The Avro 679 Manchester' was a British twin-engine medium bomber developed and manufactured by the Avro aircraft company in the United Kingdom. While not being built in great numbers, it was the forerunner of the famed and vastly more successful four-engined Avro Lancaster, which would become one of the most capable strategic bombers of the Second World War.
Avro designed the Manchester in conformance with the requirements laid out by the British Air Ministry Specification P.13/36, which sought a capable medium bomber with which to equip the Royal Air Force (RAF) and to replace its inventory of twin-engine bombers, such as the Armstrong Whitworth Whitley, Handley Page Hampden and Vickers Wellington. Performing its maiden flight on 25 July 1939, the Manchester entered squadron service in November 1940, just over twelve months after the outbreak of the war.
Operated by both RAF and the Royal Canadian Air Force (RCAF); primarily as a result of its underdeveloped, underpowered and unreliable engines, the Manchester came to be regarded as an operational failure. Production was terminated in 1941; however, the Manchester was redesigned into a four-engined heavy bomber, powered by the Merlin engine instead, which became known as the Lancaster.
The Manchester has its origins in a design produced by Avro in order to fulfil the British Air Ministry's Specification P.13/36. This was the same specification to which Handley Page had also produced their initial design for what would become the Halifax bomber. Issued in May 1936, Specification P.13/36 called for a twin-engine monoplane "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. Additionally, it had to feature provisions to conduct catapult assisted takeoffs, which would permit the carriage of the maximum payload, was also a stated requirement, although this provision was explicitly removed in July 1938. The envisioned cruising speed of the bomber was to be a minimum of 275 mph at 15,000 feet. The Air Ministry had expectations for an aircraft of similar weight to the B.1/35 specification, but being both smaller and faster.
Avro had already started work on a corresponding design prior to having received a formal invitation to tender. The company was in competition with Boulton Paul, Bristol, Fairey, Handley Page and Shorts. Vickers also had its Warwick, which was outfitted with Napier Sabre engines, but eventually chose against tendering it. In early 1937, both the Avro design and the rival Handley Page HP.56 were accepted and prototypes of both ordered; but in mid-1937, the Air Ministry exercised their rights to order the types "off the drawing board". This skipping of the usual process was necessary due to the initiation of a wider expansion of the RAF in expectation of large scale war in Europe. From 1939, it was expected that the P.13/36 would begin replacing the RAF's existing medium bombers, such as the Armstrong Whitworth Whitley, Handley Page Hampden and Vickers Wellington.
The Avro design used the Rolls-Royce Vulture 24-cylinder X-block engine, which was 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 Vulture 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 Vulture engine was chosen by Avro and not stipulated by the Air Ministry as is sometimes claimed;[N 1] other engine layouts considered included the use of two Bristol Hercules or Bristol Centaurus radial engines. 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, when the Vulture was already showing problems.[N 2]
While the Manchester was designed with a twin tail, the first production aircraft, designated the Mk I, had a central fin added and twenty aircraft like this were built. 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 and was a converted, unfinished Manchester. Avro constructed 177 Manchesters while 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 multiple orders for the Handley Page Halifax.
The Avro Manchester was designed with great consideration for ease of manufacture and repair. The fuselage of the aircraft comprised longitudinal stringers or longerons throughout, over which an external skin of aluminium alloy was flush-riveted for a smooth external surface. The wings were of a two-spar construction, the internal ribs being made of aluminium alloys; fuel was contained with several self-sealing fuel tanks within the wings. The tail shared a similar construction to the wing, featuring a twin fin-and-rudder configuration that provided good vision for the dorsal gunner.
The cockpit housed the pilot and fighting controller's position underneath the canopy, and these two crew members were provided with all-round vision. The navigator was seated aft of the fighting controller and the position included an astrodome for use of a sextant. The bomb aimer's station was housed inside the aircraft's nose, beneath the forward turret and bomb aiming was conducted using optical sights housed in this compartment. For crew comfort on lengthy missions, a rest area was situated just to the rear of the main cabin.
The aircraft's undercarriage was entirely retractable via hydraulic systems, or in an emergency, a backup air system. The doors to the bomb bay were also operated by these systems, an additional safety measure was installed to ensure that the bombs could not be dropped if the doors were shut. The bombs were housed on bomb racks inside the internal bomb bay, and other armaments such as torpedoes could also be fitted. All fuel tankage was located in the wings in order to keep the fuselage free to accommodate more armaments in the bomb bay which covered nearly two-thirds of the underside of the fuselage.
Vulnerable parts of the aircraft were armoured; the pilot had additional armour and bulletproof glass and an armoured bulkhead was to the rear of the navigator's position. The Manchester featured three hydraulically-operated turrets, located in the nose, rear and mid-upper fuselage; the addition of a ventral turret directly behind the bomb bay had been considered and tested on the second prototype, but did not feature on production aircraft.[N 3] Access to all crew stations was provided by a walkway and crew positions had nearby escape hatches.
The Manchester was powered by a pair of Vulture engines; in service these proved to be extremely unreliable. Aviation author Jon Lake stated of the Vulture: "The engine made the Manchester mainly notable for its unreliability, poor performance, and general inadequacy to the task at hand" and attributed the aircraft's poor service record to the engine troubles.
- I was one of the six original pilots to have flown with the first Manchester squadron. That was a disaster. The aircraft itself, the airframe, had many shortcomings in equipment in the beginning, but as we found out Avro were excellent in doing modifications and re-equipping the aeroplane. The engines never were and never did become reliable. They did not give enough power for the aeroplane, so we ended up with two extremely unreliable 1,750 hp engines having to haul a 50,000-pound aircraft. We should really have had 2,500 hp engines. You felt that if you'd lost one, that was it, you weren't coming home. It didn't matter if you feathered the propeller or not. There was only one way you went and that was down. I have seen an aircraft doing a run up on the ground and have two pistons come right out through the side of the engine. The original bearings were made without any silver as an economy measure, so they weren't hard enough. The bearings would collapse the connecting rod and the piston would fling out through the side of the engine and bang! Your engine just destroyed itself.