Boeing X-53 Active Aeroelastic Wing - Design and Development

Design and Development

Active Aeroelastic Wing (AAW) Technology is multidisciplinary in that it integrates air vehicle aerodynamics, active controls, and structural aeroelastic behavior to maximize air vehicle performance. The concept uses wing aeroelastic flexibility for a net benefit and enables the use of high aspect ratio, thin, swept wings that are aeroelastically deformed into shapes for optimum performance. This makes it possible to achieve the multi-point aerodynamic performance required of future fighter, bomber, and transport aircraft.

AAW Technology employs wing aeroelastic flexibility for a net benefit through use of multiple leading and trailing edge control surfaces activated by a digital flight control system. At higher dynamic pressures, AAW control surfaces are used as "tabs" which are deflected into the air stream in a manner that produces favorable wing twist instead of the reduced control generally associated with “aileron reversal” caused by trailing edge surfaces. The energy of the air stream is employed to twist the wing with very little control surface motion. The wing itself creates the control forces.

As AAW attempts to promote and use favorable wing twist response at high speeds, it is viewed as a return to an idea first pioneered by the Wright Brothers. Active aeroelastic wing technology is a design approach that enables a higher aspect ratio, more aerodynamically efficient wing. Further, an active aeroelastic wing can be used to reduce induced drag at low wing strain conditions and, at higher strain conditions, reduce maneuver air loads. Overall benefits of AAW technology to future systems include substantially increased control power, reduced aerodynamic drag, reduced aircraft structural weight, and increased design latitude in terms of wing span, sweep, and thickness. Depending on mission requirements, these benefits should mean significant reductions in air vehicle takeoff gross weight and production costs.

The pre-production version of the F/A-18 was an ideal host aircraft for proving AAW technology. The F/A-18 pre-production wing has a relatively high wing aspect ratio for a fighter and originally was designed to have sufficient strength, and to be free from buckling or flutter issues, but no additional stiffness was added for static aeroelastic issues. The X-53 F/A-18 was modified to allow two leading edge control surfaces to work in concert with its two trailing edge surfaces to control wing aeroelastic twist and provide excellent high speed rolling performance.