Spitfire Mk I Specifications
Crew: Pilot only
Powerplant: One 1,030 hp Rolls-Royce Merlin III twelve-cylinder liquid-cooled engine
Span: 36 ft 10 in (11.23 m)
Length: 29 ft 11 in (9.12 m)
Max Speed: 367 mph (582 km/h) at 18,600 ft (5,669 m)
Armament: Eight .303 in (7.7 mm) Browning machine guns mounted in wings
Photo Description: Spitfire Mark IA, X4179 QV-B, of No. 19 Squadron, on the ground at Fowlmere, Cambridgeshire, as the pilot, F/O Francis N Brinsden, undertakes a cockpit check prior to take off, 21 September 1940.
The Supermarine Spitfire stands as an iconic British single-seat fighter aircraft, widely employed by the Royal Air Force and numerous Allied nations during the Second World War. The brainchild of Supermarine’s Chief Designer, Reginald Joseph Mitchell, the Spitfire was conceived as a short-range, high-performance interceptor aircraft. Mitchell and his team started developing the Type 300 design in 1934, following the less successful Type 224 prototype. On December 1st, 1934, the British Air Ministry issued contract AM 361140/34, providing £10,000 for the construction of a single prototype.
Mitchell’s design drew heavily from the experience gained with Supermarine’s Schneider Trophy-winning seaplanes in the late 1920s and early 1930s. The Spitfire’s key attributes included a streamlined, semi-monocoque fuselage made of lightweight, all-metal construction and thin elliptical wings, which afforded it a higher top speed compared to several contemporary fighters. The aircraft was powered by the new Rolls-Royce PV-12 engine, later famous as the Merlin, and armed with eight wing-mounted .303 in (7.7 mm) Browning machine guns. Tragically, Mitchell passed away just in time to witness the prototype, K5054, take its maiden flight on March 5, 1936, at Eastleigh Aerodrome, succumbing to cancer three months later. Joseph Smith succeeded him as Chief Designer at Supermarine, overseeing further Spitfire development.
Following successful test flights at Martlesham Heath, the Air Ministry placed an order for 310 Spitfire aircraft. The Spitfire Mk I entered RAF service with No. 19 Squadron at RAF Duxford on August 4, 1938. Adored by its pilots, the new fighter was known for its speed, power, and exceptional maneuverability. The distinctive bubble canopy provided excellent visibility. The Spitfire’s performance was further enhanced by the introduction of a constant-speed propeller and increased access to 100 octane fuel from the United States. By July 1940, eighteen additional RAF squadrons were equipped with Spitfires.
During the Battle of Britain, the Spitfire became a symbol of national defiance and attained legendary status, largely due to the renowned “Spitfire Fund” organized and managed by Lord Beaverbrook, the Minister of Aircraft Production. However, initial production delays meant that the more numerous Hawker Hurricane bore a greater portion of the burden against the Luftwaffe, accounting for around 55% of enemy aircraft shot down by Fighter Command. Spitfires claimed 529 enemy aircraft destroyed but suffered the loss of 230 of their own. Spitfires were primarily deployed to engage German escort fighters while Hurricane squadrons attacked the slower bomber formations. The Spitfire and its primary adversary, the Messerschmitt Bf 109, were closely matched in overall performance. The Bf 109 could outpace the British fighter in climb and dive but lacked its maneuverability. In dogfights, the Spitfire couldn’t nose down into a steep dive without the engine momentarily cutting out due to negative g-forces. RAF fighter pilots learned to half-roll their aircraft before diving to pursue their opponents. This issue was later resolved through the use of “Miss Shilling’s orifice,” a small metal disc similar to a washer that restricted fuel flow to the carburetor.
In August 1940, the Spitfire Mk II entered service with the more powerful 1,175 hp Rolls-Royce Merlin XII engine. This marked the first version exclusively produced at the expansive new Lord Nuffield shadow factory at Castle Bromwich. All Mk IIs featured Rotol-manufactured wide-bladed propellers, increasing top speed by about 6–7 mph below 17,000 feet (5,200 m) and improving climb rates. Although combat capabilities were significantly enhanced, maximum speed performance remained lower than that of early Mk Is due to the added weight.
The majority of Mk Is and Mk IIs were equipped with eight .303 in (7.7 mm) Browning machine guns with a total of 2,800 rounds, sufficient for roughly 15 seconds of firing. It was soon evident that the small-caliber bullets struggled to penetrate the armor plating increasingly used in Luftwaffe aircraft to protect crew and vital areas. As a solution, the RAF began exploring heavier-caliber cannon options. In June 1940, No. 19 Squadron received several Mk Is fitted with two 20 mm Hispano-Suiza cannons for operational trials. This variant was known as the Mk IB, with the Browning-armed Spitfires retroactively designated as the Mk IA. Initial installations had the guns mounted on their sides to accommodate large drum magazines within the wings, resulting in unreliable Hispano cannons that frequently jammed after just one shot. Subsequent efforts led to a reliable cannon installation, and by late 1940, a number of Mk IBs armed with two cannons and four .303 in machine guns entered service.