Abstract: An optical arrangement for a helmet-mounted display for providing binocular presentation to a pilot from a single display source or for superimposing the images from two display sources on his helmet-mounted display. In one embodiment a single display source 1 provides an image which is alternately directed between left and right eyes of the pilot by means of one scanning mirror 4 and two fixed mirrors 5a and 5b. An iris 3 opens and closes in synchronism with the movement of the scanning mirror 4 in order to prevent image distortion. Because only one display source is required, the weight of the arrangement is kept to a minimum. In another embodiment, using similar core elements the images from two display sources are alternately projected on to the pilot's visor by means of similar fixed mirrors 5a and 5b and a scanning mirror 4, but using two iris' 3+ and 3" synchronised to the mirror movements one in each optical path from display source 1' (or 1") to fixed mirror 5a (or 5b).

Abstract: The invention relates to a freeboard measuring device which comprises an elongated housing having a rectangular cross-section form, a central part of the device body. A pair of fins fixedly connected to the housing on each of its sides extend substantially the length of the hosuing and have at least slightly greater lateral dimensions than the lateral dimension of the housing. The fins are triangular in cross section, with the tops of the triangles facing outwardly and providing the device with streamlined characteristics. The base of the triangles does not exceed in length the depth of the housing. The central portion has a main chamber for housing a gauging stick. The main chamber is divided into a lower and upper secondary chamber with the lower chamber having water ingress and separated from the upper chamber by a separation wall with openings to allow water to enter the upper chamber. The lower chamber has a packing of fibrous material to prevent water turbulence.

Abstract: Control apparatus comprising a lever, foot pedal or other operating member which is coupled to an electrical stepper motor operable, under the control of a computer say, to generate detents and feel forces resisting the movement of the member and thereby impart information to the operator. For example, a detent or position of marked resistance can be introduced into the movement range of say a car throttle pedal to indicate to the driver a pedal position giving optimum economy of fuel. The detent position can be changed within the overall range of pedal movement in dependence upon instant driving parameters such as speed. As well as detents, programmed and/or external condition dependent feel forces can be generated.