Air-navigation horizontal situation display

The increasing complexity and speed of modern commercial and military aircraft require assistance to the pilot in informing him of rapidly changing conditions. An integrated avionics system does this by combining the outputs of various independent sensors into a coordinated report that can be understood quickly by the pilot. These reports are presented as visual displays that may cover specific flight modes such as take-off, cruising, landing, and attack. The field of view around an aircraft makes up the horizontal situation display. This display equipment is under control of a navigation computer. It uses a transparent drum around which photographic microcharts are fastened. A folded optical system projects part of a chart through the axial center of the drum onto the viewing screen. The chart is moved along its axis and is rotated in either direction by digital longitude and latitude inputs to present the aircraft's present position and surrounding terrain. A ground-track reticle with an image of the aircraft, and a compass reticle, are similarly controlled by independent computer inputs. A Dove prism is rotated to change the orientation of the chart in the forward or north direction. A cathode-ray direct-view storage tube projects radar,televlslon,infrared,locally developed symbols,and other data on the viewing screen through an optical system that combines or alternates this information with the chart image. The chart and cathode-ray images are projected from the rear onto a screen having low reflectance. The addition of a plastic Fresnel lens concentrates the light towards the pilot.