The Lycoming LTS101 is a small turboshaft engine family subsequently associated with Honeywell and Intermountain Turbine Services. Its models include the -600, -650, -700, -750 and -850 series. EASA's December 2023 type certificate identifies Intermountain as manufacturer and certificate holder, with Honeywell listed as the previous manufacturer.[1]
Engine architecture
The compressor combines one axial stage and one centrifugal stage. A reverse-flow annular combustor supplies a single-stage gas-generator turbine, followed by a separate single-stage power turbine. The latter drives a front-mounted reduction gearbox. The certified design uses a mechanical control system, with different model arrangements and limits for the various helicopter installations.[1]
Power development
The EASA data sheet lists a five-minute takeoff rating of 459 kW for the LTS101-600A-2 and 582 kW for the -850B-2 under specified sea-level conditions. The -850B-2 also has separately defined one-engine-inoperative ratings for twin-engine installations. These temporary emergency ratings allow the remaining engine to provide additional power after loss of the other engine.[1]
BK117 improvements
The LTS101-850B-2 was used in upgraded BK117-850D2 helicopters. In 2018, Honeywell announced an increase in the mandatory inspection interval from 1,800 to 2,400 flight hours for that installation. The validation effort examined engines operating in Papua New Guinea and New Zealand, including utility and search-and-rescue aircraft, to establish whether critical components could support the longer interval.[2]
Continued support
The inspection programme involved service organisations in New Zealand, Germany and the United States, including Intermountain Turbine Services. Intermountain subsequently became the engine's OEM and advertises support for the LTS101 and related LTP101. The succession illustrates how a mature helicopter engine can continue through specialist manufacturing and maintenance organisations after leaving a larger supplier's portfolio.[2][3]