Lycoming T55

The T55 is a larger version of the T53, designed for U.S. Army helicopters. Design work began in 1954. Over 5 million hours have been flown by 3,600 T55 engines (as of 1998).


  • T55-L-11A: 3,750 hp (2796 kW)


  • Turboshaft
  • Compressor: 7-stage axial, 1-stage centrifugal
  • Turbine: 2-stage gas generator, 2-stage free
  • Pressure ratio: 8.2

used by

  • Boeing Vertol CH-47 Chinook