Vickers 253 Wellesley
Air Ministry Specification G.4/31 called for a General Purpose aircraft, capable of level bombing, army co-operation, dive bombing, reconnaissance, casualty evacuation and torpedo bombing. The Vickers Type 253 won against the Fairey G.4/31, Westland PV-7, Handley Page HP.47, Armstrong Whitworth AW.19, Blackburn B-7, Hawker PV-4 and the Parnell G.4/31.
Designed by Rex Pierson, the Type 253 was the first aircraft built which partly used the Barnes Wallis geodetic design in the fuselage. Despite an order for 150, Vickers offered their private venture monoplane design the Type 246. This used the same geodetic design principles for both the fuselage and the wings, and first flew on 19 June 1935. It had superior performance to the 246 but did not attempt to meet the multi-role requirement, being a day and night bomber only. First flown with PV 0-9 markings, the 253 showed a lower tare weight, better performance and larger payload, partly as a result of the 8.85 – 1 high aspect ratio wing.
The Wellesley evolved from Vickers' design for a general-purpose day and night bomber and coastal-defence torpedo-carrier biplane to satisfy Air Ministry Specification G.4/31, the company having decided to develop and build a monoplane aircraft to meet the same specification. When evaluated there was little doubt that the monoplane was superior, with the result that the Air Ministrv contract for the biplane was cancelled, being replaced on 10 September 1935 by one for 96 examples of the monoplane under a rewritten G.22/35 specification. The RAF ultimately ordered 176, named Wellesely, to a newly written specification 22/35, with a 14 month production run starting in March 1937.
Named the Wellesley, it was the first RAF aircraft to utilise the geodetic form of construction devised by Barnes (later Sir Barnes) Wallis; offering a lightweight structure of great strength, it was adopted later for the Wellington. The other highly unusual feature was the provision of a pannier beneath each wing to serve as a bomb container. The low-set monoplane wing was also of geodetic construction, the main landing gear was hydraulically retractable, and power plant comprised a single Bristol Pegasus radial piston engine.
To avoid disrupting the geodetic structure, the bombload was carried in two streamlined panniers under the wings. The Wellesly Mk.1 had two separate cockpits, but this was changed in the Mk.II to a single piece cockpit canopy covering the pilot and navigator positions.
Wellesley Mk Is entered RAF service in April 1937 but by the outbreak of World War II most of them had been transferred to the Middle East, where they remained operational into 1941. The RAF received the first Welleselys in April 1937, for 76 Sqn at Finningley, and eventually equipped six RAF Bomber Command squadrons in the UK, Nos 35, 76, 77 and 148 Sqdns. Later a number were sent out to No.223 Sqdn, and as the home based machines were replaced, they too were sent out to the Middle East.
The primary use of the Wellesely during the econd World War was maily in the Middle East with only four examples remaining in Britain at the start of the war. Among its significant wartime operations was the bombing of Addis Ababa in August 1940, and Wellesleys of 223 Sqn were among aircraft that wiped out an Italian destroyer flotilla attack on Port Sudan in April 1941. Losses to Italian CR.42 fighters did occur when intecepted, as the Wellesley’s defensice armament of one fixed gun flexibly mounted firing aft was poor. They remained in the region until 1941 performing maritime reconnaissance duties.
The type is remembered especially in service with the RAF's Long Range Development Flight, which was established at RAF Upper Heyford, Oxon, in January 1938. Equipment comprised six Wellesley Mk.Is modified by the installation of 28.7 lt 1010 hp / 753 kW Pegasus Mk XXII engines installed in NACA long-chord cowlings, and driving 3 blade Rotol ‘Incredible Hub’ constant-speed propellers; plus other changes which included strengthened landing gear, increased fuel capacity and the introduction of an autopilot. Adding a third crew member and a rest bunk and a folding pilot’s seat to allow mid-air pilot exchange. Between 5 and 7 November 1938, two of a flight of three of these aircraft (led by Sqn Ldr R. Kellett) succeeded in establishing a new world long-distance record, covering non-stop the 11,526km between Ismailia, Egypt, and Darwin, Australia, in just over 48 hours.
Engine: 1 x Bristol Pegasus XX, 690kW / 937 hp
Max take-off weight: 5035 kg / 11100 lb
Empty weight: 2889 kg / 6369 lb
Wingspan: 22.73 m / 74 ft 7 in
Length: 11.96 m / 39 ft 3 in
Height: 3.76 m / 12 ft 4 in
Wing area: 58.53 sq.m / 630.01 sq ft
Max. speed: 198 kts / 367 km/h / 228 mph
Service ceiling: 10600 m / 34,700 ft
Range: 964 nm / 1786 km / 1110 miles
Armament: 2 x 7.7mm machine-guns