Monday 5 December 2022

The Doomed Victorious AA Tank

The T-90 AA tank developed by the Molotov GAZ factory that won the tender but never entered mass production.

The situation in Soviet tank production changed radically in the second half of 1942. The experience in 1941 and the first half of 1942 clearly indicated new priorities. It was clear that T-34 production had to increase, as this tank turned out to be the optimal combat vehicle. It had the necessary mobility, decent armour, and powerful armament. The T-34 was often the only tank that could move cross-country in later 1941 and early 1942. The KV-1 was too heavy and the T-60 was too weak. The T-70 light tank that appeared in early 1942 was better than the T-60, but Soviet leadership had no illusions about it. It was clear by the spring of 1942 that the T-70 would not be built at as many factories as the T-60 was. The situation was difficult in the summer, and a decision was made to even spin up T-34 production in Chelyabinsk at the cost of decreasing KV production. Additionally, a decision to build the T-34 in Sverdlovsk at the site of the former factory #37 was made. Only two factories remained for the T-70: the Molotov GAZ in Gorky and factory #38 in Kirov. They would also have been used for T-34 production, but they proved unsuitable.

Status of the work on AA tanks at the GAZ as of September 1942. AA tanks on the T-60 and T-70 chassis are mentioned. In reality, they only worked on the future T-90.

Front line experience in 1942 showed that the decision to change priorities was correct. The first use of the T-70 tank revealed that it had issues when it came to crew comfort and, most importantly, armour. This was not a surprise. The age of light tanks was coming to an end, and the Germans also ceased production of these vehicles in the summer of 1942. Soviet light tanks clinged on for longer, but it was clear that their time had come. This did not mean that light vehicles would disappear altogether. The chassis of light tanks was necessary for the creation of SPGs, which were not obsolete until the very end of the war. Self propelled guns with powerful armament than the tank they were based on were in demand at the front, which experience proved time and time again as the war went on. The development of Soviet self propelled artillery did not differ much from the path it took abroad, even considering that the first SPGs went into production in the summer-fall of 1941 (including SPAAGs).

The T-90 tank prototype, September 1942.
Work on Soviet SPAAGs was expedited again after a German courier aircraft was shot down in late June of 1942. It carried a report on the trials of a Henschel Hs 129A ground attack aircraft armed with a 30 mm MK 101 autocannon. Now, the Red Army already had AA weapons, including SPAAGs. These were chiefly M-4 quad machine guns installed on GAZ-AA or GAZ-AAA trucks and similar vehicles, including a ZIS-6 truck with a 37 mm 61-K autocannon. By July of 1942 work was also underway on the SU-31 SPAAG. Another SPAAG, or rather an AA tank on the T-70 chassis, was developed starting in the spring of 1942 at OKB-15 under the direction of B.G. Shpitalniy. 

The existing weapons had a number of drawbacks, primarily poor off-road mobility. A quick solution in the shape of creating T-60 or T-70 AA tanks was pitched in early August of 1942. The concept consisted of an unchanged chassis that would carry a new turret with AA armament. This would allow the production of SPAAGs without altering existing production. Since the Molotov GAZ was in charge of producing and designing the T-70, the task of designing this tank went to them.
Unlike Savin's tanks, the T-90 had a brand new turret.

Officially, the task to build a "dual 12.7 mm DShK AA gun mount for T-60 and T-70 tanks" was given on August 8th, 1942. The actual requirements appeared slightly later, on August 16th. While the T-60 was required to use the stock "dome" turret converted for AA machine guns, no such limitation existed for the T-70. It was also required that the DShK machine guns would feed from existing ammo boxes. The ammunition capacity would be at least 500 rounds. Interestingly enough, the Molotov GAZ was instructed to develop a turret for the T-60 and they even reported in September of 1942 that they made one. In reality, this was not exactly the case. It is possible that a T-60 AA tank was developed, but it was never built. The factory was already overloaded with T-70 modernizations and had no time for the T-60. The T-70 AA tank fared better. This project led by V.S. Solovyev proceeded rapidly. He soon headed the creation of the GAZ-71 (SU-71), the first light SPG developed in Gorky.

The DShKT at maximum elevation.

The report on the T-70 AA tank was true. A prototype was built in September of 1942. It was based on T-70 tank with serial number 2207789 that received a brand new octagonal turret. The sides were 35 mm thick. As required, the top of the turret was open. A removable tarp protected the crew from precipitation. The turret ring, traverse mechanism, and overall layout were taken from the base tank. This meant that the DShKT mount was shifted to the right. This allowed the Special Design Bureau of the Experimental Design Department (OKB KEO GAZ) to carve out as much room in the fighting compartment as possible.

The machine gun mount was shifted to the right. This made the turret roomier.

The location of the sight was also rational. It was shifted to the left, which made it more comfortable to use than the sight of its competitor that was being developed in Sverdlovsk. In addition to the K-8T collimating sight, it had a TMFP telescopic sight for firing at ground targets. The first report mentions that the collimating sight mount of the "T-70 with a DShK" tank should be changed. The ammunition racks were also not ready in September. The tank that was called T-90 as of October 1942 deviated from requirements. For instance, it was impossible to mount stock ammunition boxes near the guns. Instead, they were fed from 30 round magazines, like the DK machine gun. This was not a lot, but the layout had to be taken into account, especially since loading, aiming, and everything else had to be done by one man.

The tarp that protected the crew from precipitation can be seen from this angle.

Even though the SPAAGs from Gorky and Sverdlovsk were finished in September and made their way to the NIBT Proving Grounds by October 23rd, there was no rush to test them. Some progress was only made by December. The T-90 already had ammunition racks that fit 480 rounds (16 magazines), which was judged insufficient. However, factory #37's tank had even less ammo, just 12 magazines. Inspection carried out on December 5th clearly flagged the T-90 as the leader. For example, this was the only one of the competitors to have a radio and a tray to catch spent brass. Drawbacks included a loose elevation mechanism. The AA gun mount was also superior. Unlike factory #37's tank, the T-90 had no openings in the front of the turret.

T-90 tank during trials at the NIBT Proving Grounds, December 1942.

The T-60-3 tank dropped out of trials immediately since it lacked a motor. Trials established the T-90 as a clear winner even though the weather was bad and airborne targets couldn't take flight. The T-70 AA tank had an uncomfortable and unbalanced mounting that made firing at airborne targets impossible. The T-90 had no such issue. The traverse speed was deemed insufficient and had to be increased to 10 degrees per second, but the T-70 AA tank's traverse speed was just 3 degrees per second. The tanks also drove 50 km each between December 5th and December 9th. 12 km was driven with the travel lock disengaged to determine the effect of driving on sight alignment. The T-90's accuracy was considered sufficient even after driving.

The tank was a clear favourite in trials.

The result of the trials was predictable. The T-90 was the clear leader and its list of drawbacks was short. The ammunition capacity had to be increased to 1500 rounds (a rack for zinc containers), traverse speed increased to 10 degrees per second, and small issues corrected. The NIBT Proving Grounds report also mentioned that the T-90 turret could be installed on a T-60 tank. It seemed that this was a great time to put the T-90 into production, especially since work on the SPAAGs stalled... but the T-90 disappeared. The reason for this is given in GAZ's post-war report. Only a small amount of AA tanks was needed, so the task of producing them was not given to GAZ. The work was supposed to go to factory #40 that would also build T-80 tanks, but they already had their own problems. The T-90 simply disappeared from the board for some time. Work to adapt the T-90 turret to the T-60 tank began, but that project deserves its own article.

The last attempt to put the T-90 into production. Too late and too naive.

The T-90 resurfaced in correspondence in the summer of 1943. By that point the Molotov GAZ had already developed a SPAAG on the T-60 chassis. It turned out that the turret had to be designed anew, which wasted another six months. Then the GAZ was bombed, which had a negative effect on experimental work. These delays kept happening until the Battle of Kursk where all those ground attack aircraft finally made their appearance. A decision was made to urgently produce 50 T-90 tanks at factory #38. Unfortunately, the factory had no time for this project as it was busy with the SU-76M. Introduction of the AA tank at a factory that hadn't touched the T-70 in half a year was a questionable decision. These tanks were never built. 

Sadly, the T-90 became a victim of perfectionism. No one stopped it from entering into production in December of 1942. Instead, orders were given to set up production using repaired T-60 chassis, with predictable results. In the end, the Red Army had to fight off the German ground attack aircraft with whatever they had on hand.

1 comment:

  1. Interesting that Pasholok seems to contradict himself here saying 'the age of light tanks was coming to an end' when he's extensively written about the later soviet attempts at a light tank design, and one of the highest priority AFV programs postwar was... a light tank.

    It's also an even funnier contradiction as he compares this to the Germans ceasing production, when he's broken down how that was due to utter dysfunction in Germany and the Germans had light tanks on the planning board right up until the end of war.