Beard B.B., Foley W.H. An Engine Trade Study for a Supersonic STOVL Fighter/Attack Aircraft Volume I - Trade Study Background and Methodology

Washington: National Aeronautics and Space Administration, 1982. — 65 p.A trade study to select the best main engine candidate for an advanced STOVL aircraft flight demonstrator was conducted. The aircraft uses ejectors powered by engine bypass flow together with vectored core exhaust to achieve vertical thrust capability. Bypass flow and core flow are exhausted through separate nozzles during wingborne flight. Six present day or near term turbofan engines were examined for suitability for this aircraft concept. Fan pressure ratio, thrust split between bypass and core flow, and total thrust level were the significant parameters used to compare engines. One of the six candidate engines was selected for the flight demonstrator configuration. Several smaller propulsion studies related to this aircraft concept were also conducted. A preliminary candidate for the aircraft Reaction Control System for hover attitude control was selected. A mathematical model of transfer of bypass thrust from ejectors to aft-directed nozzle during the transition to wingborne flight was developed. An equation'used to predict ejector secondary air flow rate and ram drag was also derived. Additional topics discussed include nozzle area control, ejector to engine inlet reingestion, bypass/core thrust split variation, and gyroscopic behavior during hover.