P-38 Lightning vs P-51 Mustang: Which was the Better Fighter?

[renrich]

Not to take anything away from the Hellcat, it's pilots or records but the Hellcat came on scene when the highly skilled IJN pilots were beginning to be depleted. Plus if you look at the record many of it's kills were not against fighters but bombers and later kamikazes flown by fledglings. The many kills by Mustangs, P38s and Jugs were mostly against fighters although the skill of the LW pilots gradually eroded on average.

 

[syscom3]

Renrich, dont forget that the P38 was designed to be a bomber interceptor from the onset.

The fact that it could also be used as a decent fighter and fighter-bomber speaks volumes on its basic design.

 

[drgondog]

Renrich, dont forget that the P38 was designed to be a bomber interceptor from the onset.

The fact that it could also be used as a decent fighter and fighter-bomber speaks volumes on its basic design.

Syscom - I wonder how the remembrance of the P-38 in ETO would be different if the prototype had not crashed on the Army cross country stunt - and the Lockheed team had that lost year to sort out compressibiliy, engine, dive performance and boosted ailerons by 1943 instead of mid 1944?

I had a hard time getting either Olds or Landers to give a decisive edge to the P-51 as the 'clear' best fighter. They favored the Mustang as a high altitude fighter but felt the 38L could hold its own with anything at medium to low altitude. Having said that both agreed that if the 8th AF had to have just one fighter it would have been the Merlin equipped Mustang for their choice.

Landers flat out said the 38L would have been his choice for 'beginning to end' in ALL US theatres...if only one possible - because of PTO... but not for Europe in Bomber escort role

IIRC correctly he got 6 w/P-40 and 49th, 4 w/P-38 and 55th and 4.5 w/P-51 and 78th, including a 262. Nearly an ace in three different ships

 

[renrich]

Of course Sys, and when the P38 was designed in 1937 the Allison engine that was the only feasible engine to be used put out only about 1000 HP. Around 1600 Hp was needed in a single engine fighter, unless you went really small and light. Bell went that direction and Lockheed went the two engine path which resulted in an airplane with a lot of wing which gave it good high altitude handling and also a lot of load carrying capacity which meant a lot of fuel could be carried which meant a long range. I guess the long range the AC could manage was a by product of the need for more power and was a bit of an accident. Inspired design that resulted in the best twin engined fighter of the war.

 

[drgondog]

Of course Sys, and when the P38 was designed in 1937 the Allison engine that was the only feasible engine to be used put out only about 1000 HP. Around 1600 Hp was needed in a single engine fighter, unless you went really small and light. Bell went that direction and Lockheed went the two engine path which resulted in an airplane with a lot of wing which gave it good high altitude handling and also a lot of load carrying capacity which meant a lot of fuel could be carried which meant a long range. I guess the long range the AC could manage was a by product of the need for more power and was a bit of an accident. Inspired design that resulted in the best twin engined fighter of the war.

And the big hog that became the L would out climb, out roll and out accelerate a 51D (and an F4U) in most altitudes and speed ranges...

 

[renrich]

I know I am prejudiced but all considered: performance, maintainability, survivability, versatility, cost effectiveness, length of time for pilot proficiency, short field take off and land capability, etc. I will take the Hog, the U-Bird, the Ensign Eliminator, it's big it's blue it's the F4U in it's various iterations for the one fighter concept. I believe Rex Barber who did some good in the P38 felt the same way about the Corsair.

 

[kool kitty89]

Just some notes on the P-39: the original P-39 had longer wings giving more wing ares and room for internal stores. (and easier to add external stores, plus higher wing area means more room for weight growth and better climb and turn rate) Had a larger canopy-- so more head room and better visibillity. Had a turbo (obviously). And had a shorter rear fusalage wich provided better stability. And of course the turbo...

The USAAF went crazy with streamling- the only positive thing to change was a larger tail fin for better control and stability. The longer fusalage causing COG problems, the new canopy having pooer vision and head room, wing area deopping etc.

Plus the P-39D-2, N, and Q (and a few others) wre not underpowered with a WEP of 1,320 to 1,480 hp.

The P-39 never received a Merlin like the P-40 did (albeit only 1,300 hp with a crit alt of ~19,000 ft for 1,120 hp) or the V-1710-81 of the P-40M and P-51A with 1,480 WEP at 10,400 ft and 1,120 ho at ~18,000 ft.

The XP-76 corected some of this (long wings with square tips and 236 ft2 area, and better engine-- 2-stage Allison with nearly 386 mph at 21,000 ft)

Though the P-63 was a more promising a/c with performance similar to the P-51 in range (with 3 drop tanks), climb slightly lower, speed similar and better at low altitude (P-63C had a WEP of 1,800 hp with water injection) and a critical altitude of ~23,000 ft (higher on some models). Armament was as good as the P-51A/B/C and better with a 20mm cannon with ~170 rounds. (the 37mm cannon being debatable while the 20mm was an alternate).




On the range of the P-40, it could range farther than the Mustang when wing tanks were used, though these were only avaiable for the P-40N iirc and mostly used for ferrying (max 3,100 mi at minimum cruise settings) ~1,400 miles was usual with a 141 gal drop tank. And it had the P-39 beat in range armament (by most standards) and climb (comparing the P-40M to the P-39N/Q).


The P-47D could range 2,100 mi at 206 mph with 780 US gallons total. (note this is with the 70 gal increased main tank, and not considdering the 200 gal conformal paper tank used only early when no wing plumbing was stansard, or the 215 gal steel belly tank, or the "big and ugly" 200 gal wing tanks used in the PTO)


And the P-38L could only out roll the P-47D (~86 degrees/sec at 250 mph) above 300 mph and late model F4Us (~100 degrees/sec at 250 mph) above 350 mph and the P-47N even later (108 degrees at 250 mph with less degredation at higher speeds than the D model or the F4U). The P-38L's roll kept increasing up to its redline speed and was faster than the P-51 at all speeds. It didn't exceed 80 degrees/sec until ~300 mph and did ~90 degrees at 400 mph iirc.

 

[drgondog]

And the P-38L could only out roll the P-47D (~86 degrees/sec at 250 mph) above 300 mph and late model F4Us (~100 degrees/sec at 250 mph) above 350 mph and the P-47N even later (108 degrees at 250 mph with less degredation at higher speeds than the D model or the F4U). The P-38L's roll kept increasing up to its redline speed and was faster than the P-51 at all speeds. It didn't exceed 80 degrees/sec until ~300 mph and did ~90 degrees at 400 mph iirc.

http://home.att.net/~ww2aviation/P-38-3

It would be hard to validate the roll statements against the P-51B/D and impossible against the P-51H. Interestingly enough if Lockheed's performance figures are correct the crossover point for the P-38L with boosted ailerons crossed over the 51 along with the Fw 190 at 350MPH.

The P-38J w/o boosted ailerons stayed below both the P-51B and Fw 190A at all speeds.

Having said that, I've often wondered about these charts as none of the aircraft models, including the P-38L, ever did 450mph in level flight.. Only the P-51H ever tested at that speed or above..so I would like to see something like these charts as a function of altitude as well as versions. It is also interesting that the climb performance charts and speed chart comparisons by Lockheed were carefully selected for the model of 51 (i.e P-51D vs P-38L for climb and dash speed instead of the B and H - both of which were faster and climbed as well or better).

Also interesting is that the redline dive speed for the P-38L was .68 Mach - which would imply stability and controllability but the 109G, Fw 190A and D, P-47D and P-51B/C/D/F all would excced that by .10 mach. I am assuming that is redline w/dive brakes -----> implying structural red line not aerodynamics.

 

[kool kitty89]

Anything greater than 442 mph for the P-38L would be in a dive. The P-38K probably could Best 450 mph (as long as it wasn't exceeding .68 mach) if it had been tested in WEP.

What I've wondered about the P-38K's propeller is why they didn't make kits for retrofitting new cowling and paddle props to P-38Ls in the field, as this wouldn't have caused any cease in production (the War Production board not even allowing the 2-3 weeks needed for retooling.

Or why not use a 4-bladed propeller like late-model P-39Qs did, the spinner and prop-diameter would be the same so there would be no need for new cowling and there would be more clearance for the props. (the paddle-props having a larger diameter as well) A 4-bladed prop would also be easier to fit in the field as no new cowling would be needed.

One big drawback that the P-38 never fully solved was high-speed dive capabillity, it could dive decently but even with the recovery flaps (allowed another 30-40 mph TAS to be aceived safely iirc) it was not much better than the P-51 in this category (depending on how much a pilot was willing to push the a/c), though at those speeds it would roll much better. Although it could dive about as well as 190's and 109's as well, nothing could out dive a P-47 (even a Me-262 would have trouble out accelerating a fully loaded P-47D in a dive) a late P-47D could safely dive to Mach .80 (~.82 critical) and even more with recovery flaps. The P-38's critical mach was increased to ~.75 with the dive-flaps, though the safe limit would be closer to .70.

In this respect the P-38 and P-47 were complete opposites, the P-47 easily escaping a P-38 in a dive (as long as it has decent altitude to work with) and the P-38 outclimbing the P-47 at almost any situation, except maby a P-47M or an N in clean configuration with empty wing tanks, though a P-38 with paddle props (or 4-blade) could beat this.


The 440+ mph figure for the P-38 was achieved with 100/150 fuel and high manifold pressures (either 65" Hg or 70" I can't rember) where WEP was boosted to just under (or possibly exceeding) 1,800 hp. On the same note the P-47D's R-2800-63 (or -59, wich was nearly identical) was cleared for 2,600 hp with 70" Hg (although it was limited to 2,535 hp with 65" for climb) with which it could achieve 444 mph at ~23,500 ft. (the critical altitude for 70" Hg)

The P-51 had been cleared for up to 90" Hg with 100/150 AvGas which it could exced 450 mph without wing racks, with racks (~10 mph drop in speed) it too could do ~444 mph. However the P-51 could not hold this power for long w/out having to open the radiator to full which dropped speed significantly, the P-47 and P-38 could maintain this power longer without overheating iirc due to their cooling systems and since the boost pressure was ~20" less. The P-47 could probably run the longest like this due to it's tough engine. (the R-2800-57C of the XP-47J, and P-47M/N was tested to 3,600 hp at extremly high boost pressures without failure, though there was much wear on the engines; the WEP of these engine was 2,800 hp at 2,800 rpm)

 

[drgondog]

Anything greater than 442 mph for the P-38L would be in a dive.

Actually - they were very close to critical Mach at 25,000 feet at 425mph in level flight - I'll have to check for STP. I don't believe any P-38 was rated to exceed .68 Mach. Without dive brakes they immediately went into compressibility between 430 and 440 mph at 25,000 feet. With Dive brakes they immediately hit .68 but it was controllable.

What I've wondered about the P-38K's propeller is why they didn't make kits for retrofitting new cowling and paddle props to P-38Ls in the field, as this wouldn't have caused any cease in production (the War Production board not even allowing the 2-3 weeks needed for retooling.

Or why not use a 4-bladed propeller like late-model P-39Qs did, the spinner and prop-diameter would be the same so there would be no need for new cowling and there would be more clearance for the props. (the paddle-props having a larger diameter as well) A 4-bladed prop would also be easier to fit in the field as no new cowling would be needed.

None of these changes would have helped the dive speed limit... but might have helped climb rate

One big drawback that the P-38 never fully solved was high-speed dive capabillity, it could dive decently but even with the recovery flaps (allowed another 30-40 mph TAS to be aceived safely iirc) it was not much better than the P-51 in this category (depending on how much a pilot was willing to push the a/c), though at those speeds it would roll much better.

Actually the P-38 was never close to a 51 or a 47 or F4U in a dive because of near immediately slip into compressibility if it started at high speed and altitude .. i.e 400mph at 25,000 feet when he pushes it over., or push it over and deply dive brakes. In the first case he want a long way before he could even pull out in denser air. In the second case he mainatins dive speed around .68 mach because of the drag of the brake.

The 51 would do .75 in a dive w/o power or prop. It was tested several times this way, being towed by P-61, then cut loose. The purpose of theses tests was to compare flight test treadings with experimental and calculated results from wind tunnel and analytical methods.

The dive limt of the 51 (manual) was 505 true, and IIRC about 280 IAS at 25,000 feet - but don't hold me to that. It has been way too long and I'm on the road. The manual recommended .75 but that was exceeded often in combat conditions.


Although it could dive about as well as 190's and 109's as well, nothing could out dive a P-47 (even a Me-262 would have trouble out accelerating a fully loaded P-47D in a dive) a late P-47D could safely dive to Mach .80 (~.82 critical) and even more with recovery flaps. The P-38's critical mach was increased to ~.75 with the dive-flaps, though the safe limit would be closer to .70.

KK - What is your source that the 38 could do .75 with the dive brake? It looked like the dive limit for the 38L as presented by the Lockheed thread was .68 for both the J and the L? Is that wrong in your opinion?

I do NOT know that it couldn't but it doesn't make a lot of sense that an airplane that can't match a 51 in level flight with nearly twice the Hp, also has a similar dive speed. The manual limit was .75 for the 51, the aero/drag limit was .80-.82 MAX

In this respect the P-38 and P-47 were complete opposites, the P-47 easily escaping a P-38 in a dive (as long as it has decent altitude to work with) and the P-38 outclimbing the P-47 at almost any situation, except maby a P-47M or an N in clean configuration with empty wing tanks, though a P-38 with paddle props (or 4-blade) could beat this.

I think all versions of the P-47D could also out roll the P-38 - even the P38L with boosted ailerons.. it certainly could through 400mph and I suspect at 425+ which is near max speed of P38L. If you have a comparison test or data point me in the right direction?


The 440+ mph figure for the P-38 was achieved with 100/150 fuel and high manifold pressures (either 65" Hg or 70" I can't rember) where WEP was boosted to just under (or possibly exceeding) 1,800 hp. On the same note the P-47D's R-2800-63 (or -59, wich was nearly identical) was cleared for 2,600 hp with 70" Hg (although it was limited to 2,535 hp with 65" for climb) with which it could achieve 444 mph at ~23,500 ft. (the critical altitude for 70" Hg)

The P-51 had been cleared for up to 90" Hg with 100/150 AvGas which it could exced 450 mph without wing racks, with racks (~10 mph drop in speed) it too could do ~444 mph. However the P-51 could not hold this power for long w/out having to open the radiator to full which dropped speed significantly, the P-47 and P-38 could maintain this power longer without overheating iirc due to their cooling systems and since the boost pressure was ~20" less. The P-47 could probably run the longest like this due to it's tough engine. (the R-2800-57C of the XP-47J, and P-47M/N was tested to 3,600 hp at extremly high boost pressures without failure, though there was much wear on the engines; the WEP of these engine was 2,800 hp at 2,800 rpm)

P-51 Mustang Performance
P-38 Performance Trials

441mph is a good number for P-51B at 75". It would help in the discussion if you referred to specific models and flight conditions so I knew what your were making comparisons against?

It is not a good number for the P-51H. The factory got 480+ w/o rack, but full combat load and wing tanks - only 25gal in fuse tank. at 9450 pounds

The NAA calculated performance had 487mph at 22K+ w/o racks in same condition at 9450 pounds

USAAF tested at Wright Pat with an a/c picked at random and got 451+ at 90inches at 21,600 at 9544 pounds (extra weight and drag for racks)..

If Mike's figures are right for the December 1945 test of the P-38L, it was 30mph slower than the P-51H at 26,000 feet and 60 mph slower at SL.

The climb of the H was 4680 with full combat load from SL through 4200 feet and got to 35,000 feet in 9.4 minutes, 16,000 in 4 minutes. W/O racks and the extra 100 pounds, the initial climb rate was 5,000fpm +..

The P-38L had some advantages over a P-51B, some over a D, few over an H.

Perhaps the bottom line is that in comparisons of P-38J and P-38L in air to air combat in ETO, the 51B and D had a huge edge in awards and air to air award to actual loss ratios. One can debate accuracy of awards but the process was same for 8th AF independent of the fighter.

I have no idea regarding either the MTO or PTO for similar comparisons - but the German opposition was in general far better than the Japanese.

Regards,

Bill

 

[chuckn49]

For what it is worth, my brother frequently talked about a P-38 pilot who put a 38 through sound barrier in a dive and lived to talk about it. The plane was a total loss because of structural damage to wings and tail. Also, instrument panel was pushed in due to pilot's feet on it.

He was an aeronautical engineer and believed the P-38 could exceed sound barrier and survive. I don't know how many others did that but this is the only one I ever heard of.

 

[drgondog]

For what it is worth, my brother frequently talked about a P-38 pilot who put a 38 through sound barrier in a dive and lived to talk about it. The plane was a total loss because of structural damage to wings and tail. Also, instrument panel was pushed in due to pilot's feet on it.

He was an aeronautical engineer and believed the P-38 could exceed sound barrier and survive. I don't know how many others did that but this is the only one I ever heard of.

Chuck - there are a lot of tribal legends about the first a/c and pilot to break the 'sound barrier'... all mostly from "visible evidence" of an airspeed indicator.

The airspeed instruments worked on stagnation pressure readings and did not account for compressibility - said issue becoming noticeable near .75-.80 Mach and increasingly divergent from freestream airspeed until it was worthless.

Beyond that point, the me 262 was probably the cleanest aerodynamic airframe of all the notable aircraft until the F-86.

The Me 262 in most likelihood came as close as maybe .88-.9 in a dive before the transonic shock wave moved the Center of lift too far aft or disrupted airflow over the horizontal stabilizer to the point that it couldn't recover from a nose down pitch.

The F-86 flown by Welsh probably exceeded Mach 1 in a dive and my guess that it was the 'actual' first.

As to the P-38? It was far less likely than say a Spitfire with a very thin wing or even a P-51H... both faster in a dive and far behind a Me 262.

Most ships that exceeded the mfr's recommended limits by a little too much ultimately were not able to bring it back for a refund

A claim was made for a Spit also and my belief systems are strained entirely too far to contemplate a prop driven a/c whose blade tips can't go supersonic, much less create sufficient thrust through the blade plane of the rotating prop, or have an elevator system capable of pitch control after transonic flow separtion ultimately occurs on the wing.

I would be shocked if the P-38 could get to .82 Mach straight down at full power, and even more shocked if the wings didn't come off in the dive if it made it past that point.



Regards,

Bill

 

[chuckn49]

I have no proof one way or the other and, from my own experience in the military, I know how legends get started. I am trying to recall conversations I had with him from 30 or 40 years ago so, it is possible that my memory is faulty but, somehow, I don't think so as to what he believed because it impressed me so at the time. Anyway, as I remember the story, the dude in question was an aeronautical engineer type who, for some reason, wished to be a pilot. The legend goes he was transitioning into 38s and, of course, they were warned about the compressibility problem in a dive, etc. I know my brother said it was a not unheard of disaster for a pilot to not be able to pull out of a dive in the 38. Long short, he calculated the 38 could be pulled out of a dive through some maneuver or other and, without authority, deliberately went beyond the limits imposed for safety in a dive. Result, he exceeded speed of sound, allegedly but, managed to get aircraft out of dive by standing on control panel.

 

[drgondog]

I have no proof one way or the other and, from my own experience in the military, I know how legends get started. I am trying to recall conversations I had with him from 30 or 40 years ago so, it is possible that my memory is faulty but, somehow, I don't think so as to what he believed because it impressed me so at the time. Anyway, as I remember the story, the dude in question was an aeronautical engineer type who, for some reason, wished to be a pilot. The legend goes he was transitioning into 38s and, of course, they were warned about the compressibility problem in a dive, etc. I know my brother said it was a not unheard of disaster for a pilot to not be able to pull out of a dive in the 38. Long short, he calculated the 38 could be pulled out of a dive through some maneuver or other and, without authority, deliberately went beyond the limits imposed for safety in a dive. Result, he exceeded speed of sound, allegedly but, managed to get aircraft out of dive by standing on control panel.

Chuck - he could easily be an aero and at that time not have much insight on compressible flow. Practicing aeros at the leading/bleeding edge of high speed aeo were just getting clues with the compressibility issues and the P-38/P-47 were leading indicators of a problem they didn't understand..

Wind tunnels weren't doing supersonic studies either.

So, in his mind I suspect he looked at the evidence, high IAS at high altitude (and they could do Temperature, density calculations based on altitude) based on his airspeed, the compressibility evidence on based on stick force, and the relative shambles of wrinkled skin and popped rivets.

What they didn't have is a pitot tube/airspeed system that also measured temperature and therby missed on the effect to Density in the Pressure calculations leading to freestream airspeed.

The reality for that airplane is that you could start out at 500,000 feet in a terminal dive, go well past the surface speed of sound, but during the coarse of flying that P-38, never exceed .80+ mach. The aerodynamics of first the wing, then the wing center body, then the prop fan interface are going to (all) act like drag brakes.. I suspect the first big Drag component would be the huge spike in wake drag during the transonic transition.

But simplistic as the concept is, all those drag factors added up to a drag chute effect at the high mach number to prevent it from going much past .75-.80 Mach. The reason (I suspect) that Lockheed posted the Dive Limit on the website I referenced - is they wanted to prevent the P-38 from going compressible - Period and the dive brakes on the P-38L did just that..

 

[kool kitty89]

Sorry the .75 mach figure was the wind tunnel speeds the P-38 was tested in that finally allowed Lockheed to find a solution. Another note is that very early on there was also buffeting problems around the cockpit but wing fillets solved this.

I,m not sure but I think the P-47 was able to better withstand the aerodynamic forces at high speeds (600 mph, possibly more, depending on altitude) than the P-51 or F4U, especially the later models with stronger wings and improved "blunt nosed" ailerons introduced on the D model and recovery flaps were also added to later D models.


There was a study on the Me 262 and it was found (with mathematical models) that it could exceed the sound barrier and recover under the right conditions. (a very steep dive from high altitude was required) The 262 had a trimmable tail-plane that would allow sonic dive recovery, though speed would have to decrease significantly before pulling up to prevent mechanical failure. And even so it was more than likely the wings would be warped to hell.

See: http://www.ww2aircraft.net/forum/aviation/sound-barrier-10422.html

The most accurate way to document braking the sound barrier is a sonic boom, but in a war zone this could be confused with an explosion. Welch's dives (one several weeks prior to Yeager and another less than an hour prior to Yeager's flight in the XS-1) resulted in sonic booms being heard by the locals, the second one actually shattering some windows, this was followed by the much more docile boom of the XS-1 ~30 min later. Of course many thought the loud boom was from Yeager... (according to The Amazing George Welch: Part two )

 

[drgondog]

I,m not sure but I think the P-47 was able to better withstand the aerodynamic forces at high speeds (600 mph, possibly more, depending on altitude) than the P-51 or F4U, especially the later models with stronger wings and improved "blunt nosed" ailerons introduced on the D model and recovery flaps were also added to later D models.

The failures associated with 'aerodynamics' would be lift loads on pullout, or rudder loads causing torque on the epennage/fuselage area. You could get a catastrophic failure from either of those situations when exceeding manufacturer's Limit Loads..

The F4U and P-47 and P-51B/C/D were designed using same structural engineering philosophy, and each were probably slightly stronger than the P-51H as all were designed to 12 G Ultimate versus 11G for P-51H


There was a study on the Me 262 and it was found (with mathematical models) that it could exceed the sound barrier and recover under the right conditions. (a very steep dive from high altitude was required) The 262 had a trimmable tail-plane that would allow sonic dive recovery, though speed would have to decrease significantly before pulling up to prevent mechanical failure. And even so it was more than likely the wings would be warped to hell.

The problem that I don't believe Messerschmidt ever solved, was the drastic 'pitch down' moment caused when the transonic shock wave turbulence blanked the elevator, as well as movement of the Center of Lift Aft. The drag coefficients were probably close if that 'little problem' had been solved... but the a/c was long gone before the shock wave moved to the trailing edge.

QUOTE]

Airframe design has at least three theoretical components. Aerodynamics, Stability and Control, and Structures.

The a/c may have been designed properly as far as Drag requirements, but the wing may be too thick to delay and reduce the effect of transonic shock wave on the airflow aft of the shock. The operation was a succes but the patient died - in this case the me 262.

That is one reason the typical supersonic wing has a very low thickness to chord ratio...

 

[renrich]

Don't know where the numbers you all are quoting on P38 L are coming from but I have two sources that give Vmax of the L as 414 mph at 25000 feet. Dean says that it was placarded in the cockpit that dive speeds were restricted to the equilavent of Mach 0.65. That was when the AC began to get into compressibility and buffeting commenced at Mach 0.675

 

[kool kitty89]

I've seen the 440+ figure several plases around here, aparently the 414 figure was at normal WEP, but 100/150 Avgas with increased boost and improved strength of the engines of this model aparently allowed these higher speeds. I honestly havent seen documentation of this though...

But one thing that doesn't make sence is that the P-38L's figure is slower than the P-38J's figure (422 at 25,00 ft mph iirc) at the same altitude. The L wasn't that much heavier and had more power.


The P-47D could do 444 mph at 23,400 ft (critical altitude for 70" hg for the D's turbo) with 2,600 hp at 2,700 rpm and 100/150 fuel.

See: P-47 Performance Tests
http://www.wwiiaircraftperformance.org/p-47/24june44-progress-report.pdf
http://www.wwiiaircraftperformance.org/150grade/p-47-66inch.jpg

 

[renrich]

I just found a third source(these are all books in my library) that says P38 L Vmax was 414 mph @ 25000 feet. Another source, one I quoted earlier has the performance figures on P38J and it it has Vmax of 414 mph also. This source says the additional HP given the L was diluted by the additional weight(500 lbs) To me the P38 fits in that category of AC that at a certain point additional HP cannot yield additional speed. I don't know the technical term for that but it looks like the P38 being as large as it is there is a lot of drag and the faster it goes the more drag is generated so you reach the point of diminishing returns.

 

[kool kitty89]

I found out where those guys got the speed figures: http://home.att.net/~ww2aviation/P-38-3.html (just search for P-38L + 441 or 442 or 443 mph on the forum and you'll find several threads mentioning it)

It demonstrates the 414figure at Millitary power and ~442 mph figure at WEP. And this is very close to the P-38's limit.