Hawker Hurricane
British fighter aircraft of the 1930s and 40s / From Wikipedia, the free encyclopedia
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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 (RAF). 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.
Hurricane | |
---|---|
Hurricane Mk I, R4118, similar to what would have been flown during the Battle of Britain | |
Role | Fighter aircraft |
National origin | United Kingdom |
Manufacturer | Hawker Aircraft |
Designer | Sydney Camm |
Built by | |
First flight | 6 November 1935 |
Introduction | December 1937 |
Primary users | Royal Air Force |
Produced | 1937–1944 |
Number built | 14,487 (UK and Canada) |
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 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.
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.[1][2] At the time, there was an institutional reluctance towards change within the Air Staff; some senior figures[who?] were prejudiced against the adoption of monoplane fighter aircraft, while mid-level officers were typically more open-minded.[2]
In 1934 the British Air Ministry issued Specification F.5/34 in response to demands within the Royal Air Force (RAF) 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.[3] 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.[4]
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.[5] 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.[6]
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, [N 1][7] However, the P.V.3 was not among the proposals which the Air Ministry selected to be built as prototype to official contract.[N 2] 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.[8]
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.[9]
In July 1934, at a meeting chaired by Air Commodore Arthur Tedder (director of training), 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.[10]/[page needed] 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 (F.36/34) was written around the design. In July 1935, this specification was amended to include installation of eight guns.[4][11]
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.[6] These wings were delivered in June 1936.[6]
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.[4] 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.[12] 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.[13] 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.[14]
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.[4] 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.[15]
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 315 mph (507 km/h) at an altitude of 16,200 ft (4,900 m), climb to 15,000 ft (4,600 m) in 5.7 minutes, and a stalling speed of 57 mph (92 km/h) (only marginally higher than the Gladiator biplane), the last achieved using its flaps.[4]
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.[16] Hawker's response to the issue was to request that spinning tests be waived, but the Air Ministry refused the request;[17] the situation was resolved by the Royal Aircraft Establishment (RAE), 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.[18]
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.[19][20]
Production
In June 1936 the Air Ministry placed its first order for 600 aircraft.[16] On 26 June 1936 the Air Ministry approved the type name of "Hurricane" that had been proposed by Hawker, and an informal naming ceremony occurred the following month during an official visit by King Edward VIII to Martlesham Heath.[16][21]
It was significantly cheaper than Supermarine Spitfire and took 10,300 man hours per airframe to produce, compared to 15,200 for the Spitfire, which had many parts formed by hand, with English wheels.[22] As war was looking likely, and time was of the essence in providing the RAF with an effective fighter, the authorities expected there to be problems with the more advanced Spitfire, while the Hurricane made use of well-proven manufacturing techniques.[22] The service squadrons were also already experienced in maintaining aircraft structurally similar to the Hurricane.[22] A fabric-covered wing was initially adopted in order to accelerate production, while a higher-performing stressed-skin metal wing was introduced in late 1939.[16]
The first production Hurricane I first flew on 12 October 1937, flown by Flight Lieutenant Philip Lucas and powered by a Merlin II engine. While a contract for 600 Hurricanes was received on 2 June 1936, deliveries lagged by roughly six months due to a decision in December 1936 to replace the Merlin I with the improved Merlin II, which resulted in many detail alterations.
Merlin I production ended after 180 were built. This engine had been prioritised for the Fairey Battle light bomber and the Hawker Henley, a failed competitor to the Battle briefly adapted as a target tug which shared common elements with the Hurricane design.[16] By the following December, the first four aircraft to enter service with the RAF had joined No. 111 Squadron, stationed at RAF Northolt. By February 1938, No. 111 Squadron had received 16 Hurricanes.[16] Upon the outbreak of the Second World War, over 550 Hurricanes had been produced equipping 18 squadrons, with 3,500 more on order.[23][24]
During 1940, Lord Beaverbrook, the Minister of Aircraft Production, established the Civilian Repair Organisation through which a number of manufacturers were to repair and overhaul battle-damaged aircraft including Hurricanes. Some of these were later sent to training units or to other air forces. Factories involved included the Austin Aero Company's Cofton Hackett plant and David Rosenfield Ltd, based at Barton aerodrome near Manchester.[citation needed]
The Canadian Car and Foundry of Fort William, Ontario, Canada was a major Hurricane manufacturer, producing them from November 1938 after receiving their initial contract for 40 Hurricanes. The facility's chief engineer, Elsie MacGill, became known as the "Queen of the Hurricanes".[24] The initiative was commercially driven, but was endorsed by the British government. Hawker recognised that a major conflict was inevitable after the Munich Crisis of 1938 and drew up preliminary plans to expand Hurricane production at a new factory in Canada. Under this plan, samples, pattern aircraft, and design documents stored on microfilm were shipped to Canada. In 1938/39 the RCAF ordered 24 Hurricanes to equip one fighter squadron, 20 of which were delivered, and two were supplied to Canadian Car and Foundry as pattern aircraft but one probably did not arrive, while the other was returned to Britain in 1940. The first Hurricane built at Canadian Car and Foundry was completed in February 1940.[24] Canadian-built Hurricanes shipped to Britain participated the Battle of Britain.[24]
Overall, some 14,487 Hurricanes and Sea Hurricanes were produced in England and Canada.[25] The majority of Hurricanes, 9,986 were built by Hawker (who produced the type at Brooklands from December 1937 to October 1942 and Langley from October 1939 to July 1944), while Hawker's sister company, the Gloster Aircraft Company, constructed 2,750. The Austin Aero Company completed 300 Hurricanes. Canada Car and Foundry produced 1,451 Hurricanes.[26] However those shipped to Britain were often incomplete airframes and about 80% were delivered without an engine.
In 1939, production of 100 Hurricanes was initiated in Yugoslavia by Zmaj and Rogožarski.[27] Of these, 20 were built by Zmaj by April 1941. Recognising that the supply of British-made Merlin engines might not be guaranteed, it was decided to fit one of the Yugoslavian Hurricanes with a Daimler-Benz DB 601 engine instead. This aircraft was flown in 1941.[24] In 1938, a contract for 80 Hurricanes was placed with Fairey's Belgian subsidiary Avions Fairey SA for the Belgian Air Force, and it was intended to arm these aircraft with four 13.2 mm (0.52 in) Browning machine guns. Three were built and two flown with this armament by the time of the German invasion of Belgium in May 1940, with at least 12 more constructed by Avions Fairey armed with the conventional eight rifle calibre machine gun armament.[24][28]
The Hawker Hurricane is a low-wing cantilever monoplane with retractable undercarriage and an enclosed cockpit.[29] The primary structure of the fuselage was a Warren truss box-girder with high-tensile steel longerons and duralumin cross-bracing, which were mechanically fastened rather than being welded.[30] Over this, a secondary structure composed of wooden formers and stringers covered with doped linen gave the fuselage a rounded section. The majority of the external surfaces were linen, except for a section between the cockpit and the engine cowling which used lightweight metal panels instead.[31] Camm had decided to use traditional Hawker construction techniques instead of more advanced options, such as a stressed-skin metal construction.[32] This form of construction resembled that of earlier biplanes and was already considered to be somewhat outdated when the Hurricane was introduced to service .[33] The Hurricane was initially armed with an arrangement of eight remotely-operated wing-mounted Browning machine guns, intended for conducting rapid engagements.[34] The Hurricane was typically equipped for flying under both day and night conditions, being provided with navigation lights, Harley landing lights, complete blind-flying equipment, and two-way radios. Upon its entry to service, much of the performance data was intentionally concealed from the general public, but it was known that the type possessed a speed range of 6:1.[35] A simple steel tube structure supported the engine; detachable cowling panels allowed access to most of the engine's areas for maintenance.[36] Installed underneath the fuselage, the liquid-cooled radiator has a rectangular opening to its aft; this is covered by a hinged flap, allowing the pilot to control the cooling level. An atypical feature for the era was the use of Tungum alloy pipes throughout the cooling system.[36]
Initially, the structure of the Hurricane's cantilever wing consisted of two steel spars, which possessed considerable strength and stiffness.[37] The wing was described by Flight as relatively straightforward to manufacture, employing simple vertical jigs to attach the two spars, after which the wing ribs were installed using horizontal bolts, forming separate units between the front and rear spars. Hydraulically-actuated split trailing edge flaps were fitted to the inner end of the wings.[38] This wing was predominantly fabric-covered, like the fuselage, although some lightweight metal sheets were used on the inner wing and its leading edge. The majority of the flight control surfaces, such as the Frise-type ailerons, also had fabric coverings.[38]
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.[12] "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 as much structure."[39] 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 required only three hours work per aircraft.[39]
The Hurricane had a inward-retracting undercarriage, the main undercarriage units being housed in recesses in the wing.[36] Hinged telescopic Vickers-built legs are attached to the bottom boom of the wing's forward spar, but with a angled pivot to allow the strut to be perpendicular to the thrust line when extended and angle rearwards when retracted to clear the forward spar. A hydraulic jack actuated the undercarriage.[36] Two separate hydraulic systems, one being power-operated and the other hand-operated, are present for the deployment and retraction of the undercarriage; in the event of both failing, pilots can release the retaining catches holding the undercarriage in place, deploying the wheels to the 'down' position using weight alone. A wide wheel-track was used to allow for considerable stability during ground movements and to enable tight turns to be performed.[40]
The prototype and early production Hurricanes were fitted with a Watts two-bladed fixed-pitch wooden propeller. Flight commented of this arrangement: "Many have expressed surprise that the Hurricane is not fitted with variable-pitch airscrews".[35] The original two-bladed propeller was found to be inefficient at low airspeeds and the aircraft required a long ground run to get airborne, which caused concern at Fighter Command. Accordingly, trials with a de Havilland variable-pitch propeller demonstrated a reduction in the Hurricane's 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 Rotol propeller, which came into service in time for the Battle of Britain.[41]
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.
Roland Beamont describing his first flight in a Hurricane as a trainee pilot.[42]
Camm's priority 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 roots were coated with strips of non-slip material.[43]
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 ground crew at the airfield. Damage to a stressed skin structure, as used by the Spitfire, required more specialised equipment to repair.[44] The old-fashioned structure also permitted the assembly of Hurricanes with relatively basic equipment under field conditions. Crated Hurricanes were assembled at Takoradi 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.[citation needed]
In contrast, the contemporary Spitfire used all-metal monocoque construction and was thus both lighter and stronger, though less tolerant of 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 night fighters. The Hurricane proved to be a relatively simple aircraft to fly at night, and shot down several German aircraft on night raids. From early 1941 the Hurricane was also used as an "intruder" aircraft, patrolling German airfields in France at night to catch bombers taking off or landing.[citation needed]