Rockwell-MBB X-31

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

The collaborative Rockwell-Messerschmitt-Bölkow-Blohm 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 maneuverability 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, with the first flying on October 11, 1990.^[1] 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 maneuverability. 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° angle of attack. On April 29, 1993, the second X-31 successfully executed a rapid minimum-radius, 180° 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 Dr. Wolfgang Herbst, an MBB employee and proponent of using post-stall flight in air-to-air combat.^[2] Herbst was the designer of the Rockwell SNAKE, which formed the basis for the X-31.^[3]

In the mid-1990s, the program began to revitalize and a $53 million VECTOR program was initiated capitalizing on this previous investment. VECTOR is a joint venture that includes the US Navy, Germany’s defense procurement agency BWB, Boeing's Phantom Works, and the European Aeronautic, Defense and Space Company in Ottobrunn, Germany. As the site for the flight testing, Naval Air Station Patuxent River in Maryland was chosen. 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. The technologies involved a differential GPS System based on pseudolite technology from Integrinautics and a miniaturized flush air data system from Nordmicro.^{[citation needed]}

• BuNo 164584, 292 flights – crashed on January 19, 1995, north of Edwards AFB, California. The crash was caused by ice inside the pitot tube, sending incorrect airspeed data to the flight control computers. Contributing factors included the replacement of a heated pitot tube with an unheated Kiel probe, and ground crew/pilot ignorance of an option to override computer control. The pilot ejected safely.^[4][5][6]
• BuNo 164585, 288 flights. Now on display at Oberschleißheim Museum (part of the Deutsches Museum).

Data from Jane's All The World's Aircraft 1993–94^[7]

General characteristics

• Crew: one
• Aspect ratio: 2.51:1

Performance

• Comparison of 21st century fighter aircraft
• Future Offensive Air System

Aircraft of comparable role, configuration, and era

• Grumman X-29
• Boeing X-32
• Lockheed Martin X-35

Related lists

• List of experimental aircraft
• List of military aircraft of the United States

• Dorr, Robert F. (1996). "Rockwell/MBB X-31". World Air Power Journal (Volume 24 Spring 1996). London: Aerospace Publishing: pp. 34–47. ISBN 1 874023 66 2. ISSN 0959-7050. {{cite journal}}: |issue= has extra text (help); |pages= has extra text (help); Cite has empty unknown parameters: |month= and |coauthors= (help)
• Jenkins, Dennis R., Tony Landis, and Jay Miller. SP-2003-4531, "American X-Vehicles, An Inventory—X-1 to X-50". NASA, June 2003.
• Lambert, Mark (1993). Jane's All The Worlds Aircraft 1993-94. Coudsdon, UK: Janes's Data Division. ISBN 0-7106-1066-1.
• USAF & NATO Report RTO-TR-015 AC/323/(HFM-015)/TP-1 (2001).

• Rockwell-MBB X-31 in flight.
• 
  A diagram of the Herbst maneuver.
• 
  Rear view of the X-31 in Oberschleißheim.

Wikimedia Commons has media related to Rockwell-MBB X-31.

• NASA Dryden: X-31
• James Schombert's X-Plane history
• NASA X-31 image gallery
• Flap Splitting and Setting of the X-31 Wing