NEW JET MAY LEARN THE TWIST NASA TESTING FLEXIBLE WINGS.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - The National Aeronautics and Space Administration has started test flights of a modified jet fighter exploring the use of flexible wings, an idea harking back to the days of the Wright brothers.

The AAW aircraft - the initials stand for ``active aeroelastic wings'' - made its first flight Friday at NASA's Dryden Flight Research Center in tests of whether flexible wings can improve a pilot's control of his plane.

During the flight that lasted one hour and eight minutes, NASA research pilot Dana Purifoy checked the modified Navy F-18A's flight controls, avionics systems, engine operation and newly installed test instrumentation.

Purifoy also began evaluation of the inboard and outboard leading-edge flaps used in AAW research.

``It looks like they got a good one under their belt,'' NASA spokesman Alan Brown said of the test flight.

NASA officials say the tests are steps toward the long-range goal of aircraft that sense their environment and adapt their shape, engine performance or control systems to flight conditions such as speed or direction or even damage from enemy fire or an accident.

The space agency, the Air Force and Boeing modified a Navy F-18A to reduce the stiffness of its wings. The test program will determine whether using wing twisting, rather than conventional flaps alone, will provide better control at speeds just below and above the sound barrier.

``We're extremely happy to get the aircraft off the ground after a lot of hard work by a lot of good people at Boeing, the Air Force and NASA Dryden,'' said Denis Bessette, NASA Dryden's AAW project manager. ``This is the beginning of the 21st century aircraft, where morphing technology will create wings that bend and shape themselves for aircraft control and efficient flight from low to high speeds and low to high altitudes. We're expecting very productive research.''

In the first phase of flight testing, each of the control surfaces will be moved separately at different speeds and altitudes to measure the aerodynamic effects and to see what forces are being put upon the wings.

After a hiatus to modify flight computers to take advantage of information derived from the first tests, more flights will take place next year.

A second round of flights will be conducted, probably about a year from now, in which the wings will actually be twisted. About 40 flights are expected to be flown.

The NASA researchers are paying tribute to the technique's use on the very first airplane. Wilbur and Orville Wright controlled their biplane at Kitty Hawk using cables attached to the wings. The pilot moved his hips to twist the wings.

NASA's airplane bears an emblem recognizing the Wrights' first flight in 1903.

The program could lead to other improvements besides better control at supersonic speed for military jets, officials say.

Flexible wings don't have to be as heavy as conventional wings, so the aircraft itself can be lighter, thus increasing its fuel economy and range.

The F-18A received two major modifications. The first was to replace the wing panels with more flexible ones. Ironically, the new panels are similar to the original panels that the Navy rejected during the development of the F-18A because they were too flexible and were thwarting the aileron control.

The second modification was the addition of actuators to allow the two flaps on the leading edge of each wing to operate separately of each other.

The modifications will allow the aerodynamic forces on conventional control surfaces, such as the ailerons, to twist the wings.

The test program will address the problems that occur when planes reach near-supersonic speed, program officials say.

The air pressure and turbulence change how the craft reacts when the pilot moves the wing flaps - even causing the plane to move in the opposite direction than the pilot intended.

The conventional approach has been to stiffen the wing so it won't bend when the flaps are moved.

This program does the opposite: It makes the F-18A's wings more flexible, using computer controls running conventional flaps to turn the entire wing into a control surface. The range of motion will be 5 degrees.

The $41 million test program is a joint effort by the Air Force Research Laboratory, NASA and Boeing.

CAPTION(S):

photo

Photo:

A jet fighter with active aeroelastic wings is being test-flown from Edwards Air Force Base.