The Bf 110 in the Battle of Britain
Events were now leading to a confrontation between the Luftwaffe and the RAF, in which the Bf 110 would suffer heavily. Consequently, sharp criticism of this aircraft, and by extension the entire class of twin-engined fighters followed, well beyond what is justified by the actual events. British test pilot Eric “Winkle” Brown commented that “the Messerschmitt strategic fighter was not the indifferent warplane that its showing during the battle led many to believe.” (Emphasis his.) But bad planning and poor tactical choices put the Bf 110 at a severe disadvantage.
It is as well to start by looking at the performance parameters. The Bf 110C-4, a common model at the time, was powered by two 1,100 hp Daimler-Benz DB 601A engines, and had a normal loaded weight of 6,940 kg; so its power loading was 3.15 kg/hp. The Hurricane Mk.I weighed 2,924 kg loaded and was powered by a 1,030 hp Merlin Mk.III engine, giving a better power loading, of 2.84 kg/hp. The Spitfire Mk.I, powered by the same engine, was lighter because of its more advanced structure, and the normal loaded weight of 2,812 kg resulted in a power loading of only 2.73 kg/hp. Clearly, the extra size of the Bf 110, a necessary consequence of the demand for long range and heavy armament, had to have consequences for its raw performance.
The Bf 110C-4 was claimed to be capable of a maximum level speed of 562 km/h at 7,000 m altitude, and 473 km/h at sea level. British test pilots, flying a captured C-5 reconnaissance version at lower weights, measured only 547 km/h at 6,700 m, so perhaps the German figures were too optimistic, but such variations between individual aircraft were common and the test aircraft had been assembled from two wrecks. This was still considerably faster than the 508 km/h at 5,400 m and 409 km/h at sea level of the Hurricane Mk.I, and competitive with the 557 km/h at 4,570 m of the Spitfire Mk.IA. The German fighter also performed reasonably well in the climb, with an initial rate of climb of 670 m/min, somewhat inferior to the 770 and 740 m/min attributed to the Hurricane and Spitfire. Nevertheless it could climb to 5,500 m in 7 minutes, while the Spitfire Mk.IA needed 6.85 minutes to 4,570 m, and the Hurricane 6.3 minutes.
However, during the battle of Britain 100-octane fuel was used by RAF fighters. By allowing the Merlin to run at higher pressures and generate 1,200 hp, this considerably improved their performance, especially in climb. That came as an unpleasant surprise for the Luftwaffe. The German synthetic fuel industry would produce limited amounts of 96 octane C3 fuel, and the Bf 110 would get priority for the DB 601N engine that was tuned for better performance on C3. But the chemical composition of C3 fuel would cause serious technical issues with the fuel and lubrication systems, and the DB 601N was not a success. German fighters continued to rely mostly on the 87-octane B4 fuel.
In terms of performance the Bf 110 appeared competitive enough. Its main weakness in combat against the RAF fighters was its manoeuvrability, which was good for an aircraft of its size, but no match for the opposition it faced. The wing loading of the Bf 110C-4 model, 181 kg/m2, was considerably higher than the 123 kg/m2 of the Hurricane and the 125 kg/m2 of the Spitfire, and this resulted in a larger turning circle. Also, its inferior power-to-weight ratio implied that any energy lost in a tight turn would be harder to restore, putting it in an increasingly worse position as a dogfight progressed. The handling of the Bf 110 was good at normal speeds, with effective controls and generally pleasant flying characteristics. The controls heavied up considerably at higher speeds, and the ailerons were almost immovable in fast dives. But this, it must be said, was a weakness of all fighters at the time, German and British alike.
The Bf 110 did have the notional advantage of having a rear gunner. The Luftwaffe would persist with installing flexible rear-firing armament on twin-engined fighters, and later adopted remote-controlled turrets for the Ar 240 and the Me 210 and 410. But other airforces showed themselves much less convinced of the value of defensive armament on a fighter. Realistically, in a manoeuvring combat situation, the rear gunner would have to be very lucky indeed to hit the opponent. And even if he did, the single rifle-calibre gun wasn’t effective enough against enemy fighters, especially after the latter received more protection including armour-glass windscreens.
The characteristics of the Bf 110 implied that the Zerstörer were at a serious disadvantage whenever they were forced into a defensive posture. Their speed and firepower served them well when they made hit-and-run attacks, exploiting their good climb and dive characteristics, while declining to engage in turning combat. When intercepted by RAF fighters in strength, a frequent reaction of Bf 110 crews was to seek safety in a Lufbery circle, a defensive formation in which fighters fly a ring pattern, each covering the rear of the one next ahead in the formation. While an effective tactic, this could only be maintained for as long as the fuel reserve allowed, and the RAF fighters waited above for an opportunity to strike.
Last but not least, the number of Bf 110s available for the battle was not very high. Although in 1940 the production rate was slightly over 100 per month, losses during the Polish and French campaigns meant that only about 280 aircraft were available to the three Luftflotten at the start of the campaign, with the number of fully operational aircraft being around 220 on a given day. The implication was that whenever German bombers ventured beyond the range of the Bf 109, their escort force was likely to be numerically inferior.
The Bf 110’s participation in the battle started with its contribution to attacks on convoys of merchant ships off the British coast. This so-called Kanalkampf was a curious phase as both sides risked considerable attrition for no obvious strategic purpose. But it was a task for which the Bf 110 was well enough suited, especially for the fighter-bomber missions flown by Erprobungsgruppe 210, which specialised in precision attacks against point targets such as shipping, radar installations, and airfields. It operated mostly the Bf 110C-4/B with two ETC 205 bomb racks and DB 601N engines. At the beginning of the battle the unit also operated a number of Bf 110C-6 with a powerful MK 101 30-mm cannon in a fairing under the fuselage, but operational and technical problems later led to the removal of this weapon.
The opening phase of the Battle of Britain proper in August 1940, was a sobering experience for the Luftwaffe, in which the Zerstörer suffered painful losses. Much depended on the pattern of the mission flown. The Bf 110C-5, fast and with a good altitude performance, made a good reconnaissance aircraft. And when flying Freie Jagd fighter sweeps at high altitude (above 6,700 m) over Southern England, the Zerstörer units demonstrated that the Bf 110 was indeed a dangerous opponent, and could be more than a match for the Hurricane.
Unfortunately for the Germans, this was not the pattern of the battle to come. Fighter Command soon decided to avoid contact with the fighter sweeps, and concentrate its attacks on the bomber formations. Then, flying at low and medium altitude, and robbed of the advantage of surprise by radar and the advanced command-and-control system of Fighter Command, the German crews often found themselves at a serious tactical disadvantage. This, of course, also handicapped the Bf 109, but the nimbler single-engined fighter could extract itself from an unfavourable situation with much more ease.
Low-level attack missions also turned out to be very costly in the face of a determined defence. Indicative of how just badly things could go wrong was an attack on Croydon on 15 August 1940 executed by bomb-carrying Bf 110s of Erprobungsgruppe 210, a specialist fighter-bomber unit. Serious damage was done to airfield, but while still in its attack run at low level the German force was bounced by a superior number of Hurricanes. The Bf 110s found temporary protection in a defensive circle, but finally had to make a break for home; the RAF fighters immediately fell onto their targets, shooting down seven out of the twenty-two strong enemy force, including its leader, Hauptmann Rubensdörffer. This was by no means the end of the operations of the unit; in fact fighter-bomber raids became more and more frequent. They were indeed effective against point targets, but either surprise or local air superiority were a prerequisite. The often-repeated story that the Bf 110s themselves had to be escorted by Bf 109s really applies to the fighter-bombers of Erprobungsgruppe 210, which proved otherwise too vulnerable with their combat loads.
The biggest problem was that the Bf 110 had to take on the role of escort fighter for the bombers, because the fuel capacity of the Bf 109 allowed it only a short stay over England. (In the case of Luftflotte 5 aircraft stationed in Norway, the Bf 110 was even the only possible option to provide the bombers with some protection, and then only with external fuel tanks.) But the German escort tactics were flawed. Arguably, they were not much more flawed than other early attempts to provide bomber escort, including USAAF escort tactics in 1942-1943. The Luftwaffe too had to learn by experience. Too many fighters were ordered to fly close escort in formation with the bombers, but in that position they could do little to defend the bombers and became vulnerable targets themselves. The error was made worse in early September: Against the strong opinion of the fighter leaders, they were ordered to stay closer to the bombers, and even to break off combat with enemy fighters if the bombers were threatened. Flying close escort may have been good for the morale of the bomber crews, it was not an effective tactical choice.
Bf 110 losses amounted to some 120 aircraft during August alone, some 40% of the available strength. In a proportionally high fraction of the losses, this seems to have resulted in crew fatalities, as leaving the Bf 110 in an emergency was difficult due to its cockpit design and twin tail fins. In September and October, the attrition forced the Germans to withdraw several Zerstörer units from the battle to rest and re-equip them. As the need to defend Germany against British bombers grew, several units were retrained for the nightfighting role, in which the Bf 110 would perform very well.
The failure of the Bf 110 as an escort fighter was just one more nail in the coffin of a doomed operation, but as they had been a much-propagandized part of the German air force, it became symbolic. Its importance should not be exaggerated, for at the height of the battle, Bf 110s were less than 12% of the Luftwaffe’s available force, and only just over a quarter of the fighter force. There were many more important factors that doomed the German attempt to subdue Britain to failure: The German command had seriously underestimated RAF strength, and ignored the importance of the radar and command-and-control network. The available bomber strength was insufficient, and in turn the fighter strength fell short of the requirement to provide escorts in a 2:1 ratio. Aircraft production and crew training lagged behind the RAF. Intelligence and target identification were very poor, so that many bombs were wasted on targets of little importance, and enemy losses strongly overestimated. The range of the Bf 109E was too short, the use of external drop tanks was neglected, and the available bombers had small bomb loads and weak defensive armament. Last but not least, the operation itself was handicapped by two conflicting goals, preparing for an invasion by destroying the RAF and forcing Britain to come to a negotiated peace by bombing, and neither was a realistic war plan.
This catalogue of failures should not obscure that the Bf 110 had also found a role in which it was very effective, that of a fighter-bomber. Occasional heavy losses demonstrated the need for air superiority on such operations, but a series of successful attacks also confirmed the potential of the aircraft in this role. The large Messerschmitt fighter still had a long and generally successful career ahead of it.
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