Yes, Galland was critical of EARLY P-38's. Galland's opinion was formed when the P-38 had no dive flaps and the majority of pilots in the 8th AF were relatively green. A green pilot in a plane as hard to fly as the P-38 was probably was an easy target. And if the P-38 pilot did gain the advantage, the German could dive and run. Consider that when Galland met John Lowell (a pilot of equal skill) in a later P-38, Galland said Lowell damn near killed him, and Lowell only broke off to go home for fuel. Hearing Lowell describe the fight, Galland said "You son of a squeak, you Golly-geened near killed me that day!" Several pilots of comparable skill in P-38's shot down noted German aces. So, the 8th AF still considered the P-38 to be second rate, even when the P-38 with a pilot of good skill could and often did shoot down the very best Germany had to offer.
Once again, regarding turbochargers, only the exhaust OUTLET and the intake INLET are exposed to atmoshperic pressure. Pressure on the exhaust (turbine) side is exerted by engine exhaust. This is what drives the turbocharger. The intake side (impeller, or compressor) pressurizes the intake system. Whatever manifold pressure exists, is the resistance to the force exerted to spin the turbocharger by the exhaust pressure. The amount of exhaust pressure available to drive the turbocharger on an engine operating at a given RPM and intake manifold pressure is the same regardless of the altitude. If the intake manifold pressure and RPM do not change, then turbocharger speed will not change. If you could increase RPM, or lower the intake mandifold pressure, or increase the pressure on the INLET side of the impeller housing, then you could increase turbo speed.
In the case of the GE turbocharger on the Allison V1710 on the P-38, neither housing is variable, nor is the nozzle. The speed is regulated by an oil pressure regulator. So long as oil pressure and temperature remain within normal operating parameters, the regulator is capable of bypassing enough exhaust pressure to properly limit the RPM of the turbocharger. Load on the engine is controlled by prop pitch, and therefore, at maximum throttle, with autopitch, engine RPM and load are constant. The intake side of the turbocharger is exposed to manifold pressure, in this case you state 64". That is the load seen by the turbocharger exhaust turbine. At a constant load, constant manifold pressure, and constant RPM, a constant amount of exhaust gas pressure will be generated by the engine. This constant pressure will be applied to drive the turbine side of the turbocharger, which is directly coupled to the impeller or compressor side, which is still seeing a constant intake manifold pressure of 64". No load change exists, no force change exists, so no speed change occurs. Even if you remove the load from the engine, RPM will increase but exhaust pressure will decrease. Eventually, you can increase RPM enough to overspeed the turbocharger, if the engine will turn enough RPM. If the atmospheric pressure were to drop so low that the there was not enough air available to create 64" of manifold pressure, then the load on the impeller would decrease, and the turbo would overspeed. So yes, it is possible to overspeed the turbo at high altitudes, but I find no mention of this with the P-38 or the P-47, though both did use the same turbocharger. The only evidence of turbocharger overspeed comes together with a failure of another system or part of the system. The Curtiss prop could lose its dynamic brake and over rev the engine, eventually over reving the turbo. The oil cold be allowed to get so cold it congealed in the turbocharger regulator, renderring the regulator inoperative, eventually over boosting and possibly over reving the turbocharger.
The only factual evidence against the P-38 at high altitudes was the dive problem. With the dive flaps, the P-38 could and did fight at high altitudes, and was far less likely to spin out of a fight at high altitudes and was far easier to recover.
The P-47 used the same turbocharger at the same range of altitudes. Further, the P-47 was tested in an overboost condition that exceeded all operating parameters of the engine and the turbocharger without a failure of either.
That is why a turbocharger makes a better altitude compensating device than a crank driven supercharger.
While the low critical Mach number was part of the equation, the fault the 8th AF found with the P-38 is that the early planes lacked automatic control of oil and coolant temperatures, and attempts to operate the engines at full power when they were too cold resulted in engine failures of one form or another. The early versions intercoolers were not efficient enough, and seperated the lead from the fuel, lowering the octane numbers. The requirement of Lockheed by the USAAF to use the Curtiss electric prop caused electrical and engine failures, compouned by poor maintenance training for the care of the electric props. Failure of the pilot to set the radiator doors resulted in overheating at full throttle.
However, the J and later models changed all that. The dive flaps allowed the P-38 to chase in a dive, even though the 8th refused to change their instructions and policy. The automatic controls for the oil coolers, and radiators eliminated the cooling problems, and the turbocharger overspeed due to oil congealing in the regulator. The new core type intercoolers allowed the P-38 to use the full power of the Allison. The fact that the 8th AF refused to acknowledge and take full advantage of these changes is not an indictment of the plane, but a further indictment of Doolittle and Spatz, who were chastized or removed for failure to be agressive enough. The fact that the 5th, 9th, and 15th AF's were willing and able to take full advantage of them should be considered.
The dive problems of the P-38, as noted by Gerald Brown, are well known, and acknowledged by bothe sides of the arguement. On the other hand, they are much less of a problem for the J and L models, by far the most numerous of the P-38 line. Further, several pilots were known to have figured out how to dive in a P-38 even without the dive flaps.
One of the most critical errors of the 8th AF is their complete and dismal failure to acknowledge and make use of the experienced pilots who came from North Africa. The fact that the 8th AF completely failed to utilize the skills and experience of those pilots is another prime example of incompetence in the command staff of the 8th AF, and taints their opinion. Most pilots who came to the 8th from North Africa were very successful, and what they knew would have been invaluable to the new pilots, but the 8th AF chose to completely ignore this. The 8th was never known for the use of good tactics, just the use of massively overwhelming numbers. One need only witness their insanely stupid attempts to practice mass daylight precision bombing without fighter escort.
The mere fact that the USAAF and especially the 8th AF hog tied the P-38 by denying Lockheed the use of the K-14 gunsite, the Hamilton Standard prop, and the Lockheed master combat control, and then complained bitterly about the performance of the P-38 is enough to tell even the casual observer there was something very wrong with the USAAF and the 8th in particular. The fact that the P-38 accounted for more Japanese planes than most other fighters combined should be enough to raise a few warning flags. As should the success of the P-38 over North Africa, Italy, and the Med., all with a different leadership than the 8th.
When every other group is able to get completely superior performance and results from an aircraft, and most facing the same planes and some of the same pilots as the 8th, but the 8th can barely keep it in the air, and is critcized for heavy losses and poor leadership and tactics overall and in general, you have to look closely at the command staff of the 8th AF before you lay the blame solely on the P-38.
One more little fact. The 5th AF had a guy named Major Thomas B. McGuire, a successful guy, with 38 victories. Now, Genreal Kenney and Colonel McDonald had Major McGuire write a manual to indoctrinate new pilots to the 5th AF and the Pacific theater of operations. It included the flight characteristics of every Japanese plane, the tactics of the pilots, and all the information necessary to allow the new pilot to enter combat with confidence and leave combat with success. Funny, the 8th AF had several successful P-38 pilots, but none were ever asked to write a manual to help the new pilots learn to fly their plane in combat, and give them the tactics and knowledge needed to win. The successful P-38 pilots of the 8th knew how to beat the Germans, and had moves to conquer the dive problems, and tactics that worked at high altitudes. But the knowledge was never passed on to all of the new pilots who were assigned the P-38. One more reason poor leadership in the command staff of the 8th AF was the primary and major reason for the less than stellar record of the P-38 in Europe with the 8th AF.
Like the guy said, we are generating way too much text here. Time to move on.
[ 12-06-2001: Message edited by: Renegade Savage ]
