GB840139A - Improvements in or relating to systems for indicating a variable condition of an aircraft - Google Patents

Abstract

840,139. Visible-signalling apparatus. SPECIALITIES Inc. May 5, 1958 [May 6, 1957], No. 14337/58. Class 118 (2). [Also in Group XXXIII] An indicator for use in an aircraft comprises a group of closely-spaced light sources so arranged that under normal flight conditions they are in the pilot's secondary field of vision, means being provided for exciting a selected one or ones of the sources in accordance with a flight condition of the aircraft. In the preferred embodiment the indicator provides an indication of airstream direction in a vertical plane and hence of the angle of attack of the aircraft. The indicator may alternatively be used as a side-slip indicator. In the arrangement illustrated the shaft of the instrument 10 measuring airstream direction operates through a follow-up system comprising potentiometers 13, 17, relays 15, 16 and motor 14 to position a shaft 24 in accordance with the angle of attack of the aircraft. Cams 20, 21, 22, 23 mounted on the shaft determine the conditions of four double-pole switches in accordance with the shaft position and hence the energization of the light sources 34, 35, 36 of the indicator 37. When the angle of attack has the desired value the source 35 is lit; when it is slightly too high both 34 and 35 are lit while when it is much too high only 35 is lit. Similarly when the angle is too low either 35 and 36 or 36 alone are lit. The indicator 37 is arranged behind the windscreen on the ledge above the instrument panel to one side of the pilot's normal field of view. It may be pivotally mounted and the form of the indications provided may be modified to show letters such as " H," " L " or " S," " F " instead of the converging-line patterns shown in the Figure. Further lamps 43, 44, and 45 may be arranged on the leading edge of the aircraft wing to give an indication to ground personnel of the aircraft's angle of attack. In this case, however, only three conditions are indicated, each lamp lighting singly with no provision being made for their lighting in combination.