Designed by Willy Messerschmitt and Robert Lusser, the Messerschmitt Bf 109 became the backbone of the Luftwaffe's fighter force. The Bf 109 first saw operational service in 1937 during the Spanish Civil War and was still in service at the dawn of the jet age at the end of World War II in 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 Focke-Wulf Fw 190.
Whilst the 109 was conceived as an interceptor, later models were developed to fulfil 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 is 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. Through constant development, the Bf 109 remained competitive with the latest Allied fighter aircraft until the end of the war.
Willy Messerschmitt’s iconic fighter nearly didn’t happen when the fledgling Reichsluftfahrtministerium (RLM) ("Reich Aviation Ministry") still constrained by the Armistice e Treaty of Versailles banning the construction of military aircraft after Germany's defeat in WWI, released a highly secret research paper on the future of German air-combat. The paper called for their design and development of four offensive aircraft types:
• 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.
A design tender was offered to three German companies; Arado, Heinkel and Willy's BFW with a brief to design a fighter with a top speed of 400 km/h at 6,000m, 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. 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.
All three companies were asked to deliver three prototypes for head-to-head testing in early 1935
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.
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.
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.
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. The Messerschmitt 109 made its public debut during the 1936 Berlin Olympics, when the V1 prototype was flown.
The new design was based on Messerschmitt's "lightweight construction" principle, which aimed to minimise the number of separate parts in the aircraft.
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.
Due to the wide 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 snake-like fashion which also imposed further 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.
From the inception of the design, priority was given to easy access to the power-plant, 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 power-plant could be removed or replaced as a unit in a matter of minutes.
Reflecting Messerschmitt's belief in low-weight, low-drag, simple monoplanes, the armament was placed in the fuselage. This kept the wings very thin and light. Two synchronised machine guns were mounted in the cowling, firing over the top of the engine and through the propeller arc. An alternative arrangement was also designed, consisting of a single auto cannon-firing through a blast tube between the cylinder banks of the engine, known as a Motorkanone mount in German.
When it was discovered in 1937 that the RAF was planning eight-gun batteries for its new Hawker Hurricane and Supermarine Spitfire fighters, it was decided that the Bf 109 should be more heavily armed. The problem was that the only place available to mount additional guns was in the wings. Only one spot was available in each wing, between the wheel well and slats, with room for only one gun, either a 7.92 mm MG 17 machine gun, or a 20 mm MG FF or MG FF/M cannon.
The first version of the 109 to have wing guns had one MG 17 in each wing. To avoid redesigning the wing to accommodate large ammunition boxes and access hatches, an unusual ammunition feed was devised whereby a continuous belt holding 500 rounds was fed along chutes out to the wing tip, around a roller and then back along the wing, forward and beneath the gun breech, to the wing root, where it coursed around another roller and back to the weapon.
The gun barrel was placed in a long, large-diameter tube located between the spar and the leading edge. The tube channeled cooling air around the barrel and breech, exhausting out of a slot at the rear of the wing. The installation was so cramped that parts of the MG 17's breech mechanism extended into an opening created in the flap structure.From the 109F-series onwards, guns were no longer carried inside the wings. Instead, the Bf 109F had a 20 mm gun firing through the propeller shaft.
In place of internal wing armament, additional firepower was provided through a pair of 20 mm MG 151/20 cannons installed in conformal gun pods under the wings. The conformal gun pods, exclusive of ammunition, weighed 135 kg and 135 to 145 rounds were provided per gun. The total weight, including ammunition, was 215 kg. Installation of the under-wing gun pods was a simple task that could be quickly performed by the unit's armourers, and the gun pods imposed a reduction of speed of only 8 km/h. By comparison, the installed weight of a similar armament of two 20 mm MG 151/20 cannon inside the wings of the FW 190A-4/U8 was 130 kg without ammunition.
Although the additional armament increased the fighter's potency as a bomber destroyer, it had an adverse effect on the handling qualities, reducing its performance in fighter-versus-fighter combat and accentuating the tendency of the fighter to swing pendulum-fashion in flight.
The 109 remained in production from 1937 through 1945 in many different variants and sub-variants due largely to its operational versatility and outstanding rate of climb which was superior to most Allied adversaries including the P-51D Mustang, Spitfire Mk. XIV, and Hawker Tempest Mk. V
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