TROUBLE PROBABLE CAUSE ISOLATION PROCEDURE REMEDY
Capt’s HSI compass card does not repeat F/O’s RMI compass card F/O’s RMI compass card will not drive or gives erratic readings F/O’s RMI will not synchronize Capt’s HSI and F/O’s RMI compass cards do not indicate airplane heading Instrument amplifier No. 1, capt’s HSI, F/O’s RMI Servo amplifier No. 1 or F/O’s RMI Directional gyro No. 1 Servo amplifier No. 1 F/O’s RMI Servo amplifier No. 1 or F/O’s RMI Rotate F/O’s RMI synch knob; capt’s HSI compass card does not respond to F/O’s RMI readings If replacement of components failed to correct trouble, check airplane wiring Rotate F/O’s RMI synch knob; F/O’s RMI compass card does not respond F/O’s RMI compass card responds to synch knob rotation but gives erratic readings Rotate F/O’s RMI synch knob toward dot or plus F/O’s RMI compass card does not respond to synch knob rotation F/O’s RMI compass card rotates but does not return to synchronized position Place compass transfer switch in ALTERNATE or BOTH ON 2 position Replace instrument amplifier No. 1 Replace capt’s HSI Replace F/O’s RMI Replace servo amplifier No. 1 Replace F/O’s RMI Replace directional gyro No. 1 Replace servo amplifier No. 1 Replace F/O’s RMI
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TROUBLE PROBABLE CAUSE ISOLATION PROCEDURE REMEDY
Slaving amplifier No. 1 or directional gyro No. 1 F/O’s RMI Damaged airplane wiring Capt’s HSI and F/O’s RMI compass cards do not indicate capt’s RMI heading If capt’s HSI and F/O’s RMI compass cards indicate capt’s RMI heading, perform following procedure Place compass transfer switch in NORMAL position. Rotate F/O’s RMI synch knob. Set compass card 6 to 10 degrees from synchronized reading Capt’s HSI and F/O’s HSI compass cards do not return to synchronized reading Capt’s HSI and F/O’s RMI compass cards return to synchronized reading (not airplane heading) If above isolation procedure failed to correct trouble, replace components in order listed If replacement of components failed to correct trouble, check airplane wiring CAUTION DISCONNECT FLUX VALVE BEFORE MAKING CONTINUITY CHECKS TO THE FLUX VALVE AIRPLANE WIRING Replace servo amplifier No. 1 Replace F/O’s RMI Replace slaving amplifier No. 1 Replace directional gyro No. 1 Replace F/O’s RMI Directional gyro No. 1 Flux valve No. 1 Refer to electronic wiring diagrams
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COMPASS SYSTEM - MAINTENANCE PRACTICES
1. General
A. This procedure describes the manner in which the airplane compass systems are "swung." There are two main systems, the captain's and first officer's, plus a standby compass. A method of compensation is also included for airplanes fitted with remote compensator units.
NOTE: Disregard flux valve compensator adjustments on airplanes without remote magnetic compensator.
B. The procedure is written so that the swing for the standby compass system is described separately from that for the main systems. However, all systems may be swung simultaneously, if so desired.
C. The process of "ground swinging" an airplane compass consists of accurately aligning the airplane with at least four cardinal headings in turn, and observing the deviation between known heading and compass heading, in each case. The results are then tabulated, and after all necessary adjustments have been made to reduce the deviations to specified limits, another circuit is made for the purpose of compiling the compass correction card. This card remains with the compass.
D. Deviation errors fall into two categories, "index error" and "single cycle error," each of which is summarized below.
(1)
An index error exists when the direction error remains constant both in direction and value at each check point.
(2)
A single cycle error exists when the direction error is equal, but opposite in sign, at opposite check points on the compass.
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