Editing Hawker Typhoon (section)

==Design and development==

===Origins===
[[File:Typhoon prototype1.jpg|thumb|The unarmed first prototype Typhoon P5212 taken just before its first flight. The prototype had a small tail unit and a solid fairing behind the cockpit, which was fitted with "car door" access hatches]]
Even as Hurricane production began in March 1937, [[Sydney Camm]] embarked on designing its successor. Camm had contacted the [[Air Ministry]] and asked what projects Hawker could consider, number two on their list was a single-engined fighter.<ref name="ButtlerP14">Buttler, 2004 p14</ref> Two preliminary designs were similar and larger than the Hurricane. These later became known as the "N" and "R" (from the initial of the engine manufacturers), because they were designed for the newly developed [[Napier Sabre]] and [[Rolls-Royce Vulture]], engines respectively.<ref name="Mason 1991, p. 316">Mason 1991, p. 316.</ref> Both engines used 24 [[Cylinder (engine)|cylinder]]s and were designed for over {{convert|2,000|hp|kW|abbr=on}}; the difference between the two was primarily in the arrangement of the cylinders – an [[H engine|H-block]] in the Sabre, and an [[X engine|X-block]] in the Vulture.<ref name="Thomas and Shores 1988, p. 12.">Thomas and Shores 1988, p. 12.</ref> Hawker submitted these preliminary designs in July 1937, but were advised by the Director of Technical Development to wait until a formal specification for a new fighter to replace the Spitfire and Hurricane was issued. He also cautioned that while they liked the design, they did not think the wing would be stiff enough.<ref name="Thomas and Shores 1988, p. 12."/><ref name="ButtlerP14" />

In March 1938, Hawker received the complete [[List of Air Ministry Specifications#1930-1939|Specification F.18/37]] and invitation to tender for a fighter which would be able to achieve at least {{convert|400|mph|km/h|abbr=on}} at {{convert|15000|ft|m}}, a ceiling of not less than 35,000 ft and specified a British engine with a [[Supercharger|two-speed supercharger]]. The armament fitted was to be twelve .303 inch (7.7 mm) Browning machine guns with 500 rounds per gun, with a provision for alternative combinations of weaponry.<ref>Meekcoms and Morgan 1994, p. 249.</ref> As well as Hawker, [[Gloster Aircraft Company|Gloster]], [[Supermarine]] and [[Bristol Aeroplane Company|Bristol]] submitted one or more designs each. Two prototypes of both the Type N and R were ordered on 3 March 1938<ref>Buttler 2004, pp. 13–14.</ref>   Camm and his design team started formal development of the designs and construction of prototypes.<ref name="Thomas and Shores 1988, p. 12." />{{refn|The "R" Tornado prototype, which flew before that of the Typhoon, could be identified by its ventral radiator unit and slightly rounder nose profile with a carburettor intake on top of the nose and two sets of exhaust stacks on either side of the engine cowling.<ref>Thomas and Shores 1988, pp. 12–13</ref>|group=nb}}

A contract for 500 Vulture and 500 Sabre engined fighters to F.9/37 was placed with Hawker on 10 July 1939. The official names 'Tornado' and 'Typhoon' were issued in August and December respectively.<ref name="ButtlerP15">Buttler, 2004 p15</ref>

The basic design of the Typhoon was a combination of traditional Hawker construction, as used in the earlier Hawker Hurricane, and more modern construction techniques; the front fuselage structure, from the engine mountings to the rear of the cockpit, was made up of bolted and welded [[duralumin]] or steel tubes covered with skin panels, while the rear fuselage was a flush-riveted, semi-[[monocoque]] structure.<ref name="Thomas and Shores 1988, p. 12."/>{{refn|The Typhoon and Tornado's forward fuselage structure was a refinement of techniques first developed by [[Fred Sigrist]] and Camm in 1925.<ref>Mason 1991, p. 15.</ref>|group=nb}} The forward fuselage and cockpit skinning was made up of large, removable duralumin panels, allowing easy external access to the engine and engine accessories and most of the important hydraulic and electrical equipment.<ref name="Bentley 1975, p. 545.">Bentley 1975, p. 545.</ref><ref>Thomas and Shores 1988, p. 17.</ref>

The wing had a span of {{convert|41|ft|7|in|m|adj=off}}, with a wing area of {{cvt|279|sqft|m2}}.<ref>Mason 1991, p. 328.</ref> It was designed with a small amount of inverted [[gull wing]] bend; the inner sections had a 1° [[Dihedral (aircraft)#Anhedral|anhedral]], while the outer sections, attached just outboard of the undercarriage legs, had a [[Dihedral (aircraft)|dihedral]] of {{frac|5|1|2}}°.<ref name="Thomas and Shores 1988, p. 12."/> The airfoil was a [[NACA airfoil|NACA 22 wing section]], with a [[thickness-to-chord ratio]] of 19.5% at the root tapering to 12% at the tip.<ref>Thomas and Shores 1988, p. 105.</ref>

The wing possessed great structural strength, provided plenty of room for fuel tanks and a heavy armament, while allowing the aircraft to be a steady gun platform.<ref>Thomas and Shores 1988, pp. 12, 15.</ref> Each of the inner wings incorporated two fuel tanks; the "main" tanks, housed in a bay outboard and to the rear of the main undercarriage bays, had a capacity of {{convert|40|impgal|L}}; while the "nose" tanks, built into the wing leading edges, forward of the main spar, had a capacity of {{convert|37|impgal|L}} each.<ref name="Bentley 1975, p. 545.">Bentley 1975, p. 545.</ref><ref>Air Ministry 1943/2004, p. 5.</ref> Also incorporated into the inner wings were inward-retracting [[landing gear]] with a wide track of 13&nbsp;ft {{frac|6|3|4}} in.<ref>Mason 1991, p. 329.</ref>

By contemporary standards, the new design's wing was very "thick", similar to the Hurricane before it. Although the Typhoon was expected to achieve over {{convert|400|mph|km/h|abbr=on}} in level flight at 20,000&nbsp;ft, the thick wings created a large drag rise and prevented higher speeds than the 410&nbsp;mph at {{convert|20000|ft|m}} achieved in tests.<ref>Mason 1988, p. 13.</ref>{{refn|This was a phenomenon called [[compressibility]] and [[wave drag]].<ref>Bentley 1975, p. 540.</ref>|group=nb}} The climb rate and performance above that level was also considered disappointing.<ref>Thomas and Shores 1988, p. 15.</ref> When the Typhoon was dived at speeds of over {{convert|500|mph|km/h|abbr=on}}, the drag rise caused buffeting and trim changes. These [[High-speed flight|compressibility]] problems led to Camm designing the Typhoon II, later known as the [[Hawker Tempest|Tempest]], which used much thinner wings with a [[laminar flow]] airfoil.<ref>Thomas and Shores 1988, pp. 18, 105.</ref>

===Prototypes===
[[File:Typhoon 2nd prototype 1.jpg|thumb|The second prototype P5216 in the standard RAF camouflage of 1941, possibly with yellow undersurfaces. The retractable tailwheel and main wheels now had doors fitted. Six exhaust stubs and the later standardised four cannon armament were other changes from P5212.]]
The first flight of the first Typhoon prototype, ''P5212'', made by Hawker's Chief test Pilot [[Philip Lucas]] from [[Langley, Berkshire|Langley]], was delayed until 24 February 1940 because problems with the development of the Sabre engine meant a flight engine did not arrive until December 1939.<ref name="ButtlerP15" /> Although unarmed for its first flights, ''P5212'' later carried twelve .303 in (7.7&nbsp;mm) [[M1919 Browning machine gun|Brownings]], set in groups of six in each outer wing panel; this was the armament fitted to the first 110 Typhoons, known as the Typhoon IA.<ref name="Thomas and Shores 1988, p. 16."/>{{refn|Although the four cannon were the preferred armament there was a shortage of the Châtelleraut cannon feed mechanism. Some Typhoon IAs were later converted to IB standard.<ref name="Thomas and Shores 1988, p. 16."/>|group=nb}} ''P5212'' also had a small tail-fin, triple exhaust stubs and no wheel doors fitted to the centre-section.<ref name="Mason 1991, p. 316"/> On 9 May 1940 the prototype had a mid-air [[Structural integrity and failure|structural failure]], at the join between the forward fuselage and rear fuselage, just behind the pilot's seat. Philip Lucas could see daylight through the split but instead of bailing out, landed the Typhoon and was later awarded the [[George Medal]].<ref name="Thomas and Shores, p. 13">Thomas and Shores 1988, p. 13.</ref><ref>{{London Gazette|issue=35156 |supp=y|page=2643|date=6 May 1941}}</ref>

On 15 May 1940, the [[Minister of Aircraft Production]], [[Max Aitken, 1st Baron Beaverbrook|Lord Beaverbrook]], ordered that resources should be concentrated on the production of five main aircraft types: the Spitfire and Hurricane fighters and the [[Armstrong Whitworth Whitley]], [[Vickers Wellington]] and [[Bristol Blenheim]] bombers. As a result, development of the Typhoon was slowed, production plans were postponed and test flying continued at a reduced rate.<ref>Thomas and Shores 1988, pp. 13–14.</ref>

As a result of the delays the second prototype, ''P5216'', first flew on 3 May 1941: ''P5216'' carried an armament of four [[Belt (firearms)|belt-fed]] [[20 mm caliber|20&nbsp;mm]] (0.79&nbsp;in) Hispano Mk II cannon, with 140 rounds per gun and was the prototype of the Typhoon IB series.<ref name="Thomas and Shores 1988, p. 16."/> Specification F.9/37 had been modified to include cannon armament as progress with the [[Westland Whirlwind (fighter)|Westland Whirlwind]] cannon fighter (to F.37/35) and [[Boulton Paul Aircraft|Boulton Paul]]'s twin-engined turret fighter (F.11/37) with cannon was slow.<ref>Buttler 2004 p16</ref>

In the interim between construction of the first and second prototypes, the Air Ministry had given Hawker an instruction to proceed with the construction of 1,000 of the new fighters. It was felt that the Vulture engine was more promising, so the order covered 500 Tornadoes and 250 Typhoons, with the balance to be decided once the two had been compared.

It was also decided that because Hawker was concentrating on Hurricane production, the Tornado would be built by [[Avro]] and Gloster would build the Typhoons at [[Hucclecote]].<ref name="Thomas and Shores, p. 13" /> Avro and Gloster were aircraft companies within the [[Hawker Siddeley]] group. As a result of good progress by Gloster, the first production Typhoon ''R7576'' was first flown on 27 May 1941 by [[Michael Daunt]], just over three weeks after the second prototype.<ref name="Thomas and Shores 1988, p. 16." />