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The Sptifire was introduced into RAF service on 11th August 1938, at RAF Duxford, Cambridgeshire, UK. They were used by 19 Sqn. It was designed by Reginald J. Mitchell, and was heavily based on his Schneider Trophy winning design, the S.6B. Unfortunately, Mitchell died before he had chance to see the Spitfire's sucess. The Spitfire was also used by many other allied countries throughout WWII, and it was continually used as a front line fighter up until the 1950's. The Spitfire was the most produced Allied fighter throughout WWII.
The Spitfire had many variants throughout its service life. There were eventually 26 variants of Spitfire, not including the carrier based version, the Supermarine Seafire. The first variant was the Mk IA, [N 1] which was supplemented by the similar Mk II.[N 2] Some Mk IIA aircraft were fitted with a 40 UK gallon long range fuel tank under the outer starboard wing, and were known as the Type 343.The next major variant was the Mk V (Type 349) with Merlin 45 engine. As well as A and B type wings, the Mk V introduced the 'universal' C type wing, which could carry four machine guns, one cannon and two machine guns or two cannon.
Following introduction of the superior Fw 190, it was decided, as a matter or urgency, to fit a Mk V airframe with a series 60 Merlin engine, in order to produce a new variant known as the Mk IX (Type 361), which could serve as an interim type until the dedicated Mk VIII (Type 359) could be made readily available. Initially fitted with the 'C' wing, later Mk IX aircraft received the 'E'wing, which had a 0.5in machine gun located in the inner cannon space, with the 20mm cannon moved to the outer position.  The similar Mk XVI was fitted with Merlin engines built by Packard. Later Mk XVI aircraft had enlarged rudders and cut down fuselages with 'teardrop' rear vision hoods. 
During 1940-41 work on pressure cabins by the Royal Aircraft Establishment and Supermarine led to the development of a high altitude version of the Mk VB. Known as the Mk VI (Type 350), 100 examples of this version were built, and were equipped with a pressure cabin,[N 3] Merlin 47 engine,[N 4] four bladed propeller units with Jabo blades, and pointed wingtips, which increased the wingspan to 40ft 2in. Armament was similar to the VB.
The Mk VI was followed by the Mk VII (Type 351), which was a Mk VI airframe redesigned to use the Merlin 60 series engine. 
in 1942, a pair of Mk VC in the Middle East were modified to undertake combat against high flying Ju-86 bomber and reconnaissance aircraft. One airframe eventually reached an altitude of almost 50,000ft, despite neither aircraft being fitted with preassurisation equipment. 
FloatplanesEditThe idea of equipping Spitfire aircraft with floats was first considered in response to the Norwegian campaign of 1940. A single Spitfire Mk I was adapted to take floats similar to those fitted to the third Blackburn Roc, and was known as the Type 342, but not completed before the end of the Norwegian campaign.
In 1942 the idea was revived, and Supermarine designed a set of floats with 90 percent buoyancy for the Spitfire Mk V. The floats were built and fitted by Folland Aircraft, and were attached to the wing spars some five feet from the centre-line using cantilever struts. The modified aircraft was tested as the Type 355, with one of the three examples built being flown in the Mediterranean area. in 1943 Folland fitted a set of floats to a Mk IX aircraft, which became the Type 385. All four aircraft had additional fin area, including an under fin to counteract destabilisation caused by the floats. 
The Air Ministry later requested submission of a proposal for a float variant of the F.21 Super Spitfire, but interest never progressed beyond the specification stage. Supermarine's involvement in Spitfire floatplanes was limited to design and specification work, with the actual conversions being carried out by Follands. 
Carrier Based versionsEdit
See entry for the Supermarine Seafire
Dual Trainer versionsEdit
The relative sophistication of the Spitfire led to a 1941 proposal for a two seat version of the Spitfire, which could be used for advanced training purposes.[N 5] Although the idea was not officially adopted by the British until after the war, ES127, a Mk VC assigned to 261 Squadron at Catania in Sicily, was fitted with an open cockpit in front of the original. A Mk IX was modified in 1945 at No 1 Aircraft Depot, Leningrad for use as a two seat trainer, by the installation of a second closed cockpit behind the regular one.
Specifications for Supermarine Mk. Vb SpitfireEdit
- Crewmen: one pilot
- Length: 29 ft 11 in (9.12 m)
- Wingspan: 36 ft 10 in (11.23 m)
- Height: 11 ft 5 in (3.86 m)
- Wing area: 242.1 ft2 (22.48 m2)
- Airfoil: NACA 2209.4(tip)
- Empty Weight: 5,090 lb (2,309 kg)
- Loaded weight: 6,622 lb (3,000 kg)
- Max. Takeoff Weight: 6,770 lb (3,071 kg)
- Powerplant: One Rolls-Royce Merlin 45 supercharged V12 piston engine rated at 1,470 hp (1,096 kW) at 9,250 ft (2,820 m)
- Max. Speed: 378 mph, (605 km/h)
- Combat Radius: 410 nmi (470 mi, 760 km)
- Ferry Range: 991 nmi (1,140 mi, 1,840 km)
- Service Ceiling: 35,000 ft (11,300 m)
- Climb Rate: 3,240 ft/min (13.5 m/s)
- Wing Loading: 27.35 lb/ft2 (133.5 kg/m2)
- Power to Mass Ratio: 0.22 hp/lb (0.36 kW/kg)
- Gun Armament: Eight 0.303 in (7.7 mm) Browning MGs with 350 rounds per gun
- Bomb Armament: Two 250 lb (113 kg) bombs
Specifications for Supermarine Mk. XIV SpitfireEdit
- (Unlisted specifications such as wingspan, crewmen, airfoil, and bomb armament are the exact same as the Mk. Vb)
- Length: 30 ft (9.14 m)
- Height: 10 ft (3.05 m)
- Empty Weight: 6,578 lb (2,984 kg)
- Loaded weight: 7,923 lb (3,593 kg)
- Max. Takeoff Weight: 8,488 lb (3,850 kg)
- Powerplant: One Rolls-Royce Griffon 65 supercharged V12 piston engine with 5-bladed Jablo-Rotol propellers rated at 2,050 hp (1,528 kW) at 8,000 ft (2,438 m)
- Max. Speed: 448 mph, (717 km/h)
- Combat Radius: 400 nmi (459 mi, 740 km)
- Ferry Range: 950 nmi (1,090 mi, 1,815 km)
- Service Celing: 43,500 ft (13,258 m)
- Climb Rate: 3,650 ft/min (18.5 m/s)
- Wing Loading: 32.72 lb/ft2 (159.8 kg/m2)
- Power to Mass Ratio: 0.24 hp/lb (0.42 kW/kg)
- Gun Armament: Two 20 mm (0.787-in) Hispano Mk. II cannons with 120 rounds per gun and four 0.303 in (7.7 mm) Browning MGs with 350 rounds per gun which were eventually replaced by two .50 in (12.7 mm) M2 Browming MGs with 250 rounds per gun on the Mk. XIVe variant
- ↑ Retrospective designation applied to distinguish the eight machine gun Type 300 aircraft from the IB version, the Type 331, which was fitted with two 20mm cannon and four machine guns. 
- ↑ The Mk II (Type 329) was basically the Mk I powered by a 1,175hp Merlin XII. Built at Castle Bromwich, the Mk II incorporated all the improvements developed for the Mk I, such as constant speed airscrew, on the production line. Like the Mk I, the Mk II was built with A (eight machine gun) and B (two cannon and four machine gun) wings. 
- ↑ This was fitted between the fore and aft cockpit bulkheads, and topped with a non sliding canopy to ease pressurisation. A Marshall blower provided an atmosphere differential of 2lb per sq in, reducing apparent altitude from 40,000ft to 28,000ft.
- ↑ This was the high altitude version of the Merlin 45.
- ↑ A similar proposal for a two seat version of the Hawker Hurricane had been submitted in 1939.
- ↑ http://www.wwiivehicles.com/unitedkingdom/aircraft/fighter/supermarine-spitfire-mk-i.asp
- ↑ Green, William. Famous Fighters of the Second World War. Purnell Book Services. 1975. Page 138.
- ↑ 3.0 3.1 3.2 3.3 Famous Fighters Page 130.
- ↑ Green, William. Fighters. 1975. Page 134.
- ↑ Famous Fighters Page 135.
- ↑ 6.0 6.1 6.2 6.3 Famous Fighters Page 133.
- ↑ 7.0 7.1 Famous Fighters Page 136.
- ↑ Morgan, Eric B and Edward Shacklady. Spitfire - The History. 2000. ISBN 0 946219 48 6 Page 386
- ↑ 9.0 9.1 Spitfire History Page 303
- ↑ Spitfire History Page 324