The Bell X-5 was the first

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

capable of changing the sweep of its wings in flight. It was inspired by the untested wartime P.1101 design of the

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 ...

Messerschmitt Messerschmitt AG () was a German share-ownership limited, aircraft manufacturing corporation named after its chief designer Willy Messerschmitt from mid-July 1938 onwards, and known primarily for its World War II fighter aircraft, in parti ...

company. In a further development of the German design, which could only have its wing sweepback angle adjusted on the ground, the Bell engineers devised a system of electric motors to adjust the sweep in flight.

Design and development

The

Messerschmitt P.1101 The Messerschmitt P.1101 was a single-seat, single- jet fighter project of World War II, developed as part of the 15 July 1944 Emergency Fighter Program which sought a second generation of jet fighters for the Third Reich. A prominent feature ...

V1 prototype was captured by United States troops in April 1945 from an experimental facility at Oberammergau, Germany. It was brought back to the United States, eventually being delivered to the

Bell Aircraft The Bell Aircraft Corporation was an American aircraft manufacturer, a builder of several types of fighter aircraft for World War II but most famous for the Bell X-1, the first supersonic aircraft, and for the development and production of many i ...

factory at Buffalo, New York. Although incomplete and damaged in transit, company engineering staff studied the design closely.Winchester 2005, p. 37. The P.1101 had a wing sweep that could be adjusted on the ground from 30, 40, to 45 degrees. However, this was for testing only and never intended as an operational feature. The Bell team, led by Chief Designer Robert J. Woods, submitted a proposal for a similar design, but with in-flight wing adjustment capability. Although superficially similar, the X-5 was much more complex than the P.1101, with three sweep positions: 20°, 40° and 60°, creating an inflight "variable-geometry" platform. A

jackscrew A jackscrew, or screw jack, is a type of jack that is operated by turning a leadscrew. It is commonly used to lift moderate and heavy weights, such as vehicles; to raise and lower the horizontal stabilizers of aircraft; and as adjustable suppor ...

assembly moved the wing's hinge along a set of short horizontal rails, using

disc brake A disc brake is a type of brake that uses the #Calipers, calipers to squeeze pairs of #Brake pads, pads against a disc (sometimes called a

rake Rake may refer to: Common meanings * Rake (tool), a horticultural implement, a long-handled tool with tines * Rake (stock character), a man habituated to immoral conduct * Rake (poker), the commission taken by the house when hosting a poker game ...

rotor) to create friction. There are two basic types of brake pad friction mechanisms: abrasive f ...

s to lock the wing into its inflight positions. Moving from full extension to full sweep took less than 30 seconds. The articulation of the hinge and pivots partly compensated for the shifts in

center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero. For ...

and center of pressure as the wings moved. Even so, the X-5 had vicious

spin Spin or spinning most often refers to: * Spin (physics) or particle spin, a fundamental property of elementary particles * Spin quantum number, a number which defines the value of a particle's spin * Spinning (textiles), the creation of yarn or thr ...

characteristics arising from the aircraft's flawed aerodynamic layout, particularly a poorly positioned tail and vertical stabilizer which, in some wing positions, could lead to an irrecoverable spin. This violent stall / spin instability would eventually cause the destruction of the second aircraft and the death of its Air Force test pilot in 1953. The unfavorable spin characteristics also led to the cancellation of tentative plans by the United States Air Force to modify the X-5's design into a low-cost tactical fighter for NATO and other foreign countries.

Operational history

Two X-5s were built (serial numbers 50-1838 and 50-1839). The first was completed 15 February 1951, and the two aircraft made their first flights on 20 June and 10 December 1951. Almost 200 flights were made at speeds up to

Mach The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a Boundary (thermodynamic), boundary to the local speed of sound. It is named after the Austrian physi ...

0.9 and altitudes of . One aircraft was lost on 14 October 1953, when it failed to recover from a spin at 60° sweepback. Air Force Captain Ray Popson died in the crash at

Edwards Air Force Base Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, California, Kern County, but its eastern end is in San Bernardino County, California, San Bernardino County and a souther ...

. The other X-5 remained at Edwards and continued active testing until 1955, and remained in service as a chase plane until 1958. The X-5 successfully demonstrated the advantage of a

swing-wing A variable-sweep wing, colloquially known as a "swing wing", is an airplane wing, or set of wings, that may be modified during flight, swept back and then returned to its previous straight position. Because it allows the aircraft's shape to ...

design for aircraft intended to fly at a wide range of speeds. Despite the X-5's stability problems, the concept was developed to an outboard rather than inboard hinge, and was later successfully implemented in such aircraft as the

General Dynamics F-111 The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, multirole combat aircraft. Production models of the F-111 had roles that included attack (e.g. interdiction), strategic bombing (including nuclear weapons capabiliti ...

and

Grumman F-14 Tomcat The Grumman F-14 Tomcat is an American carrier-capable supersonic aircraft, supersonic, twinjet, twin-engine, Tandem#Aviation, tandem two-seat, twin-tail, all-weather-capable variable-sweep wing fighter aircraft. The Tomcat was developed for t ...

, the Mikoyan Gurevich MiG-23 and

MiG-27 The Mikoyan MiG-27 (; NATO reporting name: Flogger-D/J) is a variable-sweep ground-attack aircraft, originally built by the Mikoyan-Gurevich design bureau in the Soviet Union and later licence-produced in India by Hindustan Aeronautics as t ...

, the Sukhoi Su-17/20/22 and

Su-24 The Sukhoi Su-24 (NATO reporting name: Fencer) is a supersonic, night fighter, all-weather tactical bomber developed in the Soviet Union. The aircraft has a variable-sweep wing, Twinjet, twin engines and a side-by-side seating arrangement for it ...

, the

Tupolev Tu-22M The Tupolev Tu-22M (; NATO reporting name: Backfire) is a supersonic, variable-sweep wing, long-range strategic and maritime strike bomber developed by the Tupolev, Tupolev Design Bureau in the 1960s. The bomber was reported as being designated ...

and

Tu-160 The Tupolev Tu-160 (; NATO reporting name: Blackjack) is a supersonic, variable-sweep wing nuclear-capable heavy strategic bomber and airborne missile platform designed by the Tupolev Design Bureau in the Soviet Union in the 1970s. The aircra ...

, the

Panavia Tornado The Panavia Tornado is a family of twin-engine, variable-sweep wing multi-role combat aircraft, jointly developed and manufactured by Italy, the United Kingdom and Germany. There are three primary #Variants, Tornado variants: the Tornado IDS ...

and the

Rockwell 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 t ...

Survivors

The sole surviving X-5 is now at the

National Museum of the United States Air Force The National Museum of the United States Air Force (formerly the United States Air Force Museum) is the official museum of the United States Air Force located at Wright-Patterson Air Force Base, northeast of Dayton, Ohio. The NMUSAF is ...

Wright-Patterson Air Force Base Wright-Patterson Air Force Base (WPAFB) is a United States Air Force base and census-designated place just east of Dayton, Ohio, in Greene County, Ohio, Greene and Montgomery County, Ohio, Montgomery counties. It includes both Wright and Patte ...

near

Dayton, Ohio Dayton () is a city in Montgomery County, Ohio, United States, and its county seat. It is the List of cities in Ohio, sixth-most populous city in Ohio, with a population of 137,644 at the 2020 United States census, 2020 census. The Dayton metro ...

. It was delivered to the museum in March 1958. It is displayed in the museum's Research & Development Hangar."Bell X-5".
''National Museum of the United States Air Force.'' Retrieved: 22 October 2016.

Specifications (Bell X-5)

References

;Notes ;Bibliography * Hallion, Richard P. ''On The Frontier: Flight Research At Dryden 1946–1981 (NASA SP4303)''. Washington, DC: National Aeronautics and Space Administration, 1984 (revised 2003 in Smithsonian edition). . * Winchester, Jim. "Bell X-5." ''Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft''. Kent, UK: Grange Books plc., 2005. .

External links

''American X-Vehicles: An Inventory X-1 to X-50'', SP-2000-4531 – June 2003; NASA online PDF Monograph
* {{Authority control Edwards Air Force Base Variable-sweep-wing aircraft X-05, Bell Single-engined jet aircraft X-5 Mid-wing aircraft Aircraft first flown in 1951 Aircraft with retractable tricycle landing gear