The Vickers Type 253 was a single engine, two seat biplane was designed by Barnes Wallis and Rex Pierson to meet the requirements of Specification G.4/31 which called for a general-purpose bombing and torpedo aircraft to replace the Westland Wapati.
It was developed in parallel with a private-venture monoplane prototype which later entered production as the Vickers Wellesley, described separately on its own web page.
The Type 423 was powered by a Bristol Pegasus engine and used a geodetic structure for the rear fuselage, drawing on the experience that Barnes Wallis had gained in the construction of airships – notably the Vickers-built R-100.
A geodesic is the shortest line between two points on a curved surface and Wallis identified this structural approach as providing efficient load distribution in a structure whilst also introducing redundant load paths to create a fail-safe and damage tolerant structure. The aim was to achieve a lattice-like structure that required no underlying secondary structure to give it strength.
In the Type 253, this system was partially introduced in the fuselage structure on the private-venture G.4/31 monoplane, developed by Vickers in parallel, adopting a full geodetic structure for both wings and fuselage.
The Type 253 (K2771) made its first flight at Brooklands on 16th August 1934 with Matt Summers at the controls and powered by a 635 ho Pegasus IIM3 engine. In early 1935, this engine was replaced with a Pegasus IIIM3.
The Type 423 was the subject of comparative trials with the G.4/31 monoplane prototype at Martlesham Heath and unfortunately it demonstrated the clear advantage of the monoplane. With its fully-geodetic structure the monoplane had a lighter empty weight and had superior performance at higher weights than the Type 423 thereby delivering better payload and range characteristics.
As a result, further development of the Type 253 was abandoned although the sole example (K2771) continued to give valuable service to the Bristol Engine Company as a flying test-bed.
Ultimately, the airframe was donated to 385 Sqn (Coulsdon & Purley) of the Air Training Corps where its ultimate fate is unkown.
Variants & Numbers
One aircraft only, serial K2771.
|Powerplant||One 635 hp Bristol Pegasus IIM3 engine|
|Span||52 ft 7 in|
|Maximum Weight||8,350 lb|
|Capacity and armament||Pilot and observer; provision for the carriage of up to 8 bombs under the wings and a torpedo between the undercarriage legs. Armament two Lewis machine guns – one forward firing and one fired from the observer position.|
|Maximum Speed||161 mph at 4,500 ft|