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NASA F/A-18 Flies First Thrust Vectoring Flight
NASA's F/A-18 High-Alpha Research Vehicle (HARV) has maneuvered in flight for the first time using a specially- designed thrust vectoring system. The successful test sets the stage for research flights over the next 2 years that could make future jet fighters safer and easier to fly at very high angles-of- attack.
Angle-of-attack or "alpha" is the term for the angle of an aircraft's body and wings relative to its actual flight path. When "alpha" increases during tight turns and maneuvers, control surfaces may not generate enough force for the pilot to maintain stability and control.
The F/A-18 HARV has three spoon-shaped paddles around the exhaust nozzle of each of its two engines. The nozzles deflect ("vector") engine thrust in different directions to maneuver and stabilize the aircraft. Thrust vectoring should give the plane better controllability at alphas up to 70 degrees.
The July 15 flight at NASA's Ames-Dryden Flight Research Facility, Edwards, Calif., is part of a continuing NASA program aimed at developing better methods to predict and control air flow over aircraft designs. The goal is to enhance aircraft controllability at high angles-of-attack.
NASA officials believe the flight was also the first time a three-axis vectoring system was controlled entirely by pilot input to a computerized flight control system during flight. NASA research pilot Edward R. Schneider called the flight "very smooth." He said the thrust vectoring control system was "more responsive" to commands than expected and control of the aircraft felt "very crisp."
During the system's first aerial test, the paddles -- made of Inconel steel and able to withstand exhaust temperatures of nearly 2000 degrees F. -- were moved by the aircraft's modified flight control system into the exhaust plume up to a maximum of 10 degrees. This amount of movement by the paddles raised the nose of the aircraft to 20 degrees angle-of-attack.
Over the next 6 months, the F/A-18 HARV is expected to fly research missions at up to 70 degrees angle-of-attack with the thrust vectoring system. During previous flights in the program, the aircraft was limited to 55 degrees angle-of- attack.
The first thrust vectoring flight test took place at 32,500 feet and 250 mph (223 knots). Schneider pitched the aircraft up and down, yawed it right and left and did several mild roll maneuvers during the test period. Aircraft speed, angle-of-attack and maneuvering will expand in each subsequent research flight.
The thrust vectoring system has been installed on the NASA aircraft to expand high-alpha maneuvering capability. It is not a prototype or production model for use on any other aircraft.
The F/A-18 flight program at Ames-Dryden is part of an integrated high angle-of-attack research and technology program conducted jointly by Langley Research Center, Hampton, Va.; Ames Research Center, Mountain View, Calif.; and Lewis Research Center, Cleveland.
The thrust vectoring system and control laws that operate it through the computerized flight control system were designed and built by McDonnell Aircraft Co., St. Louis. The software and hardware for the aircraft's computerized flight control system was developed by General Electric Corporation's Aircraft Control System Division, Binghamton, N.Y.