Rockwell-MBB X-31
Experimental · Germany · Digital Age (2010–present)
The Rockwell-MBB X-31 was a joint U.S./German experimental fighter built to test thrust-vectoring control at extreme angles of attack. Two airframes were built — one by Rockwell International in Los Angeles, one by Messerschmitt-Bölkow-Blohm in Germany — under the joint USAF/USN/German MoD Enhanced Fighter Maneuverability (EFM) programme. The X-31 first flew on 11 October 1990 and made about 580 flights through April 2003. It demonstrated controlled flight at 70° angle of attack, the Herbst manoeuvre (a 180° post-stall turn at near-zero airspeed), and fully autonomous tailless flight — the latter a separate research thread piggy-backed onto the airframe in 2003.
The X-31 used three carbon-carbon paddles deployed into the engine exhaust to deflect thrust vertically and horizontally — a much cheaper architecture than the swivelling axisymmetric nozzle that F-22 Raptor uses today. Combined with computerised fly-by-wire flight control, the paddles let the X-31 maintain controlled flight at angles of attack where conventional aerodynamic surfaces lose all authority — including 70° AoA in straight-line flight and the Herbst manoeuvre, in which the aircraft pitches up to 70° AoA, decelerates almost to zero airspeed, then yaws 180° using thrust vectoring before re-accelerating in the opposite direction.
The programme suffered one fatal accident. On 19 January 1995, X-31 #1 (s/n 164584) crashed near Edwards AFB after ice ingestion to the airspeed sensor caused the flight-control system to misread airspeed and command an extreme nose-up pitch. German DLR pilot Karl-Heinz Lang ejected at low altitude and was severely injured but survived. X-31 #2 (s/n 164585) continued flying and was used in 2003 for the VECTOR (Vectoring, Extremely short take-off and landing, Control, Tailless Operation Research) phase, where the vertical fin was deactivated entirely and thrust-vectoring alone provided yaw control — the first sustained flight of a fighter without aerodynamic yaw stability.
The X-31's data set fed directly into the F-22 Raptor (which adopted the AoA envelope and flight-control architecture), the Sukhoi Su-30/35/57 family (which uses a similar 3D-vectoring exhaust nozzle), and the F-35B's STOVL flight control. The surviving airframe (s/n 164585) is preserved at the Deutsches Museum Flugwerft Schleißheim near Munich, Germany — one of the few X-planes outside the United States.
For Kids — a shorter, friendlier version
The Rockwell-MBB X-31 was a joint American-German experimental fighter from 1990. It was built to test the idea of a fighter that could turn so sharply that its nose was pointing almost straight up while still moving forward. This is called flying at high angle of attack.
Two X-31s were built — one in Los Angeles by Rockwell and one in Germany by Messerschmitt-Bölkow-Blohm. The X-31 first flew in October 1990 and made about 580 test flights through April 2003.
The X-31's secret was three big paddles in the jet exhaust. The paddles could swing up, down, or sideways to bend the engine thrust in any direction. With this thrust vectoring, the X-31 could turn its nose 70 degrees above the wind direction without falling out of the sky.
One famous trick the X-31 could do was the Herbst maneuver — a 180-degree turn at near-zero airspeed. The plane is about as long as a school bus. Many lessons learned from the X-31 are now used in modern fighters like the F-22 Raptor and F-35 Lightning II.
Fun Facts
- The X-31 was a joint American-German experimental fighter.
- It used three paddles in the jet exhaust to bend the engine thrust in any direction.
- The X-31 could turn its nose 70 degrees above the wind direction without losing control.
- Two X-31s were built — one in Los Angeles, one in Germany.
- The plane made about 580 flights between 1990 and 2003.
- One famous X-31 trick was the Herbst maneuver — a 180-degree turn at near-zero airspeed.
Kids’ Questions
What is angle of attack?
Angle of attack is the angle between the wing and the wind blowing over it. At zero degrees, the wing is flat to the wind and gets a little lift. As the angle goes up, the lift goes up — until the wing stalls and stops working. The X-31 could fly at 70 degrees, far past the stall angle of normal planes.
What is thrust vectoring?
Thrust vectoring means bending the engine's hot exhaust in different directions to steer the plane. Most fighters use only the wings and tail to turn. A thrust-vectoring fighter can also point its engine thrust to push the nose around. This lets the plane do tight turns that wings alone cannot do.
Variants
- X-31 #1 (s/n 164584)
- First aircraft built (Rockwell, Palmdale CA). First flight 11 October 1990. Lost on 19 January 1995 to a pitot-tube icing accident; pilot ejected and survived.
- X-31 #2 (s/n 164585)
- Second aircraft (MBB, Germany). Flew the bulk of the EFM programme + the 2003 VECTOR tailless-flight phase. Preserved at the Deutsches Museum Flugwerft Schleißheim, Munich.
Notable Operators
- DARPA
- Lead U.S. agency. The X-31 was a DARPA technology-demonstration programme that drew on USAF, US Navy, and NASA resources. Both airframes were operated from Edwards AFB until 2003.
- DLR (German Aerospace Center)
- German operating partner. Provided MBB-built airframe #2, German test pilots (Karl-Heinz Lang, Ekkard Geyr von Schweppenburg, Rüdiger Knöpfel), and instrumentation. The X-31 was the first joint US-German X-plane.
- NASA
- Provided range support, NB-52B mother-ship operations, and several test pilots from the Dryden (now Armstrong) Flight Research Center.
Frequently Asked Questions
What was the Herbst manoeuvre?
A 180° post-stall turn invented by German aerodynamicist Wolfgang Herbst. The aircraft pitches up to about 70° angle of attack, decelerates almost to zero airspeed, then uses thrust vectoring to yaw 180° while still effectively stationary, then reaccelerates in the opposite direction. The X-31 demonstrated it in flight — the first time any fighter had completed it under controlled flight.
How did the X-31 vector its thrust?
Three carbon-carbon paddles deployed into the engine exhaust downstream of the nozzle. By moving the paddles independently the aircraft could deflect thrust up to about 10° in pitch and 5° in yaw. Lighter, simpler, and cheaper than a fully swivelling axisymmetric nozzle — but lower thrust margin in the vectoring axis.
Why did the X-31 crash in 1995?
Ice formed inside the pitot tube during a cold-weather flight on 19 January 1995. The flight-control system uses pitot-derived airspeed to schedule control gains; the iced sensor under-reported airspeed, the FCS commanded an extreme nose-up pitch correction, and the aircraft entered an unrecoverable departure. German DLR pilot Karl-Heinz Lang ejected at low altitude.
What is tailless flight?
Operating a fighter without its vertical tail (rudder) — using thrust vectoring alone for yaw control. The X-31 #2 was modified for the 2003 VECTOR phase to deactivate its vertical fin and rely entirely on the carbon-carbon thrust-vectoring paddles. Tailless flight is interesting because deleting the fin dramatically reduces radar cross-section — a stealth advantage.
Where can I see the X-31 today?
The surviving X-31 (s/n 164585) is preserved at the Deutsches Museum Flugwerft Schleißheim, near Munich, Germany. It is one of the few X-planes preserved outside the United States, reflecting the joint U.S.-German nature of the programme.
Sources
See Also
- Lockheed Martin F-22 Raptor — Adopted X-31 high-AoA flight-control envelope
- Lockheed Martin F-35 Lightning II — Inherited post-stall flight envelope work
- Sukhoi Su-30 family — Production thrust-vectoring fighter (3D nozzle)
- Grumman X-29 — Sister NASA high-AoA experimental aircraft
- Eurofighter Typhoon — European production multi-role fighter (no vectoring)