Hawker Tempest

thumb|Painting of two Tempest aircraft attacking a [[V-1 flying bomb in the sky above an Oasthouse.]]

The Hawker Tempest is a British fighter aircraft that was primarily used in its Mk.V form by the Royal Air Force (RAF) in the later stages of the Second World War. The Tempest, originally known as the Typhoon II, was a significantly improved derivative of the Hawker Typhoon, intended to address the Typhoon's unexpected deterioration in performance at high altitude by replacing its wing with a thinner laminar flow design. Since it had diverged considerably from the Typhoon, it was renamed Tempest. The Tempest emerged as one of the most powerful fighters of World War II and at low altitude was the fastest single-engine propeller-driven aircraft of the war.

Upon entering service in 1944, the Tempest performed low-level interception, particularly against the V-1 flying bomb threat, and ground attack supporting major invasions like Operation Market Garden. Later, it successfully targeted the rail infrastructure in Germany and Luftwaffe aircraft on the ground, as well as countering similar attacks by German fighters. The Tempest was effective in the low-level interception role, including against newly developed jet-propelled aircraft like the Messerschmitt Me 262.

The further-developed Tempest II did not enter service until after the end of hostilities. It had several improvements, including being tropicalised for combat against Japan in South-East Asia as part of the Commonwealth Tiger Force.

Design and development

Origins

During development of the earlier Hawker Typhoon, the design team, under the leadership of Sydney Camm, had already planned out a series of design improvements; these improvements culminated in the Hawker P. 1012, otherwise known as the Typhoon II or "Thin-Wing Typhoon". Other problems had been experienced with the Typhoon, such as engine unreliability, lack of structural integrity, and the inability to perform high altitude interception duties.

thumb|left|Tempest I prototype HM599 with later bubble canopy; when first flown, it had the "car-door" canopy and small tail unit.

In March 1940, engineers were assigned to investigate the new low–drag laminar flow wing developed by NACA in the United States, which was later used in the North American P-51 Mustang. A laminar flow wing adopted for the Tempest series had a maximum thickness-to-chord ratio of 14.5 per cent at the root, tapering to 10 per cent at the tip.

Another important feature of the new wing was Camm's proposal that the radiators for cooling the engine be fitted into the leading edge of the wing inboard of the undercarriage. This eliminated the distinctive "chin" radiator of the Typhoon and improved aerodynamics. The new wing and airfoil, and the use of a four-bladed propeller, acted to eliminate the high frequency vibrations that had plagued the Typhoon. The design team also chose to use the new Mark IV version of the Napier Sabre H-block 24 cylinder engine for the Tempest, drawings of which had become available to Hawker in early 1941.

In February 1941, Camm commenced a series of discussions with officials within the Ministry of Aircraft Production on the topic of the P.1012. At this point, work was undertaken by a team of 45 draughtsmen at Hawker's wartime experimental design office at Claremont, Esher to convert the proposal into technical schematics from which to commence manufacture. The Bristol Centaurus radial engine was now also considered for equipping the Typhoon and Camm was forewarned in October 1941 to expect a request for a Centaurus to be fitted. This was confirmed in February as an order for six prototypes with the Centaurus; the DTD stating that the development was highest priority.

• One Tempest Mk.I (serial number HM599), equipped with the Napier Sabre Mk.IV engine
• Two Tempest Mk.II (serial numbers LA602 and LA607), equipped with the Bristol Centaurus Mk.IV engine (LA607 later receiving a Centaurus Mk.V)
• One Tempest Mk.IV (serial number LA614), which was never completed but planned to be equipped with a Griffon 61 engine
• One Tempest Mk.V (serial number HM595), equipped with the Napier Sabre Mk.II engine

The Tempest Mk.I featured other new features, such as a clean single-piece sliding canopy in place of the car-door framed canopy, and it used wing radiators instead of the "chin" radiator. The Air Ministry had seen the Mk III as a replacement for the Hurricane in ground attack, with the narrower engine giving a better view as well but the Typhoon would be the interim aircraft for the role. In practice the Typhoon proved very good for ground attack.

Work on the Tempest Mk.IV variant was abandoned without any prototype being flown at all.

In August 1942, even before the first flight of the prototype Tempest V had been conducted, a production order for 400 Tempests was placed by the Air Ministry. This order was split, with the initial batch of 100 being Tempest V "Series I"s, powered by the Sabre IIA series engine, which had the distinctive chin radiator, while the rest were to have been produced as the Tempest I, equipped with the Sabre IV and leading-edge radiators. These 300 Tempest Is were intended to replace an order for a similar quantity of Typhoons placed with the Gloster Aircraft Company.

Tempest Mk.V

thumb|left|Tempest Mk. V prototype with [[bubble canopy and Mk. V tail, but with 20 mm Hispano Mk. II guns.]]

During early 1943, a production line for the Tempest Mk.V was established in Hawker's Langley facility, alongside the existing manufacturing line for the Hawker Hurricane.

thumb|The first production Tempest Mk. V JN729. Long-barrelled Hispano II cannon and Typhoon five-spoke mainwheels were identifying features of the first production batch of 100 Tempests Vs.

During production of the first batch of 100 Tempest V "Series Is", distinguishable by their serial number prefix JN, several improvements were progressively introduced and were used from the outset on all succeeding Tempest V "Series 2s", with serial number prefixes EJ, NV and SN. The fuselage/empennage joint originally featured 20 external reinforcing "fishplates", similar to those fitted to the Typhoon, but it was not long before the rear fuselage was strengthened and, with the fishplates no longer being needed, the rear fuselage became detachable. The first series of Tempest Vs used a built-up rear spar pick-up/bulkhead assembly (just behind the cockpit) which was adapted from the Typhoon. Small blisters on the upper rear wing root fairing covered the securing bolts. This was later changed to a new forged, lightweight assembly which connected to new spar booms: the upper wing root blisters were replaced by small "teardrop" fairings under the wings. The new spar structure of the Tempest V also allowed up to of external stores to be carried underneath the wings. Rockets were never used operationally during the war by the Mk.Vs.

Two Tempest Vs, EJ518 and NV768, were fitted with Napier Sabre Vs and experimented with several different Napier-made annular radiators, with which they resembled Tempest IIs. This configuration proved to generate less drag than the standard "chin" radiator, contributing to an improvement in the maximum speed of some 11 to 14 mph. NV768 was later fitted with a ducted spinner, similar to that fitted to the Fw 190 V1.

47 mm anti tank gun trials

thumb|Tempest SN354, outfitted with experimental 47 mm class P guns and standard smaller four-spoke wheels.

Tempest V SN354 was fitted with two experimental underwing Class P 47 mm guns (built by Vickers) just after the war. These guns were part of a project started in mid-1942 to develop a more powerful airborne anti-tank gun than the Vickers 40 mm Class S gun which had been used on the Hurricane IID. Surviving photographs suggests that the 20 mm wing guns were removed for this installation. Testing of the guns revealed that the weapon had potential, but no production was undertaken. Apart from the new engine and cowling, the Tempest II prototypes were similar to early series Tempest Vs. The Centaurus engine was closely cowled and the exhaust stacks grouped behind and to either side of the engine: to the rear were air outlets with automatic sliding "gills". The carburettor air intakes were in the inner leading edges of both wings, an oil cooler and air intake were present in the inner starboard wing. The engine installation owed much to examinations of a captured Focke-Wulf Fw 190, and was clean and effective.

On 28 June 1943, the first Tempest II, LA602, flew powered by a Centaurus IV (2,520 hp/1,879 kW) driving a four-blade propeller. LA602 initially flew with a Typhoon-type fin and rudder unit. This was followed by the second, LA607, which was completed with the enlarged dorsal fin and first flew on 18 September 1943: LA607 was assigned to engine development. Problems were also experienced with engine overheating, poor crankshaft lubrication, exhaust malfunctions and reduction-gear seizures. Because of these problems, and because of the decision to "tropicalise" all Tempest IIs for service in the South-East Asian theatre, production was delayed.

thumb|New Tempest IIs of the first production batch at Hawker Aircraft. Note the closely cowled engine and the carburettor and oil-cooler intakes in the starboard wing's inner leading edge.

Orders had been placed as early as September 1942 for 500 Tempest IIs to be built by Gloster but in 1943, because of priority being given to the Typhoon, a production contract of 330 Tempest IIs was allocated instead to Bristol, while Hawker were to build 1,800. This switch delayed production even more. On 4 October 1944, the first Tempest II was rolled off the line; the first six production aircraft soon joined the two prototypes for extensive trials and tests.

Physically, the Tempest II was longer than the Tempest Mk.V ( versus and lower. The weight of the heavier Centaurus engine ( versus was offset by the absence of a heavy radiator unit, so that the Tempest II was only some heavier overall. Performance was improved; maximum speed was at and climb rate to the same altitude took four and a half minutes compared with five minutes for the Tempest Mk.V; the service ceiling was also increased to . The Pacific War ended before they could be deployed. Work on both was ultimately dropped when Camm decided to focus design efforts upon the more promising jet engine designs he was working on instead.

Design

thumb|A Tempest Mk. V flying overhead, marked with black and white stripes used for the easier identification of [[Hawker Typhoon and Tempest aircraft. These stripes, similar to the later Invasion stripes, were used until 20 April 1944.]]

The Tempest was a single engine fighter aircraft that excelled at low-level flight. In service, its primary role soon developed into performing "armed reconnaissance" operations, often deep behind enemy lines. The Tempest was particularly well suited to the role because of its high speed at low to medium altitudes, its long range when equipped with two 45-gallon drop tanks, the good firepower of the four 20mm cannon and the good pilot visibility. The three-piece windscreen and side windows of the Tempest had directly benefited from examination of captured Focke-Wulf Fw 190s, improvements included the careful design and positioning of the frame structure, blind spots being reduced to an absolute minimum. It had a bullet-resistant centre panel made up of two layers, the outer thick and the inner .

The majority of production Tempests were powered by a single high-powered Napier Sabre II 24-cylinder engine. All versions of the Sabre drove either a four-bladed, diameter de Havilland Hydromatic or Rotol propeller. Starting with EJxxx series, on the Tempest V, both the improved Sabre IIB and IIC were used, these engines were capable of producing over on emergency boost for short periods of time. Alternative engines were used on some production variants, such as the Tempest II, for which a single Bristol Centaurus 18 cylinder radial engine was adopted, or the final Tempest VI, upon which a Napier Sabre V was used. Early on in development, the adoption of several other engines was proposed, some of which were tested upon multiple prototypes.

thumb|left|LA602, a prototype Bristol Centaurus-powered Tempest.

The main undercarriage was redesigned from the Typhoon, featuring lengthened legs and a wider track () to improve stability at the high landing speed of , and to allow tip clearance for a new de Havilland diameter four-blade propeller. The main undercarriage units were Dowty levered suspension units incorporating trunnions which shortened the legs as they retracted. The retractable tailwheel was fully enclosed by small doors and could be fitted with either a plain Dunlop manufactured tyre, or a Dunlop-Marstrand "twin-contact" anti-shimmy tyre. By the end of April 1944, these units were based at RAF Newchurch in Kent a new "Advanced Landing Ground" (ALG), where they formed 150 Wing, commanded by Wing Commander Roland Beamont. The new wing was part of the Second Tactical Air Force (2nd TAF).

Most of the operations carried out by 150 Wing comprised high-altitude fighter sweeps, offensive operations known as "Rangers", as well as reconnaissance missions. Prior to the Normandy landings, Tempests would routinely conduct long-range sorties inside German-occupied territory and penetrate into Northern France and the Low Countries, using a combination of cannons and bombs to attack airfields, radar installations, ground vehicles, coastal shipping and the launch sites for the German V-1 flying bombs. Using external drop tanks, the Tempest was able to maintain standing patrols of four and half hours off the south coast of England in the approach paths of the V-1s. Guided by coastal radar installations, Tempests would be ready for pursuit and would either use cannon fire or nudge the V-1 with the aircraft to destroy it.

thumb|left|Early Tempest Mk. V of 486 Sq April 1944. JN766 still has its black and white Typhoon-style underwing recognition bands.

thumb|left|Early Tempest Mk. V of [[No. 3 Squadron RAF|3 Sqn. being refuelled and re-armed by ground crew at Newchurch, Kent, June 1944.]]

In September 1944, Tempest units, based at forward airfields in England, supported Operation Market Garden, the airborne attempt to seize a bridgehead over the Rhine. On 21 September 1944, as the V-1 threat had receded, the Tempest squadrons were redeployed to the 2nd TAF, swapping with the Mustang III squadrons of 122 Wing, which became part of the Fighter Command units deployed on bomber escort duties. 122 Wing now consisted of 3 Sqn., 56 Sqn., 80 Sqn., 274 Sqn. (to March 1945), and 486 (NZ) Sqn. From 1 October 1944, 122 Wing was based at ALG B.80 (Volkel) near Uden, in the Netherlands.

Armed reconnaissance missions were usually flown by two sections (eight aircraft), flying in finger-four formations, which would cross the front lines at altitudes of 7,000 to 8,000 feet and once the Tempests reached their target area, the lead section dropped to or lower to search for targets to strafe, while the other section flew cover higher and down sun. After the first section had carried out several attacks, it swapped places with the second section and the attacks continued until all ammunition had been exhausted, after which the Tempests would return to base at 8,000&nbsp;ft. As many of the more profitable targets were usually some from base, the Tempests typically carried two 45-gallon drop tanks which were turned on soon after take-off. Although there were fears that the empty tanks would explode if hit by flak, it never happened and, due to the tanks being often difficult to jettison, they were routinely carried throughout an operation with little effect on performance, reducing maximum speed by and range by 2 per cent.<!--how does carrying another 90 gal of fuel reduce range?-->

Between October and December 1944, the Tempest was practically withdrawn from combat operations for overhaul and to allow operational pilots to train newcomers.

In December 1944, 52 German fighters were shot down, 89 trains and countless military vehicles were destroyed, for the loss of 20 Tempests. Following the Luftwaffes Unternehmen Bodenplatte of 1 January 1945, 122 Wing bore the brunt of low- to medium-altitude fighter operations for the Second Tactical Air Force, which had fortuitously evaded the extensive Bodenplatte raid, and had contributed to efforts to intercept the raiders. The intensity of operations persisted throughout the remainder of the war; French ace Pierre Clostermann noted in his memoirs that young, inexperienced Tempest pilots were quick to fall prey to Luftwaffe "experten", even when in superior numbers or to the flak around German aerodromes.

Against advanced German planes

Piloting a Tempest on 19 April 1945, Flying Officer Geoffrey Walkington was the first to shoot down a Heinkel He 162, the Luftwaffes latest jet fighter, which had just entered service with the I./JG 1 (1st Group of Jagdgeschwader 1 Oesau — "1st Fighter Wing Oesau"). Tempest pilots, including Clostermann, made the first Allied combat encounter with a Dornier 335 in April 1945. In his book The Big Show, he describes leading a flight of Tempests from No. 3 Squadron RAF over northern Germany, when they saw a lone unusual looking aircraft flying at maximum speed at treetop level. Detecting the British aircraft, the German pilot reversed course to evade. Despite the Tempests' considerable low altitude speed, Clostermann decided not to attempt to follow as it was obviously much quicker though one of the other two Tempests did pursue it briefly.

During 1945, Tempests scored of a number of kills against the new German jets, including the Messerschmitt Me 262. Hubert Lange, a Me 262 pilot, said: "the Messerschmitt Me 262's most dangerous opponent was the British Hawker Tempest — extremely fast at low altitudes, highly manoeuvrable and heavily armed". Some Me 262s were destroyed using a tactic known to 135 Wing as the "Rat Scramble"; Tempests on immediate alert took off when an Me 262 was reported to be airborne. They did not intercept the jet, but instead flew towards the airbase at Rheine-Hopsten, known to base Me 262s and Ar 234s. The aim was to attack jets on their landing approach, when they were at their most vulnerable, travelling slowly, with flaps down and incapable of rapid acceleration. The Germans responded by creating a "flak lane" of over 150 of the Flakvierling quadruple 20 mm AA batteries at Rheine-Hopsten, to protect the approaches. After seven Tempests were lost to anti-aircraft fire at Rheine-Hopsten in a week, the "Rat Scramble" was discontinued. For a few days in March 1945, a strict "No, repeat, No ground attacks" policy was imposed.

Air combat success ratio

In air-to-air combat, the Tempest units achieved an estimated air combat success ratio of about 8:1, scoring 239 confirmed victories (not including the additional "victories" against the unmanned V-1 flying bomb), 9 probables, and 31 losses and probable losses. The top-scoring Tempest pilot was Squadron Leader David Fairbanks DFC, an American who joined the Royal Canadian Air Force in 1941. By mid-1944, he was flying with 274 Squadron. When he was shot down and made a prisoner of war in February 1945, he had destroyed 11 or 12 German aircraft (and one shared), to make him the highest-scoring Tempest ace.

Other activities

thumb|3 Squadron RAF Tempest and air crew during a pre-mission briefing, during the [[Battle of Normandy, 1944.]]

thumb|A Tempest TT Mk. V target tug, 1948.

Early flights by RAF pilots found the Tempest, unlike the Typhoon, was buffet-free up to and somewhat beyond . Following the end of the war, the RAF decided upon the Tempest as its standard fighter, pending the introduction of newer aircraft, many of which would be developed post-war, such as the de Havilland Hornet and the de Havilland Vampire, as well as the Gloster Meteor. A number of squadrons would operate the Tempest as their final piston-engined type before converting to the new generation of jet fighters that would come to dominate the next decade and beyond. The guns on the Tempest Mk. II had fewer cartridges compared to the Tempest Mk. V and Mk. VI (162 inboard and 152 outboard). 402 built by Hawker at Langley and 50 by Bristol Aeroplane Company, Banwell.

:*Tempest F. Mk. II – (F.2) – Initial fighter version of the Tempest Mk. II. 100 built by Hawker One prototype (LA610) built.

:*Tempest F. Mk. V Series 1 – Initial production version of the Tempest Mk V. Series 1 aircraft were fitted with four long-barrel 20&nbsp;mm (.79&nbsp;in) Hispano Mk. II cannons