Flakpanzer IV (3.7 cm Flak 43) ‘Möbelwagen’ (Sd.Kfz.163/3)

German Reich (1944)
Self-Propelled Anti-Aircraft Gun (SPAAG) – 205-250 Built

As the Second World War progressed, it was becoming obvious to the German tank force that the Luftwaffe (English German Air Force) was slowly losing control of the skies over Europe. In order to protect themselves from enemy ground attack aircraft, a series of self-propelled anti-aircraft guns (SPAAG) based on tank chassis were proposed in 1942. None of these early designs would be adopted, given the severe capacity limitations of the German war industry. As a temporary solution, the Panzer IV chassis was chosen for this use, being initially armed with the 2 cm Flakvierling anti-aircraft gun. The whole concept was deemed worthwhile, but the armament was seen as too weak. In early 1944, a slightly improved model armed with the stronger 3.7 cm Flak 43 anti-aircraft gun would be adopted for service as the first of the Flakpanzer IVs.

A New Flakpanzer IV

The early German attempts to create an effective SPAAG based on a tank chassis were rather unsuccessful. The problem with these early proposals was that they were based on tank chassis that were yet to enter production, and none of these actually did so in any significant numbers, so these AA projects had to be quickly abandoned. By the later stages of the war, the overburdened German industry was simply unable to provide resources and production facilities for yet another new vehicle type.

During May 1943, various German Army commissions, including those concerned with armaments and tanks, met to discuss a proper solution to the general lack of anti-aircraft protection for the panzer divisions. After a series of discussions, it was agreed that the best solution was to reuse the Panzer IV chassis for the new SPAAG. The contract for this project was officially awarded on 8th June 1943. In order to speed up the development and production process, the whole design was to be as simple as possible. As a temporary solution, the armament would consist of the 2 cm Flakvierling. This anti-aircraft gun and its crew were to be protected by four-hinged armored walls. The firm responsible for the realization of this project was Krupp. Once the prototype was completed, it was presented to a Luftwaffe delegation for inspection on 3rd October 1943. The delegation did not have any objections and the prototype was to be used for initial testing and evaluation. The overall results were promising and a monthly production run of 20 vehicles was to begin starting in April 1944.

This was not to be, as, on 21st December 1943, it was decided to instead rearm this vehicle with the more powerful 3.7 cm Flak 43 anti-aircraft gun. The Germans were becoming aware that their 2 cm anti-aircraft gun was slowly losing its effectiveness against enemy aircraft at heights greater than 1 km. While it had a much lower firing rate, the larger 3.7 cm round offered a much greater punch. On the 3rd of January 1944, a meeting was once again held between various army branches, including some prominent figures such as Heinz Guderian, General Von Renz (anti-aircraft branch), Hitler, and Albert Speer. Hitler himself agreed to the notion that the Panzer IV chassis should be used as a temporary solution and that the second version (armed with the 3.7 cm gun) should be adopted. A production order for 20 such vehicles was issued. These were to be completed in February 1944. After that, a monthly production rate of 20 vehicles was to be carried out. The initial order included 100 such vehicles. Deutsche Eisenwerke AG was responsible for the delivery of the guns. These were to be placed on the chassis completed by Krupp.

With this, the 3.7 cm armed Flakpanzer IV project received a green light. A prototype vehicle was quickly built. This was actually the same prototype, just rearmed with the larger gun. After a brief examination, some minor changes were requested. mostly in regard to the weapon mount and the redesign of its gun shield.

The first Flakpanzer IV, together with other anti-aircraft vehicles (not specified which ones in the sources), were transported near Oksbol in occupied Denmark for firing trials. The 3.7 cm Flak 43 worked without any problem. The main issue noticed was the extensive exhaust gasses and the long flame tongues that exited from the gun breech. Both of these were not related to the design of the gun, but to the lower quality of the gunpowder used at this stage of the war.

Name

The new vehicle received the quite simple designation Flkakpanzerkampfwagen IV (or simply Flakpanzer IV). In order to help distinguish it from other similar vehicles based on the Panzer IV chassis, the armament caliber and name are often added to its designation. The vehicle itself is possibly best known by the name given mockingly by the troops that operated it. They referred to it as the Möbelwagen (English: Furniture van).

Production

While initial plans predicted that the first group of 20 vehicles would be built in February 1944, this did not happen. The actual production began in March 1944. The production went relatively smoothly, with the 20 vehicles per month quota being achieved and sometimes even surpassed. The production of this vehicle was to be terminated in October 1944. It was to be replaced by the Ostwind, which was expected to enter serial production in November 1944. As this did not occur, the production of the Flakpanzer IV continued up to April 1945, with some 240 vehicles being built in total by that point. The production number may have been slightly larger, as the documents from the Stahlindustrie (Eng. Metal Industry), which were recovered after the war, mention that 243 vehicles were completed.

Month	1944	1945
January	/	5
February	/	18
March	20	12
April	20	Unknown
May	15
June	34
July	31
August	30
September	24
October	14
November	10
December	7
In total	205	Around 35

While most sources agree that 240 such vehicles were produced, there are some that offer different production numbers. For example, author D. Nešić (Naoružanje Drugog Svetsko Rata-Nemačka) gives a figure of 250 vehicles having been built. Author B. Perrett (Panzerkampfwagen IV Medium Tank 1936-1945) states a total of 211, while Walter J. Spielberger (Gepard The History of German Anti-Aircraft Tanks) only mentions 205 vehicles being built. The most likely correct production numbers are 240 vehicles, as mentioned by T. L. Jentz and H. L. Doyle (Panzer Tracts No. 12-1 – Flakpanzerkampfwagen IV), given that they are supported by German documentation.

Design

The new Flakpanzer IV shared most of its components (besides the obvious difference in the main armament) with its Flakvierling-armed predecessor on which it was based. Still, some modifications and improvements were introduced, either at the start of or during production. The Flakpanzer IV was built using Panzer IV Ausf.H and Panzer IV Ausf.J chassis.

Suspension and Running Gear

The Flakpanzer IV suspension and running gear were the same as those of the original Panzer IV, with no changes to the overall construction. They consisted of eight small doubled road wheels on each side, suspended in pairs by leaf-spring units. There were two front-drive sprockets, two rear idlers, and eight return rollers in total. Usually, the return rollers were rubber rimmed, but by 1944, shortages of this material meant that they had to be replaced with metal return rollers.

Hull and the Engine Compartment

The original Panzer IV hull design did not receive any major change. The Flakpanzer IV utilized the Maybach HL 120 TRM engine but was slightly modified to give out 272 hp@2,800 rpm instead of the usual 265 hp@2,600 rpm.

Superstructure

The new Flakpanzer IV retained the large rectangular-shaped superstructure. In order to reduce production costs, the machine gun ball mount was replaced with a much simpler machine gun firing port. This port was protected by a round cone-shaped cap. It was like a plug, connected to a chain, and when in use, the armored cover would simply be pushed out by one of the crew members. The Panzer IV driver’s observation port remained unchanged. To the left of the driver vision port, a metal bar with a round hole inside it was welded to the front plate. Its purpose was to prevent the front folding wall from completely falling down and thus covering the driver’s view.

On top of this superstructure, a platform was added to provide the necessary room for the installation of the main armament and for the crew to work with it. In order to have access to their positions, the driver and the radio operator had two hatches, which were positioned at the front of the superstructure. In comparison to the predecessor, these were slightly enlarged.

In order to reduce the vehicle height as much as possible, the gun platform was actually lowered down inside the Panzer IV hull. Lastly, to the rear, close to the engine compartment, two additional hatches served as access points to the ammunition storage.

Fighting Compartment

The 3.7 cm Flakpanzer IV which entered production inherited most components and the overall design from the previous prototype, with some changes. The position of the main armament remained in the center of the superstructure top. Around it, there was enough room for four (or more) crew members. Some minor changes were needed to provide the necessary installation of the larger armament.

The folding walls received a number of changes to their overall design. The first Flakpanzer IV prototype had higher side walls, which were angled inward. The angled plates served to provide an additional level of protection against aerial attacks. On the 3.7 cm Flakpanzer IV, the side armor plates’ height was reduced by about 25 cm. The first 45 produced vehicles retained this slightly curved side armor. After that point, they were replaced with simpler flat armor plates. They were easier to produce and, realistically, the angled armor offered no real extra level of protection. Another interesting feature of the Flakpanzer IV were the two (one on each side) small round-shaped firing ports. One additional port was placed on the rear wall.

Whilst driving, these walls were fully raised. In a combat situation, these would be slightly lowered to engage low-flying targets or fully lowered to provide a full-around firing arc. The front and rear plates also had two small hinged parts. These could be swung outwards and allowed for the side plates to be fixed at an outward angle. This was done to allow more space for the crew during an aerial engagement while still providing protection from ground fire. In order to reduce the deployment time, the rear armor wall could be completely lowered while the remaining three were partially raised.

Armament

In order to increase the destructive power and range of the SPAAG, the 2 cm Flakvierling 38 was replaced with a 3.7 cm Flak 43 anti-aircraft gun. Although sharing the same 3.7 cm caliber as the earlier Flak 18, 36, and 37 models, the newer Flak 43 (built by Rheinmetall-Borsig) was a completely different weapon. The primary goal of this design was to be simple to operate and easy to produce. It had a new gas-operated breech mechanism which was loaded with a fixed loading tray with eight-round clips. There was also a Flakzwilling 43 version with two guns mounted on the same carriage. In order to be installed in the new vehicle, some modifications were needed. The lower part of the carriage and the original gun shield were removed. In addition, the spent ammunition basket was smaller due to the smaller working space. Only the small rectangular shield in front of the gun was left in order to cover the front embrasure opening. The Flak 43 could rotate a full 360°, with a range of gun elevation between –10° to +90°. The maximum rate of fire was 250-300 rounds per minute, but 150-180 was the more practical rpm. With a muzzle velocity of 820 mps, the maximum effective ceiling was 4,800 m.

The 3.7 cm Flak 43 was positioned on a specially designed round-shaped mount. While on this mount, it retained its 360° firing arc but the elevation was slightly reduced from –10° to –7°. With the original gun shield, the gun could not be fully rotated, even with the side wall lowered. To overcome this issue, parts of the gun shield were cut off. In order to further provide a better firing arc, the sides of this gun shield could be folded behind it. The ammunition load consisted of 400 rounds. This included 320 high-explosive and 80 armor-piercing rounds.

The first prototype armed with a 2 cm Flak gun had one major flaw. In order for the gun to fit inside the fighting compartment, parts of its gun shield had to be cut off. This meant that the gun was fixed and could not be moved until the side armor wall was partially or fully lowered. In theory, the engagement of ground targets could be done in an emergency by lowering the front wall. However, the gun would have no possibility to traverse and the driver had to move the whole vehicle to hit moving targets. The 3.7 cm armed Flakpanzer IV resolved this issue to some extent. The gun could be used to engage forward targets if only the front wall was partially or fully lowered. The firing angle would be limited when used in this role, and the crew would be exposed to return fire. Starting from around vehicle 201 (the precise vehicle is not clear), the central part of the front wall was cut off. This way, the gun could be used more effectively against ground targets. Given its late introduction, only a smaller number of vehicles would receive this modification.

The secondary armament consisted of two 7.92 mm MG 34 machine guns and at least one 9 mm MP submachine gun.

There is an old photograph that shows a Flakpanzer IV being armed with what appears to be a 3.7 cm Flak 18. The photograph itself is not clear enough to help identify the gun itself. The Flak 18 was the first German 3.7 cm anti-aircraft gun to be introduced to service in 1935. Its production and service were limited due to it being an overly complicated design. Why would the Germans use this obsolete weapon for the Flakpanzer IV is unclear. It was possible that this was used as a training vehicle, or the crew replaced the original gun with what they had on hand. At this stage in the war, the Germans were using all available resources to fight back against the Allies. The usage of two-part armored walls indicated that this was an early-produced vehicle.

Armor Protection

The Flakpanzer IV’s frontal armor hull protection was 80 mm thick. The sides were 30 mm and the rear was only 20 mm thick. The superstructure frontal armor was 50 mm thick and its remaining sides were 30 mm thick.

The armor thickness of the four sidewalls was changed three times. The first group of 20 vehicles had sidewall armor that consisted of two spaced (55 mm apart) 12 mm thick plates. The next 25 vehicles still had the space armor, but the thickness was reduced to 10 mm. The idea behind using two-spaced armor plates was that the first would absorb most of the impact and the second plate would stop the round completely. Of course, due to the low armor thickness of these two plates, it could only effectively work against small-caliber bullets and shrapnel. Anti-tank weapons could easily pierce this armor. Another downside was that it greatly complicated the overall production, as more time was needed to build these. What is unclear in the sources is if all four walls consisted of two-piece armor plates. The photographs of this vehicle obviously show that the rear and front folding walls (on the vehicles that were produced with them) were made of spaced armor plates. The side walls, on the other hand, appear to be thinner and possibly not using the spaced armor design.

After these 45 vehicles were built, someone on the German side realized that using space armor generally offered no major improvement. So its use was discarded and replaced with four single-piece 25 mm thick armor plates. In addition, the upper angled armor on the side wall was also removed from production. The sides were thoroughly flat.

In some sources, there is disagreement about the thickness of the armor side walls. To some extent, this is quite understandable if we take into account the marginal difference between the first 12 mm plates and the later 10 mm. The previous information comes from authors such as T. L.Jentz and H. L. Doyle (Panzer Tracts No. 12-1 – Flakpanzerkampfwagen IV). Author Walter J. Spielberger (Gepard: The History of German Anti-Aircraft Tanks) mentions that the later vehicles used 20 mm thick armor plates and not 25 mm.

Crew

The crew of the 3.7 cm Flakpanzer IV consisted of six, namely the commander, two gunners, a radio operator, the loader, and the driver. The radio operator and the driver were positioned inside the hull and were fully protected. The remaining crewmembers were positioned inside the fighting compartment. The gun was operated by two gunners positioned on the right side. Opposite the gunners was the loader. Behind them sat the commander. Besides his main role of commanding the whole vehicle, he also acted as an extra spotter and helped to identify targets.

Some authors, such as Walter J. Spielberger, mention that the number of the crewmembers varied between 6 to 7. This is not surprising, as this was the case with some other German combat vehicles which sometimes had more crewmembers than were officially assigned. The reasons for this may vary depending on the need or the combat situation of the unit itself. Some units may have noted that having an extra loader or spotter could help with the vehicle in combat. It could also be possible that some unit lost some vehicles and redistributed the surviving crewmembers between surviving vehicles.

Unit Distribution

As the first vehicles were completed, they were allocated for the training of the initial groups of crews. These would then be used to equip and form 8-vehicle strong Panzer Flak Zuge (English: Tank anti-aircraft platoons).

During June and July 1944, the first such units were attached to the 9th, 11th, and 116th Panzer Divisions which served on the Western Front and 6th and 19th on the Eastern Front. In the following two months, reduced strength units (with only four vehicles) were issued to 10 different Panzer Brigades serving on both fronts. After that, mixed units were formed, equipped with four Flakpanzer IVs and four Wirbelwinds (2 cm Flakvierling armed Panzer IV). It is important to note that these were theoretical strengths as, due to production limitations or logistical reasons, not all 8 vehicles would be always issued. Despite their rather small production number, slightly less than 30 anti-aircraft platoons would be formed during the war.

In Combat

Despite a large number of surviving photographs of the Flakpanzer IV being used in combat, the sources frustratingly rarely mention this vehicle’s operational service in more detail. To some extent, this is not surprising given their late introduction and low production numbers.

On 2nd October 1944, US P-47s from the 389th Fighter Squadron commanded by Lt William Grounds undertook a reconnaissance mission over Vortum Mullem in the Netherlands. They were meant to support the advance of the 7th Armored Divisions against the positions held by the 107th Panzer Brigade. This unit had the 3.7 cm Flakpanzer IV in its inventory. During an aerial attack run led by Lt William Grounds, his aircraft would be hit by a 3.7 cm round. The hit was fatal, as it destroyed the control cables located near the aircraft’s tail.

In December 1944, Flakpanzer IVs participated in the last large German offensive in the West, known as Operation Northwind. Panzer Abteilung 5 (5th Tank Battalion) had in its inventory six Panthers, five Jagdpanzer IVs, and 3 Flakpanzer IVs. Given the rather poor weather conditions, it is unlikely that they saw much use against enemy aerial targets during this offensive.
The Flakpanzer IV also saw action in the East. For example, the 20th Panzer Division, which saw heavy action in Hungary in early 1945, had 4 Flakpanzer IVs in its inventory. Some were even used in defense of Budapest before being lost.

Surviving Vehicles

Given the rather small production run, it is no surprise that only a few 3.7 cm Flakpanzer IVs have survived to this day. One can be seen at the French Musée des Blindés at Saumur. The second vehicle, which was initially stored at the Aberdeen US Army Ordnance Museum, was given back to Germany in 1970. It can now be seen at the Auto-Technik Museum in Sinsheim. The original 3.7 cm gun is currently not on display. Instead, a 4 cm Bofors gun has been placed on top.

Conclusion

The first Flakpanzer IV that entered production was a mixed bag. On one hand, it finally provided the panzer units with a vehicle that was protected (in contrast to the half-tracks, on which only the cabin was protected in the best case scenario) and had the firepower to bring down most late-war enemy aerial targets. On the other hand, its overall design was somewhat crude and ineffective. The folding walls were used intentionally in order to provide the crew with a good enough view of the surroundings to spot aerial targets before they could be engaged and with enough space to operate the gun. In theory, this would provide sufficient time to set up the 3.7 cm Flakpanzer IV and prepare for combat. The German tank branch of the army was far from satisfied with this vehicle but, given that nothing else was available, they could do little but to accept it for service.

Flakpanzer IV Technical Specifications
Crew	5-6 (Commander, two gunners, loader, radio operator, and driver)
Weight	25 tonnes
Dimensions	Length 5.92, Width 2.95, Height 3.25 m
Engine	Maybach HL 120 TR(M) 265 hp @ 2,600 rpm
Speed	42 km/h, 25 km/h (cross-country)
Range	210 km, 130 km (cross-country)
Primary Armament	3.7 cm Flak 43
Secondary Armament	Two 7.92 mm MG 34
Elevation	-10° to +100°
Wall armor	2×12 mm / 2x 10 mm or 25 mm
Superstructure armor	front 50 mm, sides 30 mm, rear 30, and top 8-10 mm
Hull armor	front 50 or 80 mm, sides 20-30 mm, rear 14.5-20 mm, and the top and bottom 10-11 mm

Sources

K. Hjermstad (2000), Panzer IV Squadron/Signal Publication.
Engelmann-Scheibert, H. A. Koch, O. W. v. (1978) Renz Flak Auf Dem Gefechtsfeld Podzun-Palla-Verlag
D. Nešić, (2008), Naoružanje Drugog Svetsko Rata-Nemačka, Beograd
P. Chamberlain and H. Doyle (1978) Encyclopedia of German Tanks of World War Two – Revised Edition, Arms and Armor press.
Walter J. Spielberger (1982). Gepard The History of German Anti-Aircraft tanks, Bernard & Graefe
Ian V. Hogg (1975) German Artillery of World War Two, Purnell Book Services Ltd.
T. L.Jentz and H. L. Doyle (1998) Panzer Tracts No.12 Flak selbstfahrlafetten and Flakpanzer
T. L.Jentz and H. L. Doyle (2010) Panzer Tracts No. 12-1 – Flakpanzerkampfwagen IV and other Flakpanzer projects development and production from 1942 to 1945.
T. L.Jentz and H. L. Doyle (2002) Panzer Tracts No. 20-2 Paper Panzers
Walter J. Spielberger (1993) Panzer IV and its Variants, Schiffer Publishing Ltd.
D. Doyle (2005) German military Vehicles, Krause Publications
J. Bernstein (2021) P-47 Vs German Flak Defenders, Osprey publishing
S. J. Zaloga (2010) Operation Nordwind 1945, Osprey publishing
B. Perrett (2007) Panzerkampfwagen IV Medium Tank 1936-1945, New Vanguard