Development of the Modern SPAAG

  As the Korean War began and tensions escalated in Asia, the United States began to supply the Japanese in the event that they would need military aid or a form of protection against the rise of the communist states in the region. The United States had already began developing their own new and improved combat vehicles for similar purposes. Because of this, they were left a large surplus of outdated military vehicles and no where to use them effectively. Hence, many were later donated to the Japanese for them to use in training new troops. The Japanese Self Defense Force was created in 1954, allowing the Japanese to have their own defensive military to protect the home island when needed. During this period, the United States had officially decommissioned the M19 Gun Motor Carriage SPAA vehicle from service. These were anti air tanks based off the M24 Chaffee chassis, and mounted twin 40mm Bofors multipurpose guns. A few of them were supplied alongside the M42 Duster.

These lend lease tanks were short lived, however. During their initial time spent in the SDF, they were used as trainers for anti air tactics and methods of engagement. Even for the Japanese Self Defense Force, the short ranged 40mm Bofors guns were inadequate and couldn't meet the requirements needed to successfully engage and destroy modern aircraft of the era. These concerns were voiced to the United States over the years ,however the US simply ignored these requests as well as Japanese requests for modern armor. Faced with the refusal of the US to supply more modern vehicles, the Japanese decided to initiate their own SPAAG program during the late 60's.

The First Prototypes
In the late 1960s the the Technical Research Department came together to conceptualize a new SPAA-like vehicle to meet the needs of the military. Their logical conclusion was to use the chassis of the Type 61 main battle tank as the starting point. While the tank was a failure to the military, the use of its chassis  for an anti aircraft tank could have given it a new lease on life; Japan had already started working on a new main battle tank project to replace it, and the choice seemed to be the best use of resources at the time.

M51 at Chiba, Japan. I have yet to receive visual details
from the SDF on the prototype vehicle. I am currently
awaiting access to the details. 

The research staff concluded instead of designing its own anti aircraft gun, it would also rely on the technology the United States left behind with the lending program. The gun they had in mind was the M51 Skysweeper, a 75mm anti aircraft system and one of the first to utilize an automated targeting system with an auxiliary predictor and gun laying radar stations in one platform. The gun relied on an autoloading mechanism with two 5 shell belts. The gun had proved to be very useful during its time, albeit fairly outdated during the 70's. Nonetheless, it was selected to be used as the candidate armament.

The first prototype was completed  in 1972, and was put through various trials. Ultimately, it was rejected by the Self Defense Force for its turret being "excessive" and unreliable. Due to this unwanted outcome, the project for a new SPAAG was canceled. No attempt  to find a suitable replacement would be attempted for six years. In 1978 the decision was made to again attempt to base a new SPAAG off the Type 61 main battle tank chassis. The Japanese Self Defense Force worked out a cooperation agreement with Oerlikon Contraves, a renowned anti aircraft gun manufacturer of the era. Oerlikon provided Japan with a design proposal for a set of 35mm autocannons on a rotatable turret design which would house a search and track radar.

The second prototype of the SPAA project. Mounting the new twin 35mm autocannon system into the Type61 chassis. It was labeled the AWX. 

Various tests were carried out using the completed prototype vehicle. It had became clear that the combined weight of the turret, radar, and computer systems was too heavy to allow the vehicle to maintain the desired level of mobility. The prototype was canceled. Instead, the hull of the newer Type74 main battle tank would be used as the chassis for the new SPAAG. The original Type 61 prototype would eventually be converted to a bridge-laying vehicle in the 80s.


The Guntank

Development and trial production of a self-propelled rapid-firing aircraft gun vehicle based off of the Type 74 MBT would begin in 1982; one set of two prototype hulls was ordered in that year. A third hull was procured in1983. The first prototype was completed at the end of 1983, and technical tests were conducted from 1984 to 1985. A practical test by the Ground Self Defense Force was carried out in 1986, and it was formulated as '87 self-propelled gun' on August 21, 1987.

National Defense Agency File H 4001B 1 &2

To save weight and avoid the flaws of the original Type 61 derivative, the turret of the Type 87 was made with a lighter composite. The replacement was the AMS 4050A Specialized aluminum alloy. A complex alloy of bulletproof materials that offered decent protection for its weight. It could not defend against dedicated anti-tank weapons, however.

The turret of Type 87 was developed by Japan Steel Works, with the radar and fire-control systems housed in a boxy structure which gives the turret a distinctive shape similar to that of the German Gepard.  The similarly is furthered by the fact that both tanks have their 35mm autocannons on the right and left sides of the turret. The variety of ammunition used for the 35mm autocannons is extensive. HEI (535g) is used for targeting general aircraft. The guns also use SAPHEI (380g) for ground targets, and APDS for armoured targets. The APDS rounds have a penetration capability of 40mm RHA at 1000 meters (at 60 degrees slope) distance with a muzzle initial velocity of 1,385 m / sec.

The 35mm's drastic gun elevation can be seen
here during this SDF exercise. 

The gun barrel is an air-cooled type, and six grooves are engraved on the outer circumference to increase the surface area and enhance the cooling efficiency. The rate of fire of 35 mm high fire aircraft gun KDA equipped on the Type87 is around 1,100 shots per minute with the gun elevation angle of  -5 to +85 degrees. The turret can rotate a full 360 degrees with no impediments. The turret and cannons are by default operated electronically, however they can also be operated manually if the need arises. The gun's elevation speed is 760 mils / second, and the turret's traverse speed is 1,000 mils / second. The turret is also equipped with two sets of smoke launchers to offer a base of protection if under threat of engagement from the ground and air, similar to the Gepard.



The detection range of the Type 87's laser detector was 360 degrees in a horizontal direction and -22.5 degrees to +90 degrees vertically. The Mitsubishi Electric Corporation was in charge of development of the tank's systems. The detection radar antenna was located to the rear of the turret, posted as a long protruding object, boasting a detection range of 20 kilometers.  The search radar antenna can continuously turn 360 degrees, and the turning speed of the antenna is 30 rpm. The dish type equipped on the top of the turret in front of the search radar antenna is a tracking radar antenna and the tracking range is said to be 20 km. The tracking radar antenna can continuously turn 360 degrees, and the range of elevation is -80 to +1, 500 mils. The turning speed of the antenna is 1,600 mils per second, and the elevation speed is 890 mils per second.

During the late 80s, Japan began to test the protection capability of composite armour. The new STC project was at the forefront of development. The Type74 had been tested with examples of composite, as was the Type87. The prototype adjusted to this by adding two spaced armour pads while the chassis remained produced in steel. The front hull was only protected by a thin 33mm RHA plate.

National Defense Agency
File H4002C 1

Although the chassis of the Type87 is a welded structure of rolled homogeneous steel based on the Type74 battle tank, the shape and composition  have been changed drastically to the point where only a few similarities remain between the two vehicles. The front plate has since adopted a method of composite armour inside the front hull of the vehicle, instead of the externally placed pockets on the prototype. The front hull remained 33mm thick, whilst behind the plate a formulation of internal fins adjustably angled, made up of mostly NERA (Non-Explosive Reactive Armour). The method used is similar to American and German designs,  which used this method of protection on the sides of their tanks, effectively defeating light guns and autocannons of the 30-50mm range.  For the Type87 this method proved adequate for its anti aircraft role.

There was a downside, however. The complexity of the armour and the technology of its turret raised the price of the vehicle to over 1.4 billion yen per unit. Due to this steep price, the SDF was forced to only produce 1-2 units a year. The series production ran until 2002, where by this time a total of 52 units were manufactured and in service. The tank remains in SDF operation to this day. Because of this, many specifications and details are considered classified. This leaves much to be questioned in terms of the secrets under the armour.

The Type87 retained the excellent mobility of the modified Type74 chassis. The tank was equipped with a Mitsubishi Heavy Industries built Type 5 10ZF22WT two-stroke 10 cylinder air-cooled turbocharged diesel engine. It was capable of forward speeds of 53 km/h with an output of 720hp at 2200 rpms. Since the suspension of the Type87 was directly copied from the Type74, the vehicle could control the hydro pneumatic movement of the chassis in the forward, backward, side to side, and up and down motions to varying degrees. While tactically useful for the type74, the Type87's suspension had acted more for novelty than anything else.

The auxiliary power unit for the tank is located to the tank's right frontal side. This station provides electrical power for the tank's fire control computer, search and tracking radar, and turret drive generator. The APU is powered by a four stroke diesel engine with 29 liters of displacement and 75hp with a 2850rpm output. It is visible through the heat exhaust panels.



I know this is a long post, but I wanted to write a brief rundown of Japanese anti aircraft tanks after the world war. It's a very complex history and I wanted to summarize it for you readers in the best fashion possible. The SDF has been kind enough to share such snipbits, and today I used information from two files belonging to the National Defense Agency. The first being H 4001B 1 &2, and second  H4002C 1.