Bell X-5

infobox Aircraft
name =X-5
type =Research aircraft
manufacturer =Bell Aircraft Corporation

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caption =
designer =Robert J. Woods
first flight =20 June 1951
introduced =
retired = December 1958
status =
primary user = U.S.Air Force
more users = NACA
produced =
number built = 2
unit cost =
developed from=Messerschmitt P.1101
variants with their own articles =

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. 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.

Design and development

The incomplete Messerschmitt P.1101 fighter prototype recovered by US troops in 1945 from the experimental facility at Oberammergau, Germany, was brought back to the United States. Although damaged in transit, the innovative fighter prototype was delivered to the Bell factory at Buffalo, New York where company engineering staff studied the design closely and led by Chief Designer Robert J. Wood, submitted a proposal for a similar design. [Winchester 2005, p. 37.]

Although superficially similar, the X-5 was much more complex than the P.1101, with three sweep positions: 20°, 40°, and 60°, creating an in-flight "variable-geometry" platform. A jackscrew assembly moved the wing's hinge along a set of short horizontal rails, using disc brakes to lock the wing into its in-flight 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 pressure as the wings moved.

Even so, the X-5 had vicious spin 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. [Hallion 1984, p. 52.]

The unfavorable spin characteristics also led to the cancellation of tentative plans by the US Air Force to modify the X-5's design into a low-cost tactical fighter for NATO and other foreign countries. [Hallion 1984, p. 47.]

Operational history

Two X-5s were built (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 (12,200 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 and continued active testing until 1955, and remained in service as a chase plane until 1958. It is now on display in the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio.

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 F-111, F-14 Tomcat and B-1 Lancer.

pecifications (Bell X-5)

aircraft specification

jet or prop?=jet
plane or copter?=plane

crew=1
capacity=
length main=33 ft 4 in
length alt=10.1 m
span main=
**Unswept: 33 ft 6 in
span alt=10.2 m)
**60° sweep: 20 ft 10 in (6.5 m
height main=12 ft
height alt=3.6 m
area main=175 sq. ft.
area alt=16.26 m².
empty weight main=6,336 lb
empty weight alt=2,880 kg
loaded weight main=
loaded weight alt=
useful load main=
useful load alt=
max takeoff weight main=9,980 lb
max takeoff weight alt=4,536 kg
engine (jet)=Allison J35-A-17
type of jet=turbojet
number of jets=1
thrust main=4,900 lbf
thrust alt=21.8 kN
thrust original=
afterburning thrust main=
afterburning thrust alt=
afterburning thrust original=
max speed main=716 mph
max speed alt=1,150 km/h
max speed more=
cruise speed main=
cruise speed alt=
cruise speed more=
never exceed speed main=
never exceed speed alt=
stall speed main=
stall speed alt=
range main=750 mi
range alt=1,207 km
range more=
ceiling main=49,900 ft
ceiling alt=15,200 m
climb rate main=
climb rate alt=
loading main=
loading alt=
thrust/weight=0.50:1
power/mass main=
power/mass alt=
armament=

ee also

aircontent
related=
similar aircraft=
* Messerschmitt Me P.1101

References

Notes

Bibiography

* 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). ISBN 1-58834-134-8.
* Winchester, Jim. "Bell X-5." "Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft". Kent, UK: Grange Books plc., 2005. ISBN 1-84013-309-2.

External links

* [http://history.nasa.gov/monograph31.pdf "American X-Vehicles: An Inventory X-1 to X-50", SP-2000-4531 - June 2003; NASA online PDF Monograph]
lists=
*List of experimental aircraft