Lead computing optical sight system (LCOSS)


The lead computing optical sight system or short LCOSS, is used to establish a visual sight reference to either air-to-air or air-to-ground weapons delivery. A red reticle is projected on a combining glass. The LCOSS features seven different modes that can be selected via the Sight Mode Knob.

LCOSS Controls

Sight mode knob


The sight mode knob selects the mode of operations which are the following:

Sight mode knobFunction
OFFDe-energizes the sight system.
STBYEnergizes the sight system for warmup but does not display any reticle.
CAGEReticle is displayed and caged at the radar boresight line (RBL).
A/GSelects the air-to-ground mode. The reticle is depressable from zero mils to 245 mils below the fuselage reference line (FRL).
A/ASelects the air-to-air lead compute mode. The reticle position is governed by the sight gyro, radar range, the CADC Sensor and the cage button on the throttle.
BIT 1 and BIT 2Energizes the lead computing amplifier relays so that fixed voltages are applied to the sight system for a self test. Displays self test pictures.

Reticle depression control


The reticle can be depressed by rotating the reticle depression knob until the readout (in one-mil increments) shows the desired sight setting. The Reticle cannot be positioned manually in azimuth.

Reticle intensity control


Rotating the reticle intensity control knob changes the brightness of the reticle.

Shutter lever control


The shutter control lever is a two position lever with positions of CL (closed) and OPEN. In the CL position a shutter is placed between the optical light source and the combining glass thus preventing damage to the optics from bright sunlight. In the OPEN position the shutter is removed and the reticle will be displayed.

Reticle Image

The reticle image that is projected onto the combining glass is composed of a fixed reticle, roll reference tabs, and a range bar. The fixed reticle consists of 2-mil diameter pipper located in the center of a 25-mil diameter segmented circle, and a 50-mil diameter completed circle.

The roll reference tabs rotate about the 50-mil circle. The roll reference tabs have two seperate functions. During the offset bombing mode and the target finding mode the roll tabs provide steering information from the WRCS. The position of the roll tabs, with respect to the fixed index tabs, indicates the angle between the ground track and course to the target. In every other mode of operation the roll tabs indicate the aircraft roll attitude, supplied by the INS.

Roll tab left rollRoll tab right roll
1 left roll tab, 2 center roll tab, 3 right roll tab1 left roll tab, 2 center roll tab, 3 right roll tab

The range bar is semicircular and appears on the inside of the 50-mil circle only when a target has been acquired by radar lockon. The instantaneous length of the range bar, and the rate at which the length is changing indicates the actual radar slant range and the range between the aircraft and the target. The minimum length of the range bar (and minimum range indication) exists at the 6 o'clock position. With gun selected the inside tab of the range bar at 6 o'clock, the actual radar range is 1000 ft. At the 5 o'clock position the range bar is 2000ft continuing with 1000ft increments per tab. The maximum range that can be shown is 6667ft with guns selected. When any other mode than GUN is selected the range bar is 3000ft at the 6 o'clock position and 6000ft at the 5 o'clock position, with increments of 3000ft per tab. The maximum displayable range is then 20000ft.

Range bar with gunsRange bar in any other mode

Reticle Cage Function

The reticle cage function is applied through the CAGE button on the throttle. With the sight operating in the (GUNS) A/A mode and with CAGE pressed (no radar lockon) the reticle is caged at radar boresight line (RBL). When CAGE is released, a pseudo range of 1000ft is supplied to the computer but the range bar is not displayed. With radar lockon the stiffening function is applied as long as CAGE is pressed. The range bar continues to indicate the actual radar range or the maximum displayable range. When CAGE is released the reticle moves in azimuth elevation to display the lead required to a maximum of 4000ft. This will only happen with GUNS selected.