Supermarine Spitfire

The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and other Allied countries before, during and after World War II. Many variants of the Spitfire were built, using several wing configurations, and it was produced in greater numbers than any other British aircraft. It was also the only British fighter produced continuously throughout the war. The Spitfire continues to be popular among enthusiasts; about 54 remain airworthy, and many more are static exhibits in aviation museums throughout the world.

The Spitfire was designed as a short-range, high-performance interceptor aircraft by R. J. Mitchell, chief designer at Supermarine Aviation Works, which operated as a subsidiary of Vickers-Armstrong from 1928. Mitchell pushed the Spitfire's distinctive elliptical wing designed by Beverley Shenstone to have the thinnest possible cross-section, helping give the aircraft a higher top speed than several contemporary fighters, including the Hawker Hurricane. Mitchell continued to refine the design until his death in 1937, whereupon his colleague Joseph Smith took over as chief designer, overseeing the Spitfire's development through its multitude of variants.

During the Battle of Britain, from July to October 1940, the public perceived the Spitfire to be the main RAF fighter, though the more numerous Hawker Hurricane shouldered a greater proportion of the burden against Nazi Germany's air force, the Luftwaffe. However, Spitfire units had a lower attrition rate and a higher victory-to-loss ratio than those flying Hurricanes because of the fighter's higher performance. During the Battle, Spitfires were generally tasked with engaging Luftwaffe fighters—mainly Messerschmitt Bf 109E series aircraft—which were a close match for them.

After the Battle of Britain, the Spitfire superseded the Hurricane to become the backbone of RAF Fighter Command, and saw action in the European, Mediterranean, Pacific, and South-East Asian theatres. Much loved by its pilots, the Spitfire served in several roles, including interceptor, photo-reconnaissance, fighter-bomber and trainer, and it continued to serve in these roles until the 1950s. The Seafire was a carrier-based adaptation of the Spitfire which served in the Fleet Air Arm from 1942 through to the mid-1950s. Although the original airframe was designed to be powered by a Rolls-Royce Merlin engine producing 1,030 hp (768 kW), it was strong enough and adaptable enough to use increasingly powerful Merlins and, in later marks, Rolls-Royce Griffon engines producing up to 2,340 hp (1,745 kW). As a result, the Spitfire's performance and capabilities improved over the course of its service life.        

Early in its development, the Merlin engine's lack of fuel injection meant that Spitfires and Hurricanes, unlike the Bf 109E, were unable to simply nose down into a steep dive. This meant a Luftwaffe fighter could simply "bunt" into a high-power dive to escape an attack, leaving the Spitfire behind, as its fuel was forced out of the carburettor by negative "g". RAF fighter pilots soon learned to "half-roll" their aircraft before diving to pursue their opponents. Sir Stanley Hooker explained the carburettor was adopted because it "increased the performance of the supercharger and thereby increased the power of the engine".

In March 1941, a metal disc with a hole was fitted in the fuel line, restricting fuel flow to the maximum the engine could consume. While it did not cure the problem of the initial fuel starvation in a dive, it did reduce the more serious problem of the carburettor being flooded with fuel by the fuel pumps under negative "g". Invented by Beatrice "Tilly" Shilling, it became known as "Miss Shilling's orifice". Further improvements were introduced throughout the Merlin series, with Bendix-manufactured pressure carburettors, designed to allow fuel to flow during all flight attitudes, introduced in 1942.

Armament

Even if the eight Brownings worked perfectly, pilots soon discovered that they were not sufficient to destroy larger aircraft. Combat reports showed that an average of 4,500 rounds were needed to shoot down an enemy aircraft. In November 1938, tests against armoured and unarmoured targets had already indicated that the introduction of a weapon with a calibre of at least 20 mm was urgently needed. A variant on the Spitfire design with four 20 mm Oerlikon cannon had been tendered to specification F37/35, but the order for prototypes had gone to the Westland Whirlwind in January 1939.Due to a shortage of Brownings, which had been selected as the new standard rifle calibre machine gun for the RAF in 1934, early Spitfires were fitted with only four guns, with the other four fitted later. Early tests showed that while the guns worked perfectly on the ground and at low altitudes, they tended to freeze at high altitude, especially the outer wing guns. This was because the RAF's Brownings had been modified to fire from an open bolt. While this prevented overheating of the cordite used in British ammunition, it allowed cold air to flow through the barrel unhindered. Supermarine did not fix the problem until October 1938, when they added hot air ducts from the rear of the wing mounted radiators to the guns, and bulkheads around the gunbays to trap the hot air in the wing. Red fabric patches were doped over the gun ports to protect the guns from cold, dirt and moisture until they were fired.

In June 1939, a Spitfire was fitted with a drum-fed Hispano in each wing, an installation that required large blisters on the wing to cover the 60-round drum. The cannon suffered frequent stoppages, mostly because the guns were mounted on their sides to fit as much of the magazine as possible within the wing. In January 1940, P/O George Proudman flew this prototype in combat, but the starboard gun stopped after firing a single round, while the port gun fired 30 rounds before seizing. If one cannon seized, the recoil of the other threw the aircraft off aim.

Nevertheless, 30 more cannon-armed Spitfires were ordered for operational trials, and they were soon known as the Mk IB, to distinguish them from the Browning-armed Mk IA; they were delivered to No. 19 Squadron beginning in June 1940. The Hispanos were found to be so unreliable that the squadron requested an exchange of its aircraft with the older Browning-armed aircraft of an operational training unit. By August, Supermarine had perfected a more reliable installation with an improved feed mechanism and four .303s in the outer wing panels. The modified fighters were then delivered to 19 Squadron 

Although R. J. Mitchell is justifiably known as the engineer who designed the Spitfire, his premature death in 1937 meant that all development after that date was undertaken by a team led by his chief draughtsman, Joe Smith, who became Supermarine's chief designer on Mitchell's death. As Jeffrey Quill noted: "If Mitchell was born to design the Spitfire, Joe Smith was born to defend and develop it."

Supermarine developed a two-seat variant known as the T Mk VIII to be used for training, but none were ordered, and only one example was ever constructed (identified as N32/G-AIDN by Supermarine). In the absence of an official two-seater variant, a number of airframes were crudely converted in the field. These included a 4 Squadron SAAF 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 few 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.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. More Spitfire Mk Vs were built than any other type, with 6,487 built, followed by the 5,656 Mk IXs. Different wings, featuring a variety of weapons, were fitted to most marks; the A wing used eight .303 in (7.7 mm) machine guns, the B wing had four .303 in (7.7 mm) machine guns and two 20 mm (.79 in) Hispano cannon, and the C, or universal, wing could mount either four 20 mm (.79 in) cannon or two 20 mm (.79 in) and four .303 in (7.7 mm) machine guns. As the war progressed, the C wing became more common. Another armament variation was the E wing which housed two 20 mm (.79 in) cannon and two .50 in (12.7 mm) Browning machine guns. Although the Spitfire continued to improve in speed and armament because of its limited fuel capacity its range and endurance were limited: it remained "short-legged" throughout its life except in the dedicated photo-reconnaissance role, when its guns were replaced by extra fuel tanks.

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. Ten of these TR9 variants were then sold to the Indian Air Force along with six to the Irish Air Corps, three to the Royal Netherlands Air Force and one for the Royal Egyptian Air Force. Currently several of the trainers are known to exist, including both the T Mk VIII, a T Mk IX based in the US, and the "Grace Spitfire" ML407, a veteran flown operationally by 485(NZ) Squadron in 1944.

Seafire

The Seafire, a name derived from sea, and Spitfire, was a naval version of the Spitfire specially adapted for operation from aircraft carriers. Although the Spitfire was not designed for the rough-and-tumble of carrier-deck operations, it was considered the best available fighter at the time. The basic Spitfire design did impose some limitations on the use of the aircraft as a carrier-based fighter; poor visibility over the nose, for example, meant that pilots had to be trained to land with their heads out of the cockpit and looking along the port cowling of their Seafire. Like the Spitfire, the Seafire also had a relatively narrow undercarriage track, which meant that it was not ideally suited to deck operations. Early Seafire marks had relatively few modifications to the standard Spitfire airframe; however cumulative front line experience meant that most of the later versions of the Seafire had strengthened airframes, folding wings, arrestor hooks and other modifications, culminating in the purpose-built Seafire F/FR Mk 47.Main article: Supermarine Seafire

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. However, contemporary Allied carrier fighters such as the F6F Hellcat and F4U Corsair were considerably more robust and so more practical for carrier operations. Performance was greatly increased when later versions of the Seafire were fitted with the Griffon engines. These were too late to see service in World War II.

Griffon-engined variants

Main article: Supermarine Spitfire (Griffon-powered variants)

As American fighters took over the long-range escorting of United States Army Air Forces (USAAF) daylight bombing raids, the Griffon-engined Spitfires progressively took up the tactical air superiority role, and played a major role in intercepting V-1 flying bombs, while the Merlin-engined variants (mainly the Mk IX and the Packard-engined Mk 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 outmanoeuvre their main German foes and other, later American and British-designed fighters.The first Rolls-Royce Griffon-engined Mk XII flew in August 1942, and first flew operationally with 41 Squadron in April 1943. This mark could nudge 400 mph (640 km/h) in level flight and climb to an altitude of 33,000 ft (10,000 m) in under nine minutes.

The final version of the Spitfire, the Mk 24, first flew at South Marston on 13 April 1946. On 20 February 1948, almost twelve years from the prototype's first flight, the last production Spitfire, VN496, left the production line. Spitfire Mk 24s were used by only one regular RAF unit, with 80 Squadron replacing their Hawker Tempests with F Mk 24s in 1947. With these planes, 80 Squadron continued its patrol and reconnaissance duties from Wunstorf in Germany as part of the occupation forces, until it relocated to Kai Tak Airport, Hong Kong in July 1949. During the Chinese Civil War, 80 Squadron's main duty was to defend Hong Kong from perceived Communist threats.

The last non-operational flight of a Spitfire in RAF service, which took place on 9 June 1957, was by a PR Mk 19, PS583, from RAF Woodvale of the Temperature and Humidity Flight. This was also the last known flight of a piston-engined fighter in the RAF. The last nation in the Middle East to operate Spitfires was Syria, which kept its F 22s until 1953.Operation Firedog during the Malayan Emergency saw the Spitfire fly over 1,800 operational sorties against the Malaysian Communists. The last operational sortie of an RAF Spitfire was flown on 1 April 1954, by PR Mk 19 Spitfire PS888 flying from RAF Seletar, in Singapore.

In late 1962, Air Marshal Sir John Nicholls instigated a trial when he flew Spitfire PM631, a PR Mk 19 in the custody of the Battle of Britain Memorial Flight, against an English Electric Lightning F 3 (a supersonic jet-engined 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 PR Mk 19. The first airframe (PM631) developed mechanical issues which removed it from the trial. Another PR Mk 19, PS853, which is now owned by Rolls-Royce, was on gate-guard duties at Binbrook, having been retired from the Battle of Britain Memorial Flight (BBMF) one year before. It had been maintained in running condition by ground crews at Binbrook, and after a short time was participating in the trials. At the end of the trials, RAF pilots found that Firestreak infra-red guided missiles had trouble acquiring the Spitfire due to a low exhaust temperature, and decided that the twin ADEN 30 mm (1 in) cannons were the only weapons suited to the task, which was complicated by the tight turning circle of the Spitfire, and the Lightning's proclivity for over-running the Spitfire. It was concluded that the most effective and safest way for a modern jet-engined fighter to attack a piston-engined fighter was to engage full afterburner at an altitude lower than the Spitfire, and behind it to perform a hit-and-run attack, contrary to all established fighter-on-fighter doctrine at that time.

General characteristics

• Crew: 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 2213 (root)
  NACA 2209.4 (tip)
• Empty weight: 5,065 lb (2,297 kg)
• Loaded weight: 6,622 lb (3,000 kg)
• Max. takeoff weight: 6,700 lb (3,039 kg)
• Powerplant: 1 × Rolls-Royce Merlin 45 supercharged V12 engine, 1,470 hp (1,096 kW) at 9,250 ft (2,819 m)

Performance

• Maximum speed: 370 mph (322 kn, 595 km/h)
• Combat radius: 410 nmi (470 mi (756 km))
• Ferry range: 991 nmi (1,135 mi (1,827 km))
• Service ceiling: 36,500 ft (11,125 m)
• Rate of climb: 2,600 ft/min (13.2 m/s)
• Wing loading: 27.35 lb/ft² (133.5 kg/m²)
• Power/mass: 0.22 hp/lb (0.36 kW/kg)

Armament

• Guns:
  • A wing
    • 8 × .303 in Browning Mk II* machine guns (350 rounds per gun)
  • B wing
    • 2 × 20 mm Hispano Mk II (60 rounds per gun)
    • 4 × .303 in Browning Mk II* machine guns (350 rounds per gun)
  • C wing
    • 4 × 20 mm Hispano Mk II cannon (120 rounds per gun)
  • C wing (Alt.)
    • 2 × 20 mm Hispano Mk II (120 rounds per gun)
    • 4 × .303 in Browning Mk II* machine guns (350 rounds per gun)
  • E wing
    • 2 × 20 mm Hispano Mk II cannon (120 rounds per gun)
    • 2 × .50 in M2 Browning machine guns (250 rounds per gun)