The Hawker Hurricane is a British single-seat fighter aircraft that was designed and predominantly built by Hawker Aircraft Ltd for the Royal Air Force(RAF). Although overshadowed by the Supermarine Spitfire, the aircraft became renowned during the Battle of Britain, accounting for 60% of the RAF's air victories in the battle, and served in all the major theatres of the Second World War.
The 1930s design evolved through several versions and adaptations, resulting in a series of aircraft which acted as fighters, bomber-interceptors, fighter-bombers (also called "Hurribombers") and ground support aircraft. Further versions known as the Sea Hurricane had modifications which enabled operation from ships. Some were converted as catapult-launched convoy escorts, known as "Hurricats". More than 14,583 Hurricanes were built by the end of 1944 (including at least 800 converted to Sea Hurricanes and some 1,400 built in Canada by Canadian Car and Foundry).
Design and development
, the prototype, photographed before its first flight in November 1935.
At the time that the Hurricane was developed, RAF Fighter Command consisted of just 13 squadrons, each equipped with either the Hawker Fury, Hawker Demon, or the Bristol Bulldog, all biplanes with fixed-pitch wooden propellers and non-retractable undercarriages. Sydney Camm's design to meet F.7/30, the Hawker P.V.3, was essentially a scaled-up version of the Fury and was not among the proposals submitted to the Air Ministry selected for building as a government sponsored prototype. After the rejection of the P.V.3, Camm started work on a cantilever monoplane with a fixed undercarriage armed with four machine guns and powered by the Rolls-Royce Goshawk. Detail drawings were finished by January 1934, but failed to impress the Air Ministry enough for a prototype to be ordered.Camm's response was to further develop the design, introducing a retractable undercarriage and replacing the unsatisfactory Goshawk with a new Rolls-Royce design, the PV-12, later to become famous as the Merlin. In August 1934, a one-tenth scale model was made and sent to the National Physical Laboratory atTeddington. A series of wind tunnel tests confirmed the aerodynamic qualities of the design were in order, and in September Camm approached the Air Ministry again. This time, the response was favourable, and a prototype of the "Interceptor Monoplane" was ordered. In November 1934, the Air Ministry issued Specification F.5/34 which, drawing on the work of Squadron Leader Ralph Sorley, called for fighter aircraft to be armed with 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 (F.36/34) was written around the design. In July 1935, this specification was amended to include installation of eight guns.
Work on the airframe was completed at the end of August 1935 and the aircraft components were taken to Brooklands, where Hawker had an assembly shed, and 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(later Group Captain) 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.
RAF trials of the aircraft at Martlesham Heath began in February 1936. Sammy Wroath, later to be the founding Commandant of the Empire Test Pilot School, was the RAF test pilot for the Hurricane: his report was favorable, stating, "The aircraft is simple and easy to fly and has no apparent vices" and going on to praise its control response. The type name "Hurricane" proposed by Hawker was approved by the Air Ministry on 26 June; an informal christening ceremony was carried out the next month when King Edward VIII paid a visit to Martlesham Heath.
Further testing showed that the Hurricane had poor spin recovery characteristics, with all rudder authority being lost. Hawker's response 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 problem was 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 came too late to be incorporated in the first production aircraft, but was introduced in the 61st built and all subsequent aircraft.
Mk I in France, November 1939, showing original fabric-covered outer wing and two-bladed propeller
Though faster and more advanced than the RAF's current front line biplane fighters, the Hurricane's constructional design was already outdated when introduced. It used the traditional Hawker construction techniques, with a Warren truss box-girder primary fuselage structure with high-tensile steel longerons and duralumincross-bracing using mechanically fastened rather than welded joints. Over this, wooden formers and stringers carried the doped linen covering. Initially, the wing structure consisted of two steel spars, and was also fabric-covered. An all-metal, stressed-skin wing of duraluminium (a DERD specification similar to AA2024) was introduced in April 1939 and was used for all of the later marks. "The metal skinned wings allowed a diving speed that was 80 mph (130 km/h) higher than the fabric-covered ones. They were very different in construction but were interchangeable with the fabric-covered wings; one trials Hurricane, L1877, was even flown with a fabric-covered port wing and metal-covered starboard wing. The great advantage of the metal-covered wings over the fabric ones was that the metal ones could carry far greater stress loads without needing so much structure beneath." Several fabric-wing Hurricanes were still in service during the Battle of Britain, although a good number had had their wings replaced during servicing or after repair. Changing the wings only required three hours work per aircraft.
The prototype and early production Hurricanes were fitted with a Watts two-bladed fixed-pitch wooden propeller. Since this was inefficient at low airspeeds, the aircraft required a long ground run to get airborne, causing concern at Fighter Command. Trials with a De Havilland variable-pitch propeller reduced the take-off run from 1,230 to 750 ft (370 to 230 m). Deliveries of these began in April 1939: this was later replaced by the hydraulically operated constant-speed Rotolpropeller, which came into service in time for the Battle of Britain.
Then, with tail trimmer set, throttle and mixture lever fully forward... and puffs of grey exhaust smoke soon clearing at maximum r.p.m. came the surprise! There was no sudden surge of acceleration, but with a thunderous roar from the exhausts just ahead on either side of the windscreen, only a steady increase in speed... In retrospect that first Hurricane sortie was a moment of elation, but also of relief. Apart from the new scale of speeds that the pilot had to adapt to, the Hurricane had all the qualities of its stable, secure biplane predecessor the Hart, but enhanced by livelier controls, greater precision and all this performance.
One of Camm's priorities was to provide the pilot with good all-round visibility. To this end, the cockpit was mounted reasonably high in the fuselage, creating a distinctive "hump-backed" silhouette. Pilot access to the cockpit was aided by a retractable "stirrup" mounted below the trailing edge of the port wing. This was linked to a spring-loaded hinged flap which covered a handhold on the fuselage, just behind the cockpit. When the flap was shut, the footstep retracted into the fuselage. In addition, both wing rootswere coated with strips of non-slip material.
An advantage of the steel-tube structure was that cannon shells could pass right through the wood and fabric covering without exploding. Even if one of the steel tubes were damaged, the repair work required was relatively simple and could be done by groundcrew at the airfield. Damage to a stressed skinstructure, as used by the Spitfire, required more specialised equipment to repair. The old-fashioned structure also permitted the assembly of Hurricanes with relatively basic equipment under field conditions. Crated Hurricanes were assembled in West Africa and flown across the Sahara to the Middle East theatre and, to save space, some Royal Navy aircraft carriers carried their reserve Sea Hurricanes dismantled into their major assemblies, which were slung up on the hangar bulkheads and deckhead for reassembly when needed.
In contrast, the contemporary Spitfire used all-metal monocoque construction and was thus both lighter and stronger, though less tolerant to bullet damage. With its ease of maintenance, widely set landing gear and benign flying characteristics, the Hurricane remained in use in theatres of operations where reliability, easy handling and a stable gun platform were more important than performance, typically in roles like ground attack. One of the design requirements of the original specification was that both the Hurricane and the Spitfire were also to be used as a night fighter. The Hurricane proved to be a relatively simple aircraft to fly at night and was to be instrumental in shooting down several German aircraft during the nocturnal hours. From early 1941, the Hurricane would also be used as an "intruder" aircraft, patrolling German airfields in France at night in an attempt to catch night bombers during takeoffs or landings.