NASA - National Aeronautics and Space Administration

Image to left: NASA's Active Aeroelastic Wing F/A-18 research jet arrived in Oshkosh, Wis., for the world's largest aviation event, AirVenture 2003, July 28.

A research jet with a curious link to the Wright Flyer flew to Oshkosh, Wis., July 28 to join the world's largest aviation event. The people and aircraft gathered at the Experimental Aircraft Association's AirVenture 2003 this week to celebrate a century of flight include a special NASA F/A-18 with the ability to twist its wings to cause the airplane to roll. That's a new twist on a very old theme -- wing warping -- exploited by Wilbur and Orville Wright.

The Wright brothers pioneered flight with aircraft that twisted, or warped, their wingtips to induce a bank instead of using hinged ailerons for the purpose. Over time, hinged ailerons and rigid wings became the practical means of aircraft roll control, and wing-warping retired to museums.

But as speeds increased in the jet age, wing-warping occasionally returned unintentionally. Pilots of the sleek, slim-wing B-47 Stratojet encountered a phenomenon at high speeds where aileron deflection caused the limber wing to twist in the opposite way, reversing the direction of roll input. Called aileron reversal, this trait was also discovered on pre-production F-18 jets, prompting production versions to have stiffer wings.

Now NASA's Active Aeroelastic Wing program capitalizes on special pliable wings to initiate roll in the modified Aeroelastic Wing F/A-18 flown to AirVenture 2003. Soon, new flight control software will prompt the ailerons and movable leading edge control surfaces to respond to normal pilot stick inputs by causing the Aeroelastic Wing testbed's wings to deflect. The roll induced in this manner will make the aircraft independent of horizontal stabilizer inputs to keep the aircraft on course in a roll.

The testbed has flown at speeds up to Mach 1.3 as engineers explore the flexibility of the special wings. With that knowledge, the testers will devise flight control software to exploit the Aeroelastic Wing phenomenon in tests next year.

This modern take-off on the Wrights' wing-warping idea made the NASA Aeroelastic Wing F/A-18 the first aircraft to wear the official Centennial of Flight insignia.

The ability to use computer flight control programs and state-of-the-art flexible wings could lead to future high-performance aircraft with lighter, less mechanically complex wings. The ability to maneuver at high speeds could become simpler, and more efficient through wing-warping. Benefits could include lighter weight, which may translate into other desirables: speed, range, or payload.

Image to right: NASA's wing-warping research jets fill the skies at the Oshkosh air show.

Wing warping could become a tool for NASA and industry designers who seek the ultimate morphing airplane, with an airframe that can change shape to constantly seek desired flight parameters throughout a wide speed range.

The program is conducted by NASA's Dryden Flight Research Center located on Edwards Air Force Base in California's Mojave Desert. It is jointly funded and managed by NASA Dryden and the Air Force Research Laboratory's Air Vehicles Directorate. Boeing's Phantom Works division in St. Louis, Mo., is the prime contractor for aircraft modifications and software development. Lockheed-Martin developed the research flight control computer.

For more information on the Active Aeroelastic Wing program, visit:

www.dfrc.nasa.gov.

Story Credit:
Frederick A. Johnsen
News Chief
NASA Dryden Flight Research Center