ZSU-23-4 Shilka

The ZSU-23-4 "Shilka" is a lightly armored, self-propelled, radar guided anti-aircraft weapon system (SPAAG). ZSU stands for Zenitnaya Samokhodnaya Ustanovka (Russian: Зенитная Самоходная Установка), meaning "anti-aircraft self-propelled mount". The "23" signifies the bore diameter in millimeters. The "4" signifies the number of gun barrels. It is named after the Russian Shilka River. Polish soldiers nicknamed it maszyna do szycia (sewing machine) due to the sound of firing guns and because the similarity of name "Shilka" and Polish word "szyć" (to sew). It is also referred to by its nickname of "Zeus"

Description
The Shilka ZSU-23-4 [ZSU = Zenitnaya Samokhodnaya Ustanovka - Anti-aircraft Self-Propelled Gun] is a Self-Propelled Anti-Aircraft Gun (SPAAG) featuring a prominent radar dish that can be folded down mounted on a modified PT-76 chassis. ZSU 23-4 Shilka, is capable of acquiring, tracking and engaging low-flying aircraft (as well as mobile ground targets while either in place or on the move). Employed in pairs 200 meters apart, 400 meters behind battalion leading elements, it is commonly used to surpress ATGM launch sites, such as TOW vehicles. The armament consists of four 23mm cannon with a maximum slant range of 3,000 meters. Ammunition is normally loaded with a ratio of three HE rounds to one AP round. Resupply vehicles carry an estimated additional 3,000 rounds for each of the four ZSUs in a typical battery. Recent (October 1997) information details ZSU-23-4 updates/modernization being offered by the Ukrainians that include: a new radar system replacing the GUN DISH radar, plus a sensor pod believed to include day/night camera, and a laser rangefinder; and mounted above radar/sensor pod is a layer of six fire-and-forget SAMs, believed to be Russian SA-18/GROUSE.

The ZSU-23-4 is a fully integrated, self-propelled antiaircraft system with four liquid-cooled 23-mm automatic cannons mounted on the front of a large, flat, armored turret. The chassis has many components borrowed from other Soviet armored vehicles, and the suspension system resembles that of the PT-76 and ASU 85 (six road wheels and no track support rollers). The driver sits in the left front of the hull, and the rest of the crew (commander, gunner, and radar operator) are located in the turret. The GUN DISH fire control radar mounted on the rear of the turret can be folded down during travel.

A number of different ZSU-23-4 models have been produced. These are primarily distinguishable externally by the types of stowage boxes on the turret and minor modifications in the mounting of the guns.

Capabilities
A platoon of four ZSU-23-4s is assigned, along with four SA-9/GASKIN SAM systems, to the antiaircraft battery of motorized rifle and tank regiments to cover the deadspace of the SA-6/GAINFUL in the division air defense umbrella. Two ZSU-23-4s usually will be in support of each of the two first-echelon battalions, each weapon normally separated by 200 meters, typically traveling 400 meters behind the battalion's leading elements.

The ZSU-23-4 is not amphibious, but has a fording capability of just over one meter. During river assault operations, the ZSU-23-4s would be ferried to the far bank immediately after the leading companies.

The ZSU-23-4 has the capability to both acquire and track low-flying aircraft targets, with an effective AA range of 2,500 meters. It also is capable of firing on the move because of its integrated radar/gun stabilization system. The high frequency operation of the GUN DISH radar emits a very narrow beam that provides for excellent aircraft tracking while being difficult to detect or evade. However, such a frequency also dictates a limited range, which can be compensated for by linking the system to other long-range acquisition radar in the area. The ZSU-23-4 also can be used against lightly armored ground vehicles.

The four guns are water cooled and have a cyclic rate of fire of 800 to 1,000 rounds per minute each. However, the guns are normally fired in bursts (2-3 rounds per barrel) to reduce ammunition expenditure and prolong barrel life. Each ZSU-23-4 carries about 2,000 rounds onboard. Supply trucks, which follow the ZSUs at a distance of 1.5 to 2.5 km, carry an estimated additional 3,000 rounds for each of the four ZSUs. Electronic target acquisition, tracking, and ranging are automated, and an onboard computer determines superelevation and azimuth lead. Conventional optical sights also are available. Two types of ammunition normally are mixed at a ratio of three Frag-HE-T rounds per one API-T round. An HEI-T round also may be fired.

TheZSU-23-4can be airlifted bytheAN-22 or II-76. The crew of the ZSU-23-4 is afforded a degree of protection by the thin armor (maximum thickness 9.4 mm in the hull, 8.9 in the turret). Collective NBC protection is provided by a radiation detection and warning system and an air filtration and overpressure system.

Limitations
Heavy machine gun fire can penetrate the hull and turret. Tread and road wheels are vulnerable to artillery fire. HE fragmentation can penetrate the armor, destroy the radar dish, or rupture the liquid coolant sleeves of the 23-mm cannons. The system also is vulnerable to ECM