The Supermarine Spitfire – 80 years

Posted on Tuesday 17th April 2012

THE SPITFIRE: IN THE NICK OF TIME

By Taylor Downing and Andrew Johnston.

Extracted from Battle Stations and reproduced by permission of Pen and Sword Books Ltd.

A work of genius, Reginald Mitchell’s new aircraft design was bold and entirely original. Its clean lines gave it the long, low appearance. The wings were very thin, to create the minimum drag, but they were extremely strong. They had a ‘D’ section leading edge of thick sheet metal and a complex spar built up from a series of box sections of decreasing size, fitting one inside the other. What Mitchell had produced was a jet-age airframe, at a time when much official thinking was still stuck in the era of the box-kite.

Breaking the mould is rarely an easy task. The new technology was regarded with suspicion by the defenders of the biplane and by many of the engineers who would have to mass produce it. Tried and trusted methods and materials would have to be discarded. As with the motor industry’s change from coach-building to welded steel, traditional crafts like woodworking, rigging and fabric skinning had to be replaced by the metal press, the power drill and the rivet gun. But Mitchell had the ability to inspire his team with his vision of the future and they set to work on the prototype airframe with a sense of growing excitement.

It was normal practice to design aircraft wings with straight edges, tapering towards the tip. In them Mitchell would have to fit the folding wheels and the four machine guns which the Air Ministry required any new fighter to carry. Mitchell’s wings would need the strength to accept two guns apiece, firing outside the prop. But then there was a change of policy. All new fighters were now to be fitted with eight guns, to inflict the maximum damage in the two or three seconds that it was estimated that accurate fire could be held on a target during airborne combat.

Mitchell had been considering the advantages of a wing with curved, rather than straight edges. It offered greater area than the more normal straight taper, but without the need to make the wing thicker. It also provided the extra room needed for more machine guns. The elliptical wing design which evolved on Mitchell’s drawing board would set the seal on the Spitfire’s success as a fighter, while at the same time creating its most beautiful and most identifiable feature.

Meanwhile, the new Rolls Royce engine had been through its testing and emerged with flying colours. Following the company policy of naming engines after birds of prey, it was christened the Merlin. In early 1936, the Merlin was fitted into the finished airframe of Mitchell’s prototype fighter, known simply by its works number K5054. On 5 March 1936, Mutt Summers, chief test pilot of the Vickers company, climbed into the tiny cockpit of the new fighter at Eastleigh Airfield, near Southampton. A small group of Supermarine staff, including R J Mitchell, had gathered to see the historic first flight of K5054. After a short run, the aircraft left the ground safely and its flying career began.

The very first Spitfire, K5054, in flight.

After its initial flights had proved satisfactory, K5054 - now named the ‘Spitfire’ - was passed to Supermarine test pilot Jeffrey Quill. He soon developed a conviction that the aircraft was destined for great things, but it clearly had its faults. The first problem was its speed. At 330 mph it was fast, but not as fast as Mitchell - or the Air Ministry - had hoped. The manual pump for raising the wheels was awkward to operate and the forward vision was very poor on the ground. The narrow wheel track also made it unstable on the uneven grass airfields which it would have to operate from. Another problem was the control surfaces.

By May 1936, a change of propeller and other detailed improvements, had raised the Spitfire’s speed to 348 mph. Mitchell had wanted 350, but it was enough. The prototype was passed to the Air Ministry for testing and, although its fighting abilities were still unknown, an order was placed for 310 Spitfires on 3 June 1936. Six hundred Hurricanes were also ordered. With the threat from Germany becoming more obvious every day, it was not a moment too soon. But the fact that twice as many Hurricanes had been ordered was an indication of problems ahead. The Spitfire had still not been fitted with guns and a number of senior members of the RAF and the Air Ministry had serious doubts about its suitability. Within the company, there were also worries. Many of the people working with Mitchell seriously doubted if Supermarine could cope with building more than 300 examples of such an advanced machine.

To produce, in sheet metal, the curved shapes of Mitchell’s design would involve elaborate construction techniques. Jigs would have to be set up as templates, within which the airframe could be built to exact dimensions. The wings, in particular, would prove a nightmare to mass produce. In the days of fabric covering, the material could be stretched to fit round awkward shapes involving compound curves, like wing tips. Sheet metal will bend easily, but in one direction only. So fixing a panel to the curved top of a wing is simple. But try also bending that curved sheet round to form a pointed wing tip and the problems start. The metal refuses to co-operate. It creases and folds up like a squashed tin can – it may even split, to relieve the stresses produced. The untidy solution is to make up the compound curve from small, overlapping segments. The best method is to hammer or press the metal into shape.

As the exhausting programme of testing continued, Mitchell devoted all his remaining energy to the project. But his health was failing rapidly. Medical tests established that an operation had not halted the spread of his cancer and he knew he had very little time left. He was now in constant pain as he fought to finish his task. The strain had taken its toll; he was barely forty, yet photographs show the face of a man of sixty. As the tests continued, Jeffrey Quill became more and more certain that the Spitfire was a vitally important aircraft. A close bond developed between him and Mitchell as they collaborated on the smallest details of performance. On 18 June 1936, the Spitfire was demonstrated to the press. Although the flight was cut short by engine problems, the headlines were ecstatic. ‘The fastest military aircraft in the world’ proclaimed The Times. It was a publicity triumph for Mitchell and Supermarine, but behind the scenes, progress was painfully slow. It was another six months before the prototype Spitfire began weapons testing and there was no hope of getting into production in the near future. Mitchell’s declining health meant that he was seen less often at Eastleigh and the project began to slip badly behind schedule. By March 1937, a whole year after its first flight, K5054 remained the only Spitfire in existence. On 22 March, an engine failure occurred in flight. Fortunately, the pilot was able to crash-land in open country, with very little damage to the airframe, but it further delayed the testing programme.

The international situation was rapidly worsening. An emergency was fast becoming a crisis and on 3 May 1938, the British government increased the Spitfire order by 200 to 510. The aircraft was still an unknown quantity, but – apart from the Hurricane – it was the only hope of avoiding going to war with a fleet of hopelessly outclassed biplanes. Twelve days later, on 15 May 1938, the first production aircraft was test flown. Deliveries were supposed to have begun in October 1937 and the original contract for 310 was due for completion by March 1939.

Duxford, north of London, was the first fighter station to receive the new Spitfires.

It was not possible to concentrate all the Spitfire production at the Supermarine factory in Southampton. The limited workshop space meant that work would have to be sub-contracted out. It was decided to build the fuselages in-house and to sub-contract wing production to other companies. Final assembly would be done by Supermarine. This system got off to a very shaky start. The wings were probably the most complicated section to manufacture and the subcontracted work was soon well behind schedule. Wingless fuselages began to accumulate in rows at the Supermarine works, while frantic efforts were made to sort out the problems. An official inspection of Supermarine during mid 1938, found seventy-eight fuselages in the factory, but only three sets of wings.

As the delays and production problems mounted up, the Air Ministry had become thoroughly disenchanted with the aircraft. In June 1939, it was proposed to call a halt to Spitfire production, once the contract for 510 had been completed. There was talk of Supermarine being given other designs to build. The bureaucrats tended to see the Spitfire as a problem, rather than an asset. Future development possibilities were ignored and it would take the Battle of Britain to show how wrong they were.

An RAF fighter pilot making a scramble to his Spitfire.

Meanwhile, Spitfire production had finally got into its stride and by the time war broke out in September 1939, Supermarine were delivering ten aircraft a week and the RAF had just over 300 machines ready for action. A large new factory was established at Castle Bromwich near Birmingham. It was run by the head of the Austin Motor Company, Lord Nuffield. His brief was to mass produce Spitfires, using his experience as a mass producer of cars. But cars are not aircraft and working on a design as sophisticated as the Spitfire was not the ideal training ground for motor mechanics.

By September 1939, they had not produced a single finished aircraft. In May 1940 Britain’s new Prime Minister, Winston Churchill, created the Ministry of Aircraft Production. Its first minister was Lord Beaverbrook – a newspaper proprietor with no experience of aircraft production, but boundless energy and determination. His first priority was to sort out the chaotic situation at Castle Bromwich. Control of the factory was passed to Vickers and after a few heads had been knocked together and new organization put in place, production got underway.

Soon the chief test pilot at Castle Bromwich, Alex Henshaw, was hard put to keep up with the output. Each new Spitfire had to be test flown, before it could be delivered for operational service. Although they were all identical in theory, many needed slight ‘tuning’ of the flight controls before they would fly straight and level. The testing could be very dangerous work and Henshaw experienced several engine failures in flight – and survived some spectacular accidents. But, like Jeffrey Quill, he was inspired by the flying qualities of Mitchell’s creation and acquired a reputation for performing seemingly impossible feats with the aircraft. When Winston Churchill came to inspect the factory, Henshaw’s dazzling display of low-level aerobatics left him in no doubt that the Spitfire was a winner.

A Spitfire IX.

Development and versions

For the Spitfire, the Battle of Britain was only the beginning. Joe Smith’s view that the design should be developed rather than replaced, was proved right. Spitfires were armed with cannon for ground attack missions, they were fitted with racks to carry bombs and rockets and a maritime version – the Seafire – was designed with folding wings, for use on aircraft carriers. When Spitfire production finally ended in 1949, more than 22,000 machines had been produced – not bad for a design which came close to being strangled in its infancy by official ‘red tape’.

It’s hard to say whether the final Spitfire, the Mark 24, was in any sense the same aircraft which had fought the Battle of Britain. It kept the name, but its engine was twice as powerful, it weighed about a ton and a half more, and was 100 mph faster. It had changed from a finely balanced rapier – described by one over-confident German pilot as a ‘pretty little toy’ – into a fearsome broadsword. Its armour-piercing cannon could demolish a locomotive, or slice the wing off an aircraft in a split-second. The big engine and big guns were revealed by tell-tale bulges in the sleek outline. A tear-drop canopy and low back, gave it an entirely different shape. Its huge, five-bladed propeller was efficient, but ungainly, and required an equally oversized tail fin and rudder, to counteract its torque. But, through most of the changes, Mitchell’s wing design survived, very much as he had conceived it in the mid-1930s. Many Spitfires lost their pointed wing tips, but the ‘clipped’ wing still retained the original’s structure – if not its purity of line. Only in the final versions, were the last vestiges of Mitchell’s original design replaced. The Spitfire became like the woodman’s favourite axe – six new handles and two new blades, but still the best axe he’d ever had. The machine changed beyond recognition, but the name survived because nobody wanted to say goodbye to the Spitfire. It represented Britain’s finest hour and, at a critical moment in history, it had proved to be the best tool for a tough job.

The Spitfire finally passed into history with the coming of the Jet Age. But not before a MkXIV managed to become the first RAF fighter to shoot down a German Me 262 jet in combat. The RAF flew its last operational Spitfire mission on 1 April 1954 and the type was officially withdrawn from service in 1957. The delta-winged, supersonic fighters that replaced the Spitfire, owed much of their success to the work of Reginald Mitchell. His vision of the future produced an airframe in 1936, that would not look unfamiliar to a present-day aircraft engineer. The brave young Spitfire pilots who fought and won the Battle of Britain have rightly earned their place in the Nation’s Roll of Honour.

A pre-war Spitfire of 19 Squadron. The aircraft pictured was the ninth production Spitfire to go into service.

Cockpit of an early Spitfire with awkward hydraulic hand pump used to raise the undercarriage.

Reginald Joseph Mitchell CBE FRAeS (20 May 1895 – 11 June 1937) joined the Supermarine Aviation Works at Southampton in 1917. He advanced quickly within the company and when it was taken over by Vickers in 1928, one of the conditions was that Mitchell was kept on as designer. He designed twenty-four aircraft between 1920 and 1936 but is best known for his work on the Supermarine Schneider Trophy series of racing aircraft which culminated in the S.6B and the Spitfire. In May, Mitchell returned from visiting Europe's leading bowel cancer specialist, who confirmed that his illness was terminal. He was just 42 years old. The loss of its leader was a devastating blow to the Spitfire team. But the crucial years between his cancer operation and his early death had seen his design process.

As the war progressed so did Mitchell’s fighter until it almost become unrecognisable from the Battle of Britain version.

Of further interest...

The Supermarine Spitfire – 80 years

Further Reading

Of further interest...

Here Comes the Luftwaffe

Australia's First Blood and the Battle of Britain

Battle of Britain Day – 15 September 1940

Australia's Few and the Battle of Britain