Versions with a turbocharger gave excellent performance at high altitude in the twin-engined Lockheed P-38 Lightning, and turbo-superchargers were fitted to experimental single-engined fighters with similar results.

When war material procurement agents from the United Kingdom asked North American Aviation to build the P-40 under license, NAA instead proposed their own improved aircraft design, using the V-1710 in their NA-73.

The accessory end had a one- or two-speed engine-driven supercharger that might have a second stage with or without an intercooler, the ignition magnetos and the customary assortment of oil and fuel pumps, all dictated by the application requirements.

[4] The ability to reverse the direction of rotation with a minimum of extra parts to achieve the task allowed the use of either a "tractor" or "pusher" propeller.

The USAAC had specified that the V-1710 was to be a single-stage supercharged engine and, if a higher altitude capability was desired, the aircraft could use their newly developed turbo-supercharger as was featured in the XP-37(YP-37), P-38, and XP-39.

[5] Although the early V-1710 powered P-39, P-40 and P-51A were limited to combat operations at a maximum of about 15,000 feet (4,600 m) they were available in comparatively large numbers and were the mainstay of some Allied Air Forces in all but the European theater of war.

The extra power of this version was derived from using exhaust turbines, not to drive a turbo-supercharger, but to return that energy to turning the crankshaft, called a turbo-compound engine.

The individual parts of the Allison series were produced to a high degree of standardization and reliability, using the best technology available at the time.

As stated previously, General Motors' policies regarding versatility meant that their Allison division would also employ modular design features on the V-1710 from its "long block" core V-12 unit outwards, so that it was capable of being mated to many different styles of turbo-superchargers and various other accessories, although the variety of turbo-superchargers available for installation was limited due to the constraints of single-engine fighter design.

General Electric was the sole source for research and production of American turbo-superchargers during this period, from its four decades worth of steam turbine engineering experience.

As a result, designers of the fighter planes that used 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 turbo-supercharger.

The original XP-39 was built with a V-1710 augmented by a General Electric Type B-5 turbo-supercharger as specified by Fighter Projects Officer Lieutenant Benjamin S. Kelsey and his colleague Gordon P.

[6] Numerous changes were made to the design during a period of time when Kelsey's attention was focused elsewhere, and Bell engineers, NACA aero-dynamic specialists and the substitute fighter project officer determined that dropping the turbocharger would be among the drag reduction measures indicated by borderline wind tunnel test results; an unnecessary step, according to aviation engineer and historian Warren M.

[7] The production P-39 was thus stuck with poor high-altitude performance and proved unsuitable for the air war in Western Europe which was largely conducted at high altitudes.

The P-39 was rejected by the British, but used by the U.S. in the Mediterranean and the early Pacific air war, as well as shipped to the Soviet Union in large numbers under the Lend Lease program.

The Soviets were able to make good use of P-39s because of its excellent maneuverability and because the air war on the Eastern Front in Europe was primarily short ranged, tactical, and conducted at lower altitudes.

The operating conditions of the Western European air war – flying for long hours in intensely cold weather at 30,000 feet (9,100 m) – revealed several problems with these engines.

These settings can contribute to over-cooling of the engine, fuel condensation problems, accelerated mechanical wear, and the likelihood of components binding or "freezing up.

[10] It was too late to correct these problems in the production lines of Allison or GE, and as the numbers of Merlin-engined P-51 Mustangs based in England mounted up through the end of 1943 and into 1944, the P-38s were steadily withdrawn from Europe until October 1944 when they were no longer used for bomber escort duty with the Eighth Air Force.

[12] Using the same P-38Gs which were proving difficult to maintain in England, Pacific-based pilots were able to use the aircraft to good advantage including, in April 1943, Operation Vengeance, the interception and downing of the Japanese bomber carrying Admiral Isoroku Yamamoto.

However, the installed engine was the V-1650-1 (a Packard-produced Merlin XX) with a slightly improved single-stage, two-speed supercharger, yielding only modest gains over the Allison V-1710.

[14] Its speed impressed the British, and the RAF quickly realized the airplane would possess excellent high altitude performance if the Allison V-1710 engine were replaced by the 60-Series Merlin.

[15] Starting with the V-1710-45 around 1943 (after the P-51 had been fitted with a Merlin 61 by Rolls-Royce), Allison attached an auxiliary supercharger to some of its engines in an effort to improve high-altitude performance.

In addition, it was tried or studied as the powerplant for many experimental and test aircraft such as the Curtiss XP-55 Ascender, North American XP-51J "lightweight Mustang", Boeing XB-38 Flying Fortress, and Republic XP-47A (AP-10), both of the latter with turbo-superchargers.

It had a short service life that was probably due to a combination of factors: poor reliability from the G-series V-1710 engines, low numbers of F-82s produced, and the arrival of jet fighters.

[21] "C" series engines were developed for highly streamlined pursuit aircraft for the USAAC, and are easily identified by the long reduction gear case.

These engines received heavier crankcases, a stronger crankshaft, SAE #50 propeller shaft, and Bendix pressure carburetors.

[22] "D" series engines were designed for pusher applications using propeller-speed extension shafts and remote thrust bearings mounted to the airframe.

[24] "F" series engines were designed for late model pursuit aircraft, and are identified by the compact external spur gear-type reduction gear box.

[25] "G" series engines were designed for high-altitude pursuit aircraft, and are identified by the auxiliary supercharger with a Bendix "Speed-Density" fuel control.