Direct indicating compass

Question 1

direct indicating compass(DIC) components

Answer 1

compass rose
card for reading- reversed for E type as viewing from the tail
lubber line etched into glass
plaque card for showing corrections

Question 2

compass ideal characteristics

Answer 2

horizontality
sensitivity
aperiodicity

Question 3

damping fluid

Answer 3

reduces friction & improves sensitivity
Characteristics:
stay liquid over operating temp range
shouldn’t expand or contract too much- has syphon tube for expansion
low viscosity
non corrosive

Question 4

Compass errors

Answer 4

variation
deviation
acceleration error
turning error

Question 5

DIC Acceleration errors

Answer 5

accelerations other than N/S direction cause error

NANDS- northern hemisphere-
acceleration north (apparent turn north),
deceleration south(apparent turn south)
Southern Hemisphere is the opposite

Question 6

DIC turning errors

Answer 6

turning errors max on N/S headings. higher lat = higher error

NUNOS- northern hemisphere
undershoot north (compass sluggish)
overshoot south (compass lively)

NH north turn -
left over reads
right under reads

NH south turn-
left under read
right over read

opposite for southern hem

Question 7

DIC swirl effect

Answer 7

swirling due to friction between fluid and casing rotates assembly in direction of the aircraft
for sluggish- increases error
for lively- reduces error

turning errors always worst when turning through the nearer pole

Question 8

DIC pre flight checks

Answer 8

check general condition
check indications
check deviation card is present