Warping wing completes successful first flight

The Boeing F/A-18A Active Aeroelastic Wing (AAW) test aircraft has successfully completed its first flight at the NASA Dryden Flight Research Centre at Edwards Air Force Base, California.

The Boeing F/A-18A Active Aeroelastic Wing (AAW), test aircraft has successfully completed its first flight at the NASA Dryden Flight Research Centre at Edwards Air Force Base, California.

The Active Aeroelastic Wing joint program involving Boeing Phantom Works, NASA and the US Air Force, is designed to enhance aircraft manoeuvrability and performance by combining new flight-control software with a modified wing that bends and twists.

Because this type of wing would require fewer moving parts for controlling flight, wings could be made thinner, lighter and more aerodynamically efficient than today’s wings and allow for greater range, payloads and fuel efficiency.

The first AAW flight was conducted on November 15 and followed three years of modification and ground testing at the NASA facility. During the 68-minute flight, NASA research pilot Dana Purifoy put the modified F/A-18A through an extensive functional checkout of aircraft flight controls, avionics systems, engine operation and newly installed test instrumentation. He also began evaluation of its aerodynamic flutter limits and differential movement of the inboard and outboard leading-edge flaps used in AAW research.

‘This first-flight milestone is one we’ve been waiting for, and it’s only the beginning of a new chapter in the combination of aerodynamics, structures and flight controls into a single integrated system,’ said Bob Krieger, president of Boeing Phantom Works. ‘I look forward to the next few months when we will verify this concept with additional AAW flight tests.’

The first phase of AAW flight-testing will include about 30 to 40 parameter-identification flights at a rate of three or four per week. Boeing Phantom Works will then use this data to refine wing-effectiveness models and design the AAW flight-control software. The second phase of research flights, to demonstrate the AAW concept with effective control laws, is scheduled to begin in 2003.

AAW technology is a high-tech update of the primitive wing-warping control system devised by the Wright brothers for their Wright Flyer, first flown December 17, 1903. The results of the AAW flight tests will ultimately provide benchmark design criteria to guide the design of future aircraft.

‘The project reflects both a return to aviation’s beginnings, and a pathway to the future-a future where aircraft will sense their environment, morph and adapt their shape to existing flight conditions,’ said Denis Bessette, AAW project manager at NASA Dryden.

The AAW F/A-18A has been modified with additional actuators, a split leading edge flap actuation system and thinner wing skins that will reportedly 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.