GB611047A - Improvements in aircraft navigation instruments - Google Patents

Abstract

611,047. Electric indicating instruments. SPERRY GYROSCOPE CO., Inc. June 8, 1945, No. 14561. Convention date, June 9, 1944. [Class 40 (i)] [Also in Groups XIX and XL (c)] An aircraft navigation instrument shows on the same dial the craft's distance from a predetermined flight path defined by radio-beam guiding means and also its distance from an independent reference such as the ground. It may consist of a cross-pointer meter M on which pointer 11 co-operates with scale 14 to show the distance of the craft from an overlapping beam or other radio glide path and movable mask 15 indicates, on the same scale 14, the altitude. In an overlapping beam-type receiver, Fig. 2, arranged to operate with beams having characteristic tone modulation, the detector 18 provides signals for the A.V.C. circuit 26 which operates both on the intermediate frequency amplifier 17 and on the audio amplifier 19 to produce a receiver gain proportional to the square of the distance from the transmitter. This renders the output across resistors 25, fed in opposition by the rectifier output of audio filters 21 and 22, substantially proportional to the linear distance of the craft from the equisignal path irrespective of the distance from the transmitter. Two independent receivers are shown in Fig. 2 co-operating with centre zero movements to indicate horizontal and vertical displacement and actuated by glide and approach path beams. The mask 15 co-operating with the vertical displacement scale is controlled by an altitude sensitive pressure capsule 31 through mechanical gearing, Fig. 6; servo mechanism, Fig. 4, or a simple D.C. electric circuit including a d'Arsonval movement, Fig. 3; (Figs. 4 and 6 not shown). A spring-loaded slip clutch, Fig. 5 (not shown), may be used to adjust the mask to the correct reading, for instance on receipt of marker beacon indications at an airport; in the electric circuit control of Fig. 3 electrical adjustment is provided by potentiometer 64 for this purpose. An index 13, representing the craft to the dial scale, is provided at the centre, or on-course, position of the meter M. This index may be attached to a gyroscope by a thin support and be free from the dial so that it will also indicate the craft's banking angle; alternatively, the index may be fixed and the dial and indicators stabilized. It is stated that the dial may be translucent and illuminated from behind with the pointers mounted either in front of or at the back of it, a pointer arm can be substituted for the mask if desired or a cathode-ray tube used to display the indications.