Sikorsky S-72 (X-Wing)

History of the Sikorsky S-72 (X-Wing)

The "S-72", which first flew on October 12, 1976, was an experimental high-speed compound helicopter from Sikorsky Aircraft. The design is part of the Rotor Systems Research Aircraft (RSRA) program from the U.S. Army and a NASA company (led by Sikorsky) that seeks to gather high-speed data on helicopter rotor characteristics by combining engine components.

Final products include the Sikorsky S-67 helicopter frame and the Sikorsky S-61 main rotor. In addition to the turboshaft engines used to drive the rotor assemblies, additional power will be provided by a pair of General Electric TF34 turbofans mounted on either side of the fuselage. A low-position straight monoplane was installed below the aircraft, while the tail rotor (pointing to port) was retained.

Only two aircraft have completed testing.

The S-72 carries a crew of two to three and is 70.6 feet long, with a wingspan of 62 feet and a height of 14.5 feet. The empty weight is 21,700 lbs and the maximum takeoff weight (MTOW) is 26,050 lbs. The rotors are powered by a pair of GE T58-GE-5 turboshaft engines rated at 1,400 horsepower, and the turbofan unit is two GE TF34-GE-400A engines rated at 9,400 pounds of thrust.

Performance specs include a top speed of 230 mph and a cruising speed of 160 mph.

The original S-72 form could be flown with or without the main rotor assembly, and due to the uniqueness of the S-72 design, an equally unique crew ejection system was developed for compound helicopters to improve helicopter survivability Helicopter Test Pilots . The process involved completely jettisoning the main rotor blades with controlled explosives and rockets, ejecting the crew from the fuselage and away. After its first flight in 1976 and subsequent testing, NASA received one of the planes in February 1979.

Data collection aside, the model did not exceed its experimental design.

A branch of the S-72 became the so-called "X-wing" aircraft, which used a fixed main rotor assembly (an "X" shape above the fuselage) that the operator could stop the flight during flight. As a result, the aircraft can take off vertically like a conventional helicopter and then fly forward at high speed using existing turbofan engines, combining the best elements of both aircraft. Lockheed completed concept work under DARPA, then attention turned to Sikorsky to modify one of the existing RSRA prototypes for testing.

The product appeared in full form in 1986, but did not fly as the program was finally abandoned in 1988.

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