What is Allison Engine Company?

The Allison Engine Company was a U.S. aircraft engine manufacturer which was acquired by Rolls-Royce plc in 1995 to become a subsidiary, Rolls-Royce Corporation.

It is best known for the Allison V-1710 V-12 engine, which was the only high-powered U.S. liquid-cooled engine design used during World War II. In the post-war era, Allison carved out niches in early jet engines and later in turboshafts for helicopter use.

History

Allison started as an engine and car "hot rodding" company servicing the Indianapolis Motor Speedway in Indianapolis. Its only regular production line item was steel-backed lead bushings, used as bearings in various aircraft engines. It also built various drive shafts, extensions and gear chains for high power engines, on demand. Another, smaller, business was the conversion of older Liberty engines to more powerful models, both for aircraft and marine use.

In the late 1920s the U.S. Army funded the development of a series of high-power engines, as part of its hyper engine series, which it intended to produce on Continental Motors' production lines. Allison's manager, N.H. Gilman, decided to experiment with its own high-power cylinder design. The result was presented to the Army in 1928, which turned down the development proposal.

In 1929, shortly after the death of James Allison, the company was purchased by the Fisher Brothers, who instructed it to use the cylinder design for a six cylinder engine for a "family aircraft". Before work on this design had progressed very far, Fisher sold the company to General Motors, which ended development due to financial pressures of the Great Depression. Nevertheless Gilman pressed ahead with the cylinder design, building a "paper project" V-12 engine. The Army was once again uninterested, but instead suggested Allison try selling it to the U.S. Navy. The Navy agreed to fund development of A and B models to a very limited degree for its airships, until the crash of the USS Macon in 1935, when the Navy's need for a 1,000 hp engine disappeared.

By this point the Army had become more interested in the design, and asked Allison to continue with a new "C" model. They had few funds of their own to invest, and Allison supported much of the development out of their own pocket. The V-1710-C first flew on 14 December, 1936 in the Consolidated A-11A testbed. The V-1710-C6 successfully completed the Army 150 hour Type Test on 23 April, 1937, at 1,000 hp (750 kW), the first engine of any type to do so. By this point all of the other Army engine projects had been cancelled or withdrawn, leaving the V-1710 as the only modern design available. It was soon found as the primary powerplant of the new generation of USAAC fighters, the P-38 Lightning, P-39 Airacobra and P-40 Warhawk.

The Army 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 this reason in particular that the V-1710 was later removed from the P-51 Mustang and replaced with the Rolls-Royce Merlin instead.

With the need for the V-1710 winding down at the end of the war, Allison found itself with a massive production infrastructure that was no longer needed. For this reason in 1947 the Army decided to take General Electric's versions of Frank Whittle's jet engines and give them to Allison to produce instead. The main production model was GE's 4,000 lbf I-40, produced as the Allison J33. By the time production ended in 1955, Allison had produced over 7,000 J33's.

Allison also took over GE's axial flow engine design, the Allison J35. The J35 was the primary powerplant for the F-84 Thunderjet and F-89 Scorpion, as well as appearing on numerous prototype designs. The J35 also finished production in 1955, by which point over 14,000 had been delivered.

Allison also started the development of a series of turboprop engines for the U.S. Navy, starting with the T38 and a "twinned" version as the T40. Eventually the Navy became interested only in the T40, but the complexities of the driveshaft arrangement doomed the engine and the project was eventually cancelled. Allison tried again with the Allison T56, basically an enlarged T38 with the power of the T40, and was eventually rewarded when this engine was selected to power the C-130 Hercules.

Over the years a family of engines, based on the T56 basic configuration has been developed, culminating in the T406/Allison AE1107 turboshaft for the V-22 Osprey, the Allison AE2100 turboprop, used on newer models of the C-130 and the Allison/Rolls-Royce AE 3007 turbofan which propels many commuter aircraft, such as the Embraer ERJ 135 family.

One of Allison's most successful projects is the Model 250 turboshaft/turboprop engine family, which was started by the Company in the early 60's, when helicopters started to be powered by turbine, rather than reciprocating, engines.

In the mid-1970s the Allison Division of General Motors Corporation in Detroit designed ceramic components into the Allison GT 404-4 truck engine. Allison continued to work with General Motors on development of Ceramic-Turbine powered engines until the early 1990's. During their work they were able to engineer fairly stable automobile engines that were capable of burning a variety of fuels including (but not limited to) gasoline, diesel, kerosene, alcohol, vegetable oil, and coal powder.

In the 1980's Allison collaborated with Pratt & Whitney on demonstrating the 578-DX propfan. Unlike the competing General Electric GE-36 UDF, the 578-DX was fairly conventional, having a reduction gearbox between the LP turbine and the propfan blades. Noise considerations, plus a significant reduction in the real cost of aviation fuel, brought the NASA funded programme to a halt.

With the acquisition of Allison, Rolls-Royce expanded its product line to the point where it can now offer engines in virtually all market segments, from helicopters (e.g AE 1107C-Liberty), to the largest widebody aircraft (e.g. Rolls-Royce Trent).

Further reading

• Daniel Whitney, Vee's for Victory!: The Story of the Allison V-1710 Aircraft Engine 1929-1948 ISBN 0-7643-0561-1

External links

• Annals of the Flying Tigers
• Allison's work on turbine engines for automobiles

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