Chap 6: Compasses Flashcards
purpose of direct reading compasses
show the direction which the aircraft is heading wrt to the earth’s magnetic meridian
reason for liquid damping
make the compass aperiodic
steady the system
lessen friction and wear
components of a liquid magnetic compass
1) magnetic system in a bowl
2) liquid damping
3) liquid expansion compensation device
4) deviation compensation device
what is magnetic deviation
error in compass indications caused by magnetic disturbances originating in the aircraft
magnetic dips are caused by
northerly/southerly turning errors
acceleration/deceleration errors heading west & east
2 types of drift in gyroscope
apparent, real drift
types of aircraft magnetism
hard iron:
occur during manufacturing & rivet/polishing
ferrous components have own magnetic fields
soft iron:
temporary & caused by magnetically soft metal parts
static electricity
When swinging a magnetic compass, the compensators are adjusted to correct for
magnetic influence deviations
horizontal and vertical axis gyro effects in poles and equator
horizontal axis gyro:
at poles: maximum drift and no topple
at equator: no drift and maximum topple
vertical axis gyro:
at poles: no drift and no topple
at equator: no drift and maximum topple
definitions of magnetic variation, deviation and dip
magnetic variation: angular difference between true and magnetic north
magnetic deviation: error in compass indications caused by magnetic disturbances originating in a/c
magnetic dip: tendency of magnetic compass to point up/down in certain latitudes
what is acceleration error
force applied through the cg of compass system which is below and offsets from the pivot
what is turning error
when turning, compass cg is offset subjected to centrifugal forces by the turn causing it to swing outwards and rotate
four advantages of remote-indicating compass system over liquid
magnetic compasses
1) stable direction indicator
2) north seeking and free from the 2 errors
3) non-drifting
4) self synchronous
what is compass swinging
compass swinging is the procedure to minimise compass reading errors
