SIRS NAVIGATION LTD
COMPONENT MAINTENANCE MANUAL
The compass bowl is filled with silicone fluid to control movement of the compass
card. Bellows (10) at the rear of the compass bowl, allow fluid volume changes.
A filling plug (190), disc (210) and washer (200) are assembled to the compass bowl
below the corrector assembly (160). A marked scale, on the front edge of the
corrector assembly gives a guide for coefficient 'A' correction.
The magnetic correctors, for coefficients 'B' and 'C', are small bar magnets installed
in the gear shafts of the corrector assembly. ‘Indicator lines’ on the end of the gear
shafts identify the direction of the magnets. Gear shaft movement can be seen on
top of the corrector assembly as an angular difference between the indicator lines
and the marked index lines. The magnetic correctors are adjusted with a corrector
key (220) that is turned inside the corrector adjustment holes, at the front of the
compass bowl.
The lamp housing assembly (230) is a plastic moulding that is assembled to the
base of the bowl and secured with a clip-fit procedure
.
A lead and socket assembly (260) is assembled to the underneath of the lamp
housing assembly.and gives electrical connection.
A ‘non-magnetic’ lamp (240) is installed into a spring inside the lamp housing
assembly and is retained by the lamp cap (250).
D. Operation
The compass operates without an electrical power supply. The magnet of the
compass card is aligned with the earths magnetic field. The direction of the aircraft
is determined with reference to a vertical lubber line positioned close to the compass
card.
Magnetic corrector magnets, at the top of the compass, can be adjusted to cancel
magnetic forces induced by the aircraft.
A light fitted at the bottom of the compass is used to light up the compass card.
PAGE 2
APR 10/03
34-25-21
The document reference is online, please check the correspondence between the online documentation and the printed version.
