Warplanes of the USA: Bell X-5

Bell X-5

(USAF Photo)

The Bell X-5 was the first aircraft capable of changing the sweep of its wings in flight. It was inspired by the untested wartime P.1101 design of the German Messerschmitt company. In contrast with 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. (Wikipedia)

(NMUSAF Photo)

Bell X-5 (Serial No. 01838), National Museum of the USAF, Dayton, Ohio.

wo X-5s were built (Serial Nos. 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 0.9 and altitudes of 40,000 ft (12,000 m). 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. 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 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,[4] and was later successfully implemented in such aircraft as the General Dynamics F-111 and Grumman F-14 Tomcat, the Mikoyan Gurevich MiG-23 and MiG-27, the Sukhoi Su-17/20/22 and Su-24, the Tupolev Tu-22M and Tu-160, the Panavia Tornado and the Rockwell B-1 Lancer.The sole surviving X-5 is now at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio. It was delivered to the museum in March 1958. It is displayed in the museum's Research & Development Hangar. (Wikipedia)

(NMUSAF Photos)

A composite photograph showing the Bell X-5’s variable-sweep wing.

(NACA Photo)

This NACA High-Speed Flight Research Station photograph of the X-5 was taken at the South Base of Edwards Air Force Base. The photograph shows the X-5 on the ramp in-front of the NACA hangar. The Bell, X-5 was flight tested at the NACA High-Speed Flight Research Station (now the NASA Dryden Flight Research Center, Edwards, California) from 1952 to 1955. The X-5 was the first aircraft capable of sweeping its wings in flight. It helped provide data about wing-sweep at angles of up to 60 degrees at subsonic and transonic speeds. There were two X-5 vehicles. Ship 1 was flown at the NACA High-Speed Flight Research Station (High-Speed Flight Station, as it was redesignated in 1954) from 1951 to 1955. Ship 2 was operated by Bell and the U.S. Air Force and was lost in a spin accident in 1953. Following the conclusion of the contractor's test program, the X-5 was grounded for installation of a NACA instrument package. The Air Force conducted a short, six-flight, evaluation program. Since the Air Force evaluation program included data collection, it was considered as part of the overall NACA effort and flights were logged as AF/NACA. In the NACA test program, the X-5 demonstrated severe stall-spin instability. The X-5 was also used as a chase plane for other research aircraft because it could vary its flying characteristics to suit the airplane it was chasing. Ship 1 flew a total of 133 flights during its three years of service. In spite of the problems with the aircraft, the X-5 provided a significant full-scale verification of NACA wind-tunnel predictions for reduced drag and improved performance that resulted from this configuration's increasing the wing sweep as the speed of the aircraft approached the speed of sound. The X-5 flight tests provided some of the design data for the Air Force F-111 and Navy F-14 tactical aircraft. Although the mechanism by which the X-5 changed its wing sweep made this particular design impractical, development of a viable variable-sweep aircraft had to await Langley Aeronautical Laboratory's concept of an outboard wing pivot in the mid-1950s. (Langley was a NACA research laboratory in Hampton, Virginia.) The X-5 was a single seat aircraft powered by an Allison J-35-A-17A jet engine. It was 33.33 feet long with a wingspan of 20.9 feet (with the wings swept back at an angle of 60 degrees) to 33.5 feet (with the wings unswept). When fully fueled, the X-5 weighed 9,875 pounds. NASA Identifier: NIX-E-799.

(NACA Photo)

Bell X-5.