Design Considerations for a V/STOL Technology Airplane

Abstract

A high speed two-engine three-fan V/STOL airplane was designed to demonstrate and develop the technology for operational V/STOL aircraft having safe engine-out characteristics. Engine-out requirements, integration of propulsion and aerodynamic controls, and propulsion installation are the major factors affecting the con- figuration. Use of variable pitch fans enchances the control system providing a responsive and versatile airplane. lift-fan airplane for research and demonstration of V/STOL technology was designed under contract to the NASA-Ames Reseach Center. The airplane is based on an operational multi-mission airplane designed for potential Navy use. The performance requirements include efficient loiter and cruise capability and high subsonic maximum speed. Maintenance and logistics considerations favor a twin engined arrangement. It will be used to examine handling requirements and develop operational techniques for the en- tire flight envelop of the operational airplane. The operational airplane is presented as the basis for the technology airplane. Engine-out requirements, aero- propulsion integration, and propulsion system installation are the major factors affecting the configuration. The Boeing design uses three variable pitch fans driven mechanically by two turboshaft engines. The Detroit Diesel Allison, Division of General Motors, and the Hamilton-Standard Division of United Technologies have worked closely with Boeing in this design. Multi-Mission Lift-Fan V/STOL The general arrangement of the airplane with the principal propulsion system components emphasized is shown in Fig. 1. The configuration is similar to that of most business jets with aft body mounted engines, a low wing, and a 'T' tail. The engines nacelles are somewhat larger than usual due to the large diameter of the low pressure ratio, high static thrust lift- cruise fans. An identical fan is located horizontally in the nose. The cross shafting between the two lift-cruise fans and the nose fan drive shaft and interconnecting T' box are ap- parent. The nose fan is disconnected by means of a clutch at the T' box during wing born flight. The lift /cruise engine/fan units rotate to provide thrust vectoring for V/STOL operation. The total installed power is determined by the requirement for single engine operation. The minimum weight (achieved by jettisoning disposable payload) is equal to the single engine emergency thrust.