Hawker Hurricane

The **Hawker Hurricane** is one two British-fighters that was commonly on the front lines.

## Characteristics

The Hawker Hurricane is a low-wing cantilever monoplane with retractable undercarriage and an enclosed cockpit. 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. Over this, a secondary structure composed of wooden formers and stringers covered with doped linen 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. Camm had decided to use traditional Hawker construction techniques instead of more advanced options, such as a stressed-skin metal construction. This form of construction resembled that of earlier biplanes and was already considered to be somewhat outdated when the Hurricane was introduced to service. The Hurricane was initially armed with an arrangement of eight remotely-operated wing-mounted Browning machine guns, intended for conducting rapid engagements. 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.

A simple steel tube structure supported the engine; detachable cowling panels allowed access to most of the engine's areas for maintenance. 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.

Initially, the structure of the Hurricane's cantilever wing consisted of two steel spars, which possessed considerable strength and stiffness. 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. 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.

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 as much structure." 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.

The Hurricane had a inward-retracting undercarriage, the main undercarriage units being housed in recesses in the wing. 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. 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.

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". 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.

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.

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. 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.

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 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.

## History

Several were seen at the British-airbase.