MG FF
The MG FF was one of the German air force in World War II used automatic cannon caliber 20 mm ( 'FF' = 'Wing Fest').
development
The Ikaria, Society for Aviation components mbH in Berlin (from 1936 in Velten near Berlin) acquired mid-1930s by the Swiss Machine Tool Factory Oerlikon the licensing rights to the short Oerlikon FF F . The MG FF in caliber 20 × 80 mm RB was developed on the basis of this weapon in caliber 20 × 72RB . Due to the longer cartridge, a larger propellant charge could be used and a higher muzzle velocity could be achieved. Since the effect of the highly explosive projectiles used did not appear to be satisfactory, various possibilities were investigated at the end of the 1930s to increase the space available in the projectile. The thin-walled mine projectile developed by Rheinmetall-Borsig contained approximately five times the amount of explosives, but weighed only 90 to 92 g instead of the 130 g of the projectiles previously used. The recoil energy released by the mine projectile when it was fired was insufficient to cleanly repeat the MG FF , so the recoil mechanism had to be adapted for the new ammunition. However, this no longer allowed the previously used ammunition of the MG FF to be fired , otherwise damage could occur. The MG FF adapted in this way was called MG FF / M and was recognizable by an "M" on the nameplate or on the weapon itself.
Design features
The MG FF was an unlocked, fully automatic recoil loader with a fixed barrel and advance ignition. H. the cartridge was fed into the chamber from the breech and ignited shortly before the end position. The use of the kinetic energy of the advancing bolt made it lighter, and the bolt no longer hit the barrel, the weapon fired more gently. A disadvantage of the system was that the indefinite ignition timing did not allow synchronized firing by a propeller circle. The Bf 109 V4 was equipped with this weapon for tests , which the RAF became aware of in November 1938. Thereupon, in May 1939, a Hawker Hurricane was tested with two 20-mm Oerlikon machine-guns .
ammunition
When MG FF / M , the more efficient mine bullets were first used. Up until now, grenades had been manufactured in such a way that the explosive charge split the projectile into splinters and caused damage to the target. Chief engineer Ludwig from the Rheinmetall Borsig company tried mainly to use the gas hammer effect resulting from an explosion to destroy it and designed a thin-walled projectile in the cargo area of which five times the amount of explosives could be accommodated. If HE shells only caused ineffective destruction by fragmentation in the sections of the fuselage and the areas that did not contain any important parts, the mine projectile resulted in so great damage there too that the airworthiness was severely impaired or the crash was caused.
New problems had to be solved in the development of this ammunition. The detonator attached to the tip of the bullet had to be made even lighter, although it was made of light metal, since the thin wall of the bullet could only withstand the acceleration of small masses. One solution was the bottom igniter developed by the Rheinmetall Borsig Group in Sömmerda . Volumes 1511, 1512 and 1513 were used for the 20 mm mine grenade. The HTA-15 mixture, which consisted of 45% trinitrotoluene , 40% hexogen and 15% aluminum pyrogrip, or the HA-41 mixture (75% hexogen, 20% aluminum pyrogrip, 5% wax) was used as the explosive charge. used.
According to service regulation (Luft) 5001, mine grenades were used in combination with incendiary grenades and tank incendiary grenades.
The ammunition was supplied through rod magazines with 15 cartridges or via drums with 45, 60 or 100 cartridges. The belt feeder developed by Ikaria / Velten since January 1941 was not used, although the tests in the Bf 109 E-7 and F-1 were satisfactory, as better weapons increasingly replaced the MG FF .
The MG FF only had high-explosive projectiles, these weighed 130 g and were fired at 600 m / s and a rate of 530 rounds per minute. The MG FF / M offered a wide range of ammunition types with a slightly lower rate of fire of 520 rounds per minute, only the mine projectiles could be fired at 540 rounds per minute.
| MG FF / M | Cartridge weight |
Bullet weight |
Propellant charge | explosive | Muzzle velocity |
Muzzle energy |
fire rate |
|---|---|---|---|---|---|---|---|
| HE grenade | 183 g | 115 g | 13.3 g | 3.7 g | 585 m / s | 19.7 kJ | 520 rounds / min |
| Tank incendiary grenade | 185 g | 115 g | 13.5 g | 0.5 g of fuel | 575 m / s | 19.3 kJ | 520 rounds / min |
| Incendiary grenade | 183 g | 115 g | 13.3 g | 3.6 g + 0.4 g fuel | 580 m / s | 19.3 kJ | 520 rounds / min |
| Tank shell | 179 g | 117 g | 13.5 g | - | 585 m / s | 19.7 kJ | 520 rounds / min |
| Mine grenade | 160 g | 90 g | 15.5 g | 18 g | 695 m / s | 22.0 kJ | 540 rounds / min |
All types of ammunition could be equipped with traces of light, glow tracks (for night fighters) and dismantlers (time fuses for self-destruction). Due to the design, mine projectiles could not be equipped with light or glow trails.
The cartridge used by the MG FF was 145.4 mm long, the case was made of steel or brass and measured 80.6 mm.
use
The MG FF was installed both rigidly and movably in Luftwaffe combat aircraft from 1937 , the MG FF / M was introduced in 1940 and by 1941 all MG FF were converted to the MG FF / M status . Typical users were the Bf 109-E series or the Fw 190 , each with two MG FF or MG FF / M rigidly built into the wings . Since the ammunition was fed by drum, this required small dents on the wing. The Bf 110 used two MG FF in the bow, as did the Do 17 Z and Do-215 night fighters. Destroyer and night fighter versions of the Ju 88C had one in the bow and two of them in a drop of weapons under the cockpit, the Do-217-J / N night fighters even used four of these weapons.
The MG FF was also found in various other fighter planes and bombers , in some cases rigidly directed forward (Do 17, Do 217, Ju 88) or in a rotating weapon turret (e.g. Fw 200 ).
The assembly between the cylinder banks of the German V12 aircraft engines was tested again and again with the MG FF , for the first time in 1937 in the Jumo 210 of the Ar 80 V1 , but this was never successful due to overheating and various other problems. Only in the Bf 109 F-1 was the MG FF / M used as a motor cannon, but there too the weapon tended to jam, especially during flight maneuvers with higher G loads.
The MG FF / M experienced a second spring from 1943, when the weapon that was actually to be retired was used for the " Weird Music " in the Bf 110. Due to their relatively short barrel, the two MG FF fitted well into the rear area of the cockpit and thus caused little additional air resistance.
Successor construction
The MG FF had some disadvantages. Both the rate of fire and the penetration power were not satisfactory. Another disadvantage was the limited ammunition capacity. At the time of the " Battle of Britain " a maximum of the 60-shot drum was available. With wing assemblies, however, often only 55 rounds were accommodated. In the further course of the war, the MG FF and MG FF / M were replaced more and more by the MG 151/20 .
Technical specifications
- Type : MG FF
- Caliber : 20 mm
- Barrel length : 822 mm
- Manufacturer : Ikaria
- Gun length : 1338 mm
- Gun height : 135 mm
- Gun width : 155 mm
- Weight : 26.3 kg
- Rate of fire (per min) : 530
- Muzzle velocity : 585 m / s
- Ammunition designation : 20 × 80 mm RB
Remarks
The origins of the Oerlikon FF series lie in the German Becker cannon in caliber 20 × 70RB developed by Reinhold Becker in 1914 .
Due to the firing mechanism, Oerlikon FF-based cannons could not fire synchronously through the propeller circle. With regard to the Fw 190, it is often said that in early versions an MG FF would have been used in the wing roots for precisely this purpose.
The MG 151/20 developed as a replacement for the MG FF used the same projectiles as the MG FF / M , but was able to use a stronger propellant charge due to the longer cartridge (20 × 82).
Many of the 20 mm automatic cannons used in World War II were based on the Oerlikon / Becker system. The Western Allies use 20 mm rapid-fire cannons as light flak, for example on ships. The Royal Air Force used 20 mm Hispano-Suiza cannons based on the Oerlikon FFS in 20 × 110 caliber. The Japanese Air Force and Navy use the 20 × 72 Oerlikon FFF in their aircraft as Type 99-1, later the 20 × 101 Oerlikon FFL as Type 99-2.