The occlusion zone is a defined area within the display of the helmet that only allows certain symbology to display. Items like the flight instruments, engine gauges and , HUD are normally included in the zone to ensure unhindered visibility.
In the real A-10C you can preview the occlusion zone and set it to various default zones or create custom ones. We don’t have this option in the A-10C II. The various settings are:
None: no occlusion zone, the same as setting all symbols to ON.
HUD – the occlusion zone just around the HUD.
INSTRMTS – the occlusion zone around the instrument panel
BOTH – the occlusion zone around both the HUD display and instrument panels (what we have in the A-10C II)
CUSTOM – pilot defined occlusion zone.