Vickers Type 253 (G.4/31) Biplane

The Vickers Type 253 general purpose biplane was the first aircraft to use the geodetic construction method devised by Barnes Wallis, and made famous on the Wellington bomber. It was designed to satisfy Air Ministry specification G.4/31, for a general purpose aircraft. Although the Type 253 won the contest, only the prototype was ever built, and production was switched the fully geodetic Vickers Wellesley.

The geodetic structure evolved from Wallis’s work on airships. On the Type 253 the fuselage was built using geodetic principles, while the wings were conventional. The fuselage was built with four conventional longerons (running horizontally along the full length of the fuselage). Light alloy members were then wrapping in two spirals – clockwise and anti-clockwise – around the longerons, producing a lattice structure. The geodetic frame would then be covered with fabric. For maximum strength the spiral members needed to follow the shortest possible path around the fuselage (in the geographical discipline of geodetics the ‘great circle’ is the shortest route between two points on a sphere). At any point on the fuselage the stresses in the opposing spiral members would be balanced against each other, producing a very strong structure at lighter weights than was possible with the standard metal frame construction in use at the start of the 1930s. Geodetic fuselages were also very resistant to damage, as would later become clear on the Vickers Wellington.

Wallis worked on two parallel designs to satisfy the G.4/31. The Type 253 was the official entry into the contest. This aircraft used a geodetic fuselage, but combined it with conventional biplane wings, using the long-established Raf 15 wing section.

The second design was the Type 246. This was a fully geodetic monoplane, using essentially the same fuselage as the Type 253 and the same engine. The resulting aircraft was lighter than the Type 246, and thus had much better performance figures, as soon became clear in comparative tests during 1935 (the figures below are for a later prototype with more powerful engine).

Specification G.4/31 called for a General Purpose aircraft, capable of operating in tropical and temperate areas, equipped to operate as a day, night and dive bomber and carry out casualty evacuation, army co-operation and reconnaissance duties. The ability to drop torpedoes later added to the list. The aircraft industry expected the winning design to be ordered in very large numbers, and so eight prototypes were designed and built (by Armstrong Whitworth, Bristol, Fairey, Handley Page, Parnell, Vickers and Westland).

All of these companies would be disappointed. Most of the designs suffered from engine or other problems. Only Vickers and Handley Page produced aircraft that came close to satisfying the original specifications (combining a torpedo bomber and a dive bomber in a single aircraft proved to be almost impossible). The final nail in the coffin of specification G.4/31 was the rise of Nazi Germany and with it the new Luftwaffe. By 1935, when the Type 253 underwent official trials, the jack-of-all-trades general purpose aircraft looked obsolete (the same year saw the first flights of the Messerschmitt Bf 109 and the Heinkel He 111). In August 1935 the Air Ministry placed an order for 150 of the Vickers Type 253 biplane, but none would be built. On 10 September 1935 the contract was modified to one for 96 of Barnes Wallis’s fully geodetic monoplane, the Vickers Wellesley.

 

Type 253

Type 281 Wellesley

Engine

Bristol Pegasus IIM.3

Pegasus X

Power

635hp

925hp

Crew

Two

Two

Span

52ft 7in

74ft 7in

Length

37ft 0in

39ft 3in

Height

12ft 6in

12ft 4in

Tare weight

4,365lb

6,812lb

All-up weight

8,350lb

11,128lb

Max speed

161mph at 4,500ft

202mph at 8,000ft

Time to 10,000ft

8 min 30 sec

9 min 30 sec

Service ceiling

21,700ft

26,200ft

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How to cite this article: Rickard, J (24 October 2008), Vickers Type 253 (G.4/31) Biplane , http://www.historyofwar.org/articles/weapons_vickers_type_253.html

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