Supermarine Spitfire – prototypes and development

The Supermarine Spitfire is probably the most famous aircraft of the Second World War. By the time production ended, over 20,000 Spitfires had been built, and the aircraft had changed engine, its loaded weight had doubled and its maximum speed increased by 90 miles per hour. Despite these changes, the Spitfire of 1945 is instantly recognisable as part of the same family as the prototype of 1936.

The family resemble can be traced even further back, to the S series of racing seaplanes, designed by Reginald J Mitchell in the late 1920s for the Schneider Trophy. In 1931 one S.6 seaplane won the trophy outright, while another raised the world air speed record to 407 mph. However, the Spitfire we know did not develop directly from the seaplanes.

Spitfire Prototype
K5054

Between them came the Supermarine Type 224. This aircraft was developed in response to an Air Ministry specification (F.7/30), issued in 1931. This called for a fighter to replace the Bristol Bulldog. Mitchell produced a monoplane with a low gull wing, open cockpit and fixed landing gear. It used a Rolls-Royce Goshawk engine, capable of producing 660 hp. Neither Mitchell nor the Air Ministry were entirely satified with this aircraft, and the contest was won by the Gloster Gladiator, which would become the last biplane fighter used by the R.A.F.

Mitchell continued to work on his fighter design. The Type 224 developed into the Type 300. This aircraft also used the Rolls-Royce Goshawk, but it was at this stage that the familiar Spitfire wings first appeared. The Type 300 was designed around an Air Ministry specification of 1934 (F.5/34), but the ministry was still not interested. It was only when the board of Vickers, who by now owned Supermarine, matched Mitchell’s aircraft with the new Rolls-Royce PV 12 engine (more famous as the Merlin) that the Air Ministry became interested. On 3 January 1935 Supermarine were given a contract to produce a prototype of the new design. Specification F.37/34 was written to describe the new aircraft (at about the same time, specification F.36/34 was based around the new Hawker Hurricane).

Work on the prototype took over a year. It was during this process that R. J. Mitchell showed his genius, refining the initial design of the Type 300 until the almost hand-built prototype was ready. The new aircraft was a very modern design. After a series of arguments within the Air Ministry it was armed with eight .303 Browning machine guns. It had an all-metal stressed-skin and metal wings, with fabric covered control surfaces. The only out-dated element of the aircraft was its two blade fixed pitch wooden propeller.

In the mid 1930s it was not at all clear how combat between monoplane fighters would develop. The Spitfire and the Hurricane represented two alternative possibilities. The Hurricane was fast, but its main strength was its manoeuvrability and turning circle. Likewise, although the Spitfire was agile and manoeuvrable, its main strength was speed. It would soon become clear that Mitchell had followed the correct route (another alternative led to the turret armed Boulton Paul Defiant).

The prototype was built around a Merlin “C” engine, providing 990 hp. It first flew on 5 March 1936 in the hands of Vicker’s chief test pilot, Captain J “Mutt” Summers. The aircraft was fast, capable of close to 350 mph in level flight. Only four months earlier the Hawker Hurricane had seemed astonishingly quick at 315 mph, while the contemporary Bf 109B could only reach 298 mph.  

The Spitfire is often described as being a small aircraft – one German visitor dismissed it as a “toy”. In fact it was four feet wider and 18 inches longer than its most famous opponent, the Bf 109. If the original production version – the Bf 109C - had still been in use in 1940, then the battle between them would have been very one-sided. It is a tribute to Mitchell’s design skills that the first version of the Spitfire was an equal for the third major version of the Bf 109.

Mitchell was present to watch the maiden flight of the Spitfire. However, his health was not robust. He had had a brush with cancer in 1933, and in 1937 it returned. On 11 June 1937 Mitchell died, aged only 42. By the time he died, the Spitfire was already famous. It had made its public debut on 27 June 1936 at the Royal Air Force Pageant at Hendon. Earlier in the month (3 June), Supermarine had received an order for 310 production Spitfires.

Mitchell was succeeded in charge of the Spitfire project by Joseph Smith, who had been the chief draughtsman on the project. It was Smith who would evolve the Spitfire through over twenty models and six years of war, making sure that it would always be able to respond to any new German threat.

Prototypes - Mk I - Mk II - Mk III - Mk V - Mk VI - Mk VII - Mk VIII - Mk IX - Mk XII - Mk XIV - Mk XVI - Mk XVIII - Mk 21 to 24 - Photo Reconnaissance Spitfires - Spitfire Wings - Timeline

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