Note: This aircraft never actually flew with the X-wing rotor. It is included to complete the historical record of this project.
It flew without the rotor to test the aircraft in an emergency configuration if the rotor had been deliberately severed from the aircraft. A "stopped rotor" system allowed the 4-blade main rotor to be stopped midflight and still generate lift as "wings". To achieve this, the blades were composed of carbon fiber containing a torsion box with flexible ducts along the edges of either side. Compressed air was released to deform the ducts along the trailing edges as needed; when in the fixed-wing configuration, the blades on the lefthand side change their effected sides to create new trailing edges suitable for the position [FLIGHT INTERNATIONAL, 22 February 1986, page 18]. The X-Wing has no tail rotor; instead, the exhaust from the T58 engines was to be directed through a nozzle to counter the main rotors generated torque.
Source: "Hybrid Helicopters: Compounding the Quest for Speed", Robb, Raymond L., Vertiflite, Summer 2006. Published by AHS International. Page 51
Design authority: Sikorsky Aircraft Corp.
Primary manufacturer: Sikorsky Aircraft Corp.
Parent type: Sikorsky S-72 RSRA
Aircraft status: Status unknown
VTOL type: Compound Helicopter
Compound type: Lift and Thrust compounded with 2 propulsors
Lift devices: 1 Single main rotor
Dedicated control device: 1 Tail rotor
Crew required: 2-3 in Side-by-side arrangement
Landing gear: Wheels (some retractable)