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The Vickers Wellesley was the first aircraft built entirely using Barnes Wallis’s geodesic construction method to enter service, and is best known for establishing a new world distance record in 1938. The Wellesley was developed as a private venture alongside the Vickers Type 253 biplane. This aircraft, which was built to meet Air Ministry specification G.4/41 for a general purpose aircraft, had a geodesic fuselage but conventional wings. At the same time as working on the Type 253, Wallis was also working on the Type 246 monoplane. This had a similar fuselage to the Type 253, but with a single geodesic wing in place of the two conventional wings of the Type 253.
The geodetic structure evolved from Wallis’s work on airships. The fuselage and wings were built with conventional longerons (running horizontally along the full length of the structure). 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.
The Type 253 won the G.4/41 contest, and in the summer of 1935 Vickers was given a contract for 150 aircraft. On 19 June 1935 the Type 246 made its maiden flight, and it soon became clear that the performance of the monoplane was superior to that of the biplane – it was after all a lighter aircraft, powered by the same engine. On 10 September 1935 the order for 150 Type 253s was replaced by one for 96 Wellesleys.
By that point the prototype had been badly damaged in a crash. It was rebuilt as the Type 281, with a more powerful engine, enclosed cabins and hydraulic retractable landing gear. The modified prototype had even better performance figures than the Type 246. The first production aircraft had its maiden flight on 30 January 1937, and the Wellesley entered squadron service later that year. A total of 177 Wellesleys would be built. The Wellesley is a peculiar looking aircraft to modern eyes, with a very wide wingspan and two widely separated cockpits.
The Wellesley is most famous for breaking the world distance record. Five aircraft were modified by the Long Range Development Unit. These aircraft were given a constant-speed propeller, had their fuel capacity increased to 1,290 gallons and had all military equipment removed. A position was added for a third crewman, along with a rest position. A Pegasus XXII engine, running on 100-octane fuel and with a smaller-than-normal supercharger was installed. On 5 November 1938 three of these aircraft took off from Ismailia (Egypt), heading for Darwin. All three aircraft broke the existing record when they reached Macassar (Celebes), but the aircraft of Flt Lt H. A. V. Hogan was then forced to land to refuel. The remaining two aircraft, of Sqn Ldr Kellet and Flt Lt A. N. Combe, landed Darwin on 7 November, after a flight of 7,157.7 miles. The record stood until 1946.
The Wellesley was not a predecessor to the Wellington. Wallis began work on both projects in 1932. The prototype Wellesley made its first flight on 19 June 1935, the prototype Wellington almost exactly one year later, on 15 June 1936.
By the time the Wellesley entered service it was already surplus to requirement. Officially designation a medium bomber, it was neither fast enough nor heavily enough armed to operate in that role against the Luftwaffe. Nos.7, 35, 76, 77, 148 and 207 Squadrons briefly operated the Wellesley from Britain, but all six squadrons had been re-equipped by April 1939.
The Wellesley saw front-line service in the Middle East and East Africa, where it was used by four squadrons (Nos.14, 45, 47 and 223). Nos. 14, 47 and 223 Squadrons used their Wellesleys during the campaign in Italian East Africa. The aircraft’s long range was put to good use in raids on the Italian airfields at Addis Ababa. After the end of the East African campaign, most of the surviving Wellesleys were quickly withdrawn from the front line, although No.47 Squadron kept some on strength until March 1943.
Engine: Bristol Pegasus XX
Power: 925hp
Crew: Two
Span: 74ft 7in
Length: 39ft 3in
Height: 12ft 4in
Tare weight: 6,812lb
All-up weight: 11,128lb
Max speed: 222mph at 15,000ft
Time to 10,000ft: 10 min 50 secs
Service ceiling: 26,100ft
Normal range: 1,100 miles
Armament: One fixed forward firing synchronized 0.303in Vickers gun and one Vickers K gun in rear cockpit
Bomb load: 2,000lb carried under the wings