Honeywell T55

The T55, company designation LTC-4, is a turboshaft engine used on American helicopters and, in turboprop form, on fixed-wing aircraft since the 1950s, and in unlimited hydroplanes since the 1980s. The Turbine Engine Division of Lycoming in Stratford, Connecticut designed it as a scaled-up version of the smaller T53, and Honeywell Aerospace of Phoenix, Arizona now produces it. More than 6,000 had been built by 2021. It serves as the engine of the Boeing CH-47 Chinook, the Bell 309 and the Piper PA-48 Enforcer, and it is the core of the Lycoming ALF 502 turbofan and of the TF series of industrial and marine gas turbines. Progressive increases in airflow, pressure ratio and turbine inlet temperature have more than tripled its power output.