Editing Hawker Tempest (section)

=== Origins ===
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".<ref>Thomas and Shores 1988, pp. 18, 105.</ref><ref name=Mason67_3_4/> 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 (geometry)|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 airfoil|NACA 4 digit series wing section]], had a maximum [[thickness-to-chord ratio]] of 19.5 per cent (root) to 12 per cent (tip),<ref name=Thomas105/> 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.<ref>J. A. D. Ackroyd. [http://aerosociety.com/Assets/Docs/Publications/The%20Journal%20of%20Aeronautical%20History/2013-02_SpitfireWing-Ackroyd.pdf "The Spitfire Wing Planform: A Suggestion."] ''Journal of Aeronautical History'', Paper No. 2013/02.</ref><ref group=nb>Both the Spitfire and the Typhoon were designed when little was known about the behaviour of air at high subsonic [[Mach number]]s, and of what would later become known as the [[Critical Mach number]]. The importance of this to high speed, high altitude flight would be discovered during combat in the [[Battle of Britain]], where the Spitfire's thinner wing gave it an advantage at higher altitudes over the thicker wing-sectioned Hurricane, which was affected to a greater extent by compressibility. Fortuitously, the Spitfire had been designed with a thin wing that was subsequently discovered by the RAE to possess a high Critical Mach No.</ref> In addition, there had been other issues experienced with the Typhoon, such as engine unreliability, insufficient structural integrity, and the inability to perform high altitude interception duties.<ref name=Mason67_3>Mason 1967, p. 3.</ref>

[[File:Hawker Tempest I HM599.jpg|thumb|left|Tempest I prototype ''HM599'' with later bubble canopy; when first flown, it had the "car-door" canopy and small tail unit.]]
In March 1940, engineers were assigned to investigate the new [[Drag (physics)|low–drag]] laminar flow wing developed by [[NACA]] in the United States, which was later used in the [[North American Aviation|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.<ref name=Thomas105>Thomas and Shores 1988, p. 105.</ref><ref name=Mason67_3/> 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.<ref name=Thomas105/><ref name=Mason67_3/> The wingspan was originally greater than that of the Typhoon at {{convert|43|ft|m|abbr=on}}, but the wingtips were later "clipped" and the wing became shorter; {{convert|41|ft|m|abbr=on}} versus {{convert|41|ft|7|in|m|abbr=on}}.<ref name=Thomas105/>

The wing [[planform (aeronautics)|planform]] was changed to a near-[[elliptical wing|elliptical]] shape to accommodate the 800 rounds of [[ammunition]] for the four 20&nbsp;mm [[Hispano-Suiza HS.404|Hispano cannon]]s, which were moved back further into the wing. The new wing had greater area than the Typhoon's,{{#tag:ref|Camm later remarked: "The [[Chief of the Air Staff (United Kingdom)|Air Staff]] wouldn't buy anything that didn't look like a [[Supermarine Spitfire|Spitfire]]."{{citation needed|date=September 2023}}|group=nb}} 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 {{convert|21|in|cm|abbr=on}} fuel bay in front of the [[cockpit (aviation)|cockpit]], with a 76&nbsp;I[[gallon|gal]] (345&nbsp;L) fuel tank.<ref name=Mason67_3_4>Mason 1967, pp. 3–4.</ref><ref name=Thomas105/> In addition, two inter-spar wing tanks, each of 28&nbsp;Igal (127&nbsp;L), were fitted on either side of the centre section and, starting with late model Tempest Vs, a 30&nbsp;Igal (136&nbsp;L) tank was carried in the leading edge of the port wingroot, giving the Tempest a total internal fuel capacity of 162&nbsp;Igal (736&nbsp;L).<ref>Tempest V Pilot's Notes 1944, pp. 6–7, 31.</ref>

Another important feature of the new wing was Camm's proposal that the [[radiator (engine cooling)|radiator]]s for cooling the engine be fitted into the [[leading edge]] of the wing inboard of the [[Landing gear|undercarriage]]. This eliminated the distinctive "[[beard|chin]]" radiator of the Typhoon and improved [[aerodynamics]].<ref name=Thomas105/><ref name=Mason67_3/> 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]].<ref>Bentley 1973, p. 95.</ref> 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.<ref name=Thomas106>Thomas and Shores 1988, p. 106.</ref> The design team also chose to use the new [[Napier Sabre|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.<ref name=Mason67_4>Mason 1967, p. 4.</ref>

In February 1941, Camm commenced a series of discussions with officials within the [[Minister of Aircraft Production|Ministry of Aircraft Production]] on the topic of the P.1012.<ref name=Mason67_4/> In March 1941 of that year, clearance to proceed with development of the design, referred to at this point as the Typhoon II, was granted. The design at the time encompassed the Sabre E.107C (as it was then known) with a four-blade propeller, 42 ft span elliptical wing with six cannon armament; while the front of the fuselage was redesigned the rear was unchanged from the Typhoon.<ref name=":0">Buttler 2004 p18</ref> At this point, work was undertaken by a team of 45 [[drafter|draughtsmen]] at Hawker's wartime experimental design office at [[Claremont (country house)|Claremont]], [[Esher]] to convert the proposal into technical schematics from which to commence manufacture.<ref name=Mason67_4/> In March 1941, the [[Air Ministry]] issued [[List of Air Ministry Specifications#1940–1949|specification F.10/41]] that had been written to fit the aircraft. The performance estimate given to MAP was 455 mph at 26,000 ft.<ref name=":0" /> In September Camm was told that the Air Ministry's Director of Technical Development that they had decided to have two Typhoons converted to the new design. By October 1941, development of the proposal had advanced to the point where the new design was finalised.<ref name=Mason67_4/>