The Hawker Tempest is a British fighter aircraft that was primarily used in its Mk.V form by the Royal Air Force (RAF) in the later stages of the Second World War. The Tempest, originally known as the Typhoon II, was a significantly improved derivative of the Hawker Typhoon, intended to address the Typhoon's unexpected deterioration in performance at high altitude by replacing its wing with a thinner laminar flow design. Since it had diverged considerably from the Typhoon, it was renamed Tempest. The Tempest emerged as one of the most powerful fighters of World War II and at low altitude was the fastest single-engine propeller-driven aircraft of the war. Upon entering service in 1944, the Tempest performed low-level interception, particularly against the V-1 flying bomb threat, and ground attack supporting major invasions like Operation Market Garden. Later, it successfully targeted the rail infrastructure in Germany and Luftwaffe aircraft on the ground, as well as countering similar attacks by German fighters. The Tempest was effective in the low-level interception role, including against newly developed jet-propelled aircraft like the Messerschmitt Me 262. The further-developed Tempest II did not enter service until after the end of hostilities. It had several improvements, including being tropicalised for combat against Japan in South-East Asia as part of the Commonwealth Tiger Force. During development of the earlier Hawker Typhoon, the design team, under the leadership of Sydney Camm, had already planned out a series of design improvements; these improvements culminated in the Hawker P. 1012, otherwise known as the Typhoon II or "Thin-Wing Typhoon". Although the Typhoon was generally considered to be a good design, Camm and his design team were disappointed with the performance of its wing, which had proved to be too thick in its cross section, and thus created airflow problems which inhibited flight performance, especially at higher altitudes and speeds where it was affected by compressibility. The Typhoon's wing, which used a NACA 4 digit series wing section, had a maximum thickness-to-chord ratio of 19.5 per cent (root) to 12 per cent (tip), in comparison to the Supermarine Spitfire's 13.2 per cent tapering to 6 per cent at the tip, the thinner design being deliberately chosen to reduce drag. Other problems had been experienced with the Typhoon, such as engine unreliability, lack of structural integrity, and the inability to perform high altitude interception duties. In March 1940, engineers were assigned to investigate the new low–drag laminar flow wing developed by NACA in the United States, which was later used in the North American P-51 Mustang. A laminar flow wing adopted for the Tempest series had a maximum thickness-to-chord ratio of 14.5 per cent at the root, tapering to 10 per cent at the tip. The maximum thickness of the Tempest wing was set further back at 37.5 per cent of the chord versus 30 per cent for the Typhoon's wing, reducing the thickness of the wing root by five inches on the new design. The wingspan was originally greater than that of the Typhoon at 43 ft (13 m), but the wingtips were later "clipped" and the wing became shorter; 41 ft (12 m) versus 41 ft 7 in (12.67 m). The wing planform was changed to a near-elliptical shape to accommodate the 800 rounds of ammunition for the four 20 mm Hispano cannons, which were moved back further into the wing. The new wing had greater area than the Typhoon's, but the new wing design sacrificed the leading edge fuel tanks of the Typhoon. To make up for this loss in capacity, Hawker engineers added a new 21 in (53 cm) fuel bay in front of the cockpit, with a 76 Igal (345 L) fuel tank. In addition, two inter-spar wing tanks, each of 28 Igal (127 L), were fitted on either side of the centre section and, starting with late model Tempest Vs, a 30 Igal (136 L) tank was carried in the leading edge of the port wingroot, giving the Tempest a total internal fuel capacity of 162 Igal (736 L). Another important feature of the new wing was Camm's proposal that the radiators for cooling the engine be fitted into the leading edge of the wing inboard of the undercarriage. This eliminated the distinctive "chin" radiator of the Typhoon and improved aerodynamics. A further improvement of the Tempest wing over that of the Typhoon was the exceptional, flush-riveted surface finish, essential on a high-performance laminar flow airfoil. The new wing and airfoil, and the use of a four-bladed propeller, acted to eliminate the high frequency vibrations that had plagued the Typhoon. The design team also chose to use the new Mark IV version of the Napier Sabre H-block 24 cylinder engine for the Tempest, drawings of which had become available to Hawker in early 1941. For further details of development, prototypes, design and variants, click here.
