Avro Manchester - Design and Development

Design and Development

The Manchester was originally designed to the Air Ministry Specification P.13/36 which was the same specification that Handley Page followed in their design of the Halifax bomber. The specification called for a twin-engine "medium bomber" for "worldwide use", which was to be capable of carrying out shallow (30°) dive bombing attacks, and carry heavy bombloads (8,000 lb/3,630 kg) or two 18 in (457 mm) torpedoes. Provision for catapult assisted takeoff to permit the maximum load was also part of the specification. Cruising speed was to be a minimum of 275 mph at 15,000 feet. The Air Ministry were expecting an aircraft of similar weight to the B.1/35 specification but smaller and faster.

Avro had already started work on a design before the invitation to tender. They were in competition with Boulton Paul, Bristol, Fairey Handley Page and Shorts. Vickers had a design but did not tender it. In early 1937 the Avro design and the Handley Page were accepted, and prototypes of both ordered but in mid 1937, the Air Ministry exercised their rights to order "off the drawing board". This skipping of the usual process was necessary because of the expansion of the RAF in expectation of war. From 1939, it was expected that the P.13/36 would replace existing medium bombers in production.

The design used the Rolls-Royce Vulture 24-cylinder X-block engine, which was essentially two Rolls-Royce Peregrine Vee cylinder blocks mounted one on top of the other, the bottom one inverted to give the "X" shape. When developed in 1935, the engine had promise — it was rated at 1,760 hp (1,310 kW) - but it proved woefully unreliable and had to be derated to 1,480-1,500 hp (1,100-1,120 kW). Avro's prototype Manchester L7246 was assembled by their experimental department at Manchester's Ringway Airport and first flew from there on 25 July 1939, with the second aircraft following on 26 May 1940. The Rolls-Royce engine was chosen by Avro and not stipulated by the Air Ministry as is sometimes claimed. The Handley Page HP.56, always intended as the backup to the Avro, was redesigned to take four engines on the orders of the Air Ministry in 1937 as the Vulture was already showing problems.

While the Manchester was designed with twin tails, the first production aircraft, designated the Mk I, had a central fin added and a total of 20 aircraft with this configuration were completed. They were succeeded by the Mk IA which reverted to the twin-fin system but used enlarged, taller fin and rudders mounted on a new tailplane with span increased from 22 ft (6.71 m) to 33 ft (10.06 m). This configuration was carried over to the Lancaster, except for the first prototype, which also used a central fin.

Avro built 177 and Metropolitan-Vickers completed 32 aircraft. Plans for Armstrong Whitworth and Fairey Aviation at Stockport/Ringway to build the Manchester were abandoned. Fairey's order for 150 Manchesters was replaced by orders for Halifaxes.