In 1936 the Hawker design team at Kingston, under the leadership of Sydney Camm, prepared two versions of a common fighter design, similar in every respect but for the engine mountings and cowlings. One aircraft was designed to take the Rolls-Royce Vulture, and was designated Type R; the other, the Type N, was to be powered by another new high-performance engine, the Napier Sabre.
The Hawker proposal was submitted to the Air Ministry in January 1937, but no action was taken by that department until January 1938, when Specification F18/37 was issued. This covered the design of a new interceptor fighter. Hawker immediately submitted their Type R/Type N proposal afresh. The Hawker tenders were accepted on 22 April 1938 and two prototypes of each aircraft were ordered on 30 August that year.
The Vulture-powered Type R, now known as the Tornado, was the first to fly, on 6 October 1939. The prototype, P5219, had a ventral radiator, a large cockpit rear fairing and a Hurricane-type fin. Originally powered by a Vulture II engine, it was fitted with a Vulture V in March 1941. This developed 2060 hp and gave the aircraft a maximum speed of 423 mph at 23,000 feet. The proposed fixed armament was twelve 0.303 in Browning machine-guns or four 20 mm Hispano cannon.
Early tests with P5219 revealed that the airflow around the outside of the ventral radiator and that over the fuselage and wings interfered with one another, resulting in very high local velocities, particularly at the thick wing roots. Problems with compressibility – the first time this phenomenon had been experienced – manifested themselves in a sharp increase in drag, accompanied by violent shuddering and vibration at speeds approaching 400 mph IAS (indicated airspeed). Photographs showed that wool tufts attached to the rear half of the radiator were actually being blown forwards. To cure the problem the radiator was moved forward to a position immediately below the Vulture engine, necessitating a complete redesign of the nose. In its new guise, P5219 was reserialled P5224.
One thousand Tornadoes had been ordered within eight days of the prototype’s first flight, and a production line for 1000 aircraft was set up by A.V. Roe (Avro), the principal subcontractor. Problems with the Vulture engine, however, continued to mount, and the operational debut of the Avro Manchester revealed even more hitherto unsuspected troubles, such as coolant circulation problems and big-end failures owing to defects in the oil circulation system. It was therefore decided to terminate production of the Vulture and cancel the Tornado production order, although the first and only Avro-built aircraft, HG641, eventually flew on 23 October 1941 fitted with a Bristol Centaurus radial engine. Its flight test programme provided much useful information in the development of the Centaurus-engined Hawker Tempest F.Mk.II.
Meanwhile, Hawker’s second proposal to specification F18/37, the 2200 hp Sabre-engined Type N prototype, now named Typhoon, had made a successful maiden flight on 24 February 1940. Soon afterwards, the Sabre engine went into full production stride; in 1940 Lord Beaverbrook was made Minister of Aircraft Production, and he immediately saw the promise of the Sabre and commandeered facilities for its manufacture. From having practically nothing, Napier suddenly found themselves with an almost embarrassing supply of premises. There were, however, no sudden floods of Sabres, because as yet there were no airframes to accommodate them.
The prototype Typhoon, P5212, was followed by the second aircraft, P5216; by this time, like the unsuccessful Tornado, it had been ordered into quantity production. The Gloster Aircraft Company Ltd at Hucclecote, Gloucester, had been selected as the principal subcontractor. It was originally hoped that the Typhoon, which was of all-metal stressed-skin construction, would be in RAF squadron service by July 1940, but the first production Typhoon Mk IA did not fly until May 1941. Delays in production were blamed on the unreliability of the Sabre engine. However, there were other problems, including a near-catastrophic structural failure of the rear fuselage of P5212, which test pilot Philip Lucas landed safely with great skill and earned himself a well-deserved George Medal.
he Typhoon’s entry into service was inauspicious. The first squadron to equip with the aircraft – No. 56, at Duxford, in September 1941 – was bedevilled by continual engine problems and structural failures, losing several pilots. Moreover, although the aircraft was fast and handled well at medium and low altitudes, its performance at high altitude was inferior to that of both the Focke-Wulf Fw 190 and the Messerschmitt Bf 109F, and its rate of climb was poor. Teething troubles kept the squadron non-operational with the type until the end of May 1942, and at one time there was talk of cancelling the Typhoon programme altogether.
There are experts who have suggested that many of the problems encountered with the Typhoon were caused by lack of expertise in handling the new complex Sabre, rather than technical defects in the engine itself. One such was L.J.K. Setright, who in his book The Power to Fly (Allen & Unwin, 1971) wrote:
By the time it came into service all too many of the really good Fighter Command pilots had gone, and those who had taken their places were generally of poorer quality and were usually given the most hasty and superficial training before being sent out to do battle… When they encountered difficulties with the Sabre they condemned what they did not understand. In fact the engine only presented two serious problems in all its service career, a record considerably less expensive than that of any other engine that springs to mind. One was a certain difficulty in starting when it was very cold. The sleeves were a very tight fit until the cylinder blocks had expanded a little as they grew warm, and many of the internal bearings were fairly tight too, so that at about freezing point or a little below it became virtually impossible to turn the engine over with its Coffman cartridge starter to get it running. The proper technique was to resort to oil dilution, a practice regularly employed by the Germans, and a simple tap in the cockpit discharged the correct amount of petrol into the lubricant in order to achieve this. Even then there were difficulties, for most of the pilots and many of the mechanics were completely unversed in the operation of the Kigass priming system and would usually mishandle it. So with one thing and another, coupled with the tendency to oil leakage inevitable because of the purblind refusal of the Air Ministry to accept paper gaskets in the joints of British-made aero-engines, although they accepted American-built Merlins with such gaskets (and although they did not know it, Napier often slipped them in when no one was looking!) a misfire or failure to get running properly when starting up from cold could have fiery consequences. Many trainee pilots were absolutely terrified of their Typhoons, largely because of this.
Problems with the Typhoon’s tail persisted, and twenty-eight aircraft were lost through structural failure of the rear fuselage before the cause was isolated. One of the problems facing the accident investigators was that no failure had occurred during a high-speed dive or other manoeuvre, which put the greatest strain on the airframe. Eventually it was found that the failures had been caused by ‘flutter’ induced in the elevators, building up to such an extent that it tore off the rear fuselage. The root cause was metal fatigue in a bracket and the positioning of the mass balance within the elevator. Once the fault had been located, the cure was relatively simple.
Wing Commander Roland Beamont, whose role in operationally testing the Typhoon was crucial to the ultimate success of the aircraft, flew the Hawker Tornado prototypes while engaged in Hurricane production testing at Hawkers in 1942. His first flight in a Typhoon was made on 8 March 1942 in a Mk IA with twelve machine-guns. He had this to say about the experience in Fighter Test Pilot (Patrick Stephens Ltd, 1986).
… Once it was established that the noise, vibration and general commotion caused by the big Sabre engine and enhanced by the draughty cockpit with rattling ‘wind-up’ side windows was not actually breaking or stopping anything, it was soon apparent that the aeroplane was pleasantly stable and responsive to controls in all axes, very manoeuvrable (and exceptionally so for that period at speeds above 400 mph) and it had a tremendous turn of speed. A 75 per cent power low-level cruise at over 300 mph was fast for those days as was a massive power ‘level’ of 385 mph; and at the advertised dive limit of 500mph there was adequate control remaining, though with heavy control forces and an impressive noise level.
High speed, however, could produce its own dangers, as one test pilot, E.W. ‘Jock’ Bonar discovered when he put a Typhoon through a series of high-speed dives to investigate oil scavenging problems. Rolling into a dive at 35,000 feet, the Typhoon accelerated vertically, very fast. Suddenly, there was a complete loss of control: the elevators, rudder and ailerons were all completely ineffective. Bonar managed to pull out using the elevator trimmers and regained full control as the aircraft descended into denser air, and was shocked to see that the skin on the wings was shuddering and flapping. Bonar landed safely, but the Typhoon was a complete write-off, the victim of an as yet unknown effect called compressibility.
In the summer of 1942, three squadrons of Typhoons – Nos 56, 266 and 609, the three forming the Duxford Wing – operated successfully against Focke-Wulf Fw 190s and Messerschmitt Bf 109s carrying out fast hit-and-run attacks on ports and other targets on the south coast of England. On 20 January 1943 the Typhoon at last showed what it could do as an interceptor. On that day twenty-eight enemy fighter-bombers, escorted by single-engined fighters, made a daylight attack on London, while diversionary attacks were made on the Isle of Wight and the Kent coast. The balloon barrage had been grounded before the raid, and there was so little warning of the incoming enemy that the defences were taken almost completely by surprise.
However, the Typhoons of No. 609 Squadron were scrambled in time to intercept the raiders on the way out. In the ensuing fight Flying Officer Johnny Baldwin – later to become the top-scoring Typhoon pilot – destroyed three Bf 109Gs, while three Fw 190s were shot down by three other No. 609 Squadron pilots.
Several more successes were achieved against the enemy fighter-bombers by No. 609 Squadron in the weeks that followed. During this period the squadron also continued to expand its offensive operations against targets on the Continent. There was no longer any doubt about the Typhoon’s effectiveness at low level, and No. 609 Squadron’s performance under the command of Roland Beamont effectively killed a last-ditch attempt by the Engineering Branch of Fighter Command, early in 1943, to have the fighter-bomber axed in favour of the American Republic P-47 Thunderbolt. By the end of the year, with the aircraft’s technical problems cured and the growing number of Typhoon squadrons – now carrying a pair of 500 lb bombs on their machines in addition to the built-in cannon armament – striking hard at the enemy’s airfields, communications and shipping, the Typhoon was heading for its place in history as the most potent Allied fighter-bomber of all.