Flight Test of the 4-Valve Fly-By-Wire/Fly-By-Optics Control System

The 4-valve fly-by-wire (FBW) control system was flight-tested in the collective channel of the Model 249 Cobra in January 1984. In addition to the basic quadredundant FBW mode, an auxiliary simplex fly-by-optics (FBO) mode was also tested. A backup mechanical mode was installed to enhance safety during the development phase. The quad-electrical control paths were dual-fail/operate; only one monitoring plane was required. The FBW mode was flown from takeoff to touchdown and included simulated first and second failures during maneuvers. The simplex FBO mode was flown at altitude only. While establishing significant advances in the state of the art, this program accomplished its two objectives: 1) to flight-validate the 4-valve FBW control concept, and 2) to develop engineering flight data on the operation of optical transducers in a helicopter flight environment.