Development and production
In 1931 the Air Ministry released specification F7/30, calling for a modern fighter capable of a flying speed of 250 mph (400 km/h). R. J. Mitchell designed the Supermarine Type 224 to fill this role. The 224 was an open-cockpit monoplane with bulky gull-wings and a large, fixed, spatted undercarriage powered by the 600 horsepower (450 kW), evaporatively cooled Rolls-Royce Goshawk engine. It made its first flight in February 1934. Of the seven designs tendered to F7/30, the Gloster Gladiator biplane was accepted for service.
The Type 224 was a big disappointment to Mitchell and his design team, who immediately embarked on a series of "cleaned-up" designs, using their experience with the Schneider Trophy seaplanes as a starting point. This led to the Type 300, with retractable undercarriage and a wingspan reduced by 6 ft (1.8 m). This design was submitted to the Air Ministry in July 1934, but was not accepted. It then went through a series of changes, including the incorporation of a faired, enclosed cockpit, oxygen-breathing apparatus, smaller and thinner wings, and the newly developed, more powerful Rolls-Royce PV-XII V-12 engine, later named the "Merlin". In November 1934, Mitchell, with the backing of Supermarine's owner Vickers-Armstrong, started detailed design work on this refined version of the Type 300.
On 1 December 1934, the Air Ministry issued contract AM 361140/34, providing £10,000 for the construction of Mitchell's improved Type 300, design. On 3 January 1935, they formalised the contract with a new specification, F10/35, written around the aircraft. In April 1935, the armament was changed from two .303 in (7.7 mm) Vickers machine guns in each wing to four .303 in (7.7 mm) Brownings, following a recommendation by Squadron Leader Ralph Sorley of the Operational Requirements section at the Air Ministry.
On 5 March 1936,[nb 2] the prototype (K5054) took off on its first flight from Eastleigh Aerodrome (later Southampton Airport). At the controls was Captain Joseph "Mutt" Summers, chief test pilot for Vickers, who is quoted as saying "Don't touch anything" on landing.[nb 3] This eight-minute flight came four months after the maiden flight of the contemporary Hurricane.
K5054 was fitted with a new propeller, and Summers flew the aircraft on 10 March 1936; during this flight the undercarriage was retracted for the first time. After the fourth flight, a new engine was fitted, and Summers left the test-flying to his assistants, Jeffrey Quill and George Pickering. They soon discovered that the Spitfire[nb 4] was a very good aircraft, but not perfect. The rudder was oversensitive, and the top speed was just 330 mph (528 km/h), little faster than Sydney Camm's new Merlin-powered Hurricane. A new and better-shaped wooden propeller allowed the Spitfire to reach 348 mph (557 km/h) in level flight in mid-May, when Summers flew K5054 to RAF Martlesham Heath and handed the aircraft over to Squadron Leader Anderson of the Aeroplane & Armament Experimental Establishment (A&AEE). Here, Flight Lieutenant Humphrey Edwardes-Jones took over the prototype for the RAF. He had been given orders to fly the aircraft and then to make his report to the Air Ministry on landing. Edwardes-Jones' report was positive; his only request was that the Spitfire be equipped with an undercarriage position indicator. A week later, on 3 June 1936, the Air Ministry placed an order for 310 Spitfires, before the A&AEE had issued any formal report. Interim reports were later issued on a piecemeal basis.
The British public first saw the Spitfire at the RAF Hendon air-display on Saturday 27 June 1936. Although full-scale production was supposed to begin immediately, there were numerous problems that could not be overcome for some time, and the first production Spitfire, K9787, did not roll off the Woolston, Southampton assembly line until mid-1938.
In February 1936, the director of Vickers-Armstrong, Sir Robert MacLean, guaranteed production of five aircraft a week, beginning 15 months after an order was placed. On 3 June 1936, the Air Ministry placed an order for 310 aircraft, at a cost of £1,395,000. Full-scale production of the Spitfire began at Supermarine's facility in Woolston, but it quickly became clear that the order could not be completed in the 15 months promised. Supermarine was a small company, already busy building Walrus and Stranraer flying boats, and Vickers was busy building Wellington bombers.
The initial solution was to subcontract the work. Although outside contractors were supposed to be involved in manufacturing many important Spitfire components, especially the wings, Vickers-Armstrong (the parent company) was reluctant to see the Spitfire being manufactured by outside concerns, and was slow to release the necessary blueprints and subcomponents.
As a result of the delays in getting the Spitfire into full production, the Air Ministry put forward a plan that its production be stopped after the initial order for 310, after which Supermarine would build Bristol Beaufighters. The managements of Supermarine and Vickers were able to convince the Air Ministry that production problems could be overcome, and a further order was placed for 200 Spitfires on 24 March 1938. The two orders covered the K, L and N prefix serial numbers.
In mid-1938, the first production Spitfire rolled off the assembly line and was flown by Jeffrey Quill on 15 May 1938, almost 24 months after the initial order. The final cost of the first 310 aircraft, after delays and increased programme costs, came to £1,870,242 or £1,533 more per aircraft than originally estimated. A production aircraft cost about £9,500. The most expensive components were the hand-fabricated and finished fuselage at approximately £2,500, then the Rolls-Royce Merlin engine at £2,000, followed by the wings at £1,800 a pair, guns and undercarriage, both at £800 each, and the propeller at £350.
Manufacturing at Castle Bromwich, Birmingham
Spitfire Mk IIA, P7666, EB-Z, "Observer Corps", was built at Castle Bromwich, and delivered to 41 Squadron
on 23 November 1940.[nb 5]
In 1935, the Air Ministry approached Morris Motors Limited to ask how quickly their Cowley plant could be turned to aircraft production. In 1936 this informal request for major manufacturing facilities was turned into a formal scheme, known as the shadow factory plan, to boost British aircraft production capacity under the leadership of Herbert Austin. He was given the task of building nine new factories, and to supplement the existing British car manufacturing industry by either adding to overall capacity or increasing the potential for reorganisation to produce aircraft and their engines.
In 1938, construction began on the Castle Bromwich Aircraft Factory (CBAF), next to the aerodrome, and the installation of the most modern machine tools then available began two months after work started on the site. Although Morris Motors, under Lord Nuffield (an expert in mass motor-vehicle construction), managed and equipped the factory, it was funded by government money. By the beginning of 1939 the factory's original, estimated cost of £2,000,000 had more than doubled, and even as the first Spitfires were being built in June 1940, the factory was still incomplete, and suffered from personnel problems. The Spitfire's stressed-skin construction required precision engineering skills and techniques that were beyond the capabilities of the local labour force, and it required some time to re-train them. There were problems with management, who ignored Supermarine's tooling and drawings in favour of their own, and the workforce continually threatened strikes or "slow downs" until their demands for higher wages were met.
In spite of promises the factory would be producing 60 per week starting in April, by May 1940 Castle Bromwich had not yet built its first Spitfire. On 17 May, Minister of Aircraft Production Lord Beaverbrook telephoned Lord Nuffield and manoeuvred him into handing over control of the Castle Bromwich plant to his Ministry. Beaverbrook immediately sent in experienced management staff and workers from Supermarine and gave control of the factory to Vickers-Armstrong. Although it would take some time to resolve the problems, in June 1940, 10 Mk IIs were built; 23 rolled out in July, 37 in August, and 56 in September. By the time production ended at Castle Bromwich in June 1945, a total of 12,129 Spitfires (921 Mk IIs, 4,489 Mk Vs, 5,665 Mk IXs, and 1,054 Mk XVIs) had been built. CBAF went on to become the largest and most successful plant of its type during the 1939–45 conflict. As the largest Spitfire factory in the UK, by producing a maximum of 320 aircraft per month, it built 12,000 aircraft of this type, before its closure in 1945.
This Spitfire PR Mk XI (PL965) was built at RAF Aldermaston
in southern England.
During the Battle of Britain, the Luftwaffe made concerted efforts to destroy the main manufacturing plants at Woolston and Itchen, near Southampton. The first bombing raid, which missed the factories, came on 23 August 1940. Over the next month, other raids were mounted until, on 26 September 1940, both factories were destroyed, with 92 people killed and a large number injured. Most of the casualties were experienced aircraft production workers.
Fortunately for the future of the Spitfire, many of the production jigs and machine tools had already been relocated by 20 September, and steps were being taken to disperse production to small facilities throughout the Southampton area. To this end, the British government requisitioned the likes of Vincent's Garage in Station Square, Reading, which later specialised in manufacturing Spitfire fuselages, and Anna Valley Motors, Salisbury, which was to become the sole producer of the wing leading-edge fuel tanks for photo-reconnaissance Spitfires, as well as producing other components.
A purpose-built works, specialising in manufacturing fuselages and installing engines, was built at Star Road, Caversham in Reading. The drawing office in which all Spitfire designs were drafted was relocated to Hursley Park, near Southampton. This site also had an aircraft assembly hangar where many prototype and experimental Spitfires were assembled, but since it had no associated aerodrome no Spitfires ever flew from Hursley.
Four towns and their satellite airfields were chosen to be the focal points for these workshops: Southampton's Eastleigh Airport; Salisbury's High Post and Chattis Hill aerodromes;[nb 6] Trowbridge's Keevil aerodrome; and Reading's Henley and Aldermaston aerodromes.
An experimental factory at Newbury was the subject of a Luftwaffe daylight raid, but the bombs missed their target and hit a nearby school.
Completed Spitfires were delivered to the airfields on large Commer "Queen Mary" low-loader articulated lorries (trucks), there to be fully assembled, tested, then passed on to the RAF.
All production aircraft were flight tested before delivery. During the Second World War, Jeffrey Quill was Vickers Supermarine's chief test pilot, in charge of flight-testing all aircraft types built by Vickers Supermarine. He oversaw a group of 10 to 12 pilots responsible for testing all developmental and production Spitfires built by the company in the Southampton area.[nb 7] Quill devised the standard testing procedures which, with variations for specific aircraft designs, operated from 1938. Alex Henshaw, chief test pilot at Castle Bromwich from 1940, was placed in charge of testing all Spitfires built at that factory. He co-ordinated a team of 25 pilots and assessed all Spitfire developments. Between 1940 and 1946, Henshaw flew a total of 2,360 Spitfires and Seafires, more than 10% of total production.
Henshaw wrote about flight testing Spitfires:
After a thorough pre-flight check I would take off and, once at circuit height, I would trim the aircraft and try to get her to fly straight and level with hands off the stick ... Once the trim was satisfactory I would take the Spitfire up in a full-throttle climb at 2,850 rpm to the rated altitude of one or both supercharger blowers. Then I would make a careful check of the power output from the engine, calibrated for height and temperature ... If all appeared satisfactory I would then put her into a dive at full power and 3,000 rpm, and trim her to fly hands and feet off at 460 mph (740 km/h) IAS (Indicated Air Speed). Personally, I never cleared a Spitfire unless I had carried out a few aerobatic tests to determine how good or bad she was.
The production test was usually quite a brisk affair: the initial circuit lasted less than ten minutes and the main flight took between twenty and thirty minutes. Then the aircraft received a final once-over by our ground mechanics, any faults were rectified and the Spitfire was ready for collection.
I loved the Spitfire in all of her many versions. But I have to admit that the later marks, although they were faster than the earlier ones, were also much heavier and so did not handle so well. You did not have such positive control over them. One test of manoeuvrability was to throw her into a flick-roll and see how many times she rolled. With the Mark II or the Mark V one got two-and-a-half flick-rolls but the Mark IX was heavier and you got only one-and-a-half. With the later and still heavier versions, one got even less. The essence of aircraft design is compromise, and an improvement at one end of the performance envelope is rarely achieved without a deterioration somewhere else.
When the last Spitfire rolled out in February 1948, a total of 20,351 examples of all variants had been built, including two-seat trainers, with some Spitfires remaining in service well into the 1950s. The Spitfire was the only British fighter aircraft to be in continuous production before, during and after the Second World War.