Type A V/STOL Propulsion System Development

Design and performance considerations associated with the development of a unique Type A V/STOL fourturbofan propulsion system concept are described. This propulsion system uses fixed horizontal nacelles with thrust vectoring nozzles installed for achieving lift, a coaxial fan flow reaction control system for pitch control and trim, and a reaction control system for roll and yaw control and engine-out roll trim. The turbofan engine is specially designed to provide continuous compressor bleed flow for the reaction control system during vertical flight while achieving low specific fuel consumption during conventional flight modes. Critical propulsion system sizing conditions are identified, and the sensitivity of aircraft takeoff gross weight to changes in control criteria requirements, engine cycle parameters, and engine rating schemes are discussed. In addition to having competitive performance characteristics, the propulsion system concept described herein has zero single-point failures, low development cost and risk, and good reliability /maintainability.