T-84 Fire Control System
The T-84 is fitted with an advanced fire-control system, and either the gunner or commander can lay and fire the main armament at stationary and moving targets while the tank is stationary or moving with a high first round hit probability.
The fire control system comprises a gunner's 1G46M day sight, Buran-Catherine-E thermal imaging sight, commander's PNK-5 observation and sighting system, PZU-7 anti-aircraft sight, 1ETs29M anti-aircraft machine gun mount control system, LIO-V ballistic computer with input information sensors, 2E42M armament stabiliser and other devices.
The gunner's 1G46M day sight has a two-axis stabilised line of sight and incorporates a laser range-finder and a missile guidance capability. It is also fitted with an automatic gyro drift compensation device. The sight field-of-view has magnification values in the range x2.7 to x12. The integral laser range-finder has a range of 9,990 m and is accurate to ±10 m. The measured distance is shown to digits together with the fire preparation and selected type of ammunition in the lower part of the gunner's sight field-of-view. The sight field-of-view is provided with gunnery ranging marks including stadiametric ranging scales for kinetic energy ammunition, chemical energy ammunition, high-explosive fragmentation ammunition as well as for coaxial machine gun. These stadiametric marks are a useful secondary method of range-finding when operating in an emergency. In order to protect the sight optics from bursts of light from the tank's own gun flash, the optical channels of the sight are fitted with light sensors which automatically shut them down at shot exit. The sight controls enable the gunner to lay quickly and accurately onto targets and track them smoothly.
The Buran-Catherine-E thermal imaging sight includes a gunner's optronic sight as well as commander's monitor and control panel. The thermal sight is usually operated by the gunner, but the commander can override the gunner and aim and fire the main or coaxial armament using his duplicate controls and thermal imaging monitor. The thermal sight enables the gunner and the commander to detect and engage targets under almost all weather conditions at long range and with high accuracy, which can be used to advantage when visibility is poor and during the hours of darkness. The thermal sight also makes it possible to disregard presence of a number of common obscurants such as battlefield smoke.
The commander's PNK-5 observation and sighting system comprises a commander's TKN-5 combined day/night sight and a gun position sensor. The commander's TKN-5 combined sight has a vertically stabilised line of sight and three channels: a day unity vision channel, a day channel with a magnification of x7.6 and a night channel with a magnification of x5.8. Besides, the sight incorporates a laser range-finder, which gives the commander an independent laser range-finding capability, as well as having a lateral lead input device. A simple switch enables the commander to change from the daylight channel to the night (image intensification) channel and back again.
The commander's anti-aircraft sight enables the commander to engage air targets by using the anti-aircraft machine gun from within the safety of the turret.
The outlet windows of the above sighting systems are provided with protective glasses which are capable of being kept clean with the help of a hydraulic and pneumatic cleaning system.
In order to calculate ballistic corrections, the LIO-V ballistic computer automatically takes into account all the inputs from the sensors including tank speed, angular target speed, gun trunnion axis cant, crosswind speed, target range, and course angle. Additionally, the following parameters are manually input: ambient air temperature, charge temperature, barrel wear ambient air pressure and so on. The computer also computes the time when the high-explosive fragmentation projectile with controlled detonation should be detonated over the target.
The fire control system has a so-called dynamic fire gating capability, i.e., after the gun firing button has been pushed, the gun will only fire when the misalignment between the line of sight and the gun bore axis is within acceptable limits. The fire gate size depends on the target range and some other factors.
The barrel of the gun can be distorted by uneven heating, arising from irregular dissipation of the heat from firing, rain on the upper surface, solar irradiation or a side wind. These effects are greatly reduced by covering the barrel with a thermal sleeve. To automatically correct for the residual thermal gun distortion when computing ballistic corrections, the tank is fitted with a muzzle reference system, which feeds information about the gun barrel distortion value into the ballistic computer.
As an option, the tank fire-control system can also include a projectile muzzle velocity sensor, which measures the velocity in question and feeds information to the tank's fire control ballistic computer after each firing of the gun to allow to automatically correct for gun bore wear, charge temperature and other factors.
To enable a broad sector of terrain to be observed, the crew stations are fitted with unity magnification periscope vision blocks. The commander's station is provided with a number of unity vision blocks to give an instantaneous 'all round' vision facility when closed down. These 'all-round' vision blocks are particularly useful for:
observing a broad sector;
map reading;
keeping stations with accompanying vehicles while on the move;
guarding against attacks by infantry armed with short range anti-tank missiles