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ZSU-23-4
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The ZSU-23-4 "Shilka" is a lightly armored, self-propelled, radar guided anti-aircraft weapon system (SPAAG). ZSU stands for Zenitnaya Samokhodnaya Ustanovka , meaning "anti-aircraft self-propelled mount", 23 stands for the caliber of the armament and 4 stands for the number of gun barrels. It is named after the Russian Shilka River. It is also referred to by its nickname of "Zeus".
previous Soviet Union self-propelled anti-aircraft gun (SPAAG), the ZSU-57-2, was armed with two 57 mm autocannons; it was aimed optically using a basic tracking and lead calculating system.
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Encyclopedia
The ZSU-23-4 "Shilka" is a lightly armored, self-propelled, radar guided anti-aircraft weapon system (SPAAG). ZSU stands for Zenitnaya Samokhodnaya Ustanovka , meaning "anti-aircraft self-propelled mount", 23 stands for the caliber of the armament and 4 stands for the number of gun barrels. It is named after the Russian Shilka River. It is also referred to by its nickname of "Zeus".
History
The previous Soviet Union self-propelled anti-aircraft gun (SPAAG), the ZSU-57-2, was armed with two 57 mm autocannons; it was aimed optically using a basic tracking and lead calculating system. The ZSU-57-2 was not particularly successful despite its very powerful autocannons; it could only carry a relatively small amount of ammunition, was inaccurate as it lacked radar, and could not fire on the move.
The ZPU series armed with 14.5 mm heavy machine guns carried on a towed mount for stationary, point air defence had a much higher rate of fire. The 23 mm version of this weapon system was known as the ZU-23-2, a towed mount carrying two 23 mm cannons.
The development of the ZSU-23-4 "Shilka" began in 1957 and the vehicle was brought into service in 1965, replacing all ZSU-57-2s in air defense units toward the beginning of the 1970s. The ZSU-23-4 was intended for AA defense of military facilities, troops, and mechanized columns on the march. Initially, tank regiments should have had the anti-aircraft artillery battalion of "Shilka" (consisting of two batteries, four ZSU-23-4s in each). At the end of 1960s, one battery was equipped with ZSU-23-4s and the other with ZSU-57-2s. Motorized rifle and tank regiment standard anti-aircraft batteries consisted of two platoons later (one platoon was equipped with four ZSU-23-4s and another with four mobile surface-to-air missile systems 9K31 Strela-1 or 9K35 Strela-10). ZSU-23-4 combined a proven radar system, the non-amphibious chassis based on GM-575 tracked vehicle and four 23 mm autocannons. This delivered a highly effective combination of mobility with heavy firepower and considerable accuracy. The ZSU-23-4 outclassed all NATO anti-aircraft guns at the time, and it is still regarded as posing a major threat for low-flying fixed-wing aircraft and helicopters.
The system was widely fielded throughout the Warsaw Pact, other pro-Soviet states and Middle East states. Around 2,500 ZSU-23-4 from 6,500 produced were exported to 23 countries. The Soviet Union's successor states continue to manufacture and supply variants of the ZSU-23-4, notably the Ukrainian 4M4 and the Belorussian 4M5.
ZSU-23-4 units saw active service in the Yom Kippur War (1973) and other Arab-Israeli conflicts, the Iran–Iraq War (1980-1988), and the First Gulf War (1990). During the 1973 Yom Kippur War, the system was particularly effective against the Israeli Air Force. Israeli pilots attempting to fly low in order to avoid SA-6 missiles were often shot down by ZSU-23-4s. During the Soviet-Afghan War ZSU-23-4 units were used widely and to great effect against mujahideen positions in the mountains, the ZSU-23-4's guns being able to elevate to a much higher azimuth than the weapons on BMPs, BTRs, T-55s, or T-62s. They were also used to suppress defensive positions around the presidential palace during the initial coup in Kabul at the start of the Soviet-Afghan war. The Russian Army used the ZSU-23-4 for mountain combat in Chechnya.
Description
The radar-guided ZSU-23-4 "Shilka" SPAAG, with its four 23 mm (0.90") autocannons, was a revolutionary SPAAG, proving to be an extremely effective weapon against enemy attack aircraft and helicopters under every weather and light condition. The ZSU-23-4 has a very high density, rate and accuracy of fire, as well as the capability for each of the four autocannons to fire its own type of projectile from separate belts. [While it is technically possible that each cannon shoots different type of ammo, there were only two types available in late 70s: OFZT and BZT, which were to be loaded in 3:1 ratio - 3 OFZT, then 1 BZT, every 10th BZT round equipped with so called "copper remover" and marked. It was strongly recommended against shooting with single barrel.] The appearance of the "Shilka" caused significant changes in NATO tactics in aircraft use at low altitude over the battlefield.
Despite its present obsolescence as a modern short-range anti-aircraft weapon, the ZSU-23-4 is still deadly for enemy light armoured vehicles, infantry and firing points as an infantry-support vehicle. With its high rate of accurate fire, the ZSU-23-4 can even neutralize tanks by destroying their gun sights, radio antennas, or other vulnerable parts. ZSU-23-4s, especially late models, have excellent performance and good systems reliability.
Based on the GM-575 tracked vehicle chassis, which used components from the PT-76 light amphibious tank, the ZSU-23-4 mounts an armored turret holding four liquid-cooled 23 mm (0.9") 2A7 autocannons linked to an RPK-2 "Tobol" Radar (nicknamed "Gun Dish"). The vehicle weighs 19 tonnes (late modifications up to 21 tonnes), has a movement range of 450 km (280 miles) and a top speed of 50 km/h (31 mph). Additional firepower of late modifications can be supplied by a roof-mounted pod of six short-range SA-18 SAMs, or side mounted SA-16s.
The crew numbers four: driver, commander, gunner and radar operator. The driver's compartment is located in the nose part of the vehicle. The fighting compartment is in the center, and the engine compartment is in the rear part of the vehicle. The ZSU-23-4 provides minimal comfort for the crew. Whereas the driver's compartment has a good self-contained air pump with an electric heating system, other crew members suffer from cold in winter because the heating system of the fighting compartment, heated handrails and floor, is ineffective. It is hot inside the vehicle in summer.
The transmission consists of a multi-plate metal-contact main clutch, a manual gearbox with five forward gears, two planetary two-step steering gears with locking frictions and two final drive groups. The vehicle chassis has six single rubber tired road wheels, a rear drive sprocket with detachable sprocket rings (lantern-wheel gear) and one idler wheel per side. The first and fifth left, and sixth right road wheels have hydraulic shock absorbers. The track is 11.904 m long, 382 mm (15") wide and has 93 links.
Because of a large number of different pipes and tubes to detach during maintenance, the repair procedure for some of the vehicle's mechanisms is hard (for example, replacement or repair of a starter). The electric drive of an air outlet hatch of a gas turbine engine (part of the vehicle's electric power supply system) has an inconvenient location (at the bottom of the hull) which causes overheating and sometimes, jamming of the electric drive. On the other hand, the construction of the electric power supply system is very reliable. Changing the main engine oil and coolant is easy, as is replacement of fuel and oil filters, and sections of the air filter.
The ZSU-23-4 can cross vertical obstacles 0.7 m (2.3') high, trenches 2.5 m (8.2') wide, has a 1.0 m (3.3') fording depth and can climb 30° gradients The ZSU-23-4 has good maneuverability and cross-country ability, but its diesel engine's power is insufficient for a vehicle of its weight. As a result, off-road acceleration capabilities are sub-par, and the vehicle lags behind MBTs and IFVs on up-hill terrain.
Each water-cooled 23 mm 2A7 autocannon has a cyclic rate of 850-1,000 rounds per minute for a combined rate of fire of 3,400-4,000 rounds per minute. The welded turret has a race ring transplanted from a T-54 medium tank with a 1,840 mm (6') diameter. The 360° rotatory turret is fully stabilised and capable of firing on the move. The turret rotation and autocannon elevation mechanisms provide very good speed and guidance accuracy. The hydraulically driven aiming mechanisms have been proven to be very reliable. Manual aim is used against ground targets. The quad automatic anti-aircraft gun AZP-23 "Amur" has a range of elevation from -4° to +85°. The GRAU designation for ZSU-23-4 turret with 23 mm (0.9") AZP-23 "Amur" quad automatic gun is 2A10. An armoured plate inside the turret protects crew members from fire and explosive gas during intense firing.
Ammunition capacity is 2,000 rounds stowed aboard (520 rounds per each upper autocannon and 480 rounds per each lower autocannon) loaded in 50-round or shorter belts. The ZSU-23-4 can use two standard types of 23 x 152 mm 450 g projectiles: BZT armour-piercing incendiary-tracer (API-T) projectile (weight 190 g, penetrates 25 mm armour at 400 m) and OFZT high explosive fragmentation incendiary-tracer (HEI-T) projectile (weight 188.5 g, self-destructed in 5-11 s); each ammunition belt contains 40 OFZT and 10 BZT rounds. HEI-T and API-T rounds are fired at muzzle velocity 980 m/s. They can be fired to a maximum horizontal range of 7 km (4.3 mi), and a vertical range of 5.1 km (3.2 mi). The effective vertical range is 1.5 km (0.93 mi) at a direct range to target of 2.5 km (1.6 mi) and target speed of 250 m/s (up to 500 m/s if a modern fire control system is used). The usual autocannon burst consists of 3-10 projectiles and target lead angle is calculated for each burst (fire without adjustment) by computer. In attacking targets on the ground, its effective range is around 2.5 km (1.6 mi). The short range of its 23 mm autocannons and relatively low explosive effect of its small-calibre projectiles mean it is less able to engage threats such as jet attack aircraft and cruise missiles than modern systems like the 9K22 Tunguska armed with more powerful 30 mm autocannons and integrated missile armaments. A special 23 mm round with composite projectiles was developed for a modern modification of SPAAG (ZSU-23-4M4) to be used against cruise missiles.
The RPK-2 "Tobol" radar operates in the J band and can detect aircraft up to 20 km (12.4 mi) away. It has excellent target tracking capability and is relatively hard to detect by the enemy. However, the radar picks up many false returns (ground clutters) under 60 m (200 ft) of altitude. The radar antenna is mounted on collapsible supports in the top rear of the turret. There is an optical alignment sight. The RPK-2 radar proved to have good protection against enemy passive electronic radar counter-measures. Nevertheless, it must be noted that the radar system of the ZSU-23-4 has a short detection range during target search, depending on weather conditions (mainly dependent on rain and snow conditions). It is hard to automatically track the target at ranges less than 7-8 km (4.3-5.0 mi) because of the high angular speed of the target at close distances. The radar needs to be reset quite often because of the unstable parameters of electronic cathode-ray tubes of the target selection system. The absence of an automatic laser range finder requires a skillful commander and gunner.
Early versions of the ZSU-23-4 sometimes had problems with "runaway guns": after prolonged periods of firing, the guns would get so hot that chambered rounds would "cook off" even if the operator was not pulling the trigger, discharging the weapon and chambering a new round, which would then also cook off, and continue to do so. This would sometimes continue until the entire belt of ammunition had been expended. [This is one of the "urban legend" kind stories. There is no such thing as "chambered round" for 23 mm autocannon. When cocked, the bolt frame rests in rearward position held by electromagnet-operated pin ("sheptalo"). There is no mechanism to "release" firing pin, and firing pin strikes the primer cap as a part of upward movement of bolt. Whoever saw the 23 mm shell case fired by Shilka could notice a groove on primer cap which is deeper toward the center. The "runaway guns" problem is only possible when electromagnet is stuck. Never heard of it, though.] Overheating barrels could jam and even break away from the vehicle. The problem resulted from a deficient cooling system and made the early ZSU-23-4s dangerous even to friendly troops standing nearby if this happened. Despite the fact that this happened seldomly, Soviet operators learned to give these machines a wide berth.(Perrett 1987:100) It was not recommended to perform continuous fire (bursts longer than 15 sec without pause) on earlier models until the problem with autocannon reliability and overheating during intense fire was solved on ZSU-23-4M (welded tubes of coolant outlet were replaced with flexible pipes). After the autocannon cooling system was improved, the autocannons became extremely reliable.
The ZSU-23-4 is equipped with an NBC system with an air filtration unit, fire-fighting equipment, TNA-2 navigational system, infrared vision device, R-123 radio set, R-124 intercom and electric power supply system consisting of a DG4M-1 single-shaft gas turbine engine (70 hp at 6,000 rpm) and a direct-current generator (which provides 27 V and 54 V direct current or 220 V 400 Hz alternate current).
Deployment
Soviet doctrine supplied the vehicle since 1965 in an anti-aircraft artillery battalion of two four-vehicle platoons for anti-aircraft defence of motor rifle and tank regiments. At the end of the 1960s one platoon was equipped with ZSU-23-4 SPAAGs while another one was still equipped with ZSU-57-2 SPAAGs. ZSU-57-2 was completely replaced with ZSU-23-4 by the beginning of 1970s. In the 1970s, Soviet motor rifle and tank regiments were equipped with an anti-aircraft missile artillery battery consisting of two platoons, one equipped with four ZSU-23-4 SPAAGs and the other with four 9K31 Strela-1 (SA-9 Gaskin) or later with four 9K35 Strela-10 (SA-13 Gopher) short-range surface-to-air missile systems which cover the dead zones of 2K12 Kub (SA-6 Gainful) surface-to-air missile systems belonging to the divisional level. Since the 1980s Soviet motor rifle and tank regiments were equipped with an anti-aircraft artillery battalion of three batteries (one was equipped with ZSU-23-4 or 9K22 Tunguska SPAAGs, the second one was equipped with 9K35 Strela-10 (SA-13 Gopher) short-range surface-to-air missile systems and the third battery with 9K38 Igla man-portable surface-to-air missiles on IFVs or APCs..
The ZSU-23-4 is very vulnerable to enemy anti-tank missiles, cannons and heavy machine guns; the armour is thin (not exceeding 15 mm) and the exposed wheels, tracks, radar, and gun barrels can easily be damaged in combat. Firing positions of ZSU-23-4 SPAAGs are typically placed near the forward edge of the battle area (FEBA) but behind the main forces, usually 600-1000m behind objectives when on the defensive or 400-600 m behind the leading tanks on the offensive. ZSU-23-4 SPAAGs are divided evenly along the troop columns on the march.
At first each ZSU-23-4 operated in combat autonomously, without target marking from regimental or divisional air defence. In 1978, the PPRU-1 (mobile reconnaissance and control post) was passed into service of the Soviet Army. PPRU-1 ("Ovod-M-SV") vehicle based on MTL-BU armoured tracked chassis and it was intended for control of motor rifle or tank regimental anti-aircraft unit equipped with ZSU-23-4 SPAAGs and 9K31 "Strela-1M" mobile surface-to-air missile systems. PPRU-1 is equipped with "Luk-23" radar and automatic fire control system associated with the divisional air defence system.
The guns are useful against low-flying aircraft and lightly protected ground targets. Due to its effectiveness against ground targets, ZSU-23-4s have been used in urban environments (e.g., Afghanistan, Abkhazia, Chechnya, Lebanon). This is primarily because the guns can elevate much higher than a tank or APC cannon, enabling Soviet/Russian armored units equipped with ZSU-23-4s to return fire against ambushes from above.
Besides the Russian Army a small amount of ZSU-23-4 is still in use by Russian marines (61st and 175th brigades of the Northern Fleet, 336th brigade of the Baltic Fleet).
Variants
- ZSU-23-4 "Shilka" (1964): pre-production and then initial production models.
- ZSU-23-4V "Shilka" (1968): modernized variant with enhanced reliability of some details, ventilation system case located on the right side of the hull. Commander vision device was added.
- ZSU-23-4V1 "Shilka" (1970): modernized variant with enhanced reliability of radar system and other details, ventilation system cases located on front bilges of the turret. Guidance-system computer was improved (as well as accuracy and efficiency of anti-aircraft fire on the move at 40 km/h). It is fitted with a slightly improved diesel engine V-6R-1.
- ZSU-23-4M "Biryusa" (1973): armed with modernized autocannons 2A7M - pneumatic loading was replaced with pyrotechnic loading (unreliable compressor was removed), welded tubes of coolant outlet were replaced with flexible pipes which increased autocannon barrel life from 3500 rounds to 4500 rounds.
- ZSU-23-4MZ "Biryusa" (Z stands for "zaproschik" - inquirer) (1977): equipped with identification friend-or-foe system "Luk". All ZSU-23-4M were upgraded to ZSU-23-4MZ level during scheduled repairs. It should be noted that army unofficially continued to use the name "Shilka" for all variants of ZSU-23-4.
- ZSU-23-4M2 (1978): so called "Afghan" variant. Reequipment performed during the Soviet War in Afghanistan for mountain combats. Radar system was removed and night-sight was added. Ammunition increased from 2,000 rounds to 4,000 rounds.
- ZSU-23-4M4 (1999): modernized variant developed by Ulyanovsk Mechanical Plant. The vehicle armed with two additional paired man-portable air-defense systems "Igla" (on each side of the turret) and equipped with laser emission sensors, electron-optical vision devices (including television system for driver) and improved weapon radar system. Mechanical transmission was replaced on hydrostatic transmission, hydraulic boosters were installed. Mobility increased to the level of main battle tanks. First shown on public during exhibition MAKS-99 in Zhukovsky.
- Donets (1999): Ukrainian modernization developed by Malyshev Tank Factory in Kharkiv. Improved turret from ZSU-23-4 armed with two additional paired man-portable air-defense systems "Strela-10" was installed on chassis from T-80UD main battle tank. Ammunition for 23 mm autocannons increased two times.
- ZSU-23-4MP "Biala" (2000): Polish upgrade, Grom anti-aircraft missiles, fully digital passive aiming devices instead of the radar.
Combat history
Operators
 - 20 were delivered from USSR. - 210 in 1995. According to another sources - 310 were delivered from USSR.  - 20+ were delivered from USSR.    - 35- - 8
- - 36 in 1995 (delivered from Russia).
 - 350 in 1995. 330 were delivered from USSR, also a new contract was signed with Russia in 2005. - 34 from Nicaragua in 1997. - 60 - 38 - 131 were delivered from USSR. - 16 were delivered from USSR. - 20 in 1995. 14 were delivered from USSR. - 100 were delivered from USSR. - 100+ - 200+ - 60 - 16 in 1995 (delivered from USSR). 44 in 2008 - 10+ - 250    - 30 - >100 were delivered from USSR. - 35 in 1995 (delivered from USSR). - 44 to 87. 150 were delivered from USSR. - 4- / - ~450 in active service in 2007 (400 are used by army and 50 by marines)
 - 400 were delivered from USSR.- - the United States operates a few ZSU-23-4 for testing. (most of them are at Camp Pendleton)
 - 28  - 100 - 30 to 40 in 1995 (delivered to South Yemen from USSR).
See also
External links
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