The Bell X-5 was produced to investigate the aerodynamic consequences of altering the wing geometry in flight, and first flew on 20 June 1951. Work on the two X-5s began in 1948, the basis of the design being the Messerschmitt P.1101 prototype that had almost been completed by the Germans at the end of World War II. Two X-5s were manufactured by Bell, differing from their German ancestor primarily in being able to adjust their wing sweep angle in flight. The variable sweep wing could be adjusted to 20, 40 or 60 degrees the hydraulic operating mechanism automatically compensating for the inevitable shift in the position of the design’s centre of gravity.
Powered by a 4900-lb (2222-kg) thrust Allison J35-A-1; turbojet located in the lower fuselage and exhausting under the tail boom. Special fairings were also fitted to ensure that the leading and trailing edges of the wing roots presented smooth aerofoil surfaces at all times.
The first prototype (50-1838) was completed on February 15th, 1951 and first flown on June 20th, 1951. A second prototype (50-1839) followed into the air on December 10th, 1951. Both airframes accounted for some 200 total flights with the first prototype netting 133 flights alone. All three wing sweep positions were trialed on the first prototype's ninth flight with success.
In practice, it was found that the X-5 inherited some particularly vicious stall-spin instability characteristics. The cause was believed to be the positioning of the tail section wihtin the design and compounded by the position of the vertical tail fin itself. As the wing sweep changed, essentially the entire aerodynamic qualities of the aircraft changed with it. The resulting action could lead the aircraft into an irrecoverable spin - this eventually occurring on October 14th, 1953 - the second prototype was lost to such a spin while running its wing sweep at 60-degrees, killing Air Force test pilot Captain Ray Popson.
The program was shelved and ultimately cancelled by the USAF. Testing did continue on with the first prototype into 1955 after which the aircraft served out the rest of her term as a chase plane until early 1958.
The remaining Bell X-5 was handed over to the National Museum of the United States Air Force in Dayton, Ohio, in March of 1958 where it resides even today as part of the Research & Development Gallery at Wright-Patterson Air Force Base.