With the P-38K, was the P-51 and F4U even necessary?

[IdahoRenegade]

The P-38s in the 20th, 55th and 364th P-38s suffered much higher losses while strafing LW airfields than P-51B's (All three 8th AF P-38s converted to P-51s in July, 1944. The 479th did not have as high percentage losses to strafing as the other 3 and were closer to Mustang average loss per aircraft destroyed on the ground.

The twin engines were a definite advantage for loss of engine in a non lethal strafing environment but consider that the F4U and P-51 losses in Korea per sortie (ALL CAS for both ships) was about the same with 51 very slightly higher - one with coolant/one without. The P-38 was a huge (and slower) target on the deck with not only greater number of vulnerable surface areas and internal components(Fuel cells of internal fuel, supercharger systems, two radiators/oil coolers, coolant lines - all vulnerable to fire from explosive 20mm flak.

But, True - that if hit in a coolant line and that engine is shut down immediately the P-38 will survive where the P-51 will not.

The P-38K does Not solve the following
1.) Has very small window between top speed in a chase from 22000+ ft to compressibility in a dive. If dive flaps are deployed, the Critical Mach increases slightly but far short of the P-51, P-47, Bf 109 and FW 190. It can't chase nor can it evade from a dive initiated at high altitude. 8th AF operations required high altitude performance envelope and the P-38 was least suited of the Big 3 for Germany. The J-15 solved many of the mechanical issues but could do nothing for the aerodynamic issues of the NACA 23018 wing near transonic.
2.) It is HUGE and easily spotted long before the P-38 driver spots the other guy - giving the other guy a tactical advantage.
3.) It P-38J/L had less Combat Radius than the P-51B/C/D/K (not by much, 675mi to 750mi) limiting target escort options for 8th AF (and 20th AF) Planners. For example no P-38J with additional 110 gallons in LE fuel cell went past the Berlin/Leipzig/Munich line when P-51s were going to Stettin and Posnan Poland and Brux, Czechoslovakia. Even if the K had been configured for a Merlin 1650 it would consume even more gas than the V-1710 and further reduce Combat Radius..

Combat losses are difficult to directly compare, especially when attacking well defended ground targets. Were the targets comparably defended? Were the attackers bounced by enemy fighters? Was the number of attacking planes comparable (the '38 was typically available in lower quantities than the Mustang)? Did the pilots have comparable experience? Was similar damage done to the targets (was one group pressing an attack harder than the other)?

By all records, the '38 had a significantly longer ACTUAL combat range than either the P-51 or P-47, at least in the hands of experienced pilots that knew how to operate it. In the Pacific, long range missions were the rule. A combat RADIUS of 1000 miles was not uncommon with later models of the '38, and some attacks on the Borneo oil fields were about 1200 miles one-way. Remember that the '38 could, and did, carry up to (2) 310 gallon external tanks.

This link makes for some interesting reading, though I can not vouch for it's accuracy: The P-38 (C.C. Jordan; MakinKid; CDB100620)

Also keep in mind that, while the '51 had a higher dive speed (due to a later onset of comprehensibility) it was a fairly poor climber vs the '38 (4750fpm vs 3200) meaning that the '38 climbed nearly 50% faster (even without the K model). Climbing ability makes it possible to gain an energy advantage quite quickly.

 

[IdahoRenegade]

The P-38s in the 20th, 55th and 364th P-38s suffered much higher losses while strafing LW airfields than P-51B's (All three 8th AF P-38s converted to P-51s in July, 1944. The 479th did not have as high percentage losses to strafing as the other 3 and were closer to Mustang average loss per aircraft destroyed on the ground.

The twin engines were a definite advantage for loss of engine in a non lethal strafing environment but consider that the F4U and P-51 losses in Korea per sortie (ALL CAS for both ships) was about the same with 51 very slightly higher - one with coolant/one without. The P-38 was a huge (and slower) target on the deck with not only greater number of vulnerable surface areas and internal components(Fuel cells of internal fuel, supercharger systems, two radiators/oil coolers, coolant lines - all vulnerable to fire from explosive 20mm flak.

But, True - that if hit in a coolant line and that engine is shut down immediately the P-38 will survive where the P-51 will not.

The P-38K does Not solve the following
1.) Has very small window between top speed in a chase from 22000+ ft to compressibility in a dive. If dive flaps are deployed, the Critical Mach increases slightly but far short of the P-51, P-47, Bf 109 and FW 190. It can't chase nor can it evade from a dive initiated at high altitude. 8th AF operations required high altitude performance envelope and the P-38 was least suited of the Big 3 for Germany. The J-15 solved many of the mechanical issues but could do nothing for the aerodynamic issues of the NACA 23018 wing near transonic.
2.) It is HUGE and easily spotted long before the P-38 driver spots the other guy - giving the other guy a tactical advantage.
3.) It P-38J/L had less Combat Radius than the P-51B/C/D/K (not by much, 675mi to 750mi) limiting target escort options for 8th AF (and 20th AF) Planners. For example no P-38J with additional 110 gallons in LE fuel cell went past the Berlin/Leipzig/Munich line when P-51s were going to Stettin and Posnan Poland and Brux, Czechoslovakia. Even if the K had been configured for a Merlin 1650 it would consume even more gas than the V-1710 and further reduce Combat Radius..

Combat losses are difficult to directly compare, especially when attacking well defended ground targets. Were the targets comparably defended? Were the attackers bounced by enemy fighters? Was the number of attacking planes comparable (the '38 was typically available in lower quantities than the Mustang)? Did the pilots have comparable experience? Was similar damage done to the targets (was one group pressing an attack harder than the other)?

By all records, the '38 had a significantly longer ACTUAL combat range than either the P-51 or P-47, at least in the hands of experienced pilots that knew how to operate it. In the Pacific, long range missions were the rule. A combat RADIUS of 1000 miles was not uncommon with later models of the '38, and some attacks on the Borneo oil fields were about 1200 miles one-way. Remember that the '38 could, and did, carry up to (2) 310 gallon external tanks.

This link makes for some interesting reading, though I can not vouch for it's accuracy: The P-38 (C.C. Jordan; MakinKid; CDB100620)

Also keep in mind that, while the '51 had a higher dive speed (due to a later onset of comprehensibility) it was a fairly poor climber vs the '38 (4750fpm vs 3200) meaning that the '38 climbed nearly 50% faster (even without the K model). Climbing ability makes it possible to gain an energy advantage quite quickly.

 

[Mike Williams]

Also keep in mind that, while the '51 had a higher dive speed (due to a later onset of comprehensibility) it was a fairly poor climber vs the '38 (4750fpm vs 3200) meaning that the '38 climbed nearly 50% faster (even without the K model). Climbing ability makes it possible to gain an energy advantage quite quickly.

Not really...

P-51B - 9,335 lbs.: "In climb the low blower critical altitude for 75 in. HG. manifold presure and 3000 RPM was 2,200 ft. At this altitude the airplane attained a maximum rate of climb of 4380 ft/min. at 75 in. Hg. manifold pressure and 3,820 ft/min. at 67 in. Hg. manifold pressure. "

FLIGHT TESTS ON THE NORTH AMERICAN P-51B-15 AIRPLANE, AAF NO. 43-24777

P-51B-15 43-24777 Rate of Climb vs Altitude

P-38J - 17,363 lbs.: "At sea level a maximum rate of climb of 4040 ft/min was attained at 70" Hg. manifold pressure and a rate of climb of 3570 ft/min at 60" Hg. manifold pressure and 3000 RPM."

Flight Tests on the Lockheed P-38J Airplane, AAF NO. 43-28392

P-38J-15 43-28392 Rate of Climb

 

[IdahoRenegade]

Interesting. This correlates more closely with what I've read for the Mustang: P-51 Mustang Performance

What was the rated boost pressure at military power? I haven't found that yet, but am looking.

 

[GregP]

The P-51 was not approved for 75 inches until more than halfway through it's wartime use. The P-38 was around from the beginning, and was in combat before the P-51 was even on a piece of paper ... but you know that. So for a good deal of the time, the P-38 would handlily outclimb the P-51. Later, when 75" was approved, the P-51 could just about climb with the P-38. Some were possibly a bit better, some not.

In speaking with MANY WWII pilots, I have yet to run across many who ran their engines at 75 inches unless in actual combat. The ones who admitted doing it while not in combat were universally over their home airfield.

In any case, thanks for the charts!

Hi Renegade,

The rated boost for Military depends on the time period. For most of its service life in WWII, Military was 61" MAP and so-called WER was 67" MAP. Near the end, they upped the maximum to 75" MAP.

The Allisons were usually rated at 57" but late in the war were approved for 70" MAP while many pilots ran them in combat at 75" MAP.

Running a piston engine hard when you are 300+ miles from home and possibly over water was not something to take lightly. I had several US "muscle cars" back in the day, and I always took them to a drag strip once they were broken in and did 1 - 3 quarter-mile runs. Mostly, I drove pretty sanely on the road. A quarter-mile run in a big-block was usually on the order of 12 - 13 seconds, and that's not much stress overall.

It's a FAR CRY from taking a P-51 with a V-1650-3/7 and running it at 75" MAP for 10+ minutes and expecting nothing bad to happen. After this event, you still had to fly home for several hours. You could do it, sure. You also might be spending a lot of time in a POW camp or shot in you parachute while descending.

From all the guys I have asked, they took care of their engines whenever they could. They never max-climbed when they could cruise-climb, and cruised at greatly reduced power when they did not expect to be attacked. They only ran them up to high cruise when they entered what they believed was hostile territory and where they expected action. Running at best ecomony was a good way to get to Berlin and back with gas to spare. The only time you have too much gas, especially at the end of a mission, is when you're on fire.

But when they needed the P-51 to growl and show some teeth, it certainly could and would. I am given to understand they cruised at the bottom end best-economy settings for 45 minutes out of the hour and ran it up to max coutinuous for 10 - 15 minutes to ensure the plugs didn't foul, and then went back to best economy settings for another 45 minuties, and followed that cycle for duration of the mission.

This is from ETO P-51 pilots and was for cruising about over the bomber stream when no action was anticipated. Naturally, when the enemy was sighted, they would run up to Mil power as gradually as the situation allowed, turn on the gunshight and guns, clear the guns, and accelerate for combat. If they saw imminent action coming, they then dropped tanks, assuming they weren't over the bomber stream or high and in its path. It was incumbent on the P-51 guys to make sure they were safe to drop tanks.

Most is common sense, but you'd be surprised how many idiotic things were done without thinking of the planes around you. More than one bomber gunner fired into a neighbor following an attacking fighter with his guns. More than one escort got caught at best economy with gunsight / guns off and tanks on, and more than one escort had a mid-air with a bomber or another fighter when not looking where he was going. It was a crowded sky in the ETO, not so much in the PTO. The other side had the same issues, although not in vast bomber streams. They had people do idiotic things, too.

Some 20 years back we had some former Luftwaffe aces come to see a Bf 109 restoration and flight, and they talked a lot among the pilots about the stupid things that happened. After they left, our pilots related some of those stories and it was remarkable how similar the idiotic things were between the two sides. Must be human nature to do stupid things with equipment once in awhile. One pilot was buzzing his own farm when he left a prop blade on his father's tractor and bellied in on one of his own family farm's fields. The Bf 109 was later retrieved and flew again, and he had the satisfaction of having mom's saurbratten before being slapped by his superior for being stupid.

Sounds familiar somehow, doesn't it? ... except maybe for the saurbratten part ... well, maybe in Minnesota or places named "Germantown."

 

[wuzak]

Greg, I think you must mean that the P-51B was not on a piece of paper when the P-38 first went into combat?

Certainly the concept behind the P-51B was being discussed around the time that the P-38 first flew in combat. The Mustang X flew less than 6 months after the P-38 entered combat, and teh P-51B prototype flew a couple of months after that.

Maximum climb was used for two reasons - in combat and for climbing to an interception. It certainly wasn't used to climb to form p ready for a long range mission.

 

[wuzak]

By all records, the '38 had a significantly longer ACTUAL combat range than either the P-51 or P-47, at least in the hands of experienced pilots that knew how to operate it. In the Pacific, long range missions were the rule. A combat RADIUS of 1000 miles was not uncommon with later models of the '38, and some attacks on the Borneo oil fields were about 1200 miles one-way. Remember that the '38 could, and did, carry up to (2) 310 gallon external tanks.

Over sea and with no enemy fighter of anti-aircraft opposition the P-38 in the Pacific theatre could fly at the optimum speed and altitude for maximum range. A speed and altitude that would be a problem in the European theatre, as flak batteries would have good target practice and the P-38 would be very vulnerable to being bounced.

 

[GregP]

The P-38's first flight was 27 Jan 1939. It was introduce into service July 1941. The overseas introduction was Sep 1942.

The P-51's first flight was 26 Oct 1940 and service introduction was Jan 1942. P-51's started with the Eight Air Force in the winter of 1943 - 1944.

So the P-38 was flying in combat for more than ayear before the p-51's hit overseas deployment. It didn't take long for the P-51 to earn it's reputation, but it also wasn't cleared for 75" MAP until well into fall 1944. so what I said above still stands.

Nobody can argue the P-51 wasn't a great fighter, but it only got clearance for high-power late in the game when the German fighters were making that necessary. The Bf 109 was always a strong climber and the Fw 190 was close to the P-51 in climb and a better turner according to both sides.

So stretching the P-51's powerband a bit gave the P-51 pilots a bit more performance when it was needed. If it wasn't, they stayed well below 75", as any sane pilot several hundred miles from home would do.

P-38's weren't any more vulnerable to being bounced than any other aircraft. They got bounced early-on because they were being flown by green combat pilots who didn't know any better. Planes aren't vulnerable to being bounced ... green pilots are. I believe if the P-38 had stayed on the ETO the pilots flying them would not have stayed green for too long and they would have come to grips as veterans by watching for the Hun in the sun, thus avoiding being bounced. Getting surprised was only done one or, at best, a few times. You either learned or died not learning it.

 

[Mike Williams]

Interesting. This correlates more closely with what I've read for the Mustang: P-51 Mustang Performance

What was the rated boost pressure at military power? I haven't found that yet, but am looking.

Military power for the Merlin engined P-51s was 61" Hg. According to the P-51 Tactical Planning Characteristics Performance Chart:
Climb of the P-51B (V-1650-7) on Military Power at 9,000 lbs was 3,480 ft./min at 5,000' and 2,200 ft./min at 25,000'
Climb of the P-51B (V-1650-7) on Military Power with fuselage tank at 9,800 lbs was 3,200 ft./min at 5,000' and 2,030 ft./min at 25,000'
Climb of the P-51D (V-1650-7) on Military Power with fuselage tank at 10,100 lbs was 3,060 ft./min at 5,000' and 1,860 ft./min at 25,000'

Military power for the P-38J was 54" Hg.
According to the P-38 Tactical Planning Characteristics Performance Chart:
Climb of the P-38J on Military Power at 16,450 lbs was 3,425 ft./min at 5,000' and 2,500 ft./min at 25,000'.
Climb of the P-38J on Military Power with L.E. tanks at 17,650 lbs was 3,200 ft./min at 5,000' and 2,200 ft./min at 25,000'

 

[wuzak]

The P-38's first flight was 27 Jan 1939. It was introduce into service July 1941. The overseas introduction was Sep 1942.

The P-51's first flight was 26 Oct 1940 and service introduction was Jan 1942. P-51's started with the Eight Air Force in the winter of 1943 - 1944.

So the P-38 was flying in combat for more than ayear before the p-51's hit overseas deployment

You said the P-38 was in combat before the P-51 was even on a piece of paper.

The first combat seen by a P-38 was in August 1942. That was more than 2 years after the P-51 was "a piece of paper", and certainly months after the Mustang X and P-51B programs had begun.

It didn't take long for the P-51 to earn it's reputation, but it also wasn't cleared for 75" MAP until well into fall 1944. so what I said above still stands.

And when was the P-38 cleared for 75inHg MAP?

The Allisons were usually rated at 57" but late in the war were approved for 70" MAP while many pilots ran them in combat at 75" MAP.

Nobody can argue the P-51 wasn't a great fighter, but it only got clearance for high-power late in the game when the German fighters were making that necessary. The Bf 109 was always a strong climber and the Fw 190 was close to the P-51 in climb and a better turner according to both sides.

I would have thought the first combat introduction of 75inHg was in response to the V-1 flying bombs?

P-38's weren't any more vulnerable to being bounced than any other aircraft. They got bounced early-on because they were being flown by green combat pilots who didn't know any better. Planes aren't vulnerable to being bounced ... green pilots are. I believe if the P-38 had stayed on the ETO the pilots flying them would not have stayed green for too long and they would have come to grips as veterans by watching for the Hun in the sun, thus avoiding being bounced. Getting surprised was only done one or, at best, a few times. You either learned or died not learning it.

I didn't say that P-38s were more vulnerable to being bounced, but rather that a P-38 being flown at best altitude and speed for range, which conditions in the PTO allowed, would be more vulnerable than a P-38 flown in the ETO with different requirements for cruising.

The ETO demanded a higher cruise speed in enemy air space than was required for maximum range, as well as the altitudes required for escort work being higher.

 

[Mike Williams]

I would have thought the first combat introduction of 75inHg was in response to the V-1 flying bombs?

This document below shows that in February 1944 Eisenhower was pushing for 150 grade fuel which allowed for a significant improvement in the performance of fighter aircraft. He wanted it for the invasion of the continent. 75" Hg. MAP was cleared for the P-51 by April 1944 (see also here). As it turned out the 8th AF Fighter command went over to 150 grade within a week of the landings in Normandy.

 

[IdahoRenegade]

Military power for the Merlin engined P-51s was 61" Hg. According to the P-51 Tactical Planning Characteristics Performance Chart:
Climb of the P-51B (V-1650-7) on Military Power at 9,000 lbs was 3,480 ft./min at 5,000' and 2,200 ft./min at 25,000'
Climb of the P-51B (V-1650-7) on Military Power with fuselage tank at 9,800 lbs was 3,200 ft./min at 5,000' and 2,030 ft./min at 25,000'
Climb of the P-51D (V-1650-7) on Military Power with fuselage tank at 10,100 lbs was 3,060 ft./min at 5,000' and 1,860 ft./min at 25,000'

Military power for the P-38J was 54" Hg.
According to the P-38 Tactical Planning Characteristics Performance Chart:
Climb of the P-38J on Military Power at 16,450 lbs was 3,425 ft./min at 5,000' and 2,500 ft./min at 25,000'.
Climb of the P-38J on Military Power with L.E. tanks at 17,650 lbs was 3,200 ft./min at 5,000' and 2,200 ft./min at 25,000'

Thank you for providing accurate info. I should know better than to get lazy and ever trust Wiki. I was under the impression that the '38 was a considerably better climber. Though I seem to remember that early J models were quite a bit heavier than the H's and previous ones. Do you know if the J25s or Ls were any lighter or better climbers?

Another point I saw discussed, I'm wondering if anyone can provide enlightenment on. The discussion involved engine HP at various altitudes. The '51 had a 2-speed mechanical supercharger. IIRC high boost was engaged at ~18k where it provided maximum boost pressure. Being a fixed speed blower, it dropped off steadily above that altitude. The discussion on the '38 was that the turbos, with their boost regulators (were they waste gates? How were they controlled?) could maintain full boost up to a considerably higher altitude. IIRC they would overspeed at 28k or so at full boost, due to the lower mass of air, and hence load, on the compressors. Is this even close to right?

(btw, this is a great forum, I'm learning a ton, thanks all)

 

[EKB]

Going from Schiffer's unit diary, the 370th Fighter Group was not impressed with the P-51 in the ground attack role, after trading in their P-38s. The headline for Chapter 21 says it all: We Don't Want Mustangs! …


Snuffy Owens, 401st FS:
" The P-51 was a great airplane, but if you had to compare them I would say, this is my opinion, the 38 was ideal for what we did. That was dive-bombing and ground support. The 51 wasn't worth a damn down on the deck. It was too easy to knock down. It was great air-to-air. That's the one thing I asked them when they told me we were going over to 51s. I said, 'And what? Are we going to be escorting or down on the deck?' 'Everything will be escort from here on out.' The first mission was right back on the ground."


Rod Colton, 402nd FS:
" The only thing that really bothered me about the P-51 is that on our dive bombing, in a P-38 you'd come in, drop your bombs and strafe, and when you pulled that thing up it would zoom up to 10,000 feet in just nothing flat. When I was coming in on a P-51, the first day I ever strafed an installation where they were shooting at us, I pulled up and at about 3,000 feet here is this P-51 going 250 miles an hour. I could see tracers coming up from the ground and I'd have to kick a right rudder and skid it and weave my way back up into the sky. You never had to do that in a P-38 because you got out of the fire zone so damn fast. It just really reached for the sky."


Elbert Lineker, 402nd FS:
" They flew a bunch of P-51s in and just said, 'Here they are'. I remember I asked, 'How about some tech orders about how to fly the thing'. They said, 'We don't have a thing on paper for you'. I was Operations Officer by then so I took one out and took it off to fly it and give the guys some idea on what to do, because we'd never had torque … I remember the first dive-bombing. We had a little dive-bombing field cut out of the forest. It was about 20 acres and there was a little shack right on the middle of it. We used the shack for a target. I remember the first time I tried to dive bomb it, I missed the whole field with both the bombs. I started diving and the torque took over and I threw the bombs clear off in the forest. We got better, but we never did get as good as we did with the 38s."



See p.292-293
Jay Jones. The 370th Fighter Group in World War II: In Action over Europe with the P-38 and P-51. Schiffer Books, 2003.

 

[GregP]

Hi Wuzak,

You are correct, I did say the P-38 was in combat before the P-51 was on paper. Actually it was FLYING before the P-51 was on paper. I didn;t say when the P-38 was cleared for extra boost because it wasn't relevant. The P-38 out climbed the P-51 in all cases until the 75" was approved, regardless of max boost the P-38 was using.

If I am not mistaken the clearing of engines for extra boost was not tied to V-1's, but to 150 grade fuel. I could be wrong there but, if you don't have the fuel performance to handle the boost, all turning up the boost will do is destroy the engine.

The pilots I have spoken with who flew in the ETO did NOT cruise faster than best economy except to clear the plugs or for combat, which includes getting ready for imminent combat, too. It wasn't necessary for much of the trip. When it was, they did. There was good radar coverage and they pretty much knew when and from where the enemy was coming from most of the time. So if there is a large gaggle of enemy A/C about 20 miles in front of you, you might as well arm 'em up, turn on the gunsight, increase rpm, increase manifold pressure, and get ready to drop the tanks and clear guns when prompted.

Now these guys could be wrong, but nobody alive except the pilots who did it can prove it. Their statements are good enough for me, if for nobody else. Up until he passed away Bud Mahurin was a regular at the museum and described things many times. We all miss him.

 

[wuzak]

Another point I saw discussed, I'm wondering if anyone can provide enlightenment on. The discussion involved engine HP at various altitudes. The '51 had a 2-speed mechanical supercharger. IIRC high boost was engaged at ~18k where it provided maximum boost pressure. Being a fixed speed blower, it dropped off steadily above that altitude. The discussion on the '38 was that the turbos, with their boost regulators (were they waste gates? How were they controlled?) could maintain full boost up to a considerably higher altitude. IIRC they would overspeed at 28k or so at full boost, due to the lower mass of air, and hence load, on the compressors. Is this even close to right?

Geared superchargers had a critical altitude for each gear ratio used. For a Merlin 60-series, as found in the P-51, there were two - these were known as LO and HI in the USAAF, but Medium Supercharged (MS) and Fully Supercharged (FS) in the RAF.

(As an aside it was also possible to have a Low Supercharged gear, but it was rare. AFAIK the only engines to be rated with an LS gear were the three speed Griffon 100-series, with LS, MS and FS gears.)

The maximum allowed boost could be obtained at sea level in LO, the boost being maintained up until the critical altitude. The boost was controlled by the throttle plate, which choked the intake to the supercharger. At critical altitude the throttle plate was open fully (why it was known as Full Throttle Height in the RAF). At this point the maximum power for the engine in that gear was being produced. After that altitude the boost and power fell away.

Early Merlins used only one gear. But that meant compromises - geared for low altitudes the engine lacked performance at high altitudes, and geared for high altitudes the low altitude performance suffered. Adding a second gear helped teh high altitude engine to fill in the performance at lower altitudes.

The critical altitudes were dependent upon boost. For war emergency (67inHg MAP/+18psi boost) the critical altitude was lower than for military power (61inHg MAP/+15psi boost) or max continuous (usually +7psi boost).

The highest power that the engine produced was in the lower gear.


The turbo in the P-38 maintained pressure to the carburettor equivalent to sea level, which enabled the engine to be set for sea level and make the maximum amount of power possible.

This could be held up until the turbocharger's critical altitude - which was defined by the turbo's rpm. The control method was a wastegate, which would bleed off exhaust gases to make sure that the turbine would only have the amount it needed to drive the compressor. Theoretically the exhaust back pressure in the turbo system would be equivalent to ejector exhausts, but practically I don't think this was the case.

Critical altitudes for the B-series turbos used in P-38s improved from around 25,000ft to around 30,000ft.

Teh actual boost that the engine saw came from the supercharger mounted to the engine. In the V-1710 it was a single stage single speed unit. The gear ratio of the supercharger for the P-38 was lower than for the P-39 or P-40 (ie the supercharger was run at lower rpm).

 

[Mike Williams]

And when was the P-38 cleared for 75inHg MAP?

A Materiel Command Memorandum, dated 16 March 1944, on Flight Tests of Fighter Aircraft with 44-1 Fuel noted that the V-1710-89 and V-1710-91 as installed in the P-38J were cleared to operated at 75" MAP.

A Materiel Command report, dated 27 March 1944, on the Preliminary 7-1/2 Hour War Emergency Rating Test of the Allison V-1710-91 Engine Operated on Grade 104/150 Fuel concluded that the Allison V-1710-91 satisfactorily completed a 7-1/2 hour preliminary War Emergency Approval Test at a rating of 2000 b.h.p. and 75 inches MAP.

A subsequent report, dated 22 April 1944, on an Attempted 7-1/2 Hr. War Emergency Rating of Allison V-1710-89 Engine as Installed in P-38J Airplane Operated on Grade 104/150 concluded that the Allison engine connecting rods failed and that the connecting rods were probably near their ultimate strength.

A Material Command Report, dated 13 May 1944, on Preliminary Flight Tests of Fighter Aircraft Using PPF 44-1 Fuel at Increased War Emergency Ratings concluded that based on the preliminary flight tests, that satisfactory operation was experienced on the P-38J airplane at 70" hg.

A Materiel Command Memorandum, dated 20 June 1944, on Project P.P.F. - Installation and Operating Instructions noted that final release had been made approving 70" MAP for the P-38.

 

[drgondog]

The P-51B was tested with 44-1 150 octane fuel in April 1944 and cleared for 75". The Fuel arrived in ETO in mid June and 8th AF reduced the 75 to 72" boost at WEP. Pilot to note on Form 4 any deviation from MP (61") and duration.. more than 5 minutes almost always mandated an engine change. The 8th was flying combat missions with 150 octane fuel in very late June, 1944 - or late spring, not fall, 1944

One notable 355th pilot Ben Johnston had just shot down two 190s for #3 and 4 and was chasing the fifth when his engine blew. Post war review indicated WEP for 10-15 minutes.

A couple of RAF P-51B's were modified to install the Rolls 100 and ran 419mph at 1600 and 454 at 18000 ft(IIRC?). It had an ROC in the 4500fpm range at 25pounds of boost at 2K (all from memory which is notoriously leaky at the moment).. this was to be a V-1 chaser. Full combat load except No fuel in 85 gallon tank..

Greg - the Mark I reached UK in January, deployed to AFDU in late April 1942 (about the time Hooker recommended that a Rolls Merlin be installed after test flying it), first combat victory credit by Hollis at Dieppe in August 1942. First Mark X test flight in October, 1942 and first XP-51B flight November 30, 1942. First delivery of the P-51B-1 in May 1943, first delivery to UK in September 1943, first deployment to 9th AF 354FG in November 1943, first combat mission (including returned Lend Lease RAF Mustang III's) December 1, 1943. First 8th AF Mustang Mission 357FG 11 February 1944.

The discussion of the P-38K as a world beater probably should be considered in light of the fact that the first P-38J-15 with Leading edge 55 gallon fuel tanks didn't fly combat in ETO until late February 1944 and the first J-25 in October, 1944 (dive flaps, boosted ailerons).

Consider that the first XP-51F flew about the time the J-15s were still dribbling into ETO in May 1944 and the P-51H contract was awarded in April 1944.

Why would AAF Material Command want to slow down delivery of the existing P-38s for the P-38K when they had already made the decision to a.) replace all ETO Fighter Group P-47 and P-38s with P-51s as they became available (yes the 56th held out), and b.) that most fighter groups flying P-38 and or P-47D in the CBI/PTO engaged in long range escort would receive P-51D and P-47N, then P-51H for the invasion of Japan?

 

[tomo pauk]

The loss of the prototype was the biggest single factor because it delayed even the consideration of mass production tooling and training for at least 18 months. Additionally the P-38 was a very complex design with respect to modularity and ease of assembly

I've never held the rivet gun, let alone being in the aircraft business myself - but Lockheed managed to churn out almost 4200 P-38s in 1944 from one (granted, a big one) factory. Almost as much as Bell produced P-39s in 1943, or Curtiss' production of P-40s in the same year, both much simpler aircraft. Lockheed have had more than 1300 P-38s ordered before Sept 1940, yet both USAAF and Lockheed missed the opportunity to have either a second source of P-38s, and/or to have the production of the Hudsons and the like outsourced. Eg. Boeing was second source for early Boston III (~A-20) bombers.
For comparison sake, in Sept 1940, the USAF ordered 733 P-47, by Oct 14 1941 the order is totaled at 850, and 3 factories are to produce it.

The AAF senior leadership was curiously enough against the concept of long range fuel tanks for combat. IIRC Colonel Ben Kelsey snuck in the design mod under the guise of Ferry Tanks in 1942 but by that time the P-47C design was complete and Republic was trying for second source manufacturers. Even if Republic had the vision, AAF exhibited no interest until 1943 when it became apparent that a.) losses for deep penetrations would be prohibitive, and b.) there was a market for a P-47 with more internal fuel also as a requirement for Combat Radius extension.

The vision from the AAF is required more, I'm afraid
We know that Lockheed simply installed wing racks on the P-38F (and retrofitted it on the P-38Es in service) and that NAA installed not just racks, but also air brakes on the A-36, so I'd say that it was much more down to the current doctrine (dogma?) whether the wing racks will be on the P-47, rather than it is about the Republic's capabilities.

 

[gjs238]

P-38's weren't any more vulnerable to being bounced than any other aircraft. They got bounced early-on because they were being flown by green combat pilots who didn't know any better. Planes aren't vulnerable to being bounced ... green pilots are. I believe if the P-38 had stayed on the ETO the pilots flying them would not have stayed green for too long and they would have come to grips as veterans by watching for the Hun in the sun, thus avoiding being bounced. Getting surprised was only done one or, at best, a few times. You either learned or died not learning it.

Colonel Harold J. Rau might disagree with that...

20th Fighter Group Headquarters
APO 637 U.S. Army
(E-2)

3 June 1944

Subject: P-38 Airplane in Combat.

To: Commanding General, VIII Fighter Command, APO 637, U.S. Army.

1. The following observations are being put in writing by the undersigned at the request of the Commanding General, VII FC. They are intended purely as constructive criticism and are intended in any way to "low rate" our present equipment.

2. After flying the P-38 for a little over one hundred hours on combat missions it is my belief that the airplane, as it stands now, is too complicated for the 'average' pilot. I want to put strong emphasis on the word 'average, taking full consideration just how little combat training our pilots have before going on as operational status.

3. As a typical case to demonstrate my point, let us assume that we have a pilot fresh out of flying school with about a total of twenty-five hours in a P-38, starting out on a combat mission. He is on a deep ramrod, penetration and target support to maximum endurance. He is cruising along with his power set at maximum economy. He is pulling 31" Hg and 2100 RPM. He is auto lean and running on external tanks. His gun heater is off to relieve the load on his generator, which frequently gives out (under sustained heavy load). His sight is off to save burning out the bulb. His combat switch may or may not be on. Flying along in this condition, he suddenly gets "bounced", what to do flashes through his mind. He must turn, he must increase power and get rid of those external tanks and get on his main. So, he reaches down and turns two stiff, difficult gas switches {valves} to main - turns on his drop tank switches, presses his release button, puts the mixture to auto rich (two separate and clumsy operations), increases his RPM, increases his manifold pressure, turns on his gun heater switch (which he must feel for and cannot possibly see), turns on his combat switch and he is ready to fight. At this point, he has probably been shot down or he has done one of several things wrong. Most common error is to push the throttles wide open before increasing RPM. This causes detonation and subsequent engine failure. Or, he forgets to switch back to auto rich, and gets excessive cylinder head temperature with subsequent engine failure.

4. In my limited experience with a P-38 group, we have lost as least four (4) pilots, who when bounced, took no immediate evasive action. The logical assumption is that they were so busy in the cockpit, trying to get organized that they were shot down before they could get going.

5. The question that arises is, what are you going to do about it? It is standard procedure for the group leader to call, five minutes before R/V and tell all the pilots to "prepare for trouble". This is the signal for everyone to get into auto rich, turn drop tank switches on, gun heaters on, combat and sight switches on and to increase RPM and manifold pressure to maximum cruise. This procedure, however, does not help the pilot who is bounced on the way in and who is trying to conserve his gasoline and equipment for the escort job ahead.

6. What is the answer to these difficulties? During the past several weeks we have been visited at this station time and time again by Lockheed representatives, Allison representatives and high ranking Army personnel connected with these two companies. They all ask about our troubles and then proceed to tell us about the marvelous mechanisms that they have devised to overcome these troubles that the Air Force has turned down as "unnecessary". Chief among these is a unit power control, incorporating an automatic manifold pressure regulator, which will control power, RPM and mixture by use of a single lever. It is obvious that there is a crying need for a device like that in combat.

7. It is easy to understand why test pilots, who have never been in combat, cannot readily appreciate what each split second means when a "bounce" occurs. Every last motion when you get bounced is just another nail in your coffin. Any device which would eliminate any of the enumerated above, are obviously very necessary to make the P-38 a really effective combat airplane.

8. It is also felt that that much could done to simplify the gas switching system in this airplane. The switches {valve selector handles} are all in awkward positions and extremely hard to turn. The toggle switches for outboard tanks are almost impossible to operate with gloves on.

9. My personal feeling about this airplane is that it is a fine piece of equipment, and if properly handled, takes a back seat for nothing that the enemy can produce. But it does need simplifying to bring it within the capabilities of the 'average' pilot. I believe that pilots like Colonel Ben Kelsey and Colonel Cass Huff are among the finest pilots in the world today. But I also believe that it is difficult for men like them to place their thinking and ability on the level of a youngster with a bare 25 hours in the airplane, going into his first combat. That is the sort of thinking that will have to be done, in my opinion, to make the P-38 a first-class all around fighting airplane.

HAROLD J. RAU
Colonel, Air Corps,
Commanding.

 

[FLYBOYJ]

Colonel Harold J. Rau might disagree with that...

20th Fighter Group Headquarters
APO 637 U.S. Army
(E-2)

3 June 1944

Subject: P-38 Airplane in Combat.

To: Commanding General, VIII Fighter Command, APO 637, U.S. Army.

1. The following observations are being put in writing by the undersigned at the request of the Commanding General, VII FC. They are intended purely as constructive criticism and are intended in any way to "low rate" our present equipment.

2. After flying the P-38 for a little over one hundred hours on combat missions it is my belief that the airplane, as it stands now, is too complicated for the 'average' pilot. I want to put strong emphasis on the word 'average, taking full consideration just how little combat training our pilots have before going on as operational status.

3. As a typical case to demonstrate my point, let us assume that we have a pilot fresh out of flying school with about a total of twenty-five hours in a P-38, starting out on a combat mission. He is on a deep ramrod, penetration and target support to maximum endurance. He is cruising along with his power set at maximum economy. He is pulling 31" Hg and 2100 RPM. He is auto lean and running on external tanks. His gun heater is off to relieve the load on his generator, which frequently gives out (under sustained heavy load). His sight is off to save burning out the bulb. His combat switch may or may not be on. Flying along in this condition, he suddenly gets "bounced", what to do flashes through his mind. He must turn, he must increase power and get rid of those external tanks and get on his main. So, he reaches down and turns two stiff, difficult gas switches {valves} to main - turns on his drop tank switches, presses his release button, puts the mixture to auto rich (two separate and clumsy operations), increases his RPM, increases his manifold pressure, turns on his gun heater switch (which he must feel for and cannot possibly see), turns on his combat switch and he is ready to fight. At this point, he has probably been shot down or he has done one of several things wrong. Most common error is to push the throttles wide open before increasing RPM. This causes detonation and subsequent engine failure. Or, he forgets to switch back to auto rich, and gets excessive cylinder head temperature with subsequent engine failure.

4. In my limited experience with a P-38 group, we have lost as least four (4) pilots, who when bounced, took no immediate evasive action. The logical assumption is that they were so busy in the cockpit, trying to get organized that they were shot down before they could get going.

5. The question that arises is, what are you going to do about it? It is standard procedure for the group leader to call, five minutes before R/V and tell all the pilots to "prepare for trouble". This is the signal for everyone to get into auto rich, turn drop tank switches on, gun heaters on, combat and sight switches on and to increase RPM and manifold pressure to maximum cruise. This procedure, however, does not help the pilot who is bounced on the way in and who is trying to conserve his gasoline and equipment for the escort job ahead.

6. What is the answer to these difficulties? During the past several weeks we have been visited at this station time and time again by Lockheed representatives, Allison representatives and high ranking Army personnel connected with these two companies. They all ask about our troubles and then proceed to tell us about the marvelous mechanisms that they have devised to overcome these troubles that the Air Force has turned down as "unnecessary". Chief among these is a unit power control, incorporating an automatic manifold pressure regulator, which will control power, RPM and mixture by use of a single lever. It is obvious that there is a crying need for a device like that in combat.

7. It is easy to understand why test pilots, who have never been in combat, cannot readily appreciate what each split second means when a "bounce" occurs. Every last motion when you get bounced is just another nail in your coffin. Any device which would eliminate any of the enumerated above, are obviously very necessary to make the P-38 a really effective combat airplane.

8. It is also felt that that much could done to simplify the gas switching system in this airplane. The switches {valve selector handles} are all in awkward positions and extremely hard to turn. The toggle switches for outboard tanks are almost impossible to operate with gloves on.

9. My personal feeling about this airplane is that it is a fine piece of equipment, and if properly handled, takes a back seat for nothing that the enemy can produce. But it does need simplifying to bring it within the capabilities of the 'average' pilot. I believe that pilots like Colonel Ben Kelsey and Colonel Cass Huff are among the finest pilots in the world today. But I also believe that it is difficult for men like them to place their thinking and ability on the level of a youngster with a bare 25 hours in the airplane, going into his first combat. That is the sort of thinking that will have to be done, in my opinion, to make the P-38 a first-class all around fighting airplane.

HAROLD J. RAU
Colonel, Air Corps,
Commanding.

This document has been posted here before. It's obvious Rau was not a fan of the P-38 and I would bet he also didn't like to fly multi engine aircraft. While He writes this memo the 475th FG is making history with the P-38..

"During World War II, the 475th Fighter Group, in combat for approximately two years, completed 3042 missions, (21,701 Sorties) and shot down 551 Japanese aircraft. On the other hand, the Group lost only 56 Planes to the Japanese. During the war, the Group took part in seven campaigns, and was awarded three Distinguished Unit Citations for outstanding performance of duty in action. In addition to Major McGuire, the unit boasted such "Aces" of the Pacific War as Col. Charles MacDonald (27), Capt. Daniel T. Roberts (14), Lt. Francis J. Lent (11), Lt. Col. John S. Loisel (11), and Capt. Elliot Summer (10), plus many more."

Aces