Flutter affects the wing assemblies of any aircraft at speed, causing a violent oscillation to take place which ultimately destroys the wing and, of course, the aircraft. For decades, the solution has been to use rigid wings which added weight, increased fuel consumption and drag and limited operational range. Today, Lockheed Martin (in conjunction with NASA Dryden Flight Research Center, Edwards AFB California) is using its X-56A test aircraft, complete with an active flutter suppression system coupled to specially-designed flexible wings, in an attempt to counter the forces of "aeroelasticity". First flight of the X-56A was recorded in July of 2013. The vehicle features a wingspan of 28 feet, weighs 480lbs and can reach speeds of 150 knots (flutter is expected around 110 knots). The X-56A incorporates a parachute system for recovery should its experimental wings fall to uncontrollable forces during flight.
The X-56A is designed as a "flying wing" blended body air vehicle with vertical surfaces added at the wingtips. The fuselage houses the twin-engine arrangement, avionics and fuel stores while the undercarriage is of a conventional wheeled tricycle arrangement. Power is served through 2 x JetCat P400 turbojet engines mounted along the top rear of the fuselage. Lockheed has produced a pair of X-56A fuselages with a modular wing system to make use two different wing types - one rigid and another flexible - both featuring active flutter suppression sensors and controls. For early testing, a basic rigid wing is being used to see verify the validity of the rigid-wing arrangement. The flexible wings will feature glass-fiber construction an active flutter controlling while the finalized rigid wings (with their own anti-flutter controls) will be tested in early 2014.
The project hopes to provide clues in the containment of the violent effects inherent in flutter during flight, encouraging the growth of more fuel efficient, longer-range aircraft for both civil and military markets. The X-56A program is expected to cover some five years of research in which Lockheed will manage twenty flights prior to handoff to NASA personnel for formal flexible wing research.
Two X-56 vehicles were built for the flight-testing program. The first has been named "Fido" and the Second "Buckeye".