Hawker Hurricane
The Hawker Hurricane is a British single-seat fighter aircraft of the 1930s–40s which was designed and predominantly built by Hawker Aircraft Ltd. for service with the Royal Air Force. It was overshadowed in the public consciousness by the Supermarine Spitfire during the Battle of Britain in 1940, but the Hurricane inflicted 60% of the losses sustained by the Luftwaffe in the campaign, and fought in all the major theatres of the Second World War.
The Hurricane originated from discussions between RAF officials and aircraft designer Sir Sydney Camm about a proposed monoplane derivative of the Hawker Fury biplane in the early 1930s. Despite an institutional preference for biplanes and lack of interest by the Air Ministry, Hawker refined its monoplane proposal, incorporating several innovations which became critical to wartime fighter aircraft, including retractable landing gear and the more powerful Rolls-Royce Merlin engine. The Air Ministry ordered Hawker's Interceptor Monoplane in late 1934, and the prototype Hurricane K5083 performed its maiden flight on 6 November 1935.
The Hurricane went into production for the Air Ministry in June 1936 and entered squadron service in December 1937. Its manufacture and maintenance were eased by using conventional construction methods so that squadrons could perform many major repairs without external support. The plane was rapidly procured prior to the outbreak of the Second World War; in September 1939, the RAF had 18 Hurricane-equipped squadrons in service. It was relied upon to defend against German aircraft operated by the Luftwaffe, including dogfighting with Messerschmitt Bf 109s in multiple theatres of action.
The Hurricane was developed through several versions: bomber interceptors, fighter-bombers, and ground support aircraft as well as fighters. Versions designed for the Royal Navy known as the Sea Hurricane had modifications including an arrestor hook near the tail, enabling operation from ships. Some were converted as catapult-launched convoy escorts. By the end of production in July 1944, 14,487 units had been completed in Britain and Canada, with others built in Belgium and Yugoslavia.
Development
Background
During the early 1930s, when Hawker Aircraft company developed the Hurricane, RAF Fighter Command had just 13 squadrons, equipped with the Hawker Fury, Hawker Demon, or the Bristol Bulldog, all biplanes with fixed-pitch wooden propellers and non-retractable undercarriages. At the time, there was an institutional reluctance towards change within the Air Staff; some senior figures were prejudiced against the adoption of monoplane fighter aircraft, while mid-level officers were typically more open-minded.In 1934 the British Air Ministry issued Specification F.5/34 in response to demands within the Royal Air Force for a new generation of fighter aircraft. Earlier, during 1933, British aircraft designer Sydney Camm had conducted discussions with Major John Buchanan of the Directorate of Technical Development on a monoplane based on the existing Fury. Mason attributes Camm's discussions with figures within the RAF, such as Squadron Leader Ralph Sorley, as having provoked the specification and some of its details, such as the preference for armaments being installed within the wings instead of within the aircraft's nose.
An outline of the "Fury Monoplane" armed with two guns in the wings and two in the nose and powered by the Goshawk engine was prepared and discussed with Roger Liptrot of the Air Ministry in December 1933. The design was reworked with the PV.12, following detailed work working drawings of the "Interceptor Monoplane" were begun in May 1934. The complete design was presented to the Air Ministry on 4 September.
Camm's initial submission in response to the earlier fighter specification F.7/30 was a development of the Fury, the Hawker P.V.3, However, the P.V.3 was not among the proposals which the Air Ministry selected to be built as prototype to official contract. After the rejection of the P.V.3 proposal, Camm started work on a new design involving a cantilever monoplane arrangement with a fixed undercarriage, armed with four machine guns and powered by the Rolls-Royce Goshawk engine. The original 1934 armament specifications for what evolved into the Hurricane were for a similar armament fitment to the Gloster Gladiator: four machine guns; two in the wings and two in the fuselage, synchronised to fire through the propeller arc. By January 1934, the proposal's detail drawings had been finished, but these failed to impress the Air Ministry enough for a prototype to be ordered.
Camm's response to this rejection was to further develop the design, introducing a retractable undercarriage and replacing the unsatisfactory Goshawk engine with a new Rolls-Royce design, initially designated the PV-12, which went on to become famous as the Merlin. In August 1934, a one-tenth scale model of the design was produced and sent to the National Physical Laboratory at Teddington, where a series of wind tunnel tests confirmed the aerodynamics were satisfactory, and in September 1934 Camm again approached the Air Ministry. This time, the Ministry's response was favourable, and a prototype of the "Interceptor Monoplane" was promptly ordered.
In July 1934, at a meeting chaired by Air Commodore Arthur Tedder, the Air Ministry Science Officer Captain F.W. "Gunner" Hill presented his calculation showing that future fighters must carry no fewer than eight machine guns, each capable of firing 1,000 rounds per minute./ Hill's assistant in making his calculations was his 13-year-old daughter Hazel Hill. Of the decision to place eight machine guns in fighters, Claude Hilton Keith, at the time assistant director of armament research and development, said "The battle was brisk and was carried into very high quarters before the implementing authority was given. My Branch had made out a sound case for 8-gun fighters and if this recommendation had not been accepted and we had been content with half-measures, it might indeed have gone ill for us during the late summer of 1940". Present at the meeting was Squadron Leader Ralph Sorley of the Air Ministry's Operational Requirements branch, who played an important role in the decision. In November 1934, the Air Ministry issued Specification F.5/34 which called for new fighter aircraft to be armed with a total of eight guns. However, by this time, work had progressed too far to immediately modify the planned four-gun installation. By January 1935, a wooden mock-up had been finished, and although a number of suggestions for detail changes were made, construction of the prototype was approved, and a new specification was written around the design. In July 1935, this specification was amended to include installation of eight guns.
The mock-up conference with Air Ministry staff was on 10 January 1935 at Kingston. The ministry order to purchase a prototype to the September proposal was placed on 21 February 1935. At the time the armament was two Vickers Mark V machine guns in the fuselage and one Browning machine gun in each wing. Work on stressed skin outer wings to replace the fabric covered ones began in July and the contract was altered in August to include another set of wings with eight guns in them; the guns were to be either Vickers or Brownings. These wings were delivered in June 1936.
Prototype and trials
By the end of August 1935, work on the airframe had been completed at Hawker's Kingston upon Thames facility and the aircraft components were transported to Brooklands, Surrey, where Hawker had an assembly shed; the prototype was fully re-assembled on 23 October 1935. Ground testing and taxi trials took place over the following two weeks. On 6 November 1935 the prototype K5083 took to the air for the first time at the hands of Hawker's chief test pilot, Flight Lieutenant George Bulman. Bulman was assisted by two other pilots in subsequent flight testing; Philip Lucas flew some of the experimental test flights, while John Hindmarsh conducted the firm's production flight trials. As completed, the prototype had been fitted with ballast to represent the aircraft's armament prior to the acceptance of the final multi-gun wing armament.By March 1936, the prototype had completed ten flying hours, covering all major portions of the flight envelope. Early testing had gone reasonably well, especially in light of the trial status of the Merlin engine, which had yet to achieve full flight certification at this time and thus severe restrictions had been imposed upon use of the engine. In early 1936, the prototype was transferred to RAF Martlesham Heath, Suffolk, to participate in initial service trials under the direction of Squadron Leader D.F. Anderson. Sammy Wroath, later to be the founding commandant of the Empire Test Pilots' School, was the RAF test pilot for the Hurricane: his report was favourable, stating that: "The aircraft is simple and easy to fly and has no apparent vices" and proceeded to praise its control response.
In the course of RAF trials, despite the problems with the Merlin engine, which had suffered numerous failures and necessitating several changes, enthusiastic reports were produced on the aircraft and its performance. The trials had proved the aircraft to possess a maximum level speed of at an altitude of, climb to in 5.7 minutes, and a stalling speed of , the last achieved using its flaps.
In the course of further testing, it was found that the Hurricane had poor spin recovery characteristics, in which all rudder authority could be lost due to shielding of the rudder. Hawker's response to the issue was to request that spinning tests be waived, but the Air Ministry refused the request; the situation was resolved by the Royal Aircraft Establishment, who established that the aerodynamic problem had been caused by a breakdown of the airflow over the lower fuselage, and could be cured by the addition of a small ventral fairing and extension of the bottom of the rudder. This discovery had come too late for the changes to be incorporated in the first production aircraft, but were introduced upon the 61st built and all subsequent aircraft.
In early 1936, the Hawker board of directors had decided, in the absence of official authorisation and at company expense, to proceed with the issue of the design drawings to the production design office and to start tooling-up for a production line capable of producing a batch of 1,000 Hurricanes.