Project Description

AFTI F-111
04.17.98
Over a span of about 23 years from 1967 to about 1990, records indicate around six General Dynamic F-111 Aardvark aircraft at the NASA Dryden Flight Research Center, Edwards, California. During this time span, four areas of significant flight testing stand out. The first tests occurred during the late 1960s when NASA worked on evaluating problems with the early F-111A (#63- 9771 and #63-9777) for the Air Force and Navy. The early 1970s through the late 1980s brought the second and third phases of testing with an on-going effort to improve the F-111A (#63-9778).

The second phase called transonic aircraft technology (TACT/F-111A) added an highly efficient supercritical wing and later the third phase applied advanced wing (Mission Adaptive Wing-MAW) flight control technologies and was called Advanced Fighter Technology Integration (AFTI/F-111A). The fourth effort, utilizing an F-111E (#67-0115), ran from 1973 to 1976, and used an engine with an electronic control system (fly-by-wire) in place of the traditional hydro-mechanical system. This program called the integrated propulsion control system (IPCS) helped validate the Digital Electronic Engine Control (DEEC) concept.

With the phasing out of the TACT program came a renewed effort by the Air Force Flight Dynamics Laboratory to extended supercritical wing technology to a higher level of performance. A joint NASA and Air Force program called Advanced Fighter Technology Integration (AFTI) was born. In the early 1980s the supercritical wing on the F-111A aircraft was replaced with a wing built by Boeing Aircraft Company System called a “mission adaptive wing” (MAW). This wing had an internal mechanism to flex the outer wing skin and produce a high camber section for subsonic speeds, a supercritical section for transonic speeds, and symmetrical section for supersonic speeds. The surface irregularities from leading edge slates was eliminated and trailing edge flap effects reduced. The use of flexible wing skins to produce a smooth upper surface brought this wing a little closer in concept to that of a bird.

A digital flight control system provided automatic changes to the wing geometry. The system had four automatic control modes: (1) Maneuver Camber Control - adjusting camber shape for peak aerodynamic efficiency; (2) Cruise Camber Control - for maximum speed at any altitude and power setting; (3) Maneuver Load Control - providing the highest possible aircraft load factor (4) Maneuver Enhancement Alleviation - in part attempting to reduce the effects of gusts on airplane ride. The AFTI/F-111 MAW system had 59 flights from 1985 through 1988. The flight test data showed a drag reduction of around 7 percent at the wing design cruise point to over 20 percent at an off-design condition. The four automatic modes were tested in flight with satisfactory results.