What does Magnetism & Compass cover?
The magnetic compass is simple but full of errors the exam loves. This topic covers variation and deviation, and the dynamic errors — turning and acceleration — that arise from magnetic dip near the poles.
What this subject covers
- Variation and deviation; true/magnetic/compass heading
- Magnetic dip and its consequences
- Turning errors (UNOS) and acceleration errors (ANDS)
- Direct-reading compass limitations
Study tip
Learn the turning and acceleration error rules cold — they are pure recall, and they appear in nearly every General Navigation paper.
Frequently asked questions
What is the difference between variation and deviation?
Variation is the angle between true and magnetic north (a property of location); deviation is the compass error caused by the aircraft's own magnetism.
What causes compass turning errors?
Magnetic dip: the vertical component of the Earth's field tilts the compass card during turns, most noticeably through north and south.
