| X-5 | |
|---|---|
 | |
| General information | |
| Type | Experimental aircraft |
| Manufacturer | Bell Aircraft Corporation |
| Designer | Robert J. Woods |
| Primary users | United States Air Force |
| Number built | 2 |
| History | |
| First flight | 20 June 1951 |
| Retired | December1958 |
TheBell X-5 was the firstaircraft capable ofchanging the sweep of its wings in flight. It was inspired by the untested wartimeP.1101 design of theGermanMesserschmitt 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.
TheMesserschmitt P.1101 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 theBell Aircraft factory at Buffalo, New York. Although incomplete and damaged in transit, company engineering staff studied the design closely.[1] 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.[2] The Bell team, led by Chief Designer Robert J. Woods, submitted a proposal for a similar design, but with in-flight wing adjustment capability.[1]
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. Ajackscrew assembly moved the wing's hinge along a set of short horizontal rails, usingdisc brakes 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 incenter of gravity andcenter of pressure as the wings moved.[citation needed]
Even so, the X-5 had viciousspin 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.[3]
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.[4]
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 toMach 0.9 and altitudes of 40,000 ft (12,000 m). One aircraft was lost on 13 October 1953, when it failed to recover from a spin at 60° sweepback. Air Force Maj. Raymond Popson died in the crash atEdwards Air Force Base. The other X-5 remained at Edwards and continued active testing until 1955,[5] and remained in service as a chase plane until 1958.
The X-5 successfully demonstrated the advantage of aswing-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,[6] and was later successfully implemented in such aircraft as theGeneral Dynamics F-111 andGrumman F-14 Tomcat, theMikoyan Gurevich MiG-23 andMiG-27, theSukhoi Su-17/20/22 andSu-24, theTupolev Tu-22M andTu-160, thePanavia Tornado and theRockwell B-1 Lancer.
The sole surviving X-5 is now at theNational Museum of the United States Air Force atWright-Patterson Air Force Base nearDayton, Ohio. It was delivered to the museum in March 1958. It is displayed in the museum's Research & Development Hangar.[7]
Data fromThe X-planes : X-1 to X-29[8]
General characteristics
Performance
Aircraft of comparable role, configuration, and era
Related lists
