GB1318873A - Vehicles having transparent wall parts - Google Patents

Abstract

1318873 Rear viewing devices BRITISH AIRCRAFT CORP Ltd 23 July 1970 [1 May 1969] 22347/69 Heading B7J A transparent enclosure, such as either of the front and rear canopies, 1 and 2, of an aircraft cockpit each of which in use has its outer surface flush with the edges of an opaque strap 4 and/or an opaque portion 3 of a fuselage, has at least one, and preferably two prisms 5 which have a refractive index greater than or equal to, that of the enclosure, each prism being positioned on the inside surface of the enclosure with the thick end 13 being closest to the nearest opaque surface and being faired into the enclosure at 15, preferably at an angle of about 30 degrees, the thin end 12 being merged into the enclosure to give a continuous smooth surface. In an aircraft cockpit there are preferably two prisms 5 for each of the canopies 1 and 2, the prisms being placed rearwardly and to either side of the observers 7 and 8. However, a single prism 6 may be used which extends across the centre line of the aircraft from one side of the canopy to the other. In use an observer 9 looks back over his shoulder. If he looks towards the thin end 12 his line of sight will be that indicated by the line 10 and any light rays entering the canopy 1 or 2 along this line of sight 10 emerge into the canopy in a direction parallel to their direction of incidence on to the exterior of the canopy. However, any light rays entering along the line of sight 11 so that they emerge from the thick end 13 emerge into the canopy having been deviated from the direction of incidence. Thus, as shown in Fig. 4, an observer can view objects along a line of sight at 90 degrees rearwards of the normal to the canopy surface when he himself has only turned his head to face rearwardly at an angle of 53 degrees to that normal.