24-25000 feet and top speed at 67" MP roughly the same top speed at 25,000 feet ~ 437 mph at full GW with slight edge to the P-51B-10, -15 and all prior blocks modified to include the 85 gallon tank.

The REAL benefit for the weight differences isn't top speed for same GW conditions. They are turn radius and Climb (notable) and acceleration (very slightly)*

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## drgondog (Feb 4, 2017)

P-51 Mustang Performance

Great site. That said, you have to look VERY carefully at each summary narrative to glean critical GW and external configuration. Most of the top speeds and climb rates contained in the various Flight Test reports are a.) do not have both full internal fuel load out (269 gallons) and full ammunition load, and b.) have the external bomb racks attached.

The other factor when looking at the three different P-51s (B/C without 85 gallon tank having the 1650-3, B/C with 85 gallon tank modified at Depot also having 1650-3, and B/C with factory 85 gallon tank but using the 1650-7) to compare with P-51D/K (all P-51D/K in combat units in ETO/MTO/PTO/CBI had 1650-7) for Performance - is that you have to look at 'apple to orange' comparisons for power plant.

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## Zipper730 (Feb 6, 2017)

drgondog said:


> *No. The P51B w/85 gallon tank, at full load out, with the same 1650-7 engine as the P-51D also at full load out is 4-5% lighter than the P-51D. Induced drag is related to Lift and proportional to the square of CL.*


So with the same engine and 85-gallon tank, the P-51D was 4-5% lighter?


> *Another point which should be made is that all the references to '440mph' points to the P-51B-1 and -5 with no 85 gallon tank and having the 1650-3 for best performance at 29,000 feet. For that condition the weight differences are closer to 10% from the fully loaded P-51D.*


So without the 85-gallon tank, the P-51B's were 10% lighter?


> *The P-51B and D with 1650-7 's both have FTH at 24-25000 feet and top speed at 67" MP roughly the same top speed at 25,000 feet ~ 437 mph at full GW with slight edge to the P-51B-10, -15 and all prior blocks modified to include the 85 gallon tank.*


Why would the P-51B have a slight advantage if it had the same fuel-load, FTH, and weighed 4-5% more?


> *The REAL benefit for the weight differences isn't top speed for same GW conditions. They are turn radius and Climb (notable) and acceleration (very slightly)*


So the P-51D would turn tighter at the same fuel status for a given engine?


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## drgondog (Feb 6, 2017)

Zipper - please re-read #107 carefully.

Also, to help you do the math

Empty Tank weight = 55 pounds
85 gallons of fuel =~ 510 pounds
6x50 caliber guns =~414 pounds
1880 rounds of 50 Cal =~ 620 pounds
4x50 caliber guns =~276 pounds
1260 rounds of 50 Cal =~ 422 pounds

The Delta in ammo/guns between the P-51A/B/C and P-51D/K is (620+414) - (422+276) = 336 pounds

The Delta in 85 gallon tank plus full fuel = 565 pounds.

Summary - The P-51B-1-NA 43-12093 with 1650-3 Merlin, as tested at Eglin, did not have a Fuselage Tank or extra 85 gallons of fuel. All P-51D had the 85 gallon tank installed at factories and when tested with full fuel and ammo, not only weighed 900 pounds more than the P-51B-1 but also had the 1650-7 Merlin.

The empty weight difference (No Guns, No Ammo, no 85 gallon fuel tank, no fuel (wings and fuselage), no bomb racks) between the P-51B and P-51D is 7205-6988 = 217 pounds

Note: Dean's data for ammo weight on pg 329 of America's 100K for 1880 rounds of 50 caliber is nearly 50 pounds too low. His data of 576 pounds would be good for 1710 rounds. That said page 328 and 329 are best single source for NAA published data across several sources.

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## Peter Gunn (Feb 6, 2017)

Trying to get a handle on all this, you guys make me feel like a real dummy...

Question on the Merlins used, or really the differences between them, specifically the 1650-3 and the 1650-7, I'm assuming one was optimized for higher altitude performance? And then how does the 1650-9 of the H model fit in?

Thanks.


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## tomo pauk (Feb 6, 2017)

The -3 was the hi-alt model, the -7 was mid-altitude among the 2-stage supercharged Merlins. Main difference between the two was the supercharger multiplication gearing. The -9 was a new version, having many common fetures with the Merlin 100 series from Rolls Royce. One of features added was provision for water injection, meaning a considerable jump in short-term power.

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## Peter Gunn (Feb 6, 2017)

Many thanks Tomo, much appreciated.


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## drgondog (Feb 6, 2017)

Tomo is correct. Much of the data for the -9 was the same as the -3 with two significant differences. The -9 FTH in High Blower (at 67") was around 26000 vs 29000 at (47") for the -3, and the engine itself was more robust to withstand 90" Boost with WI. 

The crankshaft design with end to end oil feed is a very desirable feature over the -3 and -7.


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## Peter Gunn (Feb 6, 2017)

In perusing Tomo's chart I see the use of 100/130 grade fuel, so would it be correct to assume then that they'd be running at 67" boost and not 75"?

And to further be a pain with dumb questions, what would the -9 be capable of with 44-1 and running 90" MP?


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## tomo pauk (Feb 6, 2017)

There won't be 90 in Hg of boost unless water/alcohol injection is used on the Packard Merlin. With w/a injection, 115/145 fuel (post war) and 90 in Hg of boost, the power was 2220 HP in low gear (9000 ft), or 1790 HP in high gear (22700 ft); both altitudes with ram, ie. actual flying aircraft. From here
These charts show a bit greater power: link.


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## Zipper730 (Feb 7, 2017)

drgondog said:


> Zipper - please re-read #107 carefully.
> 
> Also, to help you do the math
> 
> ...


I did the math and got a different delta and numbers than you did

P-51B-1NA
Empty: 6988 pounds
Guns & Ammo: 7686 pounds (delta: 698 lbs)
Fuel in Wings: 8790 pounds (delta: 1104 lbs)

P-51D
Empty: 7205 pounds
Guns & Ammo: 8239 pounds (delta: 1034 lbs)
Fuel in Wings: 9343 pounds (delta: 1104 lbs)
Center Tank: 9853 pounds (delta: 510 lbs)

P-51D had 1043 pounds vs 900 pounds on the P-51B (I've found a multitude of different weight figures for the P-51B also, I'm not sure what to make of them), though in truth it would be more like 533-713 because in combat you would have already either drained the center tank or had 30 gallons at max present.

As for turning performance, the P-51D had a slightly different wing and less drag. With the turning circle can I just vary the weight difference, or is this going to require more complicated calculations due to the wing and drag?


> Tomo is correct. Much of the data for the -9 was the same as the -3 with two significant differences. The -9 FTH in High Blower (at 67") was around 26000 vs 29000 at (47") for the -3, and the engine itself was more robust to withstand 90" Boost with WI.


I'm not sure if I missed something, but why would you want to reduce FTH on the P-51D's over the P-51B/C if they're being used as bomber escorts?


> The crankshaft design with end to end oil feed is a very desirable feature over the -3 and -7.


Better lubrication it sounds



Peter Gunn said:


> Trying to get a handle on all this, you guys make me feel like a real dummy...


I wouldn't say that -- it's a complicated subject and drgondog might be an aerospace engineer, and I have a combination of asperger syndrome, and obsessive compulsive disorder.


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## wuzak (Feb 7, 2017)

Zipper730 said:


> I'm not sure if I missed something, but why would you want to reduce FTH on the P-51D's over the P-51B/C if they're being used as bomber escorts?



Still more than enough performance at escort altitudes while giving improved rate of climb and level performance at altitudes where most of the fights occur.

ie better all-round performance

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## Zipper730 (Feb 7, 2017)

Wuzak,

Escort altitudes were around 24,000 to 27,000 for the B-24's, and 28,000-31,000 for the B-17's right?


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## wuzak (Feb 7, 2017)

Zipper730 said:


> Wuzak,
> 
> Escort altitudes were around 24,000 to 27,000 for the B-24's, and 28,000-31,000 for the B-17's right?



Somewhere around that.

But you are overlooking the fact that when the bombers were attacked the escorts chased after the fighters which, in most cases, saw the lose altitude.

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## drgondog (Feb 7, 2017)

Zipper730 said:


> I did the math and got a different delta and numbers than you did
> 
> P-51B-1NA
> Empty: 6988 pounds
> ...


The P-51 wing from XP51 through P-51B/D was the same wing/airfoil NAA/NACA 45-100. Only the root chord was changed on the P-51D to accommodate the new Gear Door and wheel uplock design. You may be thinking about the XP-51F/G/J and P-51H which had straight leading edge and different (but same T/C) NACA 66-(1.8) 15.5 airfoil.

If you are playing with 'textbook' turning radius calculations, Drag and Engine/Prop Efficiencies and HP as f(altitude) are not factors, and not realistic nor consistent with real world. A factor missed by the gamers, and very elusive, is the Form Drag increase as a function of Angle of Attack which is derived from wind tunnel and for axis symmetric flight only. Asymmetric flight conditions with side loads, rudder and elevator trim increments also introduce Trim Drag.

Basically, if you are serious, you need to also add cooling drag for the P-51 which is significant as high speed exhaust thrust neutralized the Cooling Drag but in Climb was a Major factor, The latter factors contribute to increments to Power Required in addition to incremental form drag and trim drag discussed above.

To the Power Available from the manufacturer charts (which sometimes include ram effect), you also need to calculate Exhaust gas Thrust. To take into consideration the Engine/Prop efficiency you have to carefully look at the airspeed and altitude because the Prop efficiency falls off in high AoA/Low speed envelope (as in high G turn).

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## bobbysocks (Feb 7, 2017)

drgondog said:


> If you are playing with 'textbook' turning radius calculations, Drag and Engine/Prop Efficiencies and HP as f(altitude) are not factors, and not realistic nor consistent with real world. A factor missed by the gamers, and very elusive, is the Form Drag increase as a function of Angle of Attack which is derived from wind tunnel and for axis symmetric flight only. Asymmetric flight conditions with side loads, rudder and elevator trim increments also introduce Trim Drag.
> 
> Basically, if you are serious, you need to also add cooling drag for the P-51 which is significant as high speed exhaust thrust neutralized the Cooling Drag but in Climb was a Major factor, The latter factors contribute to increments to Power Required in addition to incremental form drag and trim drag discussed above.
> 
> To the Power Available from the manufacturer charts (which sometimes include ram effect), you also need to calculate Exhaust gas Thrust. To take into consideration the Engine/Prop efficiency you have to carefully look at the airspeed and altitude because the Prop efficiency falls off in high AoA/Low speed envelope (as in high G turn).



Bill, you need to write a synopsis of the calculations gaming developers need to use....in all you free time of course..haha. 

I always get into discussions with these players because they are under the impression that the flight models in the games are accurate when in fact they are woefully wrong. I don't think the developers intentionally do this but in reality have no clue as to what metrics to use for the formulation of those flight models. they basically build off of someone else's work....which is wrong to begin with.

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## GregP (Feb 7, 2017)

What?!

You mean real airplanes DON'T have unlimited fuel? And you CAN'T fly them at full throttle for the entire flight? And they DON'T have unlimited ammunition, either?

Next you'll be telling me tailgraggers don't take off straight, either!


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## bobbysocks (Feb 8, 2017)

and they are wheels up with full load out after only rolling out 100 feet....

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## GregP (Feb 8, 2017)

And you can start doing rolls right after liftoff with EASE ... and gain altitude at the same time.


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## pbehn (Feb 8, 2017)

When 10% of people using sims die in training and deaths using sims are at a similar level to those in combat then sims can be accepted as realistic. I have taken on many a Bf 109 in a head on attack and not once has a bullet come through my screen (But then I am a sim ace).

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## KiwiBiggles (Feb 8, 2017)

pbehn said:


> When 10% of people using sims die in training and deaths using sims are at a similar level to those in combat then sims can be accepted as realistic. I have taken on many a Bf 109 in a head on attack and not once has a bullet come through my screen (But then I am a sim ace).



A bit unfair. I don't think air forces require that their simulators kill 10% of their trainees, but they still seem to find them useful. Simulators don't have to be realistic in every detail to be useful and interesting in many ways.


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## Zipper730 (Feb 8, 2017)

wuzak said:


> Somewhere around that.


The most efficient cruise is typically how much altitude or percentage of altitude above the critical altitude?



> But you are overlooking the fact that when the bombers were attacked the escorts chased after the fighters which, in most cases, saw the lose altitude.


Of course, and then afterwards they'd probably have to climb back into the bomber formation right?




drgondog said:


> The P-51 wing from XP51 through P-51B/D was the same wing/airfoil NAA/NACA 45-100. Only the root chord was changed on the P-51D to accommodate the new Gear Door and wheel uplock design.


Still doesn't that have an effect on the performance of the wing? Did the wing-area or aspect-ratio change at all (Most sources say no, but the shape changed so it seemed a good question to start with).


> If you are playing with 'textbook' turning radius calculations, Drag and Engine/Prop Efficiencies and HP as f(altitude) are not factors, and not realistic nor consistent with real world.


So just multiplying the difference in weight (85% so multiplying turn-radius by 0.85) is not realistic?


> A factor missed by the gamers, and very elusive, is the Form Drag increase as a function of Angle of Attack which is derived from wind tunnel and for axis symmetric flight only.


Okay, I can find the form drag formula on wikipedia; I'm not sure how to determine this data based on the presence of AoA (unless the formula already includes it).


> Asymmetric flight conditions with side loads, rudder and elevator trim increments also introduce Trim Drag.


I'm not sure where I'd be able to even find all that data.


> Basically, if you are serious, you need to also add cooling drag for the P-51 which is significant as high speed exhaust thrust neutralized the Cooling Drag but in Climb was a Major factor, The latter factors contribute to increments to Power Required in addition to incremental form drag and trim drag discussed above.


No idea where I would find that?


> To the Power Available from the manufacturer charts (which sometimes include ram effect), you also need to calculate Exhaust gas Thrust.


That varies with speed and altitude right?


> To take into consideration the Engine/Prop efficiency you have to carefully look at the airspeed and altitude because the Prop efficiency falls off in high AoA/Low speed envelope (as in high G turn).


I don't actually know how to determine propeller efficiency....



bobbysocks said:


> Bill, you need to write a synopsis of the calculations gaming developers need to use....in all you free time of course..haha.


Agreed!


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## drgondog (Feb 9, 2017)

Form Drag as a function of AoA was not suited to an analytical approach in WWII - all wind tunnel. Wikipedia is worthless for useful Physics of flight.

Power Available as a function of altitude can be found on many sites. Spitfireperformance.com is a good site for the Power curves - some have adjustments for ram effect.

Cooling Drag is wind tunnel focused.

There isn't enough time in the day to explain how to derive Propeller Efficiency. The definition is Eta= THP/SHP where THP is Useful Work Done on Airframe and SHP is Work Output of the Power Plan. There are many texts that will lead you down the path - but you have to have the Activity Factor - a non-dimensional value which is the capacity of the prop to absorb power. It can be derived via numerical integration. It is done empirically and also adjusted for profile drag of the prop and compressibility effect. One text for you to look at is Gerald Corning's Supersonic and Subsonic Airplane Design.

Also look to NACA Restricted Report, dated September, 1943, "Representative Operating Charts for Propellers Tested in NACA 20 ft. Propeller Research Research Tunnel".

Calculating Exhaust Gas Thrust (and drag) of exhaust stacks requires Po Outside static airpressure, A = Total stack opening area, Me+ Engine Charge Consumption in slugs/sec, Po/Pm = ratio of static to manifold pressure. A couple of charts are necessary. Charge Consumption for both High and Low Blower are required as a function of Brake HP.

Engine air momentum loss must be calculated to account for corrections to Power Available which require Engine Air Consumption, Engine Charge Consumption and the Fuel to Air ratio.

I have spent way too much time on this. If I am silent regarding future questions on the 'unknowable by simple calculations', please give me some slack.

Also NACA Restricted Report, dated November, 1942 "Effect of Exhaust Stack Shape on Design and Performanceof the Individual Cylinder Exhaust Gas Propulsion System"

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## pbehn (Feb 9, 2017)

drgondog said:


> I have spent way too much time on this."



I for one appreciate the time you have taken, I know I know next to nothing about aerodynamics, what I didnt know is how many fields of knowledge there are which I didn't even know existed.


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## GregP (Feb 9, 2017)

Being as rusty as I am on it, I appreciate the time spent as well. I find I can spend several hours looking up something, reviewing it, and formulating an opinion ... somewhat begrudge a lot of additional time to document it for a one-sentence question like, "how did you arrive at that conclusion?" especially considering how lousy a typist I am, not to mention how slow.

Some of you guys are very thorough at it though. We all know who they are, and I appreciate the effort expended, whether or not I see it the same way. A concise explanation goes a long way to help understanding. Well, maybe except for noconshooter's "thrust column" theory ... 

So, thanks for the time investment, guys.

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## Shortround6 (Feb 9, 2017)

drgondog said:


> I have spent way too much time on this. If I am silent regarding future questions on the 'unknowable by simple calculations', please give me some slack.



A very well said post.

If _simple calculations _would actually give even close to real answers then people wouldn't have to go to school for _years _to get a handle on even one or two aspects of flight performance. 

There is no "Fight Performance Calculations for Dummies" book available anymore than there is a "Career in Wall Street Investing for Dummies" book or "Brain surgery in 4 and 1/2 weeks". 

Aeronautical companies didn't employ engineers by the dozens (and by the time of jets by the hundreds) if simple calculations would do the job.

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## Zipper730 (Feb 11, 2017)

drgondog said:


> Power Available as a function of altitude can be found on many sites. Spitfireperformance.com is a good site for the Power curves - some have adjustments for ram effect.


Sounds good


> Cooling Drag is wind tunnel focused.


Ok


> There isn't enough time in the day to explain how to derive Propeller Efficiency.


It's in the John D. Anderson book though?


> One text for you to look at is Gerald Corning's Supersonic and Subsonic Airplane Design.


When some more money flows in and my courses are finished, I might get it...


> Also look to NACA Restricted Report, dated September, 1943, "Representative Operating Charts for Propellers Tested in NACA 20 ft. Propeller Research Research Tunnel".


That sounds good


> Calculating Exhaust Gas Thrust (and drag) of exhaust stacks requires Po Outside static airpressure, A = Total stack opening area, Me+ Engine Charge Consumption in slugs/sec, Po/Pm = ratio of static to manifold pressure. A couple of charts are necessary. Charge Consumption for both High and Low Blower are required as a function of Brake HP.
> 
> Engine air momentum loss must be calculated to account for corrections to Power Available which require Engine Air Consumption, Engine Charge Consumption and the Fuel to Air ratio.


Beyond my current pay-grade, I'll have to read up on this


> Also NACA Restricted Report, dated November, 1942 "Effect of Exhaust Stack Shape on Design and Performanceof the Individual Cylinder Exhaust Gas Propulsion System"


Fascinating




Shortround6 said:


> A very well said post.
> 
> If _simple calculations _would actually give even close to real answers then people wouldn't have to go to school for _years _to get a handle on even one or two aspects of flight performance.


Actually I've had cases where a person gave me one piece of information and it made it possible to make sense of the rest...



> There is no "Fight Performance Calculations for Dummies" book available anymore than there is a "Career in Wall Street Investing for Dummies" book or "Brain surgery in 4 and 1/2 weeks".


I see your point...


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## swampyankee (Feb 11, 2017)

pbehn said:


> When 10% of people using sims die in training and deaths using sims are at a similar level to those in combat then sims can be accepted as realistic. I have taken on many a Bf 109 in a head on attack and not once has a bullet come through my screen (But then I am a sim ace).


Certainly, the death rate in service wasn't that high. After all, aircrew had almost a 50% chance of surviving 50 missions. (8th Air Force bomber crews had casualty rates greater than infantry units).


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## pbehn (Feb 11, 2017)

swampyankee said:


> Certainly, the death rate in service wasn't that high. After all, aircrew had almost a 50% chance of surviving 50 missions. (8th Air Force bomber crews had casualty rates greater than infantry units).


These are not the same thing at all. Fifty missions is fifty flights. From starting training to becoming a qualified front line pilot with two hundred hours on P51s takes a lot more than 50 flights and the trainee is permanently learning, as he becomes proficient on one type he then gets to fly something more difficult. Loss rates are an average, while it may be true over the whole war that a crew had a 50% chance of surviving 50 missions, it is also true that they had less than 50% chance of surviving one mission like Fairey Battles in France or some unescorted RAF daylight raids. US losses on some raids were around 30% while on other raids late in the war the loss rate purely reflected the reliability of the aircraft itself.

Bomber Command losses September 1939 - May 1945: 47,268 men killed on operations. Another 8,303 killed in flying or training accidents, total 55,571. Another 1,570 groundcrew and WAAFs lost their lives from other causes.

From the table here
United States World War II Aircraft Loss Statistics during Flight Training
13,621 people died in 5533 fatal accidents while training in the US air force.

Flying at the time was dangerous in itself especially from airfields in the UK when fog is common and low cloud perfectly normal.


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