Allison V-1710 Engine




	Allison V-1710-F20R, liquid cooled engine.
	The only American liquid-cooled engine to see service in World War II was the Allison V-1710. It was one of the most important large U.S. aero engines, with over 70,000 engines produced from the time of the first in 1931 to the last in 1948. The engine was produced for several important fighters of WWII, including the P-38 Lightning, P-39 Airacobra, P-40 Warhawk, P-51A Mustang, P-63 Kingcobra, P-82 Twin Mustang and the Consolidated XA-11A, an experimental attack version of the Consolidated P-25. Allison was an Indianapolis firm that had done well in a small way with Liberty modifications and with reduction gears for others' engines. Allison became a part of general motors in 1929, and the firm today remains a GM component as "Detroit Diesel Allison Division."


The V-1710-E18 & E19 engine with extension shaft and outboard reduction gear box used on the P-39 Airacobra.

Around the time that the Army was washing its hands of the Curtiss Conqueror, Allison began to develop its own engine, at the request of Allison General manager Norm Gilman. The target was 1,000 hp, and Allison intended that the engine should be large enough to deliver this power easily. A successful V-1710-A was test run in 1931 and delivered 650 hp at 2,400 RPM on 80-octane fuel. Development proceeded slowly until the Navy entered the picture. The Navy, while not losing its attachment to air-cooled power plants for airplanes, needed liquid cooling for dirigibles. The Navy requested eliminating the supercharger (rotary induction blower) in favor of two carburetors placed in the Vee of the engine. A significant redesign was undertaken by R.M. Hazen in 1936. This "C"-model passed its 150 hour type acceptance test in 1937, establishing a rating of 1,000 hp at 2,600 rpm at sea level. A number of incremental improvements were made during the life of the "C"-model, eventually leading to "C"-models with takeoff ratings of 1,150 hp at 2,950 rpm and supporting 3,500 rpm for overspeed during dives.


The front view of an Allison V-1710-F10R or F10I.

The production Allison turned out to be the sturdy and reliable powerplant that its designers had striven for. The only thing that stood between the Allison and real greatness was its inability to deliver its power at sufficiently high altitudes. This was not the fault of its builders. It resulted from an early Army decision to rely on turbo-supercharging to obtain adequate power at combat heights. Even this decision was not a technical error. A turbo-supercharged Allison was as good a high-altitude engine as most. The trouble was that the wartime shortage of alloying materials, especially tungsten, made it impossible to make turbo-superchargers for any but a small proportion of Allison engines. Therefore, bomber engines were given priority over all others.

The few turbo-supercharged Allisons that were made, were allocated to P-38s, making the high-altitude performance of that plane its best feature. All 14,000 P-40s got gear-driven superchargers, and as a result, were never first-class fighter planes. Donaldson R. Berlin, the P-40's designer, has said that P-40s experimentally equipped with turbo-superchargers outperformed Spitfires and Messerschmitts and that if it had been given the engine it was designed for, the P-40 would have been the greatest fighter of its era. This may be to some extent the bias of a proud parent, but there is no doubt that the deletion of the turbo-supercharger ruined the P-39 .


The V-1710-85 engine with extension shaft and outboard reduction gear box used on the P-39Q Airacobra. (Photo: National Museum of The United States Air Force)

Had Allison's engineers been able to put the effort into gear-driven superchargers that Pratt and Whitney and Rolls-Royce did, it might have been a different story. As it was, there can be little doubt that the V-1710 had more potential than was actually exploited.

Specifications:
Allison V-1710-G6
Date:	1941
Cylinders:	12
Configuration:	V type, Liquid cooled
Horsepower:	1,250 hp (932 kw)
R.P.M.:	3,200
Bore and Stroke:	5.5 in. (140 mm) x 6 in. (152 mm)
Displacement:	1,710 cu. in. (28 liters)
Weight:	1,595 lbs. (707 kg)

Sources:

Ed. Ralph D. Bent, James L. McKinley. Aircraft Power Plants by the Northrop Aeronautical Institute. (New York: McGraw Hill, 1955.)
Herschel Smith. A History of Aircraft Piston Engines. (Manhattan, Kansas: Sunflower University Press, 1993.)
Ed. Glenn D. Angle. Aerosphere, 1943. (New York: Aerosphere Inc.)
Unlimited Excitement IIc; The Allison V-170 Engine. www.unlimitedexcitement.com. 2005.
National Museum of The United States Air Force; Allison V-1710 Engine. www.wpafb.af.mil. 2005.

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Updated August 6, 2005