The latitude
nut is set to 30°S and will induce drift of 15° x sinlat = 15° x sin30°
= 15° x 0.5
= 7.5°/hr clockwise (to the right) to compensate for equal and opposite Earth
rate at 30°S. Drift due to Earth rate = 15° x sinlat °/hr = 15° x sin60°
= 15° x 0.866 = 13°/hr. In the northern hemisphere the gyro appears to
drift clockwise; i.e. to the right.
If the
aircraft was stationary at 60°N we would expect to see the gyro drift at a rate
of 20.5° clockwise (to the right) because of Earth rate and latitude nut
correction (13°/hr + 7.5°/hr = 20.5°/hr). If the gyro is observed
to be drifting at a rate of 15.5°/hr to the right (clockwise) there must be
drift of 5°/hr to the left (anticlockwise) due to transport wander.