The Battle of Britain (German: Luftschlacht um England) was an effort by the German Air Force (Luftwaffe) during the summer and autumn of 1940 to gain air superiority over the Royal Air Force (RAF) of the United Kingdom in preparation for the planned amphibious and airborne forces invasion of Britain by Operation Sea Lion. Neither the German leader Adolf Hitler nor his High Command of the Armed Forces (Oberkommando der Wehrmacht, or OKW) believed it was possible to carry out a successful amphibious assault on Britain until the RAF had been neutralised. Secondary objectives were to destroy aircraft production and ground infrastructure, to attack areas of political significance, and to terrorise the British people into seeking an armistice or surrender.
The British date the battle from 10 July to 31 October 1940, which represented the most intense period of daylight bombing. German historians usually place the beginning of the battle in mid-August 1940 and end it in May 1941, on the withdrawal of the German bomber units in preparation for Operation Barbarossa, the campaign against the Soviet Union.
The Battle of Britain was the first major campaign to be fought entirely by air forces; the British in the defensive were mainly using fighter aircraft, and the Germans used a mixture of bombers with fighter protection. It was the largest and most sustained bombing campaign attempted up until that date. The failure of Nazi Germany to destroy Britain's air defence or to break British morale is considered its first major setback.Bungay 2000, p. 388.
Fighter aircraft
Main types: Hurricane, Spitfire and Bf 109 The most famous fighter aircraft used in the Battle of Britain were the British Hawker Hurricane and Supermarine Spitfire Mk I, and the German Messerschmitt Bf 109 E variant (Emil) single-engined fighters. Although the Spitfire had attracted more attention from the public, the Hurricanes were more numerous and were responsible for most of the German losses, especially in the early part of the battle. The turn-around time (re-arm and refuel) for the Spitfire was 26 minutes, while the Hurricane's was 9 minutes, which increased its effectiveness.
Many of the Spitfires used in the battle were purchased privately. Money raised by towns, companies, clubs or individuals was used to buy Spitfires for £5,000 each with the purchaser having naming rights. Queen Wilhelmina of the Netherlands donated £215,000 to purchase 43 Spitfires.
The Spitfire and Bf 109E were well-matched in speed and agility, and both were somewhat faster than the Hurricane.Price 2002, p. 78. However, the slightly larger Hurricane was regarded as an easier aircraft to fly and was effective against Luftwaffe bombers.Bungay 2000, p. 74. The Royal Air Force's preferred tactic was to deploy the Hurricanes against formations of bombers and to use the Spitfires against the fighter escorts. The view from the "blown" clear cockpit hood of the Spitfire was considered fair, while upwards good; view to the rear was considered fair for a covered cockpit. The curved Perspex windscreen however was very bad optically and caused considerable distortion, which made long-distance visual scanning difficult. Spitfire pilot Jeffrey Quill made recommendations for the installation of "optically true" glass into the side panels to solve the problem.Delve 2007, p. 24. The Hurricane had a higher seating position, which gave the pilot a better view over the nose than the Spitfire. The upper canopy panels of the Bf 109 through its E-3 subtype were curved, while the E-4 and later Emil subtypes were modified for better visibility with flat panels and the new design was often retrofitted to earlier 109s.
Handling and general overview Each of the three main fighters had advantages and disadvantages in their control characteristics; much of the air combat during the battle occurred at about 20,000 feet or lower. Due to its sensitive elevators, if the stick was pulled back too far on the Spitfire in a tight turn:
During tight turns the "twist" or washout designed into the wing by Reginald Mitchell meant that the wing root would stall before the wingtips, creating the shuddering and clattering referred to. This noise was a form of stall warning, reminding the pilot to ease up on the turn.Bungay 2000, p. 78. British testing in September 1940 revealed that some Bf 109 pilots succeeded in keeping on the tail of the Spitfire, despite the latter aircraft's superior turning performance, because a number of the Spitfire pilots failed to tighten up the turn sufficiently. The gentle stall and good control under "g" of the Bf 109 were of some importance, as they enabled the Luftwaffe''' pilot to get the most out of the aircraft in a circling dog-fight by flying very near the stall. The Bf 109 used leading edge slats which automatically deployed prior to stalling, but also made it much more difficult to continue chasing either a Hurricane or Spitfire with a tight turn in aerial combat manoeuvres, from the slats intermittently opening in tight turns (on the wing to the "inside" of a turn) during dogfights, even causing problems during a takeoff if they opened unevenly.
The Rolls-Royce Merlin engine of the British fighters had the drawback of being equipped with a float-type carburettor which cut out under negative "g" forces. The direct-fuel injected Daimler-Benz DB 601 engine gave the 109 an advantage over the carburettor-equipped engine; when an RAF fighter attempted to "bunt" (the diving entry into an outside loop) and dive away from an opponent as the 109 could, their engines would temporarily cut out for the duration of the negative-g forces. This ability to perform negative-g manoeuvres without the engine cutting out gave a 109 pilot better ability to disengage at will.McKinstry 2007, p. 205.
On the question of comparative turning circles in combat, Spitfires and Hurricanes benefited from their lower wing loading compared with the Bf 109: the Royal Aircraft Establishment estimated the Spitfire's turning circle – without height loss – as 212 m (700 ft) in radius (the Hurricane's would be slightly tighter) while the 109E's was estimated as 270 m (890 ft) radius at 3,657 m (12,000 ft).Green 1980, p. 70. Other sources variously list a turn radius of between 125 m (410 ft) and 170 m (558 ft)at ground level and 230 m (754 ft) at 6,000 m (19,690 ft) for the 109E.Baubeschreibung für das Flugzeugmuster Messerschmitt Me 109 mit DB 601, 1939. Reprint: Luftfahrt-Archiv Hafner.Radinger and Schick 1999. The Emil was smaller than either RAF fighter, and it was more difficult to land and take off than the Spitfire and Hurricane.Bungay 2000, p. 199. At high speeds controls tightened considerably, and the Bf 109E needed more strength to manoeuvre than either of its main opponents. Of all three fighters, the Bf 109E would possess the highest roll rate, with the aileron controls being brisk and responsive; the Spitfire had the highest aileron forces, but both the Spitfire and the Messerschmitt's rate of roll suffered at high speed.
Overall the differences in performance between the Bf 109 and Spitfire were marginal and in combat they were surmounted by tactical considerations such as which side had seen the other first, which side had the advantage of altitude, numbers, pilot ability etc. with the main difference between the two aircraft being the Spitfire's tighter turning ability and the Bf 109's faster climb rate.Price 2002, p. 78.
Armament Both RAF fighters were armed with eight .303 Browning machine guns in the wings, harmonised by the squadrons to allow the bullets to converge at a distance. The Brownings had a high rate of fire and even a short burst from the eight machine guns sent out a large number of bullets. Although efficient against many aircraft, the small calibre bullets were often unable to penetrate the armour plating which was being increasingly used in Luftwaffe aircraft to protect crew and vital areas. An incendiary round, called the "De Wilde" was available, and this could do more damage than the standard "ball" rounds.Bungay 2000, p. 176.
During the battle at least one Hurricane was experimentally armed with a single Hispano 20 mm cannon in a pod under each wing although it proved to be too slow and sluggish on the controls to be effective.Price 1980, pp. 22, 41, 156. Several Spitfires, designated Spitfire Mk. IBs, were also modified to carry a Hispano cannon in each wing panel. 19 Squadron was equipped with this version in June 1940. On entering combat in August this first cannon armed Spitfire failed to create an impact, with the guns often jamming and unable to fire. When it did work, however, the Hispano was an effective weapon, with its shells easily able to penetrate the armour plating and self-sealing fuel tanks of Luftwaffe aircraft.Price 1996, pp. 20–21, 53.
The Emil's main armament depended on the subtype. The E-1 was armed with four MG 17 7.92mm machine guns; two cowl guns above the engine with 1,000 rounds per gun, and two in the wings with 500 rounds per gun. The E-3, E-4 and E-7s retained the fuselage armament of the E-1 but replaced the MG 17 wing guns with two 20 mm cannons, one in each wing with 60 rpg; either MG FFs (E-3) or the more advanced MG FF/M (E-4 and E-7) that could fire the new German steel-cartridge Minengeschoß mine shell ammunition. Although the explosive shells had greater destructive power than the bullets of the Brownings, these cannon's low muzzle velocity and the limited ammunition capacity of their sixty-round drum magazines meant that the armament was not markedly superior to the RAF fighter's eight machine guns.
Three or four hits from the cannons were usually enough to bring down an enemy fighter and, even if the fighter was able to return to base, it would often be written off.Price 1982, p. 76. For example, on 18 August a brand new Spitfire of 602 Squadron was hit by 20 mm shells which exploded in the structure of the rear fuselage. Although the crippled aircraft was successfully landed back at its airfield it was subsequently deemed to be unrepairable.Price 1980, pp. 132–133, photo section between pp. 150–151.
The MG FF/M, used in the Bf 109E-4, was modified to fire the more destructive, high-capacity mine-shells propelling the lighter shells at greater velocities than the MG FF.Williams and Gustin 2003, p. 23.Williams and Gustin 2003, p. 313. The early shells of this type had contact fusing, detonating on contact with the skin of the airframe rather than penetrating, then exploding.Bungay 2000, p. 197. The more streamlined Bf 109 F-1, issued in small numbers starting in October, carried two cowl MG-17s and a single 20mm MG FF/M in the fuselage as an engine-mounted Motorkanone, firing through the propeller hub.
Fuel tanks A drawback of the Hurricane was the presence of a fuel tank just behind the engine firewall, which could catch fire and within a few seconds severely burn the pilot before he managed to bail out. This was later partly solved by fitting a layer of "Linatex" fire-resistant material to the tank, and an armoured panel forward of the instrument panel. Another hazard was presented by the main wing root mounted fuel tanks of the Hurricane, which were vulnerable to bullets fired from behind.Bungay 2000 The main fuel tanks of the Spitfire, which were mounted in the fuselage forward of the cockpit, were better protected than that of the Hurricane; the lower tank was self-sealing and a panel of 3 mm thick aluminium, sufficient to deflect small calibre bullets, was wrapped externally over the top tanks. Internally they were coated with layers of "Linatex" and the cockpit bulkhead was fireproofed with a thick panel of asbestos.Price 1996, pp. 18–21.