German WWII fighter aircraft family
The Messerschmitt Bf 109 is a monoplane fighter aircraft that was designed and initially produced by the German aircraft manufacturer Bayerische Flugzeugwerke (BFW). Together with the Focke-Wulf Fw 190, the Bf 109 formed the backbone of the "Luftwaffe's" fighter force during the Second World War. It was commonly called the Me 109 by Allied aircrew and some German aces, even though this was not the official German designation.
The Bf 109 was designed by Willy Messerschmitt and Robert Lusser, who worked at BFW during the early to mid-1930s. It was conceived as an interceptor. However, later models were developed to fulfill multiple tasks, serving as bomber escort, fighter-bomber, day-, night-, all-weather fighter, ground-attack aircraft, and aerial reconnaissance aircraft. It was one of the most advanced fighters when the fighter first appeared, being furnished with an all-metal monocoque construction, a closed canopy, retractable landing gear, and powered by a liquid-cooled, inverted-V12 aero engine. First flown on 29 May 1935, the Bf 109 entered operational service during 1937; it was first used in combat during the Spanish Civil War. 
During the Second World War, the Bf 109 was supplied to several states and was present in quantity on virtually every front in the western hemisphere; the fighter was still in service at the end of the conflict in 1945. It continued to be operated by several countries for many years after the conflict. The Bf 109 is the most produced fighter aircraft in history, a total of 34,248 airframes having been produced between 1936 and April 1945. Some of the Bf 109 production took place in Nazi concentration camps through slave labor.
The Bf 109 was flown by the three top-scoring fighter aces of all time, who claimed 928 victories among them while flying with "Jagdgeschwader" 52, mainly on the Eastern Front. The highest-scoring, Erich Hartmann, was credited with 352 victories. The aircraft was also flown by Hans-Joachim Marseille, the highest-scoring ace in the North African campaign, who shot down 158 enemy aircraft (in about a third of the time). It was also flown by many aces from other countries fighting with Germany, notably the Finn Ilmari Juutilainen, the highest-scoring non-German ace. He scored 58 of his 94 confirmed victories with the Bf 109. Pilots from Hungary, Romania, Bulgaria, Croatia, Slovakia and Italy also flew the fighter. Through constant development, the Bf 109 remained competitive with the latest Allied fighter aircraft until the end of the war.
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Design and development.
Origins.
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 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 projected fighter needed to have a top speed of at , 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 . Power was to be provided by the new Junkers Jumo 210 engine of about . 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 synchronized, 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 maneuverability, 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; 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 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.
Prototypes.
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. 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. 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 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.
Design competition.
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.
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 (but could be dropped by the emergency arm). 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 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 redesign the He 112. The Messerschmitt 109 made its public debut during the 1936 Berlin Olympics when the V1 prototype was flown.
Design features.
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