The Spitfire was designed by R. J. Mitchell who was chief designer at Supermarine Aviation Works, a subsidiary of Vickers-Armstrongs. He continued to refine the design until his death from cancer in 1937, whereupon his colleague Joseph Smith became chief designer. Its elliptical wing had a thin cross-section, allowing a higher top speed than the Hawker Hurricane and many other contemporary designs.
The distinctive silhouette imparted by the wing planform helped the Spitfire to achieve legendary status during the Battle of Britain. There was, and still is, a public perception that it was the RAF fighter of the Battle, in spite of the fact that the more numerous Hurricane shouldered a great deal of the burden against the potent Luftwaffe. Much loved by its pilots, the Spitfire saw service throughout the whole of the Second World War, in most theatres of war, in several roles and in many different variants. The Spitfire was to continue to serve as a front line fighter and in secondary roles for several air forces well into the 1950s.
The Spitfire will always be compared to its main adversary, the Messerschmitt Bf 109: both were among the finest fighters of their day and followed similar design philosophies of marrying a small, streamlined airframe to a powerful liquid-cooled inline engine.
R. J. Mitchell's 1931 design to meet Air Ministry specification F7/30 for a new and modern fighter capable of 250 mph, the Supermarine Type 224, resulted in an open-cockpit monoplane with bulky gull-wings and a large fixed, spatted undercarriage powered by the 600 horsepower evaporative-cooled Rolls-Royce Goshawk engine. This made its first flight in February 1934. This aircraft 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. The F7/30 design accepted was the biplane Gloster Gladiator.
Mitchell had already begun working on a new aircraft, designated Type 300, based on the Type 224. With a retractable gear and 6 ft shorter wingspan, the aircraft was submitted to the Air Ministry in July 1934, but again was not accepted. The design evolved through a number of changes, including an enclosed cockpit, oxygen breathing-apparatus, even smaller and thinner wings, and the newly-developed and much more powerful Rolls-Royce PV-XII engine, later named the Merlin. In November 1934, Mitchell, with the backing of Supermarine's owner, Vickers-Armstrongs, started detailed design work on the Type 300. The Air Ministry issued a contract AM 361140/34 on 1 December 1934, providing £10,000 for the construction of Mitchell's "improved F.7/30 design". On 3 January 1935, the Air Ministry formalised the contract and a new Specification F.10/35 was written around the aircraft.
Just 15 months later, after several major design changes and refinements, on 5 March 1936 the sleek new prototype (K5054) took off on its first flight from Eastleigh Aerodrome (later Southampton Airport). At the controls was Captain J. "Mutt" Summers, (Chief Test Pilot for Vickers (Aviation) Ltd.), who was reported in the press as saying "Don't touch anything" on landing. This flight was just four months after the maiden flight of the contemporary Hawker Hurricane.
Testing continued until 26 May 1936, 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).
The Air Ministry placed an order for 310 aircraft on 3 June 1936, before any formal report had been issued by the A&AEE, interim reports being 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 which could not be overcome for some time and the first production Spitfire K9787 didn't roll off the Woolston, Southampton assembly line until mid-1938. The first and most immediate problem was that the main Supermarine factory at Woolston was already working at full capacity fulfilling orders for Walruses and Stranraers. Although outside contractors were supposed to be involved in manufacturing many important Spitfire components, especially the wings, Vickers-Armstrongs (the parent company) were extremely reluctant to see the Spitfire being manufactured by outside concerns and were slow to release the necessary blueprints and sub-components. As a result of the innumerable delays in getting the Spitfire into full production, the Air Ministry put forward a plan that production of the Spitfire be stopped after the initial order for 310, after which Supermarine would build Bristol Beaufighters. The managements of Supermarine and Vickers were able to persuade the Air Ministry that the problems could be overcome and further orders were placed for 200 Spifires on 24 March 1938 (the two orders covered the K, L and N prefix serial numbers).
The word dates from Elizabethan times and refers to a particularly fiery, ferocious type of person. The name had previously been used unofficially for Mitchell's earlier F.7/30 Type 224 design. Mitchell is reported to have said that it was "just the sort of bloody silly name they would choose", possibly an oblique reference to the Type 224.
Mitchell's design aims were to create a well balanced high performance fighter aircraft which would be able to fully utilise the power of the Merlin engine and, at the same time would be relatively easy to fly. To that end his design team developed an airframe which, for its day, was complex.
The exceptionally well streamlined semi-monocoque duralumin fuselage featured a large number of compound curves and was built up from a skeleton of 19 frames, starting from the main engine bulkhead, or frame number one. Aft of the engine bulkhead were five half frames to accommodate the fuel tanks and cockpit. From the seventh, which was the frame to which the pilot's seat and (later) armour plating was attached, to the 15th, which was mounted at a forward angle just forward of the tailfin, the frames were oval in shape, each reducing slightly in size, and had numerous holes drilled through them to lighten the structural weight as much as possible without weakening them. Frame 16 formed a double bulkhead with frame 17, which was extended to form the main spar of the vertical fin; frame 18 formed the secondary spar. Just aft of this the 19th frame formed the rudder post. A combination of 14 longitudinal stringers and two main longerons helped form a light but rigid structure to which sheets of alclad stressed skinning were attached. There was plenty of room to later fit camera equipment and fuel tanks.
The skin of the fuselage, wings and tailplane was attached with rivets, and in critical areas, such as the wing forward of the main spar where an uninterrupted airflow was required, flush rivets were used. In some areas, such as the rear of the wing, the top was riveted and the bottom fixed by woodscrews into sections of spruce; later pop-riveting would be used for these areas. From 1943 on, flush riveting was used throughout the entire airframe; the first version of the Spitfire to change to flush riveting was the Mk XII closely followed by all Castle Bromwich built Mk IXs. At first the ailerons, elevators and rudder were fabric covered. However, once combat experience showed that the fabric covered ailerons became impossible to use at high speeds the fabric was replaced with a light-alloy, enhancing control throughout the speed range.
It has been suggested that Mitchell copied the wing shape of the Heinkel He 70. Mitchell's aerodynamicist, Beverley Shenstone, however, has pointed out that the He 70 was designed to fulfill a completely different role and that other aircraft also had elliptical wings. The Spitfire wing was much thinner with a completely different section. As a practical engineer Mitchell was fully aware of the efficiency of the elliptical wing, as were Siegfried and Walter Günther, who designed the Heinkel.
A design aspect of the wing which contributed greatly to its success was an innovative spar boom design, made up of five square concentric tubes which fitted into each other. Two of these booms were linked together by an alloy web creating a lightweight and very strong main spar. The undercarriage legs were attached to pivot points built into the inner, rear of the main spar and retracted outwards and slightly backwards into wells in the non-load carrying wing structure. The narrow undercarriage track was considered to be an acceptable compromise as it allowed the landing impact loads to be transmitted to the strongest parts of the wing structure.
Ahead of the spar, the thick-skinned leading edge of the wing formed a strong and very rigid D-shaped box, which took most of the wing loads. At the time the wing was designed this D-shaped leading edge was intended to house steam condensers for the evaporative cooling system intended for the PV XII. The constant problems with the evaporative system in the Goshawk led to the adoption of a 100% glycol cooling system, together with a new radiator duct design, devised by a Fredrick Meredith of the RAE at Farnborough, which used to cooling air to generate thrust, greatly reducing the drag produced by the radiators. This meant that the leading edge structure lost its function as an evaporator, but it was later to become very useful as it was able to be adapted to house integral fuel tanks of various sizes.
The wing section used was a NACA 2200 series which had been adapted to create a thickness to chord ratio of 13% at the root reducing to 6% at the tip. A dihedral of six degrees was adopted to give increased lateral stability.
Another feature of the wing was its washout. The trailing edge of the wing twisted slightly upward along its span, the angle of incidence decreased from +2 degrees at its root to -1/2 degree at its tip. This caused the wing roots to stall before the tips, reducing tip stall that may have resulted in a spin. This washout was first featured in the wing of the Type 224 and became a consistent feature in subsequent designs leading to the Spitfire. In a tight turn the disturbance of the slipstream near the wing-root caused a distinctive "juddering" through the control column and fuselage skin, warning the pilot that the Spitfire was nearing a stall. This was described in the pilot's manual:
If the stick was pulled back too far on the Spitfire in a tight turn, the aircraft could stall rather violently, flick over on to its back, and spin. Knowledge of this undoubtedly deterred Spitfire pilots from tightening their turns when being chased, particularly if they were inexperienced. The pilot's task was not made easier by the fact that the elevator was exceedingly sensitive; during tight turns or loops in bumpy conditions, movements to the pilot's body due to bumps were liable to cause movement of the controls and large and sudden fluctuations in g load. The very effective elevator, coupled with the instability in pitch of the Spitfire made it very easy for the pilot to greatly exceed the 10 g limit imposed on the airframe and the wings would certainly fail if this occurred.
The elliptical wing was able to reach a safe Mach number of 0.83 and maximum of 0.86 without encountering the problem of Mach-induced aileron flutter, a phenomenon which continued to blight many newer designs.
At first the complexity of the wing design, especially the precision required to manufacture the vital spar and leading edge structures, caused some major hold-ups in the production of the Spitfire. This was amplified when the work was put out to sub-contractors, most of whom had never dealt with metal-structured, high-speed aircraft. Over time, however, these problems were overcome and thousands of these wings, of six basic types, were built. One flaw in the thin-wing design of the Spitfire manifested itself when the aircraft was brought up to very high speeds. When the pilot attempted to roll the aircraft at these speeds, the aerodynamic forces on the ailerons were enough to twist the entire wingtip in the direction opposite of the aileron deflection (much like the way an aileron trim tab will deflect the aileron itself). This so-called aileron reversal resulted in the Spitfire rolling in the opposite direction to the control column input and occurred at much lower airspeeds than on other contemporary designs. In March 1943, R.A.E. noted that at 400 mph I.A.S., roughly 65% of aileron power was lost due to wing twist. The new wing of the Spitfire F Mk 21 and its successors was designed to help alleviate this problem.
The ellipse also served as the design basis for the Spitfire’s fin and tailplane assembly, once again exploiting the shape’s favourable aerodynamic characteristics. Both the elevators and rudder were shaped so that their centre of mass was shifted forward thus reducing control surface flutter. The longer noses and greater propeller wash resulting from larger engines in later models necessitated increasingly larger vertical and, later, horizontal tail surfaces to compensate for the altered aerodynamics, culminating in those of the Mk 22/24 series which were 25% larger in area than those of the Mk I.
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 another purpose built site at Hursley Park, near Southampton. This site also had an aircraft assembly hangar, with its associated aerodrome, where many of the prototype and experimental Spitfires were assembled and flown.
Four towns and their satellite airfields were chosen to be the focal points for these workshops. They were:
Henshaw noted on the development of the Spitfire: 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 the Spitfire 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 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 were 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 continual production before, during, and after the Second World War.
The Spitfire achieved legendary status during the Battle of Britain but continued to play increasingly diverse roles throughout World War II and beyond, often in air forces other than the RAF. The Spitfire became the first high-speed photo-reconnaissance aircraft to be operated by the RAF. Sometimes unarmed, they flew at high, medium and low altitudes, often ranging far into enemy territory to closely observe the Axis powers and provide an almost continual flow of valuable intelligence information throughout the war. In 1941 and 1942 PRU Spitfires provided the first photographs of the Freya and Würzburg radar systems and, in 1943, helped confirm that the Germans were building the V1 and V2 Vergeltungswaffe ("vengeance weapons") by photographing Peenemünde, on the Baltic Sea coast of Germany.
In the Mediterranean the Spitfire blunted the heavy attacks on Malta by the Regia Aeronautica and Luftwaffe and, from early 1943, helped pave the way for the Allied invasions of Sicily and Italy. Over the Northern Territory of Australia RAAF Spitfires helped defend the port city of Darwin against air attack by the Japanese Naval Air Force.
Beginning in late 1943, high-speed diving trials were undertaken at Farnborough to investigate the handling characteristics of aircraft travelling at speeds near the sound barrier (i.e. the onset of compressibility effects). Because it had the highest limiting Mach number of any aircraft at that time, a Spitfire XI was chosen to take part in these trials. Due to the high altitudes necessary for these dives, a fully feathering Rotol propeller was fitted to prevent overspeeding. It was during these trials that EN409, flown by Squadron Leader J. R. Tobin, reached 606 mph (975 km/h, Mach 0.891) in a 45 degree dive. In April 1944 the same aircraft suffered engine failure in another dive while being flown by Squadron Leader A. F. Martindale, when the propeller and reduction gear broke off. Martindale successfully glided the Spitfire 20 miles (32 km) back to the airfield and landed safely.
On 5 February 1952, a Spitfire 19 of No. 81 Squadron RAF based in Hong Kong reached probably the highest altitude ever achieved by a Spitfire. The pilot, Flight Lieutenant Ted Powles, was on a routine flight to survey outside air temperature and report on other meteorological conditions at various altitudes in preparation for a proposed new air service through the area. He climbed to 50,000 feet (15,240 m) indicated altitude, with a true altitude of 51,550 feet (15,712 m). The cabin pressure fell below a safe level, and in trying to reduce altitude, he entered an uncontrollable dive which shook the aircraft violently. He eventually regained control somewhere below 3,000 feet (900 m) and landed safely with no discernible damage to his aircraft. Evaluation of the recorded flight data suggested that, in the dive, he achieved a speed of 690 mph (1,110 km/h, Mach 0.94), which would have been the highest speed ever reached by a propeller-driven aircraft.
The critical Mach number of the Spitfire's original elliptical wing was higher than the subsequently-used laminar-flow-section, straight-tapering planform wing of the follow-on Supermarine Spiteful, Seafang and Attacker, illustrating that Reginald Mitchell's thoughtful and practical engineering approach to the problems of high speed flight had paid off handsomely.
As its designer, R.J. Mitchell will forever be known for his most famous creation. However, the development of the Spitfire did not cease with his premature death in 1937. Mitchell only lived long enough to see the prototype Spitfire fly. Subsequently a team led by his Chief Draughtsman, Joe Smith, would develop more powerful and capable variants to keep the Spitfire current as a front line aircraft. As one historian noted: "If Mitchell was born to design the Spitfire, Joe Smith was born to defend and develop it."
There were 24 marks of Spitfire and many sub-variants. These covered the Spitfire in development from the Merlin to Griffon engines, the high speed photo-reconnaissance variants and the different wing configurations. The Spitfire Mk V was the most common type, with 6,487 built, followed by the 5,656 Mk IX airframes produced. Different wings, featuring a variety of weapons, were fitted to most marks; the A wing used eight .303 machine guns, the B wing with four .303 machine guns and two 20 mm Hispano cannon, and the C or Universal Wing which could mount either four 20 mm cannon or two 20 mm and four .303 machine guns. As the war progressed, the C wing became more common. The final armament variation was the E wing which housed two 20 mm cannon and two .50 inch Browning heavy machine guns.
Supermarine developed a two-seat variant to be used for training and was known as the T Mk VIII, but no orders were received for this aircraft and only one example was ever constructed (identified as N32/G-AIDN by Supermarine). However, in the absence of an official two-seater variant, a number of airframes were crudely converted in the field. These included an RAF Mk VB in North Africa, where a second seat was fitted instead of the upper fuel tank in front of the cockpit; although it was not a dual-control aircraft and is thought to have been used as the squadron "run-about." The only unofficial two-seat conversions that were fitted with dual-controls were a small number of Russian lend/lease Mk IX aircraft. These were referred to as Mk IX UTI and differed from the Supermarine proposals by using an inline "greenhouse" style double canopy rather than the raised "bubble" type of the T Mk VIII.
In the postwar era, the idea was revived by Supermarine and a number of two-seat Spitfires were built by converting old Mk IX airframes with a second "raised" cockpit featuring a bubble canopy. These TR9 variants were then sold to the Indian Air Force and a total of nine to the Irish Air Corps. Today, only a handful of the trainers are known to exist, including both the T Mk VIII and a T Mk IX based in the U.S., and the "Grace Spitfire" ML407 – a variant of the Mk IX that is a privately owned (formerly IAC-162) TR9 and operates out of Duxford, UK. The second cockpit of this aircraft has been lowered and is now below the front cockpit. IAC-161 (Previously PV202) has also been recently restored to flying condition.
The Seafire II was able to outperform the A6M5 Zero at low altitudes when the two types were tested against each other during wartime mock combat exercises. Contemporary Allied carrier fighters such as the F6F Hellcat and F4U Corsair, however, were considerably more robust and practical for carrier operations. A performance advantage was regained when late-war Seafire marks equipped with the Griffon engines supplanted their Merlin-engined predecessors.
The first Rolls Royce Griffon-engined Mk XII flew on August 1942, but only five had reached service status by the end of the year. This mark could nudge 400 mph in level flight and climb to an altitude of 30,000 ft (10,000 m) in under eight minutes. Although the Spitfire continued to improve in speed and armament, range and fuel capacity were major issues: it remained "short-legged" throughout its life except in the dedicated photo-reconnaissance role, when its guns were replaced by extra fuel tanks.
Newer Griffon-engined Spitfires were being introduced as home-defence interceptors, where limited range was not an impediment. These faster Spitfires were used to defend against incursions by high-speed "tip-and-run" German fighter-bombers and V-1 flying bombs over Great Britain.
As American fighters took over the long-range escorting of USAAF daylight bombing raids, the Griffon-engined Spitfires progressively took up the tactical air superiority role as interceptors, while the Merlin-engined variants (mainly the Mk IX and the Packard-engined XVI) were adapted to the fighter-bomber role. Although the later Griffon-engined marks lost some of the favourable handling characteristics of their Merlin-powered predecessors, they could still out-manoeuvre their main German foes and other, later American and British-designed fighters. The distinctive Merlin sound of a supercharger whine and the accompanying whistle from the under-wing radiators was replaced by a deeper, throatier growl.
In late 1962, Air Marshal Sir John Nicholls instigated an interesting trial when he flew a Spitfire against the supersonic Lightning F 3 interceptor in mock combat at RAF Binbrook. At the time British Commonwealth forces were involved in possible action against Indonesia over Malaya and Nicholls decided to develop tactics to fight the Indonesian Air Force P-51 Mustang, a fighter that had a similar performance to the Spitfire PR 19. He concluded that the most effective and safest way for a modern jet-engined fighter to attack a piston-engined fighter was from below and behind; contrary to all established fighter-on-fighter dictum.
There are approximately 44 Spitfires and a few Seafires airworthy worldwide, although many air museums have examples on static display. For example, Chicago's Museum of Science and Industry has paired a static Spitfire with a static Ju 87 R-2/Trop. Stuka dive bomber.
:::::::::(Captured)::::::(co-belligerent Kingdom of Italy - post Sept. 1943 armistice):::::::::::::::::
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