After the defeat of Germany in the First World War by the Treaty of Versailles, it was forbidden to have and develop anti-aircraft artillery. The anti-aircraft artillery units re-created in the early 30s for the purpose of conspiracy until 1935 were called "railway battalions", and the anti-aircraft artillery systems, designed in Germany in the period from 1928 to 1933, had the designation "arr. eighteen". Thus, in case of inquiries from Great Britain and France, the Germans could answer that these were not new weapons, but old ones, designed in 1918, even before the end of the First World War.
All this fully applied to the 37-mm anti-aircraft automatic gun 3, 7 cm Flak 18 (German 3, 7 cm Flugzeugabwehrkanone 18) created by the specialists of the Rheinmetall Borsig AG concern in 1929 on the basis of the developments of the Solothurn Waffenfabrik AG company. The 37-mm assault rifle was intended to combat aircraft flying at altitudes up to 4000 m. Due to the high muzzle velocity of the armor-piercing projectile, this gun, before the appearance of anti-cannon armor, could hit any armored vehicle.
The cannon automatics worked due to the recoil energy with a short barrel stroke. The shooting was carried out from a pedestal gun carriage, supported by a cruciform base on the ground. In the stowed position, the gun was transported on a four-wheeled cart. The designers paid great attention to the ease of maintenance and maintainability of the anti-aircraft gun. In particular, threadless connections were widely used in it.
The 37-mm anti-aircraft gun 3, 7 cm Flak 18, after lengthy military trials, officially entered service in 1935. For firing a 37-mm anti-aircraft gun, a unitary shot known as 37x263B was used, which, in combination with a barrel length of 2106 mm, depending on the type and mass of the projectile, accelerated it to 800 - 860 m / s. Cartridge weight - 1, 51-1, 57 kg. An armor-piercing tracer projectile weighing 680 g accelerated to 800 m / s. The thickness of the armor pierced by the armor-piercing tracer at a distance of 800 m at an angle of 60 ° was 25 mm. The ammunition load also included shots: with fragmentation-tracer, fragmentation-incendiary and fragmentation-incendiary tracer grenades, an armor-piercing high-explosive projectile, as well as a subcaliber armor-piercing tracer projectile with a carbide core.
Power was supplied from 6-charge clips on the left side of the receiver. Rate of fire - up to 150 rds / min. The mass of the gun in the combat position is 1760 kg, in the stowed position - 3560 kg. Calculation - 7 people. Angles of vertical guidance: from -7 ° to + 80 °. In the horizontal plane, there was the possibility of a circular attack. Guidance drives are two-speed. The maximum firing range at air targets is 4200 m.
In general, the 37-mm anti-aircraft gun was quite efficient and quite effective against aircraft at a distance of up to 2000 m, and could successfully operate against lightly armored ground targets and manpower in line-of-sight aisles.
The baptism of fire 3, 7 cm Flak 18 took place in Spain, where the gun performed well on the whole. However, there were many complaints about the excessive weight in the transport position, the reason for which was the heavy and uncomfortable four-wheeled "cart". Despite the fact that by the beginning of World War II, this 37-mm anti-aircraft gun was replaced in production with more advanced models, its operation continued until the end of hostilities.
Already in 1936, using the artillery unit 3, 7 cm Flak 18 and a new gun carriage, the anti-aircraft machine gun 3, 7 cm Flak 36 was created. The mass of the system in the combat position was reduced to 1550 kg, and in the stowed position - to 2400 kg. While maintaining the ballistic characteristics and rate of fire of the previous modification, the elevation angles were increased in the range from -8 to + 85 °.
Such a significant weight reduction was achieved mainly due to the transition to a new four-frame carriage with a detachable two-wheel sprung travel. She was transported at speeds up to 50 km / h. The installation of the cannon on the cart and removal from it was carried out using a chain winch. The ballistic characteristics and rate of fire of the gun remained the same.
In the next modification 3, 7 cm Flak 37, an improved anti-aircraft sight Sonderhänger 52 with a calculating device was introduced. The fire control of the anti-aircraft battery was carried out using the Flakvisier 40 rangefinder. Thanks to this, it was possible to significantly increase the effectiveness of firing at distances close to the limit. From earlier models, the 3, 7 cm Flak 37 in the firing position can be distinguished by a modified barrel cover, which is associated with a simplified production technology.
In addition to the standard carriages, 3, 7-cm Flak 18 and Flak 36 anti-aircraft guns were installed on railway platforms, various trucks and armored personnel carriers. In 1940, the production of self-propelled anti-aircraft guns began on the chassis of the 5-ton half-track Sd. Kfz.6 tractor, designated Sd. Kfz.6 / 2.
An unarmored ZSU weighing 10, 4 tons was armed with a Flak 36 cannon, and its crew consisted of 5 people. In total, 339 self-propelled guns were transferred to the Wehrmacht. However, under the conditions of the Eastern Front, unarmored self-propelled guns suffered heavy losses. This was especially true when repelling low-altitude bombing and assault strikes by Soviet aviation and in the case of providing fire support to ground units.
In 1942, on the basis of the 8-ton SdKfz 7 half-track tractor, the ZSU was created, which was put into service under the symbol Sd. Kfz.7 / 2. This self-propelled gun weighed 11.05 tons and was armed with a 37-mm Flak 36 cannon. Based on the experience of combat use, the anti-aircraft self-propelled gun received light armor protection for the engine and driver's cab. Until January 1945, more than 900 of these self-propelled guns were built, most of them fought on the Eastern Front.
Unlike towed 37-mm anti-aircraft guns deployed at prepared firing positions as part of the battery, the calculation of self-propelled anti-aircraft guns when firing at air targets, due to more constrained conditions, as a rule, did not use an optical rangefinder, which negatively affected the accuracy of shooting. In this case, amendments to the sight were made in the course of firing, based on the trajectory of the tracer shells relative to the target.
ZSU with 37-mm anti-aircraft guns on the chassis of half-track transporters were actively used on the Eastern Front, operating mainly in the front-line zone. They were involved in escorting transport convoys and were part of the anti-aircraft battalion that provided air defense for some tank and motorized (panzergrenadier) divisions. Compared to self-propelled anti-aircraft guns armed with 20-mm and 30-mm machine guns (especially with quad), 37-mm guns had a lower combat rate of fire. But much heavier and more powerful 37-mm shells made it possible to fight air targets flying at a distance and height inaccessible to anti-aircraft guns of a smaller caliber. At close values of the initial velocity, the 37-mm projectile weighed one and a half to two times more than the 30-mm (640 - 680 g versus 330 - 500 g), which ultimately determined a significant superiority in muzzle energy (215 kJ versus 140) …
The experience of combat use has shown that the partially armored anti-aircraft self-propelled gun Sd. Kfz.7 / 2 turned out to be more adapted to the realities of the Eastern Front than the 20-mm SPAAG on a tank and half-track chassis. A 37-mm high-explosive projectile weighing 640 g, containing 96 grams of TNT mixed with pentrite, when hit, inflicted critical damage on Il-2 and Il-10 attack aircraft. The best height reach made it possible to use the 37-mm ZSU against medium-altitude targets in the interests of air defense of various kinds of ground-based stationary objects. In addition, in the event of a breakthrough by Soviet tanks, 37-mm self-propelled guns often played the role of a mobile anti-tank reserve. At a distance of up to 500 m, armor-piercing shells could confidently overcome the protection of light and medium tanks. In the case of targeted use against armored vehicles, the ammunition load of 37-mm anti-aircraft guns could include a sub-caliber projectile weighing 405 g, with a tungsten carbide core and an initial speed of 1140 m / s. At a distance of 600 m, along the normal, it pierced 90 mm armor. But due to the chronic shortage of tungsten, 37mm APCR shells were not often used. In addition, the occasional use of the ZSU Sd. Kfz.7 / 2 against Soviet tanks was a purely forced measure.
The calculation of 37-mm self-propelled guns was partially covered only by an 8-mm anti-splinter shield, and the thin armor of the cockpit and engine compartment protected from rifle caliber bullets fired from a distance of no closer than 300 m. The German ZSU could not withstand a direct collision even with light tanks, and were able to operate successfully only from an ambush.
In general, the 3, 7 cm Flak 36 and 3, 7 cm Flak 37 assault rifles met the requirements for 37-mm anti-aircraft guns. However, when firing at rapidly moving air targets, it was highly desirable to increase the combat rate of fire. In 1943, the 37-mm towed anti-aircraft gun 3, 7 cm Flak 43, created by the concern Rheinmetall Borsig AG, entered service. The vertical guidance angle of the barrel was increased to 90 °, and the principle of operation of the automatic artillery unit was significantly revised. The short stroke of the barrel during recoil was combined with a gas vent mechanism that unlocks the bolt. Due to this, it was possible to combine several operations and reduce the time required to complete all actions during the production of a shot.
Simultaneously with the increase in the rate of fire to 250 rds / min, due to the introduction of an effective spring-hydraulic damper, it was possible to reduce the recoil and shock loads on the gun frame. Thanks to this, the mass of the gun in the combat position was 1300 kg, in the transport position - about 2000 kg. To increase the practical rate of fire to 100 rds / min and the length of the continuous burst, the number of shots in the clip was increased to 8 units. The mass of a clip with 8 shots is about 15 kg.
The barrel length, ammunition and ballistics of the Flak 43 remain unchanged compared to the Flak 36. The gun was transported on a single-axle sprung trailer, with pneumatic and hand brakes, as well as a winch for lowering and raising the gun when it was transferred from the traveling position to the combat position and vice versa. In exceptional cases, shooting from a cart was allowed, while the horizontal firing sector did not exceed 30 °. The Flak 43 artillery unit was mounted on a triangular base with three frames, on which it rotated. The beds had jacks for leveling the anti-aircraft gun. The lifting mechanism is sector, with one aiming speed. The swivel mechanism had two aiming speeds. The balancing of the swinging part was carried out by a balancing mechanism with a spiral spring.
Taking into account the experience of hostilities, the new anti-aircraft gun had a steel shield with two folding side flaps, which reduced the vulnerability of the calculation when repelling air attacks and shelling from the ground. To increase the effectiveness of anti-aircraft fire, the aiming from a single anti-aircraft fire control device was adopted as the main one. At the same time, individual sights were retained for use outside the 3, 7 cm Flak 43 anti-aircraft battery. In the Wehrmacht, towed anti-aircraft guns 3, 7 cm Flak 43 were reduced to batteries of 9 guns. In the anti-aircraft battery of the Luftwaffe, placed in stationary positions, there could be up to 12 37-mm cannons.
As in the case with other 20-37-mm rapid-fire anti-aircraft guns, 3, 7 cm Flak 43 were used to create a ZSU. Initially, they tried to mount a new 37-mm anti-aircraft machine gun on the chassis of the SdKfz 251 half-track armored personnel carrier. However, the troop compartment of the armored personnel carrier turned out to be too cramped to accommodate a sufficiently massive anti-aircraft gun, crew and ammunition. In this regard, the specialists of Friedrich Krupp AG went the already beaten track, creating a 37-mm version of the Furniture Car. By analogy with a quad 20-mm SPAAG on a tank chassis, recovered Pz. Kpfw IV modifications H and J with a dismantled turret.
A box of 20-mm armor plates was assembled around the anti-aircraft machine gun in the transport position, which could protect the gun and the crew from bullets and light fragments. Sometimes, to preserve the ability to fire from the stowed position, a cutout was made in the frontal sheet. When conducting anti-aircraft fire, the armor plates were folded back, forming a flat platform. The mass of the ZSU in the combat position was within 25 tons, the mobility was at the level of the base chassis. The crew of the car consisted of six people. Although the self-propelled gun was originally called Flakpanzerkampfwagen IV (literally - Combat anti-aircraft tank IV), the name Möbelwagen (German furniture car) stuck more.
The first 37-mm ZSU on the chassis of a medium tank were sent to the troops in March 1944. By August 1944 self-propelled guns 3, 7 cm FlaK 43 auf Pz. Kpfw. IV "Möbelwagen" were equipped with separate anti-aircraft divisions (8 vehicles each) of three armored divisions on the Western Front and two armored divisions on the Eastern Front.
In the future, a number of tank brigades were equipped with mixed anti-aircraft battalions, which included 4 ZSU with 37-mm anti-aircraft guns and 4 ZSU with 20-mm machine guns. It is now impossible to establish the exact number of 37-mm Furniture Cars built. Most sources agree that just over 205 units were produced.
ZSU 3, 7 cm FlaK 43 auf Pz. Kpfw. IV had a number of significant drawbacks. To transfer the installation from the traveling position and back, it was necessary to unfold and raise heavy armor plates, which required time and considerable physical effort. At the firing position, the entire crew of the installation, except for the driver, was on an open platform and was very vulnerable to bullets and shrapnel. In this regard, it was considered advisable to create an anti-aircraft self-propelled gun with a turret. Since the gunner had to be able to independently detect air targets, and when firing a 37-mm machine gun, a large amount of powder gases fell into the fighting compartment along with spent cartridges, the turret had to be made open from above.
In July 1944, Ostbau Werke produced the first prototype of the ZSU with a 37-mm FlaK 43 anti-aircraft gun installed in a rotating turret on the chassis of a Pz. Kpfw IV tank. The thickness of the armor of the hexagonal turret was 25 mm. The turret housed a 37-mm Flak43 automatic anti-aircraft gun, sighting devices, a combat crew, and 80 rounds in cassettes. The rest of the ammunition in the amount of 920 rounds was in the turret boxes. The calculation of the ZSU consisted of 5 people.
The ZSU, designated 3, 7 cm Flak 43 auf Sfl Pz. Kpfw IV, later became better known as the Flakpanzer IV "Ostwind" (German Anti-Aircraft Tank IV "East Wind"). Compared to the Pz. Kpfw IV serially produced at this time, the security of the anti-aircraft self-propelled gun was less. The creators of the ZSU quite reasonably considered it superfluous to install anti-cumulative screens on it, since it was not supposed to operate in the first line of battle formations. In August 1944, an order was placed for the production of 100 vehicles. Serial production of the Flakpanzer IV "Ostwind" was established at the Deutsche Eisenwerke plant in Duisburg, but before the collapse of Nazi Germany, no more than 50 self-propelled anti-aircraft guns were delivered.
As in the case with other SPAAGs based on the Pz. Kpfw IV, tanks recovered from combat damage were mainly used as a base. There were also plans to create a 37-mm SPAAG on the chassis of the outdated Pz. Kpfw. III and Pz. Kpfw. 38 (t) tanks, however, it never came to the practical implementation of these projects. In fairness, it should be said that the German "anti-aircraft tank" Flakpanzer IV "Ostwind" was the best in its class and during the war years had no serial analogues in other countries.
The twin 37-mm anti-aircraft gun was designated Flakzwilling 43 (Gemini 43). The artillery machines were located one above the other, and the cradles on which the machines were installed were connected to each other by a thrust forming a parallelogram articulation. Each machine was located in its own cradle and formed a swinging part rotating relative to its annular pins.
With the vertical arrangement of the machines, in the case of a shot from one barrel, there was no dynamic torque in the horizontal plane, knocking down the aiming. Due to the presence of individual trunnions for each machine gun, disturbances affecting the swinging part of the anti-aircraft installation were minimized. Such a constructive solution improved the accuracy of fire and the aiming conditions of the gun, and also in the event of the failure of one gun, it was possible to fire from the second without disrupting the normal aiming process. It was also possible to use machines from single installations without any modifications.
The disadvantages of such a scheme are a continuation of the advantages: with a vertical arrangement, the height of the entire anti-aircraft installation and the height of the line of fire increased. In addition, such an arrangement is only possible for side-fed vending machines.
In general, the creation of a paired 37-mm installation has justified itself. The weight of the Flakzwilling 43 has increased by about 40% compared to the Flak 43, and the combat rate of fire has almost doubled.
Work was also carried out on a horizontal twinned 37-mm anti-aircraft gun using the Flak 43 artillery unit. It was planned to install it on the ZSU created on the basis of the Pz. Kpfw. V "Panther" tank.
The prototype of the vehicle, designated Flakzwilling 3, 7cm auf Panzerkampfwagen Panther, was built in 1944 and had only a turret layout. Due to the overload of the German industry with military orders, this project remained in development.
Until March 1945, the Wesserhutte and Durrkopp factories manufactured 5918 37-mm Flak 43 anti-aircraft guns, and 1187 twin Flakzwilling 43.3.7-cm Flak 43 and Flakzwilling 43 automatic anti-aircraft guns were in service with air defense units, both in the Luftwaffe and in Wehrmacht, and were widely used in the final stage of World War II. Despite the higher level of combat characteristics, the Flak 43 could not completely displace the Flak 36/37 from production lines - the production of different types of 37-mm anti-aircraft guns was carried out until the end of the war.
In 1945, they tried to adapt a significant part of the available 37-mm anti-aircraft guns for firing at ground targets. Thus, the German command intended to plug the gaps in the anti-tank defense, in parallel, the anti-aircraft guns were supposed to provide air defense of the front edge. Due to low mobility, automatic anti-aircraft guns were used mainly in pre-equipped positions in defense nodes. Due to their good penetration and high rate of fire for their caliber, they posed a certain danger to Soviet medium T-34 tanks and light armored vehicles. Their fire was especially destructive in cities, where camouflaged anti-aircraft guns were able to fire from a minimum distance.
