Rotorcraft Convertible Engines for the 1990'S

Two rotorcraft studies sponsored by NASA were executed by General Electric and Detroit Diesel Allison. The goal was to identify at tractive techniques for implementing convertible powerplants for the ABC, Folded Tilt Rotor, and X-wing type high-speed , high-L/D rotorcraft; to determine the DOC and fuel savings benefits achieved thereby; and to define research required to bring these powerplants into existence by the 1990's. These studies are reviewed herein and the different methods of approach are pointed out as well as the key findings. Fan/ shaft engines using variable inlet guide vanes or torque converters, and turboprop powerplants appear attractive. Savings in DOC and fuel consumption of over 15 percent are predicted in some cases as a result of convertible engine use rather than using separate engines for the thrust and the shaft functions. Areas of required research are fan performance (including noise), integrated engine/rotorcraft control, torque converters, turbine design, airflow for rotorcraft torque control, bleed for lift flow, and transmissions and clutches.