Rockwell-MBB X-31

Rockwell-Messerschmitt-Bölkow-Blohm X-31
Company type	Experimental aircraft project
Industry	Aerospace, Defense
Founded	1990; 36 years ago
Founder	Rockwell, Messerschmitt-Bölkow-Blohm (MBB)
Area served	United States, Germany
Key people	Dr. Wolfgang Herbst
Products	X-31 experimental aircraft
Parent	Rockwell, MBB

The Rockwell-Messerschmitt-Bölkow-Blohm X-31 represents an experimental aircraft designed to evaluate fighter jet thrust vectoring capabilities. Developed collaboratively by Rockwell and MBB within the framework of a US-German Enhanced Fighter Maneuverability initiative, its goal was to improve pitch and yaw control, achieving superior agility compared to standard fighter jets. Equipped with a sophisticated flight control system, the X-31 was capable of stable flight at elevated angles of attack where conventional airplanes would typically stall. Two prototypes were constructed, with one remaining intact.

Design and development

As the inaugural international X-plane project, the X-31 was overseen by DARPA with the US Navy’s NAVAIR acting as the military liaison. NASA contributed to the program through its Langley and Dryden Flight Research Centers, while the US Air Force Flight Test Center also took part in evaluation flights.

The aircraft’s design introduced a novel airframe but integrated numerous components sourced from existing platforms—these included the wing type and intake from the British Aerospace EAP, wing planform inspired by the Eurofighter TKF-90, cockpit and electrical systems derived from the F/A-18 Hornet, landing gear and fuel pumps borrowed from the F-16 Fighting Falcon, leading-edge flap actuators from the F-16XL, control actuators adapted from the V-22 Osprey, landing gear wheels and brakes supplied by Cessna Citation, an emergency air-start system from the F-20 Tigershark, as well as canard control vanes taken from the B-1 Lancer. Utilizing these flight-proven components helped mitigate developmental risks and reduce costs. Rockwell pioneered a "fly-away tooling" approach wherein fuselage frames served dual purposes as tooling fixtures, thereby simplifying assembly for both aircraft.

The prototype’s maiden flight occurred on October 11, 1990, followed by over 500 test sorties through 1995. It featured a canard delta wing configuration complemented by movable computer-regulated canards for pitch control and thrust-vectoring nozzles enhancing maneuverability. The cranked-delta wing combined with fixed aft strakes contributed to improved stability. Testing verified that thrust vectoring allowed stable flight even in the absence of a vertical stabilizer.

Significant achievements included controlled flight at a 70° angle of attack in 1992 and performing a swift 180° post-stall turn—known as the "Herbst maneuver"—in 1993, showcasing agility beyond traditional limits. This maneuver was named after Dr. Wolfgang Herbst of MBB, whose work influenced the aircraft’s design.

By the mid-1990s, the project transitioned into the $53 million VECTOR program initiated in 2000 under a US-German partnership. VECTOR involved collaboration among the US Navy, Germany’s BWB, Boeing Phantom Works, and DASA; Sweden initially participated but later withdrew. Flight testing was conducted at Naval Air Station Patuxent River. Between 2002 and 2003, the X-31 demonstrated exceptional short takeoff and landing performance using advanced inertial navigation combined with differential GPS technology, culminating in the first autonomous crewed landing at high angle of attack guided by precise navigation systems.

Aircraft built

BuNo 164584, completed 292 flights – lost in an accident on January 19, 1995 near Edwards AFB, California. The crash was caused by ice accumulation in the pitot tube that fed erroneous airspeed information to the flight control computers. Factors contributing included replacing a heated pitot tube with an unheated Kiel probe and insufficient awareness regarding manual override of computer controls. The pilot successfully ejected. In 2005, NASA produced "X-31: Breaking the Chain," a documentary analyzing this event and emphasizing the aircraft’s groundbreaking computer-assisted flight capabilities enabling maneuvers beyond those possible with conventional jets.
BuNo 164585, flew 288 missions with its final flight in 2003. It is currently exhibited permanently at Deutsches Museum Flugwerft Schleissheim in Germany.

Additional Resources

Design and development

Aircraft built

Further Reading

Additional Resources