In response to an Air Force request in 1952 for a 373 - 522 kW (500- to 700-hp) turboprop engine, Lycoming produced two designs, both of which could be converted to turboshafts to power helicopters by removing the propeller gearbox. Lycoming was awarded a contract to develop a free-turbine turboshaft engine, designated LTC1 (military designation T53-L-1). It was military qualified in 1958, and the first production engine was delivered in 1959.
The front-drive, concentric-shaft design became a widely accepted U.S. standard for turboshaft engines. The T53 gave Lycoming its start in the aircraft gas turbine business and played a key role in the expansion of the Army's airmobile role during the Vietnam War. The T53 powered the Bell UH-1 Iroquois (Huey) and AH-1 Huey Cobra helicopters and the Grumman OV-1 Mohawk airplane.