The collaborative U.S.-German Rockwell-MBB X-31 Enhanced Fighter Maneuverability program was designed to test fighter thrust vectoring technology. Thrust vectoring allows the X-31 to fly in a direction other than where the nose is pointing, resulting in significantly more manuverability than most conventional fighters.
An advanced flight control system provides controlled flight at high angles of attack where conventional aircraft would stall.
Two X-31s were built, and over 500 test flights were carried out between 1990 and 1995. The X-31 featured fixed strakes along the aft fuselage, as well as a pair of movable computer-controlled canards to increase stability and manuverability. There are no horizontal tail surfaces, only the vertical fin with rudder. Pitch and yaw are controlled by 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.
During flight testing, the X-31 aircraft established several milestones. On November 6, 1992, the X-31 achieved controlled flight at a 70-degree angle of attack.
On April 29, 1993, the second X-31 successfully executed a rapid minimum-radius, 180-degree turn using a post-stall maneuver, flying well beyond the aerodynamic limits of any conventional aircraft.
This revolutionary maneuver has been called the "Herbst Maneuver" after Wolfgang Herbst, a German proponent of using post-stall flight in air-to-air combat.
From 2002 to 2003 the X-31 flew extremely short takeoff and landing approaches first on a virtual runway at 5,000 feet in the sky, to ensure that the Inertial Navigation System/Global Positioning System accurately guides the aircraft with the centimeter accuracy required for on the ground landings. The program then culminated in the first ever autonomous landing of a manned aircraft with high angle of attack (24 degree) and short landing.
(This text was adapted from http://www.wikipedia.org/ )(GFDL)
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