Propulsion system integration configurations for future prop-fan powered aircraft

Previous studies conducted by NASA, Pratt & Whitney, and other aircraft industry companies have indicated that a new high-speed propeller, the prop-fan, coupled with an advanced turboprop engine, can lead to a 20-30% reduction in fuel burned and a 10-13% reduction in direct operating costs relative to a comparable technology turbofan-powered aircraft. Under a recently completed NASA-sponsored study, numerous propulsion system integration options were investigated, including the gearbox, engine inlet, oil cooling, and mounting concepts. The advanced technology turboprop engine can be combined with a single- or counter-rotation prop-fan, installed either as a pusher or a tractor configuration on the wing or attached to the fuselage. The pros and cons of these combinations are discussed from an engine designer's point of view. In addition, critical technology questions that must be answered before industry will commit itself to a development program are addressed.