Improvements in or relating to ground-based flight simulators

896,404. Grounded aircraft trainers. COMMUNICATIONS PATENTS Ltd. Jan. 11, 1960 [Nov. 4, 1958], No. 35369/58. Class 4. . The subject matter is the same as that disclosed in Specification 896,403 with reference to Figs. 1 and 2 thereof, with the following additions. A sheet of heat absorbing glass may be placed between the lamp 9 and transparency 1. The transparency may be of enamel fused on to heat resisting glass. The illuminated area of the transparency may be made triangular or oval, by an appropriately shaped reflector 10. The image may be rotated on screen 17 by using a Dove prism instead of mirrors 19, 20. The camera 22 may be fixed, varying altitude being simulated by replacing lens 6 by a zoom lens operated by the altitude servo 30, and varying pitch by a mirror on the optical axis of lens 21 and rotated by the pitch servo 32. Screen 25 may have a lenticular surface to minimize scattering of light therefrom on to screen 17. At low altitudes, a simulated altitude signal is taken from a potentiometer connected to the height servo 30, and together with a roll signal is used to compute roll and " bounce " movements on touch down, to provide corresponding visual simulation. According to the Provisional Specification, the servos used may be slaved to the corresponding servos of the flight computer, which operates the aircraft instruments, or may replace the corresponding flight computer servos when the visual display is in use, or two flight computers may be used, one when there is no visual display, and one when the visual display is in use, e.g. during simulated landing and take-off. Specification 896,405 also is referred to.