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

Timppa said:

Check this link

The Math Behind Turning

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Timppa - excellent link - good foundation tutorial. Wrong to apply universally without careful understanding of significant variations between aircraft that are accounted for by 'rough estimates' and 'assumtions' in his model.

I will give some detailed thoughts perhaps tomorrow when I have time to discuss specifics (if you wish).

Here are some immdediate observations.

Thrust based on Hp. The equation is correct for Thp for sea level but does not include exhaust thrust, or if applicable - Meredith effect'. Not so important for SL, very important for 30,000 feet.

I scanned the report so may have missed whether he not only introduces the Hp contribution from max available at the altitude point where the supercharger can no longer supply 100% requirements, but also the mass flow rate through the propeller disk as density reduces with height.

I did not take particular note regarding fundamental comparison of Hp vs altitude differences between different engines as a function of supercharger/turbo efficiency.

His tutorial regarding the factors and approach at Calculating Thrust available from a prop/engine/gear standpoint from the view of a preliminary design standpoint is very good - and necessary when a significant body of flight test data across an entire altitude/hp/boost and speed results are not available.

In this forum, neither flight test nor manufacturer specs are 100% reliable, nor are all the aircraft data available for the ships we wish to compare.

Drag = He correctly balances Total Drag with the Thrust.

He illustrates Cd0 and IIRC used 'about .020' for the P-51D. It may be off a little but the important point is that Total Drag = Induced plus Parasite (sum of all non lift components) Drag. He is able to manipulate the relative contributions at each point in the velocity and Lift range correctly as long as he is in level flight. He correctly obtains Induced Drag (for the wing) as a function of CL.

I take issue that this is adequate for the full range of CL's from straight and level flight to max bank/max CL flight for maintaining altitude - as we are trying to do with these equations. I may have missed where he factors in Trim Drag.

Cd0, as presented, is the level flight clean Parasite Drag which, for this build up for a Mustang, is Cd0 of the clean wing/body/tail combo. This means no elevator or rudder or aileron (or manuevering flap or full flap) deflections to incrementally provide lift(and drag) forces to the system.

Before we get tangled up in semantics I realize 'delta CD' for the flap/manuevering flap deployment is not an add to parasite drag - but it is an add to the total drag of the system offsetting available Thrust to reach equilibrium.

Skip the transition however and go straight to CLmax.

For the clean (no flap, manuevering flap - elevator, rudder or aileron deflection) configuration the Cd0 is still useful - but not of itself enough as the a/c is in a max bank angle with necessary rudder, elevator, aileron deflection - all contibuting measurable and significant drag incrementally to the clean configuration Induced and Parasite Drag. So, you have to calculate Trim drag.

In the case of a P-38J-25, when only manuevering flaps are deployed, you have to determine the contribution to Total CL max, as well as the extra drag, of this new wing body combination because it a.) should slow the a/c down (some), and b.) tighten the turn (some) in contrast to clean turn configuration.

You will not know until you have introduced the new factors into the free body force balance whether the P-38 has improved turn performance relative to max turn rate of turn... but you cannot insert level flight 'clean' - and flaps down Vstall in these equations for a P-38 with 8 degree manuevering flaps down..

I did this overview in a hurry - I will come back and edit the brainfarts later.

i would pick the mustang due to this one the mustang has more aces in the than the P-38 and two the had the k-14 gyro sight which was user friendly three the mustang can pull higher g loads than the p-38 now the p-38 was the premiere USAAC fighter in the pacfic in the early stages of the war and the mustang at that was starting to show it's protential now when the late stages of the war was going on we where going higher into the stratosphere we needed a fighter that can keep with the b-29 well the p-38 has the range but not the alt perfomance so the only plane that can do and it had a great track record was the P-51D mustang which proved it self agianst german aircrafts even though they were not as manouverable was the jap planes but there on thing that jap suffer the most compressability the P-38 couldnt do it becuase it had horrible compressability like the Jap planes did. Mustang Pilots use to joke about who would win in a compressability fight between a Zero and a P-38 neither they both have to bail out. People tend to forget the mustang was a high speed turning aircraft and the mustang did get alot of kills in the pacific due to the fact that the japanese would follow the into a high speed dive and then the mustang with it have a great Zoom climb after the dive which is it's energy retention the p-38 could never do this becuase of the compressability issue the later p-38's had a dive break but there has been reports that the dive break would rip right off if speed are too high ruffly around 480 mph TAS which at that speed compressablilty hasnt touch the mustang compressability hits the mustang until 600 IAS the mustang has a max dive speed of 615 mph IAS with full compressability the mustang has a safe pull dive of 505 mph IAS which had a red line now the saying about the tail section ripping off that was becuase they would be comming out of high dive around 520mph IAS and yank the stick back hard the mustang was be pulling an agonizing 9.5 g's which is beyond structural limits the max safe g limit is 8 g's and can push -2.5 g's. which would be phsyically impossible for the p-38 to achieve now the mustang has near laminar flow wings not pure laminar becuase the matanance would be to much. the mustang has better lift to drag ratio than the p-38 and the mustang has a better roll rate than the p-38 93 degrees a second vs to the p-38's 74 degrees a second but the p-38 does have a slight atvanges in acceleration with it 2.4 mph a second vs the mustangs 2.2 mph but it doesnt matter when your in a sustain turn it the fighter with the best e bleed will win and the mustang will beat every time at any speed and any alt. the mustang wins by far why else would other country's would want the plane that was a war winner and why would we keep it in service well into the 1950's remember the mustang fought in three wars WWII Korea and Vietnam yes the mustang Fought in Vietnam with the Thai Airforce

mach driver said:

i would pick the mustang due to this one the mustang has more aces in the than the P-38 and two the had the k-14 gyro sight which was user friendly three the mustang can pull higher g loads than the p-38 now the p-38 was the premiere USAAC fighter in the pacfic in the early stages of the war and the mustang at that was starting to show it's protential now when the late stages of the war was going on we where going higher into the stratosphere we needed a fighter that can keep with the b-29 well the p-38 has the range but not the alt perfomance so the only plane that can do and it had a great track record was the P-51D mustang which proved it self agianst german aircrafts even though they were not as manouverable was the jap planes but there on thing that jap suffer the most compressability the P-38 couldnt do it becuase it had horrible compressability like the Jap planes did. Mustang Pilots use to joke about who would win in a compressability fight between a Zero and a P-38 neither they both have to bail out. People tend to forget the mustang was a high speed turning aircraft and the mustang did get alot of kills in the pacific due to the fact that the japanese would follow the into a high speed dive and then the mustang with it have a great Zoom climb after the dive which is it's energy retention the p-38 could never do this becuase of the compressability issue the later p-38's had a dive break but there has been reports that the dive break would rip right off if speed are too high ruffly around 480 mph TAS which at that speed compressablilty hasnt touch the mustang compressability hits the mustang until 600 IAS the mustang has a max dive speed of 615 mph IAS with full compressability the mustang has a safe pull dive of 505 mph IAS which had a red line now the saying about the tail section ripping off that was becuase they would be comming out of high dive around 520mph IAS and yank the stick back hard the mustang was be pulling an agonizing 9.5 g's which is beyond structural limits the max safe g limit is 8 g's and can push -2.5 g's. which would be phsyically impossible for the p-38 to achieve now the mustang has near laminar flow wings not pure laminar becuase the matanance would be to much. the mustang has better lift to drag ratio than the p-38 and the mustang has a better roll rate than the p-38 93 degrees a second vs to the p-38's 74 degrees a second but the p-38 does have a slight atvanges in acceleration with it 2.4 mph a second vs the mustangs 2.2 mph but it doesnt matter when your in a sustain turn it the fighter with the best e bleed will win and the mustang will beat every time at any speed and any alt. the mustang wins by far why else would other country's would want the plane that was a war winner and why would we keep it in service well into the 1950's remember the mustang fought in three wars WWII Korea and Vietnam yes the mustang Fought in Vietnam with the Thai Airforce

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This was the hardest post I ever had to follow based on total lack of punctuation and structure.

Hopefully you will read enough of ithis thread that you will find many fact based rebuttals to several comments, all of which are well documented by reliable sources.

Don't take my word for the arguments but pause and think about what has been said in various debates.

You may correct some of your misconceptions regarding structure, design versus ultimate loads, failure modes which cause the airframe to fail, etc.

Regards,

Bill

Welcome to the forum and looking forward to engaging in debates with you.

P-38's first flight was 1/27/1939.
P-51's first flight was 10/26/1940.
Yet both entered service April/May 1942 and made their first kills in August 1942.
- The P-51 could have entered service and made kills earlier if more support were provided by the US Army.
- The P-51 could have been flying with the Merlin engine earlier as well.
- The P-38 had the support it needed, but suffered a long protracted development with many many issues that needed to be worked through.

10,037 P-38's were made.
15,875 P-51's made, even though it was a later design with a later first flight.

P-51 cost less.
P-51 was easier to produce.
P-51 was easier to maintain.
P-51 consumed less fuel.
P-51 service continued into Korean war, and beyond.

P-38 development plodded on for so long.
One could say the P-38 was "ahead of its time" and encountered phenomena that took more time to work through than anticipated. If the P-38 hadn't taken so long to develop, it's quite possible there never would have been a need for the P-51.
However, if P-51 development had been given priority earlier, it's quite possible there wouldn't have been a need for the P-38.

Now if the P-38 had been available for combat right after Pearl Harbor, or had it's bugs worked out in time to support European strategic bombing from the get-go, I might be swayed to support the P-38 instead of the P-51.

Put it another way...
If we could wave a magic wand and make all the P-38's problems disappear...
And make both the P-38 and P-51 available on the same day and made their combat debuts on the same day...
Which would be the overall better plane?

It would still be the P-51 for the reasons listed above.
We could build more and fly them with less logistical strain.

The North American Aviation P-51 Mustang was a long-range single-seat World War II fighter aircraft. Designed, built and airborne in just 117 days, the Mustang first flew in RAF service as a fighter-bomber and reconnaissance aircraft before conversion to a bomber escort, employed in raids over Germany, helping ensure Allied air superiority from early 1944.[2] The P-51 was in service with Allied air forces in Europe and also saw limited service against the Japanese in the Pacific War. The Mustang began the Korean War as the United Nations' main fighter, but was relegated to a ground attack role when superseded by jet fighters early in the conflict. Nevertheless, it remained in service with some air forces until the early 1980s.
As well as being economical to produce, the Mustang was a fast, well-made, and highly durable aircraft. The definitive version, the P-51D, was powered by the Packard V-1650, a two-stage two-speed supercharged version of the legendary Rolls-Royce Merlin engine, and was armed with six .50 in (12.7 mm) M2 Browning machine guns. :l The Mustang was a revolutionary and an invaluable addition to the Americans as well as the British who made thier version,which I believe was the Mustang 1.Also,kudos to Soren and SoundBreaker Welch? ;good points.And,finally,if i had to pick the best non-American plane,I'd pick the bf-109 or the Junker Stuka(sorry,just some random opinions...)
So...yeah...Mustang for me too... :]

It's the P-51 for me. I remember reading that the P-38 had to watch its airspeed in a dive because it had more trouble pulling out than a P-51 did. Something about the flow of air over the wings and tail at higher speeds that made the P-38 less manueverable.

It was not just a case of which aircraft was better, it was a case of how was it used. Agreed the P-51 had the range, UNTIL the work of Lindbergh and the P-38. Both AC had good armament, but the P-38's bullets shot straight forward, where the P-51s had to shoot past that big glorious prop, therefore along with the 20mm canon on the P-38 the shooting range was not limited to where the bullets crossed. Both AC had good ceilings and good mannueverability, but the P-38 had the telltale double contrail compared to the P-51. The P-51 was squirley down low, that wonderful maneuverability becoming deadly at low altitude.

As far as the dive question goes. The P-38 was originally designed for Bomber Interception. Kelly Johnson never considered it for real dogfighting. So when dogfighting in Europe, early in the war, going into a dive at high altitude, the shockwave from the leading edge would essentially lock the elevator (actually, a power assist here would have worked but I have never seen it applied) so that until speeds dropped in the lower atmosphere it would become impossible to come out of the dive. Dive brakes were finally created, but the AC carrying them to the European theater (a DC-6 or 7) was shot down by a Spitfire and the plane was taken out of service in the Eighth Airforce.

The P-38 worked in Africa, the Pacific, and in Europe when the fuel question and the dive brakes were fully worked out in the P-38J model. The P-51 with the Allison engine was failure, but once they put the Merlin Engine in the body of the P-51 with it's newer wing design and it's increased fuel carrying capability the P-51D was a great AC. So both AC had their strengths, did a good job and had a great career. The P-51 won the after war question primarily due to the single engine vs double engine fuel quesiton...and the f-82, double mustang might prove where the p-38 could have gone... Still I love the p-38 for it's excellent gun platform, symmetry, and smoothness for recon and a fire platform. I love the p-51 for it's looks and it's maneuverability at altitude.

JayK58 said:

The P-51 was squirrelly down low, that wonderful maneuverability becoming deadly at low altitude.

The P-51 with the Allison engine was failure...

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In fairness, the Merlin P-51's best altitude was that at which it escorted the bombers, at lower altitudes closer to ground level, it was arguably no more than a match for the Fw190. If he allows too much of his airspeed to get sucked off in a knife-fight then the better low-speed handling characteristics of the Bf109 will also land the P-51 driver in trouble.

That's a little harsh, the Allison P-51 was an exemplary aircraft at ground level up to about 16,00ft where the all too well defined limits of the V-1710 pegged all things Allison-powered. The installation of the Merlin certainly realised the P-51's full potential but didn't in the process make the Allison P-51 an outright failure.

If the P-51 with the Allison was a failure the P-40 must have been a total waste of time and good aluminium.

JayK58 said:

The P-51 was squirley down low, that wonderful maneuverability becoming deadly at low altitude.

Exactly what are you referring to?

As far as the dive question goes. The P-38 was originally designed for Bomber Interception. Kelly Johnson never considered it for real dogfighting. So when dogfighting in Europe, early in the war, going into a dive at high altitude, the shockwave from the leading edge would essentially lock the elevator (actually, a power assist here would have worked but I have never seen it applied)

First, the shockwave started at the 1/4 chord point or near the max t/c point of the wing. It didn't 'lock the elevator', per se, but the new aerodynamc center changed the Moment Coefficient, which caused the nose to pitch down. When this occurred, the stick forces required to overcome the pitch down moment was extreme. The power Boost was tried but they (LOCKHEED) quit when they kept running out of tail booms (AND TEST PILOTS) when trying to apply boosted elevator to a tail that wasn't stressed for those loads.

so that until speeds dropped in the lower atmosphere it would become impossible to come out of the dive. Dive brakes were finally created, but the AC carrying them to the European theater (a DC-6 or 7) was shot down by a Spitfire and the plane was taken out of service in the Eighth Airforce.

the dive flap/brake kits were lost en route on a ship IIRC, but either way was the same effect. The mid range P-38Js labored on w/o the mods until the P-38J started arriving in -25 series with production equipment and boosted ailerons. The P-38's and P-47s were already 'arranged' for swaps with 9th AF to get all their allocated Mustangs in return - approximately late January 1944 - before the flap/brake mod kits were lost.

The P-38 worked in Africa, the Pacific, and in Europe when the fuel question and the dive brakes were fully worked out in the P-38J model the P-38J-25)(. The P-51 with the Allison engine was failure (????), but once they put the Merlin Engine in the body of the P-51 with it's newer wing design The 51A-K had exactly the same wing except for the inboard starke between fuse and Main gear. What was different is the P-51A wing was lowered 7" to accomodate the required new lower cowl once the Merlin was stuffed in) The P-51H wing had a slightly different airfoil from all ther earlier versionsand it's increased fuel carrying capability the P-51D was a great AC.

The P-51B/C prior to the -7 had the 85 gallon fuse kit retrofitted by March 1944. After that all P-51B-7 and above through the P-51D/K had the same 85 Gallon Tank. Only the P-51H had the smaller 55 gallon tank to eliminate aft cg problem.


So both AC had their strengths, did a good job and had a great career. The P-51 won the after war question primarily due to the single engine vs double engine fuel quesiton...and the f-82, double mustang might prove where the p-38 could have gone... Still I love the p-38 for it's excellent gun platform, symmetry, and smoothness for recon and a fire platform. I love the p-51 for it's looks and it's maneuverability at altitude.

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Both great airplanes - as you pointed out the P-38 was easier for the Germans to spot and Identify before being spotted so it gave them a tactical edge to decide to fight or flee depsnding on tactical situation.

Bill has explained the dive problems of the early P38s in engineer terms but for us laymen, the early P38s got into trouble in dives in Europe because they started getting into compressibility, ( "the sound barrier") which caused the airplane to become uncontrollable and sometimes the tail came off. That problem was not as prevelant in the Pacific or Africa because the air over Europe was colder and the speed of sound varies according to air temperature. (the colder the air the lower the speed of sound)

The P38 early on had other issues such as engine reliability, poor cockpit heating and it took a while for a pilot to become proficient in the airplane. It was always a big target with a lot of places a bullet could disable it. It's early initial roll rate was poor. Some pilots said that it needed two engines so it could come back on one. One reason Lindberg picked the Ryan to cross the Atlantic is that two engines doubled the probability of having engine problems over one.

The P51 had much fewer problems to deal with and in almost every respect was superior to the P38.

P38! Always!

Imagine 2 apposing air-forces. Each air-force have only one type for ALL TYPES OF MISSIONS (intercepting, ground attack/bombing, air-superiority etc) which would you use?

Also...I have read somewhere in one of my thousands of WW2 aviation books, , that during training of fresh pilots, after the P38's instructor told the students about the P38 wonderful qualities, the P51 instructor told the class to disregard everything the '38 instructor had said. Naturally the '38 instructor heard this and immediately challenged him to a dual.

The two planes were lined up next to each other.

On take-off the 38 destroyed the 51 as you could almost instantly apply full power in the 38, not so on the 51(excessive torque)

P38 - 1
P51 - 0

So...as 51 were getting to altitude the 38 already started to Boom Zoom

P38 - 2
P51 - 0

Only when they started from the same altitude the odds were even. I will go and check toningt for that snipped and post it here

edd

eddie_brunette said:

P38! Always!

Imagine 2 apposing air-forces. Each air-force have only one type for ALL TYPES OF MISSIONS (intercepting, ground attack/bombing, air-superiority etc) which would you use?

"Imagine" that cost is important - both acquisition and spares, crew training and maintenance, operating cost (fuel, oil)..

Advantage - by 2:1 ratio aquisition cost ------> Mustang
Advantage - by 2:1 ratio operating expense---> Mustang

P-38 -0
P-51 -2

Also...I have read somewhere in one of my thousands of WW2 aviation books, , that during training of fresh pilots, after the P38's instructor told the students about the P38 wonderful qualities, the P51 instructor told the class to disregard everything the '38 instructor had said. Naturally the '38 instructor heard this and immediately challenged him to a dual.

The two planes were lined up next to each other.

On take-off the 38 destroyed the 51 as you could almost instantly apply full power in the 38, not so on the 51(excessive torque)

P38 - 1
P51 - 0

"Imagine" the P-38 losing and engine during take off - big torque roll with split seconds to recover - and visualize big hole at the end of the runway killing pilot and totally destroying the P-38. P-51 pilot bellies it in, minimal damage to P-51 and pilot OK.

P-38 - 0
P-51 - 1

So...as 51 were getting to altitude the 38 already started to Boom Zoom?

P38 - 2
P51 - 0

Imagine P-51H which climbs about the same as a 38J, depending on weight, runs faster, dives faster than best P-38.. booming and zooming

P-51H - 1
P-38J - 0

Imagine P-51 pilot able to spot P-38 farther away than P-38 pilot can spot Mustang (same eyesight assumed), which puts the Mustang in a position to decide whether it can attack from a superior tactical position or leave if not favorable

P-51B/D/H - 1
P-38 - 0

Only when they started from the same altitude the odds were even. I will go and check toningt for that snipped and post it here

edd

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"Imagine" pilots of equal skills.

"Imagine an Air Force that only has a limited budget and has to spend twice as much for the P-38's as the Mustangs to acquire and support.

"imagine 1000 Mustangs to 500 P-38s in the theatre, and imagine the 500 P-38s may only fly half the sorties in contrast to 500 Mustangs. Now the 1000 plane Mustang force can put four times as many fighters in the air on a given day. Say you need 500 Mustangs or P-38s to escort the bombers on a given day. You either send up 250 on the same day for mission one, and none the next day while 500 more Mustangs escort again?

Bomber crews happy?

Ditto strafing mission sortie count, or recon, or ground support.

P-38 can clearly carry more bomb weight so that is one mission factor it will excel in - and with max fuel have slightly more range...

But that is about it. The Mustangs were FAR more effective in bomber escort, far more effecive in air superiority and far more effective in destruction of enemy aircraft on the ground, had fewer training accidents, cheaper to buy, cheaper to operate - plus or minus the same performance - harder to see.

Even with twin engines the P-38 had a terrible ratio for aircraft destroyed on the ground to the number of aircraft (P-38) lost while strafing - while the twin engines offered some reliabilty when an engine was lost to mechanical reasons, a coolant hit or fuel/fuel fuel line was curtains for both of them - an the P-38 was an easier target to see and hit by flak crews.

Just a few thoughts on the subject.

I think for one the change over from the 38 and 47 to the 51 has to say something about endurance/range and this was what the 8th AF needed for bomber protection, same can be said for the US forces in the southern sphere the 15th AF. Bill has covered this in some detail previously

Dead on!

well the thought pattern came from a few the 8th AF chaps like Jack Ilfrey, Jack told me in a similar paragraph autographed in his book to me, loved the P-38 for the ground attack actions but maneuverable it was not in a dog fight if pressed closely besides having to turn back when the 17's were going farther and farther into the interior of the Reich

Erich said:

well the thought pattern came from a few the 8th AF chaps like Jack Ilfrey, Jack told me in a similar paragraph autographed in his book to me, loved the P-38 for the ground attack actions but maneuverable it was not in a dog fight if pressed closely besides having to turn back when the 17's were going farther and farther into the interior of the Reich

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Erich - Interesting comment from Cactus Jack. I have noted during my many perusings that P-38J escort line of radius seemed to be as far as Berin or Leipzig but haven't uncovered any to Brux or Posnan (or Munich for that matter), and certainly not any of the various Shuttle Missions when the 479th and 364th were still flying P-38s.

Fighter Pilot University: P-51 vs P-38

A Robin Olds interview on the P-38 vs P-51..

N'other Olds interview - worth the time to listen to it..
Fighter Pilot University: Robin Olds Defines Fighter Pilot

nice site! i like it! thanks...