Bell Shows Off Its New X-5
Robert Woods and Bell Aircraft unveiled their similar X-5 in the early 1950s. The major difference in the Bell mount was in the use of in-flight variable geometry wings, this made possible by a collection of electric motors within a system as designed by Bell engineers. The wing arrangement allowed the X-5 the capability to adjust wing sweep between three pre-set positions of 20-, 40- and 60-degree angles as needed, making her a more complex form of the German type. 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.
X-5 Specifications
The X-5 was fitted with a single Allison J35-A-17 turbojet engine of 4,900lbs thrust. Maximum speed was listed between 690 and 716 miles per hour with a cruise speed of about 600 miles per hour. A reported service ceiling of 50,700 feet (hence the pressurized cockpit) was given as was a listed range between 500 and 750 miles. She maintained an empty weight of 6,336lbs and a maximum take-off weight (MTOW) of 9,980lbs when fully-fueled. No armament was ever installed. Her variable wing sweep gave her a 32 foot, 9 inch span when extended and a 22 foot, 8 inch span when swept.
Tragedy Befalls the X-5 Program
In practice, it was soon found that the X-5 inherited some particularly vicious stall-spin instability characteristics - perhaps the price of basing such a project on the incomplete German program. 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 in the process. As such, the program was shelved and ultimately cancelled by the USAF killing any chances of the X-5 becoming the low-cost tactical fighter the Americans envisioned. Testing did, however, continue on with the first prototype into 1955 to which the aircraft served out the rest of her term as a chase plane until early 1958 - her variable wing sweep proving helpful in keeping pace with various other aircraft under development.
Beyond the X-5
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.
Some of the flight data garnered from the X-5 program directly served in the development of the Grumman F-14 Tomcat and the General Dynamics F-111 Aardvark "swing-wing" combat production aircraft, though the Bell's particular internal wing sweep mechanism was completely revamped for these two advanced aircraft designs.
It is of note that the Saab 29 "Tunnan" shares striking similarities to both the Messerschmitt Me P.1101 and the Bell X-5.
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