S.A.M. #62: The Neverliner

Another flying wing - this time from Great Britain:

Of the many tailless aircraft projects that reached the advanced development stage during the mid-1940s, the Armstrong Whitworth A.W. 52 jet-powered flying wing stands out, for its visionary approach to the jetliner of the future. Although the aircraft flew after the war, its design reflects the advanced thinking of British designers during the latter stages of the war.

The Armstrong Whitworth project consisted of a logical progression of experiments, commencing with wind tunnel model tests, followed by a glider that was a half-scale model of a 34,000-pound powered aircraft. This in turn was to be half the size of a projected airliner that would weigh about 180,000 to 200,000 pounds. The object of the designs was to combine the merits of the tailless design with the advantages of the laminar-flow wing. This arrangement could theoretically result in an aircraft with a total parasite drag about one-third of that of a conventional aircraft.

Following successful wind tunnel tests, design work started on the A.W. 52G glider in May 1942, and it was finally towed into the air for the first time three years later, in March 1945. Built mainly of wood, the two-place craft was controlled by wing tip elevons that were hinged to the trailing edges of "correctors" hinged to the wing. Correctors provided trim in pitch and also corrected the pitching moment resulting from flap operation. Spoilers fitted to the upper surface of the wing and a vertical fin and rudder at each wing tip completed the control arrangement. An anti-spin parachute was housed at the base of each rudder. Boundary-layer control was provided over the outer section of the wings by the suction of the boundary-layer air into a slot located in front of the elevons. This prevented the breaking away of the air flow over the wing and delayed wing tip stall at low speed. Wind-driven pumps were mounted on each main landing gear leg to provide power for the boundary-layer control.

Flight tests of the A.W. 52G proceeded well enough to confirm theoretical calculations. The next step in the development plan was the production of two A.W. 52 jet-powered research aircraft with a design weight of about 34,000 pounds. Configuration of the powered aircraft closely resembled that of the glider version, with the obvious addition of two 5000-pound thrust Rolls Royce Nene turbojets buried in the wing centre section on either side of the cockpit.

Boundary-layer control suction was provided by the turbojets, with the suction slots in the wing connected by ducts to the engine air intakes. Designed for speeds of 400-500 mph, the aircraft also had an ejection seat for the pilot only, retractable tricycle landing gear, pressurized cockpit, and thermal de-icing of the wings using jet exhaust.

The test pilot for Armstrong Whitworth, E.G. Franklin, flew the first A.W. 52 (TS 363) on November 13, 1947. The second aircraft, TS 368, fitted with Rolls-Royce Derwents, flew almost a year later, on September 1, 1948. Although the A.W. 52 was an impressive attempt to further the state of the art, the test flights were disappointing. Laminar flow was not achieved, and landing and takeoff distances exceeded those experienced with a conventional aircraft of similar wing loading. Elevator control of the aircraft was extremely sensitive.

The first aircraft was lost on May 30, 1949, due to an asymmetric flutter that caused the pilot to abandon the aircraft in flight. Although the second model subsequently underwent a research program on airflow behaviour on sweptback wings at the Royal Aircraft Establishment at Farnborough, until September 1953, Armstrong Whitworth abandoned further development efforts. Investigation established that the structure had failed under the tremendous loads experienced at airspeeds of about Mach 0.9.