The FlaK 18 was an anti-aircraft artillery piece that was used by Germany during World War II.
The FlaK 18 was the first in a series of 37mm autocannons used to combat aircraft. Notably, the FlaK 18 was far more effective at downing an aircraft once a hit was scored versus the previous FlaK 30 20mm anti-air gun. It also utilized much of the same mechanical features as the 20mm weapon. The FlaK 18 had an effective ceiling for firing of about 4,800 meters while its rate of fire maxed out at about 80 rounds per minute. The type's total weight meanwhile was about 1,750 kg when in combat position and 3,560 kg when traveling.
However, the mount and carriage used with the FlaK 18 were both large, cumbersome, and had many problems. Besides overly complicated, the FlaK 18's carriage was very expensive which did not aid production. Due to these issues, production of the FlaK 18 was cut short in favor of the much improved FlaK 36 derivative.
The FlaK 36 design included numerous refinements and proved to be a success in practice because of it. Some notable changes include a new three-legged mount for combat operation and a new light trailer designated the Sonderhänger 52. Further improving on the then standard German anti-aircraft weapon, the FlaK 37 used an eight round magazine and a new Flakvisier 40 computer sight to better target aircraft. Its weight was much reduced from past models, now 1,550 kilograms and it had an improved muzzle velocity of 820 meters per second. Allowing for combat against ground targets, the FlaK 37 had an elevation range from -8 to +85 degrees. The last improvement in the 3.7 cm FlaK series was the FlaK 43.
By the time the FlaK 43 had been designed, German production required a design which could be produced quickly and cheaply. Having improvements based on the aircraft-mounted Rheinmetall MK 103, the FlaK 43 had a simplified sight and used a gas-operated breech system. Practical rate of fire was also significantly raised, to around 150 rounds per minute and its weight was further decreased to 1,219 kilograms. The final three variants of the series were all variants not related to the core model. The first of these was the 3.7 cm Flakzwilling 43, a modified version which put two FlaK 43s together into a dual mount, one above the other. Next was the Bordkanone BK 3.7cm, an aircraft modification designed to destroy tanks from above. It was designed to be used on such aircraft as the Junkers Ju 87, Messerschmitt Bf 110, and Henschel Hs 129. The final variant was the FlaK 42, a conversion for use on German U-Boats. Being based on an earlier 3.7 cm autocannon, the FlaK 42 had a lower overall rate of fire of 50 rounds per minute.
The FlaK 18 was first developed in 1934 by Rheinmetall-Borsig and Solothurn as a harder-hitting version of the FlaK 30. Following the unsuccessful trials of the FlaK 18 and the ending of production, the FlaK 36 entered development and eventually service by 1937. From there, the 3.7 cm FlaK system became the standard anti-aircraft gun used by Germany, supplemented by the smaller 2cm FlaK 30. In total, some 20,000 examples of various 3.7 cm FlaK guns had been produced throughout the war.
- Ivanov, A. German Artillery during World War II. (2003), Page 41
- Lepage, Jean-Denis. The Illustrated Handbook of Flak:German Anti-Aircraft Defences 1935-1945. Spellmount (2012), Page 90