Design works began in March of 1934, bare weeks after the RLM issued specifications for a small single-seat fighter/interceptor. The 109 would see extensive service with the German Luftwaffe between 1937 and 1945. It would become one of the most famous and iconic fighter aircraft of the World War II, with notable fighter aces scoring over 300 aerial victories in the 109.
The Bf 109A-0 to C-1 were armed with only 2 7.92mm MG 17's in the cowling, synchronized to fire through the propeller arc. C-1 through E-3 had 2 additional MG 17's mounted in the wings. The Bf 109A-D models were powered by the 660-690 HP Jumo 210-series engines.
The Bf 109E saw the first major redesign, being strengthened structurally to carry the heavier, but much more powerful 1,085 HP DB 601 engine. The Bf 109E-4 saw the first major increase in firepower, with 2 MG FF and later MG FF/M 20mm cannons replacing the 2 7.92mm Mg 17's in the wings. However, due to the drum-fed design of the MG FF, ammunition was limited to 60 rounds per gun. Experiments with belt-feeding didn't yield serious results. The E-4 was able to reach a speed of 295mph at sea level with emergency power (similar to WEP on US fighters), which was faster than many contemporary, and even planned fighters, such as Hawker Hurricane, A6M "Zero", Ki-43, and was only slightly slower than Supermarine Spitfire.
The Bf 109F was the second major change to the series, featuring a redesigned wing with rounded tips, which increased roll rate, redesigned cooling system, and fuselage aerodynamics. The F-1 through F-2 was armed with the same 2 Mg 17's in the cowling, and 1 Mg 121 15mm engine mounted cannon with 200 rounds, or an MG FF/M, firing through the propeller hub and were powered by the 1,159 HP DB 601N engine. The F-3 through 4 had the hub canon replaced with the more powerful Mg 151/20, which fired the larger more powerful 20mm MG FF/M round, and was used on all subsequent German fighter and ground-attack aircraft. Firepower could be further increased by mounting 2 MG 151/20 cannons in streamlined gondolas underneath each wing. They were powered by the 1,332 HP DB 601E. Top speed at sea level for the 601E powered fighters was 326mph.
Late F and early G models were widely considered to be the high-water mark of the design, displaying excellent manoeuvrability and handling characteristics, and good firepower and speed. But the constant need for increased speed and firepower would ensure continual upgrades and increases in weight.
The Bf 109G-1 through -4 were highly similar to the 109F-4, save that they used the more powerful 1,455 HP DB 605 engine. Odd numbered variants were built as high-altitude fighters with a pressurized cockpit and GM-1 boost, while even numbered variants were non-pressurized, air superiority fighters and fighter-bombers. The later G series (G-5 through G-14) was produced in a multitude of variants, with upgraded armament and provision for a number of kits of pre-packaged parts known as Umrüst-Bausätze, which was shown with a "Ux" with "x" being a number denoting which Umrüst kit was installed. Field kits known as Rüstsätze were also available for the G-series but those did not change the aircraft designation.
By early 1944, the continued advancement of allied and soviet fighters necessitated the use of MW-50 water injection boost and high-performance superchargers, boosting engine output to 1,800–2,000 PS (1,775-1,973 HP), in order to increase performance. While largely successful, the weight continued to climb as a result of the constant upgrades, which had a large negative impact on the manoeuvrability. The G-6 in particular was often seen as a 'step backwards' by its pilots, trading off speed, climb rate, and manoeuvrability, in exchange for replacing the 7.92mm MG's for 2 13mm MG 131's. However, subsequent G models again increased the speed and climb, while maintaining the firepower. The G-5 onwards was also able to replace the hub mounted Mg 151/20 for the far more powerful 30mm Mk 108 cannon, carrying 65 rounds of ammunition.
While the cannon was harder to aim, it greatly increased the effectiveness against bombers. Even a single hit was usually enough to destroy any fighter, even the heavily armoured P-47.
The Bf 109K-4 was the last production variant of the series was introduced in Fall of 1944, armed with 2 13mm MG 131's in the cowling, and 1 propeller hub mounted Mk 108 30mm cannon, and powered by the 1,973 HP DB 605D engine, the 109K-4 or "Kurfust" was a match for any allied or soviet fighter, vastly superior in vertical performance to all but the La-7 and Spitfire Mk 14, and low level speed compared to all but La-7, Hawker Typhoon/Tempest, F4U-1A and P-51H.
Performance was simply staggering, achieving a previously unheard of 4600 ft/min rate of climb, which actually increased at a linear rate until just below 5000ft where it topped of at ~4750 ft/min after which it steadily decreased, but still never falling below 4000 ft/min until over 15,000ft with emergency power.
Overall, the 109 developed a well deserved reputation as being a capable and deadly fighter. While beginning in 1941, it was supplemented by the Focke-Wulf Fw 190, it was never entirely replaced. On the Eastern front, while the Soviets had much respect for the 190, they still considered the 109 to be more dangerous of the two. The 109 served in all capacities, including fighter, interceptor, night-fighter, fighter-bomber, and reconnaissance fighter. It was also flown by noted aces such as Adolf Galland, Hans Joachim Marseille, Gustav Rödel, Eric Hartmann, and the commander of the first operational jet squadron, Walter Nowotny.
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