As the Hurricane was the culmination of a design theme extending back to the 1920s, Hawker’s next fighter, designed to meet Specification F.18/37, had to be much more radical. Although the centre and front fuselage featured the familiar tubular construction with detachable panels for maintenance purposes, the rear fuselage aft of the cockpit was of stressed skin construction and was attached to the forward section at four points. The wings consisted of two built-up box spars and ribs, the whole covered with flush-riveted Alclad sheet. The wing exhibited a modest crank with 1 degree of anhedral on the inner section, changing to 5½ degrees dihedral on the outer section. A wide-track, inward-retracting undercarriage was located at the point of wing crank, the outer wings being designed to house a total of twelve 0.303 in Browning machine-guns, although this armament fit was soon dropped in favour of four 20-mm Hispano cannon. Two versions were proposed, the Tornado with a Rolls-Royce Vulture 24-cylinder ‘X’ layout engine and the Typhoon, powered by a 24-cylinder Napier Sabre sleeve-valve engine. Both units had the potential of producing around 2000 hp. As each engine was still a long way from being fully developed, two very similar prototypes were ordered as insurance against one being a failure.
Development problems with the Napier Sabre engine meant that the Tornado was the first to take to the air, when Philip Lucas flew the prototype (P5219) on 6 October 1939. Early flight testing went well until the aircraft was flown at speeds approaching its design maximum of 400 mph, when excessive drag was experienced at the exit of the radiator, which was mounted under the centre section. This problem was eventually solved by moving the radiator under the nose, a position also adopted for the Typhoon. The latter joined its stablemate in the air on 24 February 1940, but the first aircraft (P5212) was very nearly lost on 9 May when a failure occurred in the rear fuselage monocoque where it joined the cockpit section. Rather than bale out, Philip Lucas elected to stay with his stricken aircraft and carried out a successful landing, for which he was subsequently awarded the George Medal.
The second Tornado (P5224) was flown on 5 December 1940 and, together with P5219, was fitted with a Vulture V of 1980 hp early the following year in place of the original 1760 hp Vulture II. P5224 was eventually delivered to A&AEE in late 1941 for performance and handling trials. This was some time after a similar assessment had been carried out on the Typhoon, as the Vulture engine had also hit serious development problems. Flying was carried out at an all-up weight of 10,690 lb at a CG 11.6 in forward of datum (the design limits were 12.6 in to 9.6 in forward of datum).
The recommended flap setting on take-off was 30 degrees, with the tail trim set slightly forward of central (slightly nose heavy) and with rudder bias halfway to the full left position. Even so, there was a strong tendency to swing to the right, which became very pronounced as full throttle was reached, but this could easily be held by applying left rudder. For take-off, the tail could be easily raised with only a small throttle opening. Retraction of the undercarriage produced noticeable tail heaviness, which could be held before re-trimming, but there was no trim change when the flaps were raised. Sufficient rudder bias was available to trim the aircraft ‘feet off’ in the climb.
The handling characteristics were virtually identical to the Typhoon, although the Tornado appeared to have greater longitudinal stability. All normal aerobatics could be performed without difficulty and dives were made up to 450 mph IAS. The aircraft was very pleasant to fly in MS gear, but a rather disconcerting vibration was felt in FS gear, which was at its worst at maximum power. The source of this vibration could not be determined, but it was less apparent when flying with a weak fuel mixture. If the throttle was opened very slowly, the engine would run smoothly for about thirty seconds before the vibration recommenced. This particular phenomenon was of considerable concern and it was belived that, in time, it might have a serious effect on the aircraft’s structure. Similar high-frequency vibration had also been experienced with the Typhoon and although modifications to the engine mountings reduced this characteristic, it was not entirely eradicated.
The stall speed with flaps and undercarriage up was 82 mph IAS, reducing to 61 mph IAS with flaps and undercarriage down. Characteristics at the stall were similar to the Typhoon, but the actual stall speeds were considerably lower. The best approach speed was 90 mph IAS and the landing was straightforward and easy to perform.
As P5224 was only at A&AEE for a limited period, climbing trials consisted of one climb in MS gear and one in FS gear. The results were combined to produce the Tornado’s climb performance with supercharger gear being changed at 10,000 ft. The maximum rate of climb was found to be 3500 ft/min up to full throttle height in MS gear at 3200 ft and the time to reach 20,000 ft was 7.2 minutes. The full throttle height in FS gear was 16,800 ft which was achieved in 5.8 minutes with a rate of climb of 2550 ft/min. The service ceiling was 34,900 ft, this height being reached in 29 minutes, by which time the rate of climb had reduced to 100 ft/min. The full results were as follows:
During the climb, oil-cooling requirements were met for temperate summer conditions, but not for tropical summer conditions. The performance of the radiator did not fulfil either requirement.
Level speed runs were only made in FS gear and during these trials boost was limited by the automatic boost control to 8 lb/sq.in instead of 9 lb/sq.in. Ballast was added to obtain the correct weight of 10,690 lb. The maximum speed was recorded as being 398 mph at 23,300 ft, but it was considered that had full boost been available a top speed of 400 mph would have been achieved. Other results are included in the table:
Although the Rolls-Royce Vulture performed reasonably well in the Tornado, it had also been selected to power the twin-engined Avro Manchester bomber but suffered chronic reliability problems. The Manchester had been rushed into service in November 1940. However, a spate of engine failures did not bode well and as little improvement had been made by the middle of the following year, future contracts for the aircraft were cancelled and the decision was also taken to terminate production of the Vulture. Had the Tornado programme gone ahead, it would have been produced by Avro at its factory at Yeadon near Leeds, as Hawker was fully occupied with the Hurricane. Before cancellation, the first production Tornado (R7936) was flown on 29 August 1941. This aircraft was subsequently used for trials work with Rotol and de Havilland contra-rotating propellers. A third Tornado prototype (HG641) had also been ordered and this was flown for the first time on 23 October 1941. It was powered by a 2210 hp Bristol Centaurus CE.4S 18-cylinder radial engine and was used as a development aircraft for the Typhoon II, which became the Tempest (see Chapter 7).
With the demise of the Tornado, this left just the Typhoon, which was itself beset by development difficulties, many of which were also engine related. The first Typhoon to be tested by A&AEE was P5212, which was put through its paces as the Battle of Britain was reaching its climax. The aircraft was flown by Flight Lieutenant Sammy Wroath from the Hawker airfield at Langley near Slough, his subsequent report being generally favourable.
Access to the cockpit was via hinged ‘car-type’ doors on either side of the fuselage. In addition, the roof panel could also be opened. A retractable handhold was located on the outside of each door and was connected to the locking handle on the inside. This was considered to be an unsatisfactory arrangement, as it was felt that the handhold might be used by a member of the ground crew when climbing down from the wing, which could lead to the door being unlocked without the pilot being aware. A problem had already occurred during the first dive to limiting speed by Philip Lucas, when one of the handles had been sucked out by air pressure, thereby unlocking the door.
The view to either side was good, but that ahead was blocked by the engine. Of more significance was a complete lack of vision to the rear, caused by solid fairings behind the pilot’s head and the fact that no rear view mirror was fitted. The curved side panels of the windscreen gave rise to some slight distortion, as did the moulded roof, which was particularly bad at the edges. Large side windows were provided, operated by a cable and sprocket gear, and these formed excellent clear view panels. However, the operating mechanism left something to be desired as it was not robust enough, and could not be shut at speeds above 250 mph IAS, as the upper edge did not enter its locating groove as a result of distortion caused by suction.
The cockpit itself was roomy and comfortable, all the flying controls could be moved freely and the rudder bar was easily adjusted. The controls for the throttle, propeller, two-speed supercharger, radiator shutter, flaps and undercarriage were all located on the left-hand side of the fuselage and fell easily to hand. The elevator and rudder trim controls were also positioned to the pilot’s left but were considered to be too close to the fuselage side for easy operation. The indicators were also rather small and the readings were difficult to distinguish. There was a ‘spongy’ feel to the elevator trimmer, which was very sensitive and would have benefited from lower gearing. A hand pump was provided to the left of the pilot’s seat in case of failure of the engine-driven hydraulic pump, and for emergency operation of the undercarriage a trip mechanism could be operated to allow the wheels to drop to the down position by gravity. The fuel cocks, switches and indicators were all located on the right-hand side of the cockpit.
The noise levels in the cockpit were very low in comparison with other fighter aircraft of the period, even when flying at limiting speed in dives, and this was considered to be one of the best features of the Typhoon. Should it be necessary to make an emergency exit, the pilot had first to release both door latches, before pulling down on a lever on each side of the cockpit to withdraw the hinge pins of the cabin doors which, together with the roof, were jettisoned. The system had been tried in the air at a speed of about 350 mph IAS and had worked well. Should the aircraft overturn on the ground, it was thought that the side doors would open sufficiently for the pilot to be able to get out.
Flight trials were carried out at a take-off weight of 10,620 lb. Ground handling was good, the Dunlop brakes operated smoothly and the aircraft showed no tendency to ‘peck’. On take-off, there was a strong swing to the right, especially at full throttle, but this could be controlled by rudder, which was moderately light and effective. Prior to take-off, the rudder trim was normally set to one-half left to help counteract the swing. Although the optimum flap setting to achieve the shortest take-off run was 45–50 degrees, it was recommended that the flaps be set to 30 degrees to combine an acceptable take-off performance with reasonable safety. Once airborne, no difficulty was experienced in maintaining directional control and there was sufficient rudder bias to allow the aircraft to be climbed ‘feet off’.
In level flight the aircraft was stable about all three axes, the controls being light, effective and well harmonised. Because of the torque effect of the propeller, the Typhoon was easier to bank to the right than to the left, and during tight turns, less back stick was required to maintain a turn to the right. Like the Tornado, some vibration was experienced, particularly during steep turns at about 320 mph IAS (3150 rpm, +3 lb/sq.in boost), which was attributed to the engine mountings. Some trouble was experienced with the fuel system, which consisted of four self-sealing tanks (two main tanks in the wings and two in the nose) with a total capacity of 154 gallons. When drawing fuel from the main tanks, the port tank tended to empty first, as a result of which air was sucked into the system and the engine cut. However, if the supply was quickly switched to the nose tanks, it picked up again immediately.
Several dives were made up to 475 mph IAS, during which the aircraft was extremely steady with no tendency towards wing drop so that it could be held on a target with ease. The ailerons were moderately light and effective up to this speed and there was no sign of over-balancing or snatching. The elevator and rudder controls were also moderately light and well harmonised with the ailerons, yaw being applied at speeds of 430–50 mph IAS without any sign of the rudder over-balancing. As the aircraft exhibited a degree of tail heaviness in the dive requiring a moderate push force to overcome, the level of acceleration forces on recovery was not excessive.
No comprehensive stalling tests were carried out at this stage, but stall speeds with flaps and undercarriage up and down were 88 and 70 mph IAS respectively, which were somewhat higher than the figures recorded on the Tornado. Slow speed turns could be made with ease and, with the flaps and undercarriage down, turns of 30 degree angle of bank were made down to 80 mph IAS with a low fuel load. The best speed to lower the wheels on the approach was 160 mph IAS and although this led to some fore-and-aft pitching, it was not considered serious. When in the landing configuration, the best approach speed was 100 mph IAS, with touchdown occurring at 72 mph IAS. The tail could be easily lowered and full braking did not cause any swing, neither was there any indication of nose heaviness.
The Typhoon was fitted with a de Havilland Hydromatic three-blade propeller of 14 ft diameter, but performance testing was complicated to a certain extent by a temporary limitation of 3150 rpm for the change over from MS to FS gear so that climbing trials were carried out in FS supercharger from 8000 ft. A maximum rate of climb of 2730 ft/min was achieved at full throttle height of 15,500 ft. The best climbing speed was 200 mph IAS up to 16,000 ft, reducing by 4 mph per 1000 ft thereafter. One climb was made to 29,000 ft, although this had to be abandoned owing to ignition trouble. Further testing had to be discontinued due to failure of the radiator which had to be removed for repair by the manufacturers. The estimated absolute ceiling was 33,000 ft. The full results were as follows:
The take-off run was measured at 525 yards when corrected for zero wind and ISA conditions, with 845 yards being needed to clear 50 ft. In comparison with the Tornado, the Typhoon was faster by around 10 mph, with a maximum speed of 410 mph TAS at a full throttle height of 19,800 ft in FS gear. The maximum speeds were recorded from 10,000 ft.
TAS – mph
IAS – mph
After his experiences with P5212, Sammy Wroath compiled a reasonably favourable assessment praising in particular its speed, its light and well harmonised controls, and its relatively quiet cockpit. However, he criticised the Typhoon’s lack of altitude performance, its poor rearward vision, oversensitive elevator trimmer and inadequate cockpit heating as height was gained. Problems had also been experienced with the radiator, as there had been inadequate engine cooling, even when operating in temperate conditions.
Further testing with P5212 looked at aileron response, stalling, the effect of gun-firing and behaviour in the dive. The method of testing aileron response involved placing the aircraft in a 45-degree bank, then applying one quarter opposite aileron and measuring the time taken to roll back through level flight to 45 degrees opposite bank. This particular test was carried out over a wide speed range from 240–460 mph IAS with very consistent results. The time taken varied from 4¾–5¾ seconds, which reflected the lack of heaviness of aileron control as speed was increased. Just before the stall the nose was very high with general vibration and tail buffeting. As the aircraft stalled, the starboard wing dropped sharply to an angle of about 45 degrees, followed by the nose, but there was no tendency to spin. Once the control column was moved forward, recovery was immediate and only around 300 ft in height was lost. Both the rudder and elevator remained effective up to the stall, but the ailerons began to lose their effectiveness, though they remained adequate if large angles were used.
Firing the twelve Browning machine-guns did not produce any vibration or change in handling qualities, and from the pilot’s point of view their operation was hardly noticeable. On one occasion, when only the guns on the port side fired, only a very slight yaw to port was recorded. During diving trials it was found that the cabin roof opened slightly at speeds above 470 mph IAS, but even after the locking mechanism was tightened, a fractional gap could still be seen. In the dive the aircraft behaved in similar fashion to that noted in the first series of tests with the ‘sponginess’ of the elevator trimmer being particularly bad. The engine and propeller functioned satisfactorily, with the constant speed unit keeping rpm at 3700 throughout, and the cabin doors stayed firmly shut, unlike on some early test flights. The maximum endurance was measured at 2¼ and 1½ hours for flight at 15,000 ft and 25,000 ft respectively which, although meeting the requirements of the time, was considered to be a little disappointing.
Although the Typhoon had an impressive turn of speed at low to medium levels, it was obvious at an early stage that its thick wing was not conducive to high levels of performance at altitude. Its relatively high wing loading at 38½ lb/sq.ft also conspired against manoeuvrability. At the time that P5212 was being tested, the first examples of the Messerschmitt Bf 109F were seen in the skies over Britain. This aircraft was capable of fighting effectively at higher altitudes than its predecessor, the Bf 109E. If this trend was to be repeated in bomber design, as seemed likely with Junkers Ju 86P reconnaissance aircraft regularly flying over the UK at altitudes up to 40,000 ft, Fighter Command would have had to fight at a serious disadvantage, should attacks on the scale of the Battle of Britain be repeated. Sydney Camm was quick to offer a ‘thin wing’ F.18/37, which was to evolve into the Tempest, but in the meantime the RAF would have to make do with the Typhoon and more advanced versions of the Spitfire.
Despite the fact that the Typhoon was the RAF’s fastest fighter by a considerable margin when it entered service with 56 Squadron in September 1941, there was no guarantee that it would remain in that position for very long, as the development programme was in serious trouble in several respects. Napier was struggling with the Sabre engine, in particular with frequent failures caused by uneven wear of the sleeve valves. Even by the end of 1942 the time between overhauls (TBO) was still only twenty-five hours. The Typhoon was also badly affected by carbon monoxide (CO) contamination, although this tended to vary between individual aircraft. Improved sealing of the cockpit did not completely eradicate the problem and as a result pilots had to be on oxygen whenever the engine was running. There were also a worrying number of in-flight break-ups caused by failure of the rear fuselage at the transport joint. A modification programme was initiated to reinforce this particular area, but structural failures continued to occur and were to do so throughout the Typhoon’s career, albeit with reduced frequency. Other possible causes of these accidents were failure of the elevator mass-balance or elevator flutter, but a conclusive answer was never found.
For a considerable time the future of the Typhoon was in doubt, with ‘pro’ and ‘anti’ factions within Fighter Command arguing their respective cases. A suitable role was needed for the Typhoon and for a time it was considered as a night-fighter, working with twin-engined Havocs equipped with Turbinlite aerial searchlights. But the difference in speed between the two aircraft proved to be too great and the whole concept was soon abandoned. It was also suggested that the Typhoon be fitted with Airborne Interception (AI) radar and R7881 was fitted with AI.VI in early 1943. To assess the suitability of the Typhoon for night flying R7617 was delivered to Boscombe Down for testing in August 1942.
As tested, R7617 weighed 10,770 lb and was powered by a Sabre II with a fully balanced crankshaft. The instrument panel was illuminated by floodlights low down on each side of the cockpit, with dimmer switches being fitted on the panel itself. The compass had its own light with a dimmer. Landing lights were located in each leading edge and could be dipped by a lever fitted to the engine control box. Unfortunately, the cockpit lights tended to dazzle the pilot and cause reflections, but when the intensity was lowered to overcome this there was then insufficient light to read the instruments. In addition, the fuselage to the side of the pilot was not illuminated so that the elevator and rudder trimmers were in darkness.
It was almost impossible to see through the curved side panels of the windscreen at night and the view directly forward was only moderate, but with the side windows wound down the pilot could see adequately to the side and down. When flying at full throttle, the exhaust could be seen as a yellowish-blue flame if the pilot moved his head to one side, but it did not interfere significantly with his night vision. The Typhoon’s stability in the air made night flying relatively easy, the greatest difficulty being experienced on landing, owing to the poor forward view, which meant that the aircraft had to be put down further to one side of the flare path than was usual with other types. In the event, R7881 was the only Typhoon to be fitted with AI radar, as by mid 1943 the night-fighter role was being adequately fulfilled by the Mosquito, which offered only marginally reduced performance, but with the advantages of greater endurance, twin engines and a two-man crew to share the workload.
In December 1942 Typhoon IB R7673 arrived at A&AEE for spinning trials to determine the best method of recovery. The take-off weight was 11,040 lb and the aircraft was in full operational trim apart from lacking an aerial mast and aerials. Spins were made to the right and left from 15,000 ft and 25,000 ft, the method of entry being from a turn at a speed of about 95 mph IAS. When spinning to the left from 15,000 ft, the aircraft was reasonably steady, although some fore-and-aft pitching was apparent. The rate of rotation was considered to be rather slow for such a heavy aircraft with a high wing loading, the nose position being well below the horizon. On the first spin full opposite rudder was applied after two turns, followed by a slow forward movement of the control column, but after three more turns there was still no sign of recovery. The throttle was therefore opened, whereupon the aircraft responded immediately. Two more spins were made to the left and on both occasions recovery commenced as soon as anti-spin controls were applied, leading to the assumption that in the first case ‘full’ opposite rudder had not been quite full enough. The total height loss in a two-turn spin, including recovery, was 3300 ft. Spins to the right were very similar, except that the height loss was around 3800 ft.
Spins to the left from 25,000 ft were very much the same as those carried out at the lower height, but spins to the right were somewhat different. On entering the spin, the nose fell below the horizon, as was to be expected, but it then rose again so that after one turn it was above the horizon. As the aircraft commenced its second turn the nose fell once more, after which a recovery was attempted but without success as the nose stayed down and the rate of rotation increased. There was also considerable ‘kicking’ on the rudder control. In this instance the use of engine was not attempted as opening the throttle would only cause the aircraft to yaw to the right, i.e. into the spin. Instead, the control column was moved backwards and forwards in an attempt to make the aircraft pitch. Although this appeared to have no effect initially, a slow recovery was commenced after about another three turns. Considerable height was lost during this procedure, level flight eventually being regained at 17,000 ft.
By mid 1942 the Typhoon was in service with Nos 56, 266 and 609 Squadrons of the Duxford Wing and was also replacing Hurricanes with Nos. 1, 257 and 486 Squadrons. As the only aircraft at the time capable of catching the Focke-Wulf Fw 190A, which was being used for low-level hit-and-run raids on coastal towns, it was important to have precise figures for climb and level-speed performance. In addition, an Fw 190 had just been presented to the RAF by an errant Luftwaffe pilot and was thus available for comparison. R7700 was used to assess the Typhoon’s capabilities, the trials being carried out from June to September 1942. The aircraft was powered by a Sabre II of 2180 hp and was fitted with a transparent fairing to the rear of the cockpit instead of the solid fairing, which had been the subject of much criticism. The maximum permissible settings for the Sabre II at the time of testing were 3500 rpm, +6 lb/sq.in (climb); and 3700 rpm, +7 lb/sq.in (level flight, limited to five minutes).
The aircraft was climbed to 31,000 ft with the radiator shutter open at the best climb speed, which was 185 mph IAS decreasing by 3 mph per 1000 ft above 16,000 ft. The supercharger was changed from MS to FS gear at 12,600 ft. The maximum rate of climb was 2790 ft/min in MS gear at 6300 ft and 2000 ft/min in FS gear at 17,800 ft. The service ceiling was estimated to be 32,200 ft with an absolute ceiling of 33,000 ft. Other results were as follows:
The maximum speed performance in level flight was tested with radiator shutters in the closed position and in MS gear the best figure achieved was 376 mph TAS at 8500 ft with 394 mph TAS being recorded in FS gear at 20,200 ft. Other speeds at selected heights were as follows:
On 19 August 1942 the Duxford Wing took part in the ill-fated Dieppe operation. One Dornier Do 217 was claimed destroyed for the loss of two Typhoons of No. 266 Squadron. Several important lessons were learned after this particular shambles, one of which was that overwhelming tactical air power would be necessary if an invasion of Northern France was to stand any chance of success. The desperate need for fighter-bombers was to put an end, once and for all, to the calls for the Typhoon to be taken out of service. From the beginning of 1943 its role was to be geared very much towards ground attack, initially with 250-lb and 500-lb bombs mounted on racks under the wings, but ultimately with 1000-lb bombs. Trials were carried out at Boscombe Down in September 1942, to determine whether carrying underwing stores affected the aircraft’s handling characteristics.
The aircraft used, Typhoon IB R7646, was flown with 500-lb medium case bombs on faired racks, although it was also tested with the fairings removed. With both bombs and fairings in place, the take-off weight was 12,155 lb. The first tests were made with bomb racks and fairings but no bombs, to check for vibration which had been experienced on all aircraft previously flown by the establishment. Vibration levels were found to be more pronounced but, in addition, a further vibration was felt which had not been noted on other aircraft. This occurred only at speeds between 110–140 mph IAS with the engine throttled right back and with flaps and undercarriage up, and was quite violent, being felt throughout the aircraft. It was not experienced with the engine on, or with flaps and undercarriage down, and there was also a marked reduction when the flaps were lowered by 20 degrees.
With two 500-lb bombs in place on faired racks the take-off run was noticeably longer, but the characteristics were generally the same, except that any bouncing or bucketing was slightly more pronounced. In the air, the handling was very much the same, although lateral control was rather heavier and vibration levels were more intense, which made the aircraft unpleasant to fly. At climbing speed the aircraft was unstable, becoming just stable at cruising speed and stable at maximum speed. It was also stable when gliding on the approach with the flaps and undercarriage down. The stalling characteristics were also similar, although the actual speeds were, as expected, a little higher at 93 mph IAS and 70 mph IAS respectively with the flaps and undercarriage up and down. With the aircraft trimmed for maximum level speed, dives were carried out up to 400 mph IAS. Up to 350 mph IAS the Typhoon’s behaviour was normal, but above this speed buffeting was experienced. This was slight at first but tended to increase with speed and was quite marked between 380–400 mph IAS, although as it did not affect the steadiness of the aircraft, it was considered acceptable. The left wing tended to drop with increases in speed and the ailerons became slightly heavier, but, even at limiting speed, control remained good. The speed performance in level flight at 8000 ft with two 500-lb bombs was 336 mph IAS, which was 36 mph IAS less than that achieved with the aircraft in the clean configuration.
The aircraft was also flown with a bomb carried under the port wing only, to assess the handling characteristics in the asymmetric condition. When the starboard bomb was dropped at 240 mph IAS, the pilot could hardly detect when it left the aircraft as there was no immediate change in lateral trim. At moderate to fast speeds the aircraft was only slightly out of trim (left wing low), there was no tendency to overbank to the left, nor was any difficulty experienced in banking quickly to the right. At slower speeds the effect of the asymmetric load became more pronounced and at speeds near the stall, or on the approach glide, the stick had to be held over to the right to keep the port wing up.
The characteristics at the stall were the same as with both bombs attached and even with the bomb on the port wing, the right wing still tended to drop. In the dive the Typhoon’s behaviour was very similar to the two-bomb case, except that there was slightly less buffeting. The aircraft was not landed in the asymmetric condition, but it was felt that the level of control was sufficient in an emergency. However, it was recommended that the aircraft be put down on a runway to avoid the possibility of a bounce causing the left wing to drop, as there might not be enough aileron control to raise it. The aircraft was also flown with a single bomb under the starboard wing with similar results. When flown without fairings fitted, the Typhoon handled in similar fashion, except in the dive when a slight but continuous pitching set in above 300 mph IAS, together with slight lateral and directional instability, which made it impossible to keep the aircraft steady. This became worse with increase in speed and the dive was discontinued at 360 mph IAS.
Just as the Tornado had been intended for production by Avro, the Typhoon was produced by Gloster, another firm in the Hawker Siddeley group of companies, at its factory at Hucclecote. The Typhoon continued to be developed throughout its life, in particular the hood, which was revised several times. The final design incorporated a sliding ‘bubble’ canopy in place of the original doors, which were often likened to those from an Austin 7 car. To reduce drag, the aerial mast was replaced by a whip aerial and fairings were added to the cannon barrels and exhausts. Late production machines also featured a four-blade de Havilland propeller, which was tested on DN340 at A&AEE in September 1943. Particular attention was paid to longitudinal and directional stability and control as adverse comments had been received from the squadrons.
The characteristics on take-off were similar to those of previous Typhoons, except that the swing to the right appeared to be slightly less strong. Directional stability was tested in the climb by trimming the aircraft and then displacing the rudder through a small distance in either direction, to see if it would return to its original position when released. But in the event, it tended to remain in the displaced position and the aircraft would skid along with the nose about 3 degrees removed from the direction of travel. When larger rudder displacements were made, the nose made some effort to return to the trimmed state, but tended to take up the same position noted above. In terms of longitudinal stability, if the elevator was moved to give a speed change of around 10 mph IAS and then released, a sharp divergence in speed, either up or down, occurred.
The instability in yaw and pitch was also apparent in cruising flight up to 230 mph IAS, after which the effect decreased with speed, although it was still present to some extent even at maximum speed. Turns without the use of rudder showed no sign of tightening, although stick force was very light, but if right rudder was used in a turn to the right the aircraft did tighten up due to the gyroscopic forces of the propeller. DN340 was only dived to 450 mph IAS instead of its limiting speed of 525 mph IAS due to bad weather. As the instability tended to decrease with speed, high-speed dives were not too much of a problem, the aircraft tending to return to its trimmed position when the rudder was displaced. However, rudder trimming was found to be very sensitive and a change in yaw produced a most unpleasant fore-and-aft pitching motion.
The four-blade propeller brought about a big improvement in the level of vibration, which significantly reduced, although there was a regular engine ‘beat’ about once every second between 2900–3200 rpm. Although stability had worsened slightly, the reduced level of vibration far outweighed this. However, it was felt that the tendency to skid might introduce difficulties as regards aiming at a target. As part of the investigations into structural break ups, it had been proposed to fit an inertia weight to the Typhoon’s control column and this system had already been tested on R7700. It was found that the high levels of vibration experienced on this aircraft were transmitted via the weight to the pilot’s hand on the stick. This was considered unacceptable, but the reduced vibration with the four-blade propeller meant that this complaint was no longer valid and later aircraft were fitted with an inertia weight and a carefully mass-balanced elevator (late production Typhoons were also fitted with the enlarged Tempest tail to improve longitudinal stability, especially when carrying two 1000-lb bombs).
The Typhoon was to be fitted with a wide variety of underwing stores, including smoke bombs, long-range tanks, anti-personnel bombs and napalm. However, it will forever be remembered for its use of one particular weapon, the 3 in rocket projectile or RP, a rather crude, simple device that could pack a devastating punch. Each rocket consisted of a 3 in diameter cast iron pipe containing the propellant, with four cruciform stabilising fins at one end and a 60-lb semi-armour piercing warhead at the other.
In April 1944, brief handling trials were performed by EK497 at Boscombe Down at a take-off weight of 12,245 lb with eight RP in place. In many areas the RP installation did not affect the handling characteristics ; the take-off, although noticeably longer, was similar and the controls were not adversely affected in any way. Longitudinal stability was actually improved over that of the clean aircraft, which made it more pleasant to fly. This was due to a forward shift in CG of approximately 1½ in when RPs were fitted. Stall speeds of 95 mph IAS and 78 mph IAS were recorded with the gear up and down, the nose and starboard wing dropping, as was to be expected. Recovery was immediate on relaxation of back pressure on the control column.
Dives were made up to 480 mph IAS with the engine set to 3500 rpm, +6 lb/sq.in boost and the aircraft trimmed for level flight. Very little buffeting was experienced, which was in marked contrast to the carriage of other stores where buffet had been the limiting factor. Owing to additional drag over that of the clean aircraft, acceleration in the dive was extremely slow, especially at speeds above 450 mph IAS. It was this that imposed a practical limit of 480 mph IAS, rather than any undesirable handling characteristics. When approaching to land, it was recommended that a speed of 110 mph IAS be used, which was 5 mph above that for a clean aircraft.
The vibration levels encountered with EK497 were extremely bad and were well above the average in intensity. It was present over the whole range of engine speeds and was especially noticeable when any force was applied to the control column. However, this was not considered to be due in any way to the presence of the RP installation, rather that the machine being used was inherently worse than the norm. A&AEE stated that it was ‘most unsatisfactory’ that Gloster should deliver an aircraft for service in such a condition.
The tactics used by RP Typhoons depended to a large extent on the type of target. When attacking concentrations of tanks, gun positions, observation posts and the like, a dive of around 60 degrees would be commenced from 8000 ft, with the rockets being fired in a salvo when passing around 4000 ft. For attacks against smaller targets such as individual tanks, a shallow dive of about 25 degrees would be used from an initial height of 3500 ft, the rockets being ripple-fired when the range had decreased to 500–1000 yards. The Typhoon’s steadiness in the dive made it an excellent launch platform, but wind drift and gravity drop would tend to compound pilot-induced errors caused by any slight pitch or yaw of the aircraft at the point of firing. In addition to the actual destruction caused by the rocket-firing Typhoons, their use severely restricted the movement of German forces in daylight hours and also had a profound effect on the morale of the Wehrmacht.
With the invasion of Northern France in June 1944 the Typhoon came into its own and was to be the premier Allied fighter-bomber for the rest of the war. It was often employed in ‘Cab Rank’ patrols over the front line, to be called down at any time to deliver its massive firepower of two 500/1000-lb bombs or eight 60-lb RPs and four 20-mm Hispano cannon. It was also to achieve fame in several famous actions, none more so than that at Falaise in Normandy.
On 7 August 1944 the German 7th Army launched an attack from Mortain, comprising four Panzer divisions to split the American forces, but the Allies had already been forewarned by Ultra decrypts and the full weight of tactical air power was soon unleashed. The advance quickly faltered and turned into a retreat, which, by 15 August was centred on Falaise. It was here that the rocket-firing Typhoons began to decimate the German Tiger tanks, which were trapped in a relatively small pocket, unable to move. Nowhere was the devastating effect of the Typhoon’s ‘aerial artillery’ demonstrated more clearly and less than 10 per cent of the tanks committed to battle were to escape. In addition to close support duties, the Typhoons of 2nd Tactical Air Force ranged well behind the front line on interdiction sorties, attacking transport and communications as well as ‘high value’ targets such as bridges and enemy HQ buildings.
Although the Typhoon was less than successful as an interceptor, it was to find its true role as a fighter-bomber. Its subsequent record vindicated those who had supported its continued existence in the face of numerous attempts to kill it off by the ‘Spitfire lobby’ and factions within Engineering. Ironically, the Germans were to play a role in saving the Typhoon. For a period of twelve months (until the arrival of the Spitfire IX in appreciable numbers in late 1942), it was the only aircraft on the RAF’s inventory capable of dealing with the Focke-Wulf Fw 190A, which was becoming an increasing embarrassment in the low-level Jabo role. Having survived into 1943, the technical difficulties that afflicted the Typhoon were gradually overcome and it was ready to take its place in history. Although 3330 Typhoons were built, only one (MN235) has survived and is currently displayed at the RAF Museum at Hendon.