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CIA - Early Merkava 1 Fire Control System

CIA Document Excerpt About Merkava 1 FCS


US attaches have reported the existence of a project (Project 761) to standardize the fire-control procedures of all various Israeli Army tanks by retrofitting them with a standard computer-based system. The Israelis have approached US companies about terms of sale or licensed production of gyro-scopes; resolvers; analog-to-digital converters; micro-processors; and large-capacity, random-access memories suitable for use in tank fire-control systems. These inquiries may be related to Project 761.


The Israelis have announced two newer Merkava models -- the Merkava II and III. The Merkava II is in development, and a prototype may be completed. Israeli press reports claim that the Merkava II may enter production in 1983. The Merkava III is in a design stage and is intended for production in the late 1980s. It may have a turbine engine. The new Merkava models are planned to have improved fire-control systems, armor protection, and suspensions. The Israelis have not specified the fire-control changes.


The first Merkava gun drives may have been installed without stabilizing provisions; historically the Israelis have preferred to fire from a halt. Stabilizing circuits have been retrofitted and adopted for new production.


Merkava's 105mm rifled gun is built by Israel Military Industries (IMI) and is designated the M64-L71A.
The gun is a version of the US M68 gun, which in turn is a US adaptation of the British L7 gun).
A thermal sleeve is provided with most Merkava guns. The Israelis specify that their gun can fire 7 rounds per minute in the field; a trained crew once demonstrated a firing of 12 rounds per minute.


The Merkava commander has a panoramic periscope probably identical to the TRP-2A commander's sight in West German Leopard I tanks. The external sight head resembles the Leopard I's, and published specifications are identical to those of the TRP-2A. The commander's sight is supplied by Israeli Aircraft Industries (IAI). The Israeli sight is specified to have 4- to 20-power zoom magnification, a counterrotating link, and coupling to the gunner's sight. The counter-rotating link keeps the sight pointed at an acquired target as the turret traverses toward the target. 


The Merkava's gunner's sight is mounted in a channel cut into the right front of the turret. Steel ribs set across the channel protect the sight from ricocheting small arms rounds. An armored lid covers the sight when it is not in use.


The gunner's sight is a daylight periscope containing an Nd:YAG laser rangefinder made by the Israeli firm El-Op and a computer-driven reticle. The exact designation and configuration of the sight in deployed Merkavas is unknown. Different international publications have described the sight as having zoom magnification to 12 power or as having two magnifications, unity and 8 power. The acronym SLS, mentioned by some Israelis, may refer to the sight, part of the sight, or an optional night sight.


The Merkava computers are M13-series digital-electronic ballistic computers built by the Israeli firm Elbit. The Merkava fire-control system is often referred to as the Elbit system. The computer receives ranges from the laser rangefinder and several other ballistic inputs from other sensors. The computer then calculates the super-elevation and traverse-offset angles, including a moving-target lead angle in the traverse offset. The angle signals are applied to a ballistic drive that displaces the reticle in the gunner's sight. The reticle is probably linked by a servomechanism to the gun drive machinery, so that it shifts back to center as the gun approaches the correct azimuth and elevation. 


The super-elevation signal is also sent to the hydraulic elevation part of the gun drive. This signal may be used to raise the gun automatically to firing elevation.


The laser rangefinder, cant, and traverse-rate sensors automatically send signals to the computer. The traverse-rate sensor measures the turret traverse rate as the gunner follows a moving target. The computer also automatically receives feedback signals measuring the actual super-elevation and offset angles of the reticle to ensure that these angles match the calculated angles. Ammunition choice can be entered into the computer by any of the turret crew from their control panels. The gunner can enter throw-off angles for each type of ammunition to compensate for the gun jumping up and to one side as it fires. He can also enter windspeed, charge temperatue, gun-barrel droop, and air pressure. The range is displayed to the gunner for use in any manual aiming or range verification. A gun-wear estimate, based on the number of rounds that have been fired from the gun, is stored in the computer.


Elbit also built a model of the Merkava computer and sensor subsystem with automatic sensors for all of the computer inputs. The company claimed in advertisements that the automatic sensor model is being exported (possibly South Africa - Olifant project).


Early Merkava tanks may have had a different computer that was similar to the cam-operated computers in the early US M60s. In 1979 a US attache report on the early production models of Merkava described the computer as a ballistic computer taken directly from M60 supplies. M60 computers were designated M13s by the United States.


The gunner's computer-control panel has a provision for aligning the sight and gun boresights. The alignment procedure may involve introducing an electronic bias in the computer to compensate for the small sight misalignments, instead of precise mechanical misalignments. 


For night firing, all Merkava I tanks have a 1-kilowatt EOS xenon searchlight, probably a passive night sight to replace the commander's panoramic periscope, and possibly an optional gunner's night sight. The searchlight is permanently mounted at the turret rear in a spaced-armor recess. A reflector controlled by the commander opens over the searchlight and directs the beam; the searchlight itself is under armor.
Early production Merkavas had no gunner's night sight, much to the dissatisfaction of the Israeli tankers. The Israelis probably require a gunner's night sight, but none have been identified. The Israelis are also interested in thermal-imaging sights for the Merkavas.


The Merkava gun drive is probably a stabilized electrohydraulic drive designed by the US firm Cadillac Gage and made in Israel under license. Earlier Merkavas had nonstabilized gun drives by Cadillac Gage, called the S.H.L in Israeli publications, but have probably been fitted with an add-on stabilization option.


The Merkava shown at the first official unveiling of the tank at the independence day show in Jerusalem in 1978 had a cylindrical fitting on the top center of the turret. The cylinder was not seen on other Merkavas. The cylinder is unidentified but superficially resembles the Leopard II commander's sight head.




Main gun: 105mm M64-L71A (Israeli made M68).

Gunnery devides: Periscopic daylight sight with Nd:YAG laser rangefinder.
M13A1 digital electronic computer.
Optional night sight.
EOS xenon white/IR searchlight.

Gun drive: S.H.L electrohydraulic drive with optional or retrofitted stabilizing unit.

Commander's sights: Panoramic periscope similar to German TRP-2A.
Separate passive night sight.



https://www.cia.gov/library/readingr...00890001-1.pdf

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