Hawker Typhoon
The Hawker Typhoon was a British single-seat fighter-bomber, produced by Hawker Aircraft. It was intended to be a medium-high altitude interceptor, as a replacement for the Hawker Hurricane, but several design problems were encountered and it never completely satisfied this requirement.
The Typhoon was originally designed to mount twelve.303 inch Browning machine guns and be powered by the latest engines. Its service introduction in mid-1941 was plagued with problems and for several months the aircraft faced a doubtful future. When the Luftwaffe brought the new Focke-Wulf Fw 190 into service in 1941, the Typhoon was the only RAF fighter capable of catching it at low altitudes; as a result it secured a new role as a low-altitude interceptor.
The Typhoon became established in roles such as night-time intruder and long-range fighter. From late 1942 the Typhoon was equipped with bombs, these bomb-carrying aircraft being nicknamed "Bomphoon" by the press. From late 1943 RP-3 rockets were added to its armoury. With those weapons and its four 20 mm Hispano autocannon, the Typhoon became one of the Second World War's most successful ground-attack aircraft.
Design and development
Origins
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. Two preliminary designs were similar and larger than the Hurricane. These later became known as the "N" and "R", because they were designed for the newly developed Napier Sabre and Rolls-Royce Vulture, engines respectively. Both engines used 24 cylinders and were designed for over ; the difference between the two was primarily in the arrangement of the cylinders – an H-block in the Sabre, and an X-block in the Vulture. 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.In March 1938, Hawker received the complete Specification F.18/37 and invitation to tender for a fighter which would be able to achieve at least at, a ceiling of not less than 35,000 ft and specified a British engine with a two-speed supercharger. The armament fitted was to be twelve.303 inch Browning machine guns with 500 rounds per gun, with a provision for alternative combinations of weaponry. As well as Hawker, Gloster, Supermarine and Bristol submitted one or more designs each. Two prototypes of both the Type N and R were ordered on 3 March 1938 Camm and his design team started formal development of the designs and construction of prototypes.
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.
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. 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.
The wing had a span of, with a wing area of. It was designed with a small amount of inverted gull wing bend; the inner sections had a 1° anhedral, while the outer sections, attached just outboard of the undercarriage legs, had a dihedral of °. The airfoil was a NACA 22 wing section, with a thickness-to-chord ratio of 19.5% at the root tapering to 12% at the tip.
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. 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 ; while the "nose" tanks, built into the wing leading edges, forward of the main spar, had a capacity of each. Also incorporated into the inner wings were inward-retracting landing gear with a wide track of 13 ft in.
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 in level flight at 20,000 ft, the thick wings created a large drag rise and prevented higher speeds than the 410 mph at achieved in tests. The climb rate and performance above that level was also considered disappointing. When the Typhoon was dived at speeds of over, the drag rise caused buffeting and trim changes. These compressibility problems led to Camm designing the Typhoon II, later known as the Tempest, which used much thinner wings with a laminar flow airfoil.
Prototypes
The first flight of the first Typhoon prototype, P5212, made by Hawker's Chief test Pilot Philip Lucas from 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. Although unarmed for its first flights, P5212 later carried twelve.303 in 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. P5212 also had a small tail-fin, triple exhaust stubs and no wheel doors fitted to the centre-section. On 9 May 1940 the prototype had a mid-air 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.On 15 May 1940, the Minister of Aircraft Production, 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.
As a result of the delays the second prototype, P5216, first flew on 3 May 1941: P5216 carried an armament of four belt-fed 20 mm Hispano Mk II cannon, with 140 rounds per gun and was the prototype of the Typhoon IB series. Specification F.9/37 had been modified to include cannon armament as progress with the Westland Whirlwind cannon fighter and Boulton Paul's twin-engined turret fighter with cannon was slow.
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. 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.
Operational service
Low-level interceptor
In 1941, the Spitfire Mk Vs, which equipped the bulk of Fighter Command squadrons, were outclassed by the new Focke-Wulf Fw 190 and suffered many losses. The Typhoon was rushed into service with Nos. 56 and 609 Squadrons in late 1941, to counter the Fw 190. This decision proved to be a disaster, as several Typhoons were lost for unknown reasons and the Air Ministry began to consider halting production of the type.In August 1942, Hawker's second test pilot, Ken Seth-Smith, while deputising for Lucas, carried out a straight and level speed test from Hawker's test centre at Langley, and the aircraft broke up over Thorpe, killing the pilot. Sydney Camm and the design team immediately ruled out pilot error, which had been suspected in earlier crashes. Investigation revealed that the elevator mass-balance had torn away from the fuselage structure. Intense flutter developed, the structure failed and the tail broke away. Modification 286 to the structure and the control runs partially solved the structural problem. Mod 286, which involved fastening external fishplates, or reinforcing plates, around the tail of the aircraft, and eventually internal strengthening, was only a partial remedy, and there were still failures right up to the end of the Typhoon's service life. The Sabre engine was also a constant source of problems, notably in colder weather, when it was very difficult to start, and it suffered problems with wear of its sleeve valves, with consequently high oil consumption. The 24-cylinder engine also produced a very high-pitched engine note, which pilots found very fatiguing.
The Typhoon did not begin to mature as a reliable aircraft until the end of 1942, when its excellent qualities – seen from the start by S/L Roland Beamont of 609 Squadron – became apparent. Beamont had worked as a Hawker production test pilot while resting from operations, and had stayed with Seth-Smith, having his first flight in the aircraft at that time. During late 1942 and early 1943, the Typhoon squadrons were based on airfields near the south and south-east coasts of England and, alongside two squadrons with the Griffon-engined Spitfire XII, countered the Luftwaffes "tip and run" low-level nuisance raids, shooting down a score or more bomb-carrying Fw 190s. Typhoon squadrons kept at least one pair of aircraft on standing patrols over the south coast, with another pair kept at "readiness" throughout daylight hours. These sections of Typhoons flew at or lower, with enough height to spot and then intercept the incoming enemy fighter-bombers. The Typhoon finally proved itself in this role; for example, while flying patrols against these low-level raids, 486 Squadron claimed 20 fighter-bombers, plus three bombers shot down, between mid-October 1942 and mid-July 1943.
The first two Messerschmitt Me 210 fighter-bombers to be destroyed over the British Isles were shot down by Typhoons in August 1942. During a daylight raid by the Luftwaffe on London on 20 January 1943, four Messerschmitt Bf 109G-4s and one Fw 190A-4 of JG 26 were destroyed by Typhoons. As soon as the aircraft entered service, it was apparent the profile of the Typhoon resembled a Fw 190 from some angles, which caused more than one friendly fire incident involving Allied anti-aircraft units and other fighters. This led to Typhoons first being marked up with all-white noses, and later with high visibility black and white stripes under the wings, a precursor of the markings applied to all Allied aircraft on D-Day.