Bf 109E-4/Trop of JG 27
off the North African coast, mid-1941
The Messerschmitt Bf 109, was a German World War II fighter aircraft that was the backbone of the Luftwaffe's fighter force. The Bf 109 first saw operational service during the Spanish Civil War (1939) and was still in service at the dawn of the jet age at the end of World War II (1945). It was one of the most advanced fighters of the era, including such features as all-metal monocoque construction, a closed canopy, and retractable landing gear. It was powered by a liquid-cooled, inverted-V12 aero engine. From the end of 1941, the Bf 109 was steadily being supplemented by the superior Focke-Wulf Fw 190.
It was commonly called the Me 109 most often by Allied aircrew and even amongst the German aces themselves even though this was not the official German designation. The "Bf 109" designation was issued by the German ministry of aviation and represents the developing company Bayerische Flugzeugwerke and is a rather arbitrary figure.
It was designed by Willy Messerschmitt (hence Me 109) and Robert Lusser, who worked at Bayerische Flugzeugwerke, during the early to mid-1930s.
Originally conceived as an interceptor, later models were developed to fulfill multiple tasks, serving as bomber escort, fighter-bomber, day-, night-, all-weather fighter, ground-attack aircraft, and as reconnaissance aircraft. It was supplied to and operated by several states during World War II, and served with several countries for many years after the war. The Bf 109 was the most produced fighter aircraft in history, with a total of 33,984 airframes produced from 1936 up to April 1945.
The Bf 109 was flown by the three top-scoring German fighter aces of World War II, who claimed 928 victories among them while flying with Jagdgeschwader 52, mainly on the Eastern Front. The highest scoring fighter ace of all time, Erich Hartmann, flew the Bf 109 and was credited with 352 aerial victories. The aircraft was also flown by Hans-Joachim Marseille, the highest scoring German ace in the North African Campaign who achieved 158 aerial victories. It was also flown by several other aces from Germany's allies, notably Finn Ilmari Juutilainen, the highest scoring non-German ace on the type, and pilots from Italy, Romania, Croatia, Bulgaria and Hungary. Through constant development, the Bf 109 remained competitive with the latest Allied fighter aircraft until the end of the war.
Design and development
During 1933, the Technisches Amt (C-Amt), the technical department of the Reichsluftfahrtministerium (RLM) ("Reich Aviation Ministry"), concluded a series of research projects into the future of air combat. The result of the studies was four broad outlines for future aircraft:
- Rüstungsflugzeug I for a multi-seat medium bomber
- Rüstungsflugzeug II for a tactical bomber
- Rüstungsflugzeug III for a single-seat fighter
- Rüstungsflugzeug IV for a two-seat heavy fighter
Rüstungsflugzeug III was intended to be a short range interceptor, replacing the Arado Ar 64 and Heinkel He 51 biplanes then in service. In late March 1933 the RLM published the tactical requirements for a single-seat fighter in the document L.A. 1432/33.
The fighter needed to have a top speed of 400 km/h (250 mph) at 6,000 m (19,690 ft), to be maintained for 20 minutes, while having a total flight duration of 90 minutes. The critical altitude of 6,000 metres was to be reached in no more than 17 minutes, and the fighter was to have an operational ceiling of 10,000 metres. Power was to be provided by the new Junkers Jumo 210 engine of about 522 kW (700 hp). It was to be armed with either a single 20 mm MG C/30 engine-mounted cannon firing through the propeller hub as a Motorkanone, or two engine cowl-mounted 7.92 mm (.312 in) MG 17 machine guns, or one lightweight engine-mounted 20 mm MG FF cannon with two 7.92 mm MG 17s. The MG C/30 was an airborne adaption of the 2 cm FlaK 30 anti-aircraft gun, which fired very powerful "Long Solothurn" ammunition, but was very heavy and had a low rate of fire. It was also specified that the wing loading should be kept below 100 kg/m2. The performance was to be evaluated based on the fighter's level speed, rate of climb, and manoeuvrability, in that order.
It has been suggested that Bayerische Flugzeugwerke (BFW) was originally not invited to participate in the competition due to personal animosity between Willy Messerschmitt and RLM director Erhard Milch;[nb 1] however, recent research by Willy Radinger and Walter Shick indicates that this may not have been the case, as all three competing companies—Arado, Heinkel and the BFW—received the development contract for the L.A. 1432/33 requirements at the same time in February 1934. A fourth company, Focke-Wulf, received a copy of the development contract only in September 1934. The powerplant was to be the new Junkers Jumo 210, but the proviso was made that it would be interchangeable with the more powerful, but less developed Daimler-Benz DB 600 powerplant. Each was asked to deliver three prototypes for head-to-head testing in late 1934.
Design work on Messerschmitt Project Number P.1034 began in March 1934, just three weeks after the development contract was awarded. The basic mock-up was completed by May, and a more detailed design mock-up was ready by January 1935. The RLM designated the design as type "Bf 109," the next available from a block of numbers assigned to BFW.
The first prototype (Versuchsflugzeug 1 or V1), with civilian registration D-IABI, was completed by May 1935, but the new German engines were not yet ready. In order to get the "R III" designs into the air, the RLM acquired four Rolls-Royce Kestrel VI engines by trading Rolls-Royce a Heinkel He 70 Blitz for use as an engine test-bed.[nb 2] Messerschmitt received two of these engines and adapted the engine mounts of V1 to take the V-12 engine upright. V1 made its maiden flight at the end of May 1935 at the airfield located in the southernmost Augsburg neighborhood of Haunstetten, piloted by Hans-Dietrich "Bubi" Knoetzsch. After four months of flight testing, the aircraft was delivered in September to the Luftwaffe's central test centre at the Erprobungsstelle Rechlin to take part in the design competition.
In 1935, the first Jumo engines became available so V2 was completed in October using the 449 kW (600 hp) Jumo 210A engine. V3 followed, the first to be mounted with guns, but it did not fly until May 1936 due to a delay in procuring another Jumo 210 engine.
After Luftwaffe acceptance trials were completed at their headquarters Erprobungsstelle (E-Stelle) military aviation test and development facility at Rechlin, the prototypes were moved to the subordinate E-Stelle Baltic seacoast facility at Travemünde for the head-to-head portion of the competition. The aircraft participating in the trials were the Arado Ar 80 V3, the Focke-Wulf Fw 159 V3, the Heinkel He 112 V4 and the Bf 109 V2. The He 112 arrived first, in early February 1936, followed by the rest of the prototypes by the end of the month.
Because most fighter pilots of the Luftwaffe were used to biplanes with open cockpits, low wing loading, light g-forces and easy handling like the Heinkel He 51, they were very critical of the Bf 109 at first. However, it soon became one of the frontrunners in the contest, as the Arado and Focke-Wulf entries, which were intended as "backup" programmes to safeguard against failure of the two favourites, proved to be completely outclassed. The Arado Ar 80, with its gull wing (replaced with a straight, tapered wing on the V3) and fixed, spatted undercarriage was overweight and underpowered, and the design was abandoned after three prototypes had been built. The parasol winged Fw 159, potentially inspired by the same firm's earlier Focke-Wulf Fw 56, was always considered by the E-Stelle Travemünde facility's staff to be a compromise between a biplane and an aerodynamically more efficient, low-wing monoplane. Although it had some advanced features, it used a novel, complex retractable main undercarriage which proved to be unreliable.
Bf 109 E-3, c. 1939/1940
Initially, the Bf 109 was regarded with disfavour by E-Stelle test pilots because of its steep ground angle, which resulted in poor forward visibility when taxiing; the sideways-hinged cockpit canopy, which could not be opened in flight; and the automatic leading edge slats on the wings which, it was thought, would inadvertently open during aerobatics, possibly leading to crashes. This was later borne out in combat situations and aerobatic testing by various countries' test establishments. The leading edge slats and ailerons would flutter rapidly in fast tight turns, making targeting and control difficult, and eventually putting the aircraft into a stall condition. They were also concerned about the high wing loading.
The Heinkel He 112, based on a scaled-down Blitz, was the favourite of the Luftwaffe leaders. Compared with the Bf 109, it was also cheaper. Positive aspects of the He 112 included the wide track and robustness of the undercarriage (this opened outwards from mid wing, as opposed to the 109s which opened from the wing root), considerably better visibility from the cockpit, and a lower wing loading that made for easier landings. In addition, the V4 had a single-piece, clear-view, sliding cockpit canopy and a more powerful Jumo 210Da engine with a modified exhaust system. However, the He 112 was also structurally complicated, being 18% heavier than the Bf 109, and it soon became clear that the thick wing, which spanned 12.6 m (41 ft 4 in) with an area of 23.2 m2 (249.7 ft2) on the first prototype (V1), was a disadvantage for a light fighter, decreasing the aircraft's rate of roll and manoeuvrability. As a result, the He 112 V4 which was used for the trials had new wings, spanning 11.5 m (37 ft 8.75 in) with an area of 21.6 m2 (232.5 ft2). However, the improvements had not been fully tested and the He 112 V4 could not be demonstrated in accordance with the rules laid down by the Acceptance Commission, placing it at a distinct disadvantage.
Because of its smaller, lighter airframe, the Bf 109 was 30 km/h (20 mph) faster than the He 112 in level flight, and superior in climbing and diving. The Commission ultimately ruled in favour of the Bf 109 because of the Messerschmitt test pilot's demonstration of the 109's capabilities during a series of spins, dives, flick rolls and tight turns, throughout which the pilot was in complete control of the aircraft.
In March, the RLM received news that the British Supermarine Spitfire had been ordered into production. It was felt that a quick decision was needed in order to get the winning design into production as soon as possible, so on 12 March the RLM announced the results of the competition in a document entitled Bf 109 Priority Procurement, which ordered the Bf 109 into production. At the same time, Heinkel was instructed to radically re-design the He 112. The Messerschmitt 109 made its public debut during the 1936 Berlin Olympics, when the V1 prototype was flown.
As with the earlier Bf 108, the new design was based on Messerschmitt's "lightweight construction" principle, which aimed to minimise the number of separate parts in the aircraft. Examples of this could be found in the use of two large, complex brackets which were fitted to the firewall. These brackets incorporated the lower engine mounts and landing gear pivot point into one unit. A large forging attached to the firewall housed the main spar pick-up points, and carried most of the wing loads. Contemporary design practice was usually to have these main load-bearing structures mounted on different parts of the airframe, with the loads being distributed through the structure via a series of strong-points. By concentrating the loads in the firewall, the structure of the Bf 109 could be made relatively light and uncomplicated.
An advantage of this design was that the main landing gear, which retracted through an 85-degree angle, was attached to the fuselage, making it possible to completely remove the wings for servicing without additional equipment to support the fuselage. It also allowed simplification of the wing structure, since it did not have to bear the loads imposed during takeoff or landing. The one major drawback of this landing gear arrangement was its narrow wheel track, making the aircraft unstable while on the ground. To increase stability, the legs were splayed outward somewhat, creating another problem in that the loads imposed during takeoff and landing were transferred up through the legs at an angle.
The small rudder of the Bf 109 was relatively ineffective at controlling the strong swing created by the powerful slipstream of the propeller during the early portion of the takeoff roll, and this sideways drift created disproportionate loads on the wheel opposite to the swing. If the forces imposed were large enough, the pivot point broke and the landing gear leg would collapse outward into its bay. Experienced pilots reported that the swing was easy to control, but some of the less-experienced pilots lost fighters on takeoff.
Because of the large ground angle caused by the long legs, forward visibility while on the ground was very poor, a problem exacerbated by the sideways-opening canopy. This meant that pilots had to taxi in a sinuous fashion which also imposed stresses on the splayed undercarriage legs. Ground accidents were a problem with rookie pilots, especially during the later stages of the war when pilots received less training before being sent to operational units. At least 10% of all Bf 109s were lost in takeoff and landing accidents, 1,500 of which occurred between 1939 and 1941. The installation of a fixed "tall" tailwheel on some of the late G-10s and 14s and the K-series helped alleviate the problem to a large extent.
Freely moving, automatic leading edge slats
on a Bf 109E. By using high-lift devices, the handling qualities of the Bf 109 were considerably enhanced.
From the inception of the design, priority was given to easy access to the powerplant, fuselage weapons and other systems while the aircraft was operating from forward airfields. To this end, the entire engine cowling was made up of large, easily removable panels which were secured by large toggle latches. A large panel under the wing centre section could be removed to gain access to the L-shaped main fuel tank, which was sited partly under the cockpit floor and partly behind the rear cockpit bulkhead. Other, smaller panels gave easy access to the cooling system and electrical equipment. The engine was held in two large, forged, Elektron magnesium alloy Y-shaped legs, one per side straddling the engine block, which were cantilevered from the firewall. Each of the legs was secured by two quick-release screw fittings on the firewall. All of the main pipe connections were colour-coded and grouped in one place, where possible, and electrical equipment plugged into junction boxes mounted on the firewall. The entire powerplant could be removed or replaced as a unit in a matter of minutes, a potential step to the eventual adoption of the unitized-powerplant Kraftei engine mounting concept used by many German combat aircraft designs, later in the war years.
Another example of the Bf 109's advanced design was the use of a single, I-beam main spar in the wing, positioned more aft than usual (to give enough room for the retracted wheel), thus forming a stiff D-shaped torsion box. Most aircraft of the era used two spars, near the front and rear edges of the wings, but the D-box was much stiffer torsionally, and eliminated the need for the rear spar. The wing profile was the NACA 2R1 14.2 at the root and NACA 2R1 11.35 at the tip, with a thickness to chord ratio of 14.2% at the root and 11.35% at the tip.
Another major difference from competing designs was the higher wing-loading. While the R-IV contract called for a wing-loading of less than 100 kg/m2, Messerschmitt felt this was unreasonable. With a low wing-loading and the engines available, a fighter would end up being slower than the bombers it was tasked with catching.