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It was an inferior design to the Merlin. That's why the P51 received Britain's finest aero engine.
Cheers
John
I think this is the main problem. The U.S. Army Air Corps bet on the wrong horse. If they had emphasized mechanically driven superchargers as Britain and Germany did the Allison engine might have turned out just fine.Allison had been leaning heavily towards exhaust-driven turbochargers instead of the more common mechanically-driven superchargers
Allison had been leaning heavily towards exhaust-driven turbochargers instead of the more common mechanically-driven superchargers, feeling that their added performance more than made up for the added complexity.
Thus little effort was invested in equipping the V-1710 with a reasonable supercharger, and when placed in aircraft designs like the P-39 or P-40 which lacked the room for a turbo the engine suffered tremendously at higher altitudes.
It was for this reason in particular that the V-1710 was later removed from the P-51 Mustang and replaced with the Rolls-Royce Merlin.
The Merlin was a better developed aero engine and more appropriate for the needs of WW2 fighters. Mind you, the lack of power was not Allison's fault but,the US Army's thing about turbo chargers.
Turbosuperchargers were indeed highly successful in U.S. bombers, which were exclusively powered by radial engines. The P-47 fighter had the same combination of radial engine (R-2800) and turbosupercharger and was also successful, apart from its large bulk, which was caused by the need for the ductwork for the aft-mounted turbosupercharger.
However, mating the turbocharger with the Allison V-1710 proved to be problematic. As a result, designers of the fighter planes that utilized the V-1710 were invariably forced to choose between the poor high-altitude performance of the V-1710 versus the increased problems brought on by addition of the turbosupercharger. The fates of all of the V-1710 powered fighters of World War II would thus hinge on that choice.
The P-38 was the only fighter to make it into combat during World War II with turbosupercharged V-1710s. The operating conditions of the Western European air war – flying for long hours in intensely cold weather at 30,000 feet revealed several problems with the turbosupercharged V-1710. These had a poor manifold fuel-air distribution and poor temperature regulation of the turbosupercharger air, which resulted in frequent engine failures (detonation occurred in certain cylinders as the result of persistent uneven fuel-air mixture across the cylinders caused by the poor manifold design). The turbosupercharger had additional problems with getting stuck in the freezing air in either high or low boost mode; the high boost mode could cause detonation in the engine, while the low boost mode would be manifested as power loss in one engine, resulting in sudden fishtailing in flight. These problems were aggravated by suboptimal engine management techniques taught to many pilots during the first part of WWII, including a cruise setting that involves running the engine at a high RPM and low manifold pressure with a rich mixture. These settings can contribute to overcooling of the engine, fuel condensation problems, accelerated mechanical wear, and the likelihood of components binding or "freezing up."
Details of the failure patterns were described in a report by General Doolittle to General Spatz in January 1944. In March 1944, the first Allison engines appearing over Berlin belonged to a group of P-38H pilots of 55FG, engine troubles contributing to a reduction of the force to half strength over the target. It was too late to correct these problems in the production lines of Allison or GE, and so the P-38s were steadily withdrawn from Europe until they were no longer used for bomber escort duty with the Eighth Air Force by October 1944. A few P-38s would remain in the European theater as the F-5 for photo reconnaissance.
I think this is the main problem. The U.S. Army Air Corps bet on the wrong horse. If they had emphasized mechanically driven superchargers as Britain and Germany did the Allison engine might have turned out just fine.
I have been confused by the allison V-1710 engine. In 1940, It appears to roughly be equivalent to the Merlin and the DB-601A, around 1050-1150 hp, and in 1945 was generating 1600 hp in the P-38/P-82. But it was always associated with poor altitude performance. Wouldn't this be cured by an adequate compressor ala Merlin, and wouldn't this have corrected the problem, for, say, the P-51A? Why wasn't this accomplished?
1. Once it became obvious from the XP-37 and the XP-39 that you could not count on turbos for fighters Allison could have made a two-speed supercharger for the V-1710 very easily. It might not have been as good as the Merlin's but it would have added valuable performance to the P-39, P-40, and P-51. In fact, Allison could have done this very easily because unlike the Merlin the crankcase, reduction gears, and supercharger accessory case of the Allison were separate parts. The supercharger accessory case for the V-1710 was great for production since the same one could be used in all of the versions and only a change in impeller and gear ratio had to be made. BUT by sticking with that one design Allison doomed the V-1710 to single speed. By 1941 everybody but everybody was going to at least two speed superchargers.
It was an inferior design to the Merlin. That's why the P51 received Britain's finest aero engine.
Cheers
John
What was the arrangement on the P-82?
Sense prevailed in the end with RR Merlins.
Cheers
John
Dav, I appreciate you starting this thread. Many questions I have had for a long time are being answered by some well informed posters. Many thanks and keep up the good work, all!
What was the arrangement on the P-63 and P-82?