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Bell X-5

The Bell X-5 became the initial aircraft with the ability to alter the sweep of its wings while in flight.

It drew inspiration from the untried wartime P.1101 design by the German Messerschmitt company.

Expanding on the German concept, where the wing sweepback angle could only be adjusted on the ground, Bell engineers created a system using electric motors to modify the sweep mid-flight.

The United States troops recovered the incomplete Messerschmitt P.1101 fighter prototype from Germany in 1945.

Despite being damaged during transportation, the innovative prototype was taken to the Bell factory in Buffalo, New York.

There, the company’s engineering team closely examined the design and, under the leadership of Chief Designer Robert J. Woods, put forward a proposal for a comparable aircraft.

The X-5 differed significantly from the P.1101, featuring a more intricate design with three sweep positions: 20°, 40°, and 60°, establishing a dynamic “variable-geometry” configuration during flight.

A jackscrew mechanism adjusted the wing’s hinge by sliding along short horizontal rails, while disc brakes secured the wing in place at different angles.

Transitioning from fully extended to fully swept back took under 30 seconds.

The flexibility of the hinge and pivots helped counterbalance changes in the centre of gravity and centre of pressure as the wings adjusted position.

Despite this, the X-5 exhibited severe spin characteristics due to its flawed aerodynamic configuration, specifically a badly positioned tail and vertical stabilizer.

In certain wing positions, these flaws could result in an unrecoverable spin, leading to the destruction of the second aircraft and the tragic loss of its Air Force test pilot in 1953.

Moreover, the unfavourable spin characteristics of the X-5 ultimately led to the abandonment of the United States Air Force’s tentative plans to transform its design into an affordable tactical fighter for NATO and other foreign nations.






33 ft 4 in (10.16 m)


30 ft 6 in (9.30 m)

Lower wingspan

20 ft 9 in (6.32 m) swept at 60° sweep


12 ft 0 in (3.66 m)

Wing area

175 sq ft (16.3 m2)



NACA 64A011


NACA 64A08

Empty weight

6,350 lb (2,880 kg)

Gross weight

9,875 lb (4,479 kg)


1 × Allison J35-A-17A turbojet engine,

4,900 lbf (22 kN) thrust at sea level


Maximum speed

705 mph (1,135 km/h, 613 kn)


750 mi (1,210 km, 650 nmi)

Service ceiling

42,000 ft (13,000 m)




National Museum of the United States Air Force

National Aeronautics and Space Administration

Bell Aircraft Since 1935-Alain J. Pelletier.













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