X-Wing Potential for Navy Applications

The X-Wing is a four-bladed, extremely rigid rotor/wing capable of being started and stopped in flight. It uses circulation control blowing over Coanda surfaces of symmetric airfoils to produce lift and control. When stopped, the rotor/wing is flown in an "X" configuration with two forward-swept wings and two aft-swept wings. The X-Wing promises to be the first V/STOL concept which can deliver both the efficient low-downwash-velocity hover typical of a helicopter and the efficient high-speed cruise capability of modern fixed-wing aircraft. With X-Wing's large diameter hovering rotor, the controllability and power required in the VTOL mode are similar to conventional helicopters. In the stopped mode, aircraft parasite drag is low, resulting in lift-to-drag ratios typical of conventional airplanes. Because hover power required is low, a high-speed twin-engine X-Wing aircraft will have an OEI envelope which includes a speed range from 0 to over 300 knots. The X-Wing concept has been under development by the U.S. Government and industry for over 15 years. In 1983, Sikorsky Aircraft was awarded a contract by NASA to design, fabricate, and flight test a full-scale X-Wing on the NASA/Army Rotor Systems Research Aircraft (RSRA). This work is well underway; detail design is completed, hardware fabrication and systems testing is underway, and the first flight is scheduled for 1986. This paper presents the attributes of the X-Wing, the potential of X-Wing for future high-speed VTOL missions, and illustrates this potential with aircraft conceptual design studies which extend the X-Wing technology development beyond the current RSRA/X-Wing program. Two aircraft designs have been developed. The first design is an X-Wing concept demonstrator aircraft for the 1990 time period. This makes maximum use of the RSRA/X-Wing hardware. The second design is an operational demonstrator for a production aircraft with an IOC date of 2000.