X-31
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The Rockwell-Messerschmitt-Bölkow-Blohm X-31 is an experimental jet aircraft designed to test fighter
thrust vectoring Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to Aircraft flight control system, control the Spacecra ...
technology. It was designed and built by Rockwell and
Messerschmitt-Bölkow-Blohm Messerschmitt-Bölkow-Blohm (MBB) was a West Germany, West German aerospace manufacturer. It was formed during the late 1960s as the result of efforts to consolidate the West German aerospace industry; aircraft manufacturer Messerschmitt AG merged ...
(MBB), as part of a joint
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
and
German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...
''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 A conventional fixed-wing aircraft flight control system (AFCS) consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. ...
provided controlled flight at high angles of attack where conventional aircraft would stall or lose control. Two aircraft were built, of which one has survived.


Design and development

As the first international X-plane program, the Defense Advanced Research Projects Agency (
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adva ...
) was the US Government's top-level management, with the
US Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
serving as the military agent through Naval Air Systems Command ( NAVAIR).
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
supported the X-31 program through its
Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, near the Chesapeake Bay front of Langley Air Force Base, is the oldest of NASA's field centers. LaRC has focused primarily on aeronautical research but has also ...
and
Dryden Flight Research Center The NASA Neil A. Armstrong Flight Research Center (AFRC) is an aeronautical research center operated by NASA. Its primary campus is located inside Edwards Air Force Base in California and is considered NASA's premier site for aeronautical rese ...
. The US Air Force Flight Test Center was a Participating Test Organization. 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 British Aerospace
Experimental Aircraft Programme The British Aerospace EAP (standing for ''Experimental Aircraft Programme'') is a British technology demonstrator aircraft developed by aviation company British Aerospace (BAe) as a private venture. It was designed to research technologies to b ...
(choice of wing type with canards, plus underfuselage intake), the German TKF-90 (wing planform concepts and underfuselage intake),
F/A-18 Hornet The McDonnell Douglas F/A-18 Hornet is an all-weather supersonic, twinjet, twin-engine, carrier-based aircraft, carrier-capable, Multirole combat aircraft, multirole combat aircraft, designed as both a Fighter aircraft, fighter and attack airc ...
(forebody, including cockpit, ejection seat, and canopy; electrical generators),
F-16 Fighting Falcon The General Dynamics F-16 Fighting Falcon is an American single-engine supersonic Multirole combat aircraft, multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superio ...
(landing gear, fuel pump, rudder pedals, nosewheel tires, and emergency power unit), F-16XL (leading-edge flap drives),
V-22 Osprey The Bell Boeing V-22 Osprey is an American multi-use, tiltrotor military transport aircraft, military transport and cargo aircraft with both vertical takeoff and landing (VTOL) and short takeoff and landing (STOL) capabilities. It is designed ...
(control surface actuators),
Cessna Citation The Cessna Citation is a family of business jets manufactured by Cessna that entered service in 1972. In the fifty years following the type's first flight in 1969, more than 7,500 Citations were delivered, forming the largest business jet flee ...
(main landing gear's wheels and brakes), F-20 Tigershark (hydrazine emergency air-start system, later replaced) and
B-1 Lancer The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It has been nicknamed the "Bone" (from "B-One"). , it is one of the United States Air Force's three strategic bombers, along with th ...
(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 from 1990 to 1995. The X-31 is a canard
delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...
, 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 The Eurofighter Typhoon is a European multinational twin-engine, supersonic, canard delta wing, multirole fighter. The Typhoon was designed originally as an air-superiority fighter and is manufactured by a consortium of Airbus, BAE Syste ...
,
Dassault Rafale The Dassault Rafale (, literally meaning "gust of wind", or "burst of fire" in a more military sense) is a French Twinjet, twin-engine, Canard (aeronautics), canard delta wing, Multirole combat aircraft, multirole fighter aircraft designed and ...
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 35 Draken The Saab 35 Draken (; ''The Kite'', ambiguous with ''The Dragon'') is a Swedish interceptor aircraft, fighter-interceptor developed and manufactured by Saab AB, Svenska Aeroplan Aktiebolaget (Saab AB, SAAB) between 1955 and 1974. Development of ...
and the 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. Similar to a
tailless aircraft In aeronautics, a tailless aircraft is a fixed-wing aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin (vertical stabilizer), and/or vertical rudder. Theoretical advanta ...
, there are no moveable horizontal tail surfaces, only the vertical fin with
rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (usually air or water). On an airplane, the rudder is used primarily to counter adverse yaw ...
. Pitch and roll are controlled by the canard with the aid of the three paddles directing the exhaust (
thrust vectoring Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to Aircraft flight control system, control the Spacecra ...
). Eventually, simulations and flight tests on one of the X-31s showed that flight would be stable 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 outside the range of angle of attack normal for conventional aircraft. This 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. Herbst was the designer of the Rockwell SNAKE, which formed the basis for the X-31. In the mid-1990s, the program began to revitalize and so the US and Germany signed a Memorandum of Agreement in April 1999 to start collaboration on the VECTOR program to capitalize on this previous investment. The $53 million VECTOR program began in January 2000. VECTOR is a joint venture that includes the US Navy, Germany's defense procurement agency BWB, Boeing's Phantom Works, and
DASA DASA (officially Deutsche AeroSpace AG, later Daimler-Benz AeroSpace AG, then DaimlerChrysler AeroSpace AG) was a German aerospace manufacturer. It was created during 1989 as the aerospace subsidiary arm of Daimler-Benz, Daimler-Benz AG (later D ...
; it was initially expected to involve Sweden, which pulled out due to fiscal constraints. As the site for the flight testing,
Naval Air Station Patuxent River Naval Air Station Patuxent River , also known as NAS Pax River, is a United States naval air station in St. Mary’s County, Maryland on the Chesapeake Bay near the mouth of the Patuxent River. It is home to Headquarters, Naval Air Systems Comm ...
in Maryland was chosen. From 2002 to 2003, the X-31 flew extremely short takeoff and landing approaches first on a virtual runway at in the sky, to ensure that the
Inertial Navigation System An inertial navigation system (INS; also inertial guidance system, inertial instrument) is a navigation device that uses motion sensors (accelerometers), rotation sensors (gyroscopes) and a computer to continuously calculate by dead reckoning th ...
/
Global Positioning System The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide ge ...
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 crewed 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.


Aircraft built

* 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 A Kiel probe is a device for measuring stagnation pressure or stagnation temperature in fluid dynamics. It is a variation of a Pitot probe where the inlet is protected by a "shroud" or "shield." Compared to the Pitot probe, it is less sensitive ...
, and ground crew/pilot ignorance of an option to override computer control. The pilot ejected safely. NASA issued in 2005 a film, "X-31: Breaking the Chain", reviewing the events.Archived a
Ghostarchive
and th
Wayback Machine
The novelty of the X-31 trials was computer control of its revolutionary flight controls (canard wing and engine baffles) to effect maneuvers impossible for conventional jet fighters. The film discusses at length the combination of independent errors (e.g. that the accompanying chase pilot could not hear the test pilot's radio conversation with his base) in prompting loss of control, when the test pilot (correctly) ejected to save his life. Film of the crash shows the aircraft in unusual attitudes as the computer applied its false data to attempt to control flight after the pilot ejected. * BuNo 164585, 288 flights, the last one being in 2003. Put on permanent display at
Deutsches Museum Flugwerft Schleissheim Flugwerft Schleissheim is an aviation museum located in the German town of Oberschleißheim near Munich, it forms part of the Deutsches Museum collection and complements the aviation exhibits on display at the main site. The museum was opened on ...
in Germany.


Specifications (X-31)


See also


References


Bibliography

* * Jenkins, Dennis R., Tony Landis, and Jay Miller
SP-2003-4531, "American X-Vehicles, An InventoryX-1 to X-50"
NASA, June 2003. * * USAF & NATO Report RTO-TR-015 AC/323/(HFM-015)/TP-1 (2001)


External links






NASA X-31 image gallery



"X-31: Breaking the Chain" video of crash and investigation
{{DEFAULTSORT:Rockwell-Mbb X-31 Canard aircraft Edwards Air Force Base X-31 NASA aircraft X-31 X-31, Rockwell-MBB Delta-wing aircraft Single-engined jet aircraft Articles containing video clips Aircraft first flown in 1990 1990s German experimental aircraft Three dimension thrust vectoring aircraft 1990s international aircraft Germany–United States military relations Aircraft with retractable tricycle landing gear