An airplane operating at 35°S latitude is using only the magnetic compass (vacuum system failed) and begins a right turn from a heading of 300° through North to a heading of 030°. How should the pilot use the compass indication to roll out on the correct heading?
- ARoll out exactly when the compass reads 030°; hemisphere has no effect on turns through North
- BContinue the turn past the point where the compass reads 030°, because in the Southern Hemisphere the compass leads (overshoots) the turn near North, the reverse of Northern Hemisphere errors
- CRoll out when the compass reads 000° and then make an additional right turn
- DRoll out early, before the compass reads 030°, because the compass lags the turn near North in the Southern Hemisphere
Show answer & explanationAnswer & explanation
Correct answer: B. Continue the turn past the point where the compass reads 030°, because in the Southern Hemisphere the compass leads (overshoots) the turn near North, the reverse of Northern Hemisphere errors
Compass turning error is reversed in the Southern Hemisphere. In the Northern Hemisphere, the compass lags (undershoots) near North and leads (overshoots) near South. South of the equator, this is reversed: the compass leads (overshoots) near North and lags near South, so the pilot must continue turning past the indicated heading near North before rolling out.
Why the other options are wrong
- A. Hemisphere significantly affects compass turning error due to magnetic dip direction.
- C. This overcorrects and does not reflect the actual compass lead error.
- D. This describes Northern Hemisphere behavior, not Southern Hemisphere.
Southern Hemisphere Compass Turning Error
Compass turning errors are reversed south of the magnetic equator: the compass leads (overshoots) near North and lags (undershoots) near South, opposite of Northern Hemisphere UNOS behavior.
- Northern Hemisphere: Undershoot North, Overshoot South (UNOS)
- Southern Hemisphere: reverse — Overshoot North, Undershoot South
- Caused by opposite direction of magnetic dip vector below the equator
Memory trick: South of the line, flip the sign — UNOS becomes ONUS.