#X wing front view full
#X wing front view plus

The X-wing was perhaps the most technically challenging concept Sikorsky had ever worked on. The S-72 RSRA is described in another section of this Sikorsky Product History.

#X wing front view full

It thus would permit initial rotor/wing stopping and starting tests to be done in an orderly build-up fashion, without requiring the rotor to support its full design lift during initial conversions. It had auxiliary propulsion and drag brakes to offload or overload the rotorвЂ™s horizontal thrust requirements. It had a variable incidence wing which could offload or overload the rotorвЂ™s lifting requirements. The S-72 RSRA was a unique aircraft designed solely for testing advanced helicopter rotors. Sikorsky was contracted in 1982 for this development, with the idea of testing the rotor/wing on the recently delivered NASA/Army/Sikorsky RSRA (Rotor Systems Research Aircraft). diameter wind tunnel modelДЇrom the success of these tests, DARPA and the Navy, with additional support from NASA, decided to progress to a larger-scale flight test of the X-Wing rotor/wing. More than 30 automatic rotor stops and starts were conducted, most at 180 knots, as part of the test programвЂќ

During this period the system was tested in helicopter, fixed-wing, and conversion flight modes with the moment feedback control system in open- and closed-loop operation. In the spring of 1979, the test module entered the NASA Ames 40 x 80 wind tunnel for seven weeks of exhaustive testing. Following the feasibility activity, a flight worthy rotor system design and fabrication was initiated in mid-1977, with whirl tower testing commencing in late 1978. Using available small turboshaft engines, a flight envelope of approximately Mach 0.70 at 20,000 feet would have been expected. This design was created in order to place the critical rotor/hub/control system development in proper perspective. A small elite team of Lockheed engineers was formed which initially performed an aircraft preliminary design and analysis of a small 3000 pound flight test vehicle with a 25 foot diameter rotor/wing. вЂњThe focal point for all of the experimental and analytical work during 1976-1979 was a large-scale flight worthy rotor and control system demonstration. Quoting the winter 1982 AIAA Student Journal in an article on the X-Wing by Robert M. In 1976 DARPA (the Defense Advanced Research Projects Agency) joined the Navy in X-Wing development. This then evolved into the X-Wing concept where circulation control airfoils could produce lift in either direction and allow the rotor/wing to maintain lift and control while starting and stopping rotation. Taylor Naval Ship Research and Development Center (DTNSRDC) extended Professor CheesmanвЂ™s idea of lift control on a cylinder using circulation control by blowing tangential to a rounded trailing edge of a streamlined shape similar to a conventional airfoil. X-Wing promised high subsonic speeds with low disc loadingД®ngineers at the U.S. The rotor would then be stopped and stowed for cruise efficiency. He believed that such a rotor could be stopped and started in flight if used on a winged vehicle, and employed only for takeoff and landing. Thus it can be used as a virtual flap on an airfoil. The Coanda principle is that if air is blown tangentially over a surface it will adhere and follow the surface until the curvature gets too great and it detaches. Cheesman employed the Coanda principal to create and then modulate the lift on a cylindrical rotor blade. The X-Wing concept is based on the initial work of Professor Ian Cheeseman of the University of Southhampton, England, and his experiments with what some called a вЂњFlying StovepipeвЂќ.

#X wing front view plus

Because of its low hovering disc loading plus the power to fly at high subsonic speeds, a two-engined X-wing aircraft could hover and fly a good portion of its flight envelope on only one engine. It has the promise of breaking the trend of VTOL aircraft where higher speed requires higher hovering disc loadings (weight of the aircraft divided by the area of the rotor disc, expressed as lbs./sq.ft.) Additionally it can achieve fixed wing flight without the need for a separate wing, promising a lower weight empty fraction (empty weight/gross weight)over those concepts that need both a rotor system and a wing. It uses a large-diameter four-bladed stiff rotor system that can be stopped in flight to become an вЂњXвЂќ wing. The X-Wing is one of a number of concepts proposed to combine the hovering capabilities of the helicopter with the speed potential of fixed wing aircraft.