page_title: Hawker Tempest
section_title: Prototypes
hierarchical_section_title: Hawker Tempest / Design and development / Prototypes
caption_attribution_description: English: Hawker Tempest
context_page_description: The Hawker Tempest is a British fighter aircraft primarily used by the Royal Air Force in the Second World War. The Tempest, originally known as the Typhoon II, was an 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 was the fastest single-engine propeller-driven aircraft of the war at low altitude.
  Upon entering service in 1944, the Tempest was used as a low-level interceptor, particularly against the V-1 flying bomb threat, and as a ground attack platform, in which it supported major events such as Operation Market Garden. Later, it successfully targeted the rail infrastructure in Germany and Luftwaffe aircraft on the ground, as well as countering such attacks by German fighters. The Tempest was effective in the low-level interception role, including against newly developed jet-propelled aircraft such as the Messerschmitt Me 262.
context_section_description: On 18 November 1941, a contract was issued by the Air Ministry for a pair of prototypes of the "Typhoon Mark II"; the new fighter was renamed "Tempest" on 28 February 1942. Complications were added to the Tempest program by external factors in the form of engine issues: the Rolls-Royce Vulture engine and corresponding Hawker Tornado aircraft which was being developed in parallel were both terminated. Due to this previous experience on other programs, the Air Ministry was sufficiently motivated to request that a total of six Tempest prototypes be built using different engines so that, if a delay hit one engine, an alternative powerplant would already be available. This measure turned out to be prudent, as engine development was not trouble-free on some of the variants of the Tempest.
  The six prototypes were built as a single Mk.I, HM599, powered by a Sabre IV, two Mk.IIs (LA602 and LA607) equipped with the Centaurus IV, a Mk.III (LA610) with a Griffon IIB, a Mk.IV (LA614) with a Griffon 61, and a Mk.V (HM595) with the Sabre II. The Tempest Mk.I featured other new features, such as a clean single-piece sliding canopy in place of the car-door framed canopy, and it used wing radiators instead of the "chin" radiator. Due to development difficulties with the Sabre IV engine and its wing radiators, the completion of the Mk.I prototype, HM599, was delayed, and thus it was the Mk.V prototype, HM595, that would fly first.
  On 2 September 1942, the Tempest Mk.V prototype, HM595, conducted its maiden flight, flown by Philip Lucas from Langley, Berkshire, England. HM595, which was powered by a Sabre II engine, retained the Typhoon's framed canopy and car-style door, and was fitted with the "chin" radiator, similar to that of the Typhoon. It was quickly fitted with the same bubble canopy fitted to Typhoons, and a modified fin that almost doubled the vertical tail surface area, made necessary because the directional stability with the original Typhoon fin had been reduced over that of the Typhoon by the longer nose incurred by the new fuel tank. The horizontal tailplanes and elevators were also increased in span and chord; these were also fitted to late production Typhoons. Test pilots found the Tempest a great improvement over the Typhoon in performance; in February 1943 the pilots from the A&AEE at Boscombe Down reported that they were impressed by "a manoeuvrable and pleasant aircraft to fly with no major handling faults".
  On 24 February 1943, the second prototype HM599 first flew, representing the "Tempest Mk.I" equipped with the Napier Sabre IV engine; this flight had been principally delayed by protracted problems and slippages encountered in the development of the new Sabre IV engine. HM599 was at first equipped with the older Typhoon cockpit structure and vertical tailplane. The elimination of the "chin" radiator did much to improve overall performance, leading to the Tempest Mk.I quickly becoming the fastest aircraft that Hawker had built at that time, having attained a speed of 466 mph (750 km/h) during test flights.
  On 27 November 1944, the Tempest Mk.III prototype, LA610, conducted its first flight; it was decided to discontinue development work on the Mk.III, this was due to priority for the Griffon engine having been assigned to the Spitfire instead. Work on the Tempest Mk.IV variant was abandoned without any prototype being flown at all. The Tempest Mk.II, which was subject to repeated delays due to its Centaurus powerplant, was persisted with, but would not reach production in time to see service during the Second World War. Continual problems with the Sabre IV meant that only the single Tempest Mk.I (HM599) was built; consequently, Hawker proceeded to take the Sabre II-equipped "Tempest V" into production instead.
  In August 1942, even before the first flight of the prototype Tempest V had been conducted, a production order for 400 Tempests was placed by the Air Ministry. This order was split, with the initial batch of 100 being Tempest V "Series I"s, powered by the 2,235 hp (1,491 kW) Sabre IIA series engine, which had 
caption: Tempest V prototype HM595 with early "car door" cockpit structure and small tail unit.
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