The Honeywell T55 is a turboshaft engine family closely associated with the Boeing Chinook helicopter. Two T55s have powered the aircraft since its first flight in 1961. Successive versions have provided increasing output for heavier payloads and demanding military and civilian operations.[1]Chinook pilot goes from facing enemy fire to firefightingHoneywell · honeywellaerospace.com · Accessed 2026-09-13Open source details
Power growth
Honeywell records an initial output of 1,600 shaft horsepower, followed by development into the approximately 5,000-shaft-horsepower class. The family has consequently changed substantially while retaining its place on the same basic helicopter programme. The T55-714A became an important part of the Chinook's improved capability in high-altitude and hot-weather conditions.[2]T55 Turboshaft EngineHoneywell · honeywellaerospace.com · Accessed 2026-09-13Open source details[1]Chinook pilot goes from facing enemy fire to firefightingHoneywell · honeywellaerospace.com · Accessed 2026-09-13Open source details
Heavy-lift missions
The engine powers both CH-47 and MH-47 installations. In military service the Chinook carries troops, ammunition and supplies and supports air-assault operations. Civilian aircraft also use the available power for demanding lifting work. Honeywell's account of a Columbia Helicopters CH-47D describes a firefighting conversion with a 2,800-gallon internal tank, demonstrating how military transport capacity could be redirected to civilian operations.[1]Chinook pilot goes from facing enemy fire to firefightingHoneywell · honeywellaerospace.com · Accessed 2026-09-13Open source details
Upgrade approach
Honeywell's later T55 development targets the 6,000-shaft-horsepower class. The manufacturer's product material describes an upgrade approach intended to require only minor aircraft changes and to permit installation during engine overhaul. Maintainer feedback and lessons from existing Chinook operation informed the changes, linking additional performance with practical support considerations.[2]T55 Turboshaft EngineHoneywell · honeywellaerospace.com · Accessed 2026-09-13Open source details
Aircraft integration
Published characteristics for the later configuration include a 15,066-rpm output shaft speed and an engine length of approximately forty-seven inches. Delivering substantial power within a compact package is important on the Chinook, where the engines supply the tandem-rotor drive system. The programme's long development history reflects continuing adaptation of the propulsion system as the aircraft's missions and payload requirements evolved.[2]T55 Turboshaft EngineHoneywell · honeywellaerospace.com · Accessed 2026-09-13Open source details