NASA Dryden Flight Research Center Collection

X-31 in flight - Post Stall Maneuver

Two X-31 Enhanced Fighter Maneuverability (EFM) demonstrators were flown at the Rockwell International Palmdale, California, facility and the NASA Dryden Flight Research Center, Edwards, California, to obtain data that may apply to the design of highly-maneuverable next-generation fighters. The program had its first flight on October 11, 1990, in Palmdale; it ended in June 1995.

Two X-31 Enhanced Fighter Maneuverability (EFM) demonstrators were flown at the Rockwell International facility, Palmdale, California, and the NASA Dryden Flight Research Center, Edwards, California, to obtain data that may apply to the design of highly-maneuverable next-generation fighters. The program had its first flight on October 11, 1990, in Palmdale; it ended in June 1995.

The X-31 program demonstrated the value of thrust vectoring (directing engine exhaust flow) coupled with advanced flight control systems, to provide controlled flight during close-in air combat at very high angles of attack. The result of this increased maneuverability is an airplane with a significant advantage over conventional fighters.

"Angle-of-attack" (alpha) is an engineering term to describe the angle of an aircraft body and wings relative to its actual flight path. During maneuvers, pilots often fly at extreme angles of attack -- with the nose pitched up while he aircraft continues in its original direction. This can lead to loss of control and result in the loss of the aircraft, pilot or both.

Three thrust-vectoring paddles made of graphite epoxy mounted on the exhaust nozzle of the X-31 aircraft directed the exhaust flow to provide control in pitch (up and down) and yaw (right and left) to improve control. The paddles can sustain heat of up to 1,500 degrees centigrade for extended periods of time. In addition the X-31 aircraft were configured with movable forward canards and fixed aft strakes. The canards were small wing-like structures set on the wing line between the nose and the leading edge of the wing. The strakes were set on the same line between the trailing edge of the wing and the engine exhaust. Both supplied additional control in tight maneuvering situations.

The X-31 research program produced technical data at high angles of attack. This information is giving engineers and aircraft designers a better understanding of aerodynamics, effectiveness of flight controls and thrust vectoring, and airflow phenomena at high angles of attack. This understanding is expected to lead to design methods that provide better maneuverability in future high performance aircraft and make them safer to fly.

An international test organization of about 110 people, managed by the Advanced Research Projects Agency (ARPA), conducted the flight operations at NASA Dryden. The ARPA had requested flight research for the X-31 aircraft be moved there in February 1992. In addition to ARPA and NASA, the international test organization (ITO) included the U.S. Navy, the U.S. Air Force, Rockwell

International, the Federal Republic of Germany, and Daimler-Benz Aerospace (formerly Messerschmitt-Bolkow -Blohm and Deutsche Aerospace). NASA was responsible for flight research operations, aircraft maintenance, and research engineering once the program moved to Dryden.

The No. 1 X-31 aircraft was lost in an accident Jan. 19, 1995. The pilot, Karl Heinz-Lang, of the Federal Republic of Germany, ejected safely before the aircraft crashed in an unpopulated desert area just north of Edwards.

The X-31 program logged an X-plane record of 580 flights during the program, including 555 research missions and 21 in Europe for the 1995 Paris Air Show. A total of 14 pilots representing all agencies of the ITO flew the aircraft.

This 34-second movie clip shows the aircraft as it slides backwards, thrust vectoring the tail over the top, turning the stall into a loop in which the aircraft then reverses it's heading and resumes level flight.

1995

X-29 Still photos of this aircraft are available in several resolutions at
http://www.dfrc.nas…[ http://www.dfrc.nas…]

Dryden Flight Research Center

NASA

Edwards Air Force Base

Rockwell International

X-31

Enhanced Fighter Maneuverability

EFM

Palmdale

thrust vectoring

maneuvering

canards

strakes

international test organization

Advanced Research Projects Agency

ARPA

U.S. Navy

the U.S. Air Force

the Federal Republic of Germany

Daimler-Benz Aerospace

Messerschmitt-Bolkow -Blohm

Deutsche Aerospace

Karl Heinz-Lang

California

Edwards Air Force Base

Germany

Paris

Dryden Flight Research Center (DFRC)

February 1992

October 11, 1990

June 1995

1995

1990

1992

EM-0036-08

SPD-DRYDEN-EM-0036-0 8

http://www.dfrc.nas…