The Allison T61 (known internally as the Allison 550-B1) was a turboprop engine that was to power the 1959 version of the proposed Lockheed Super Hercules military and civil freight aircraft. The

U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...

(USAF) had helped Allison fund the development of the T61 for four years. Lockheed had received orders from

Pan American World Airways Pan American World Airways, originally founded as Pan American Airways and commonly known as Pan Am, was an American airline that was the principal and largest international air carrier and unofficial overseas flag carrier of the United States ...

and

Slick Airways Slick Airways was a cargo airline from the United States, that operated scheduled and chartered flights between 1946 and 1966. The airline was founded by Earl Slick, a Texas aviator and multimillionaire who along with his brother had inherited $ ...

for a total of 18 aircraft, but both orders were contingent on the military ordering the aircraft by September 30, 1959, around the date that the USAF's engine development contract expired. The development contract was extended temporarily to November 30, 1959, but the T61 development effort was canceled by January 1960, after USD$37.5 million had been put into the engine's development. Four T61 engines had run on the test stand at the time of cancellation. The Allison T61 produced at takeoff, of which came from the propeller, with of residual jet thrust. It had a similar appearance to the

Allison T56 The Allison T56 is an American single-shaft, modular design military turboprop with a 14-stage axial flow compressor driven by a four-stage turbine. It was originally developed by the Allison Engine Company for the Lockheed C-130 Hercules tra ...

but with a split compressor section instead of a single stage. The T61 improved on the

power-to-weight ratio Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...

of the T56 by 30%. The Air Force had also given Allison's Aeroproducts Operations division a USD $4 million contract to develop a , four-bladed propeller to use on the T61-powered Super Hercules.

Specifications

See also

References

Bibliography

External links