Abstract: The apparatus comprises a sighting unit, such as helmet 10 carrying a cathode-ray tube 11 and a semi-reflecting screen 13 enabling a user to view a display superimposed on an outside scene. The sighting unit carries a detector unit 15 which determines the movements of the helmet 10 without reference to apparatus external to the helmet, and preferably comprising some form of gyroscopic apparatus. The helmet also carries a boresight detector 16 which forms part of correction means operable to correct automatically from time to time for errors in the output of the detector unit.

Abstract: Apparatus for detaching helmet-mounted equipment (6) from the helmet (4) of a vehicle-mounted user (1) includes a quick-release fastening (8) securing the equipment to the helmet. A removal cord (11) passes from the equipment by way of a guide (10) and is attached to the vehicle (12). The action of the apparatus is to remove the equipment from the helmet to a position of safety when the user has to leave the vehicle in an emergency.