Bell X-5 - Definition and Overview

Bell X-5
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Description
Role	Variable geometry prototype
Crew	1
First Flight	June 20, 1951
Manufacturer	Bell Aircraft Corporation
Dimensions
Length	33 ft 4 in	10.1 m
Wingspan (unswept) (60° sweep)	33 ft 6 in 20 ft 10 in	10.2 m 6.5 m
Height	12 ft 0 in	3.6 m
Wing area	ft²	m²
Weights
Empty	lb	kg
Loaded	lb	kg
Maximum takeoff	9,800 lb	4,400 kg
Powerplant
Engines	1x Allison J35-A-17
Thrust	4,900 lb	21.8 kN
Performance
Maximum speed	716 mph	1150 km/h
Range	N/A
Service ceiling	49,900 ft	15,200 m
Rate of climb	N/A
Wing loading	N/A
Thrust/Weight	0.50:1
Three view diagram
Bell X-5

The Bell X-5 was the first aircraft capable of changing the sweep of its wings in flight. It was inspired by the untested war-time P.1101 design of the German Messerschmitt company. However, whereas the German design could only be adjusted on the ground, the Bell engineers devised a system of electric motors to adjust the sweep in flight.

The X-5 had three sweep positions: 20°, 40°, and 60°. A jack screw assembly moved the wing's hinge along a set of short horizontal rails, using disc 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 in center of gravity and center of lift as the wings moved. Even so, the X-5 had vicious spin characteristics, which in some wing positions led to an irrecoverable spin--this led to the destruction of the second aircraft and the death of a test pilot.

Two X-5s were built. The first was completed 15 February 1951, and the two aircraft made their first flights on 20 June 1951 and 10 December 1951. Almost 200 flights were made at speeds up to Mach 0.9 and altitudes of 40,000 ft (12,195 m). On 14 October 1953 USAF Captain Ray Popson died in a crash at Edwards Air Force Base during spin testing. The other X-5 remained at Edwards until 1958, being used as a chase plane after its own research program had been completed in 1955. It is now on display in the USAF Museum.

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 later successfully implemented in such aircraft as the General Dynamics F-111 and F-14 Tomcat.

Aircraft serial numbers

• 50-1838, 133 flights
• 50-1839, 26 flights

Also See

• X-plane

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