Gyroscopic Test for the T800-LHT-800 Turboshaft Engine 921955
The T800-LHT-800 is a modern technology 970 kW (1300 shp) class turboshaft engine that has been developed for the U.S. Army's Comanche helicopter and various civil applications. The increased maneuverability of these modern helicopters places high gyroscopic loads on the rotating components of gas turbine engines. The T800 Engine System Specification requires an infinite life at gyroscopic rotations of 0.9 rad/s and the capability to withstand gyroscopic moments associated with rotation up to 2.5 rad/s for a duration of 30 sec.
Development of a shafting system and rotor design that could operate under these high gyroscopic moments presented a significant design challenge. This was addressed through several design iterations, a development test, and significant stress and dynamics analysis. The engine's gyroscopic capability was demonstrated during a qualification gyroscopic test by operating at maximum rated gas generator and power turbine rotor speeds while being subjected to gyroscopic moments imposed by rotation about an axis perpendicular to the engine centerline at rotational rates as high as 2.5 rad/s.
Prior to the T800-LHT-800 engine test, gyroscopic testing of a turboshaft engine had never previously been attempted. The engine's turboshaft design and full authority digital electronic control added complexity to the test conduct. The engine qualification test, which was designed to satisfy military requirements, was successfully completed in July 1992. Test results verified the T800-LHT-800 engine's capability to operate satisfactorily when subjected to gyroscopic loads without significant unrecoverable performance loss or hardware problems that could cause part failure or premature engine removal from the airframe.
This paper discusses the T800 engine, requirements for gyroscopic loads, design evolution, development of gyroscopic testing capability, and results of the qualification test.