In early 1936, Air Ministry Specification C26/31 was published, calling for the development of a transport and bomber aircraft capable of carrying 24 fully equipped soldiers or 2,000 kg of bomb load, with a top speed of over 300 km/h and a range of at least 1,500 km with a full payload. This aircraft was intended to replace the Vickers Valentia twin-engine biplanes that had been in service since the late 1920s. These aircraft were used in the British Empire, especially in India and Afghanistan, but also in southern Africa. Due to the prevailing operating conditions in these regions, a fixed landing gear and a high-wing design were required. The invitation to compete went out to Armstrong Whitworth, Bristol, Handley Page and Vickers. The following proposals were submitted, A.W. 23 by Armstrong Whitworth, Type 130 by Bristol, H.P.52 by Handley Page and Type 230 by Vickers. After reviewing the documents, one prototype each was ordered from the A.W.23, Bristol Type 130, and Handley Page H.P.52. Vickers had in the meantime withdrawn its design.
The AW.23 was developed under the direction of John Lloyd and was a cantilever twin-engined low-wing monoplane, with retractable landing gear and a twin tail mounted on the horizontal stabilizer. Powered by two air-cooled 14-cylinder radial engines of own manufacture Armstrong Siddeley Tiger VI with 820 hp takeoff power each, which propelled two fixed wooden four-blade propellers. To reduce drag, the engines were covered with a NACA cowling. The boxy fuselage was built in the conventional Armstrong Whitworth manner, with braced steel tubing covered with fabric. The enclosed cabin accommodated the two pilots and the radio operator, and the bombardier was located in the nose of the fuselage, where he also operated the machine gun located in the forward turret. The fuselage formed the cargo bay and, when used as a troop carrier, accommodated 24 fully equipped soldiers. There were seven trapezoidal and two rectangular windows on each side, and a cargo door measuring 1.24 m x 1.70 m. When used as a bomber, two 453 kg bombs were mounted on mounts under the wings near the fuselage. The wings built up on single light-alloy box spar structure with sheet metal webs corrugated vertically and spanwise, with sheet-metal covered nose ribs.
Campbell Orde flew the prototype, K3585, on 4 June 1935, and before the end of the month it appeared at the Hendon Display. The choice of Tiger engines also proved unwise, and served to delay the aircraft’s delivery to Martlesham Heath until late in 1936, and then only for take-off and landing measurements. By then, not only had the Bombay been adjudged the C.26/31 winner, but it was entering production. Alan Cobhan acquired the AW.23 from Armstrong Whitworth for his company Flight Refuelling Ltd, which was engaged in the problem of aerial refueling. For this purpose, the AW.23 was modified and given the civilian registration G-AFRX. The trials were aimed at refueling the Short Empire flying boat Cambria with the civilian registration G-ADUV by using hoses and high-pressure pumps during flight. In early 1940, the trials were unsuccessfully abandoned and AW.23 was parked at Sussex. There it was destroyed in a German air raid on August 11, 1940.
Oliver Tapper: Armstrong Whitworth Aircraft since 1913
Francis Mason: The British Bomber since 1914