Rockwell-MBB X-31

X-31
The X-31 aircraft returns from a test flight for VECTOR.
Role	Experimental aircraft
National origin	United States / Germany
Manufacturer	Rockwell / Messerschmitt-Bölkow-Blohm
First flight	11 October 1990
Primary users	DARPA NASA DLR
Number built	2

The Rockwell-Messerschmitt-Bölkow-Blohm X-31 was an experimental jet fighter designed to test fighter thrust vectoring technology.

It was designed and built by Rockwell and Messerschmitt-Bölkow-Blohm (MBB), as part of a joint US and German Enhanced Fighter Maneuverability program to provide additional control authority in pitch and yaw, for significantly more maneuverability than most conventional fighters. An advanced flight control system provided controlled flight at high angles of attack where conventional aircraft would stall or lose control. Two aircraft were built, of which only one has survived.

The X-31 design was essentially an all-new airframe design, although it borrowed heavily on design elements and sometimes actual parts of previous production, prototype, and conceptual aircraft designs, including: the Experimental Airplane Program (choice of wing type with canards, plus underfuselage intake), and the German TKF-90 (wing planform concepts and underfuselage intake), F/A-18 (forebody, including cockpit, ejection seat, and canopy; electrical generators), F-16 (landing gear, fuel pump, rudder pedals, nosewheel tires, and emergency power unit), F-16XL (leading-edge flap drives), V-22 (control surface actuators), Cessna Citation (main gear's wheels and brakes), F-20 (hydrazine emergency air-start system, later replaced), B-1 (spindles from its control vanes used for the canards). This was done on purpose, so that development time and risk would be reduced by using flight-qualified components. To reduce the cost of tooling for a production run of only two aircraft, Rockwell developed the "fly-away tooling" concept (perhaps the most successful spinoff of the program), whereby 15 fuselage frames were manufactured via CNC, tied together with a holding fixture, and attached to the factory floor with survey equipment. That assembly then became the tooling for the plane, which was built around it, thus "flying away" with its own tooling.

Two X-31s were built, with the first flying on October 11, 1990. Over 500 test flights were carried out between 1990 and 1995. The X-31 is a canard delta, a delta wing aircraft which uses canard foreplanes for primary pitch control, with secondary thrust-vectoring control. The canard delta had earlier been used on the Saab Viggen strike fighter, and has since become common on fighters such as the Eurofighter Typhoon, Dassault Rafale and Gripen which were all designed and flew several years before the X-31. The X-31 featured a cranked-delta wing (similar to the Saab J35 Draken and F-16XL prototype), and fixed strakes along the aft fuselage, as well as a pair of movable computer-controlled canards to increase stability and maneuverability. There are no moveable horizontal tail surfaces, only the vertical fin with rudder. Pitch and yaw are controlled by the canard with the aid of the three paddles directing the exhaust (thrust vectoring). Eventually, simulation tests on one of the X-31s showed that flight would have been stable had the plane been designed without the vertical fin, because the thrust-vectoring nozzle provided sufficient yaw and pitch control.

...
Wikipedia