STOVL engine/airframe integration

Abstract

A capable, supersonic, Short Takeoff, Vertical Landing (STOVL) tactical combat fighter aircraft must have a highly integrated engine and airframe. Vertical landing and short takeoff with powered lift require dividing engine flow between front and rear nozzles for resultant vertical thrust through the aircraft center of gravity. Several effects of exhaust jets can influence cycle selection and system configuration. These considerations affect engine location, special exhaust nozzle systems, cycle bypass ratio, aircraft supersonic drag, engine fuel consumption, and dry-engine thrust. In jet-borne flight, the aircraft pitch, roll, yaw, and altitude control are provided by modulation of front and rear exhaust thrust and compressor bleed. Satisfying these demands is challenging, but good solutions are being found in ongoing design studies initiated September 1986 by NASA and the Department of Defense. Even though a bypass ratio of about 1.0 may be needed for hover thrust balance, emerging engine technologies allow fan pressure ratios of 4 to 5. Resulting high pressures in front ducts and nozzles minimize frontal area, provide high specific thrust, and reduce fuel consumption for high combat thrust levels. New materials and structural concepts reduce the weight of aircraft, engines, and vectoring STOVL nozzles. Digital electronic controls enable the necessary integration of propulsion flight controls.