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Active Aeroelastic Wing (AAW)

Back To The Future

After completing the first phase of its flights tests in April, NASA's Active Aeroelastic Wing (AAW) F/A-18A research aircraft became an attraction at three major Midwest air shows during the summer of 2003.

Active Aeroelastic Wing being flown on the F/A-18A

The modified Navy jet fighter was first featured as part of NASA's Centennial of Flight exhibit at the Dayton International Air Show at Dayton International Airport, Dayton, Ohio, July 17 — 20. Following its appearance at Dayton, the AAW F/A-18A then headed to Grissom Air Reserve Base north of Kokomo, Ind., for display at the Grissom Community Air Show July 26—27. The final stop on the Midwest air show circuit for the NASA research aircraft was at Wittman Regional Airport in Oshkosh, Wis., for the Experimental Aircraft Association's AirVenture 2003 from July 29 through Aug. 4.

The red-and-white aircraft finished the 50-flight first phase of data flights in the AAW program on April 15, with about half the flights flown at supersonic speeds. The primary objectives for the supersonic test points in the AAW project were to initiate supersonic aerodynamic flutter and wing load clearance, and complete functional flight checkpoints that require supersonic flight. Previous flights in the first "parameter identification" phase focused on flight envelope expansion, flutter clearance and characterization of wing flexibility at subsonic speeds.

Boeing's Phantom Works is now using data obtained from the first flight phase to refine wing effectiveness models and design the AAW flight control laws. The second phase of research flights to demonstrate the AAW concept with effective control laws should begin in early 2004, about 100 years after the Wright Brother's first powered flight on December 17, 1903.

AAW is a joint project of the U.S. Air Force Research Laboratory (AFRL), Boeing's Phantom Works and NASA Dryden. The program intends to demonstrate improved aircraft roll control through aerodynamically induced wing twist on a full-scale manned supersonic aircraft—essentially a 21st century, high-tech update of the primitive wing-warping control system devised by the Wright brothers for their 1903 Wright Flyer.

The project reflects both a return to aviation's beginnings, and a gateway to the future--a future where aircraft will sense their environment, morph, and adapt their shape to the existing flight conditions. These aircraft will take advantage of years of evolutionary lessons exhibited in bird-like flight.

AAW research could also enable thinner, higher aspect-ratio wings on future aircraft, which could result in reduced aerodynamic drag, allowing greater range or payload and improved fuel efficiency. Data obtained from flight tests at Dryden will provide benchmark design criteria as guidance for future aircraft designs.

The initiation of AAW flight tests on Nov. 15, 2002 followed a three-year period of modification and ground testing at NASA Dryden, located at Edwards Air Force Base in Southern California's high desert.

The test aircraft has been modified with additional actuators, a split leading edge flap actuation system and thinner wing skins that will allow the outer wing panels to twist up to five degrees. The traditional wing control surfaces—trailing edge ailerons and the leading and trailing edge flaps—are used to provide the aerodynamic force needed to twist or "warp" the wing. Project engineers hope to obtain almost equivalent roll performance of production F/A-18s at transonic and supersonic speeds without using the horizontal stabilators and with smaller control surface deflections.

The AAW program receives its funding from the AFRL's Air Vehicles Directorate and NASA's Office of Aerospace Technology. The Boeing Company performed the AAW F/A-18 modifications under contract with the AFRL Air Vehicles Directorate. The eight-year program's total cost is about $41 million, of which about $25 million is in direct costs and about $16 million in in-kind services.

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