Definition
An aircraft heading in the general direction of south, used in the context of magnetic compass behavior to describe headings near 180° where specific compass errors occur during turns and acceleration. On a southerly heading in the Northern Hemisphere, the magnetic compass leads the actual turn when rolling out, requiring rollout past the desired heading by approximately the latitude in degrees plus half the bank angle.
Plain English
A heading pointed roughly south. Pilots talk about 'southerly headings' because the magnetic compass behaves in a particular way when the aircraft is pointed in that direction, and the rollout from a turn has to be timed differently than on other headings.
Context Anchor
Seen in compass-turn training and instrument flying discussions when learning how the magnetic compass behaves during turns near south.
Derivation
Southerly' comes from 'south' plus the suffix '-erly,' meaning 'in the general direction of.' It does not mean exactly 180°; it means in the southward region of the compass. This matters because compass errors near south behave similarly across a range of headings, not just at 180° exactly.
Why Pilots Care
When flying partial panel or relying on the magnetic compass, knowing you are on a southerly heading tells you which rollout rule to apply. Get this wrong and you will overshoot or undershoot your target heading, which matters during instrument procedures where heading accuracy is required.
Intuition Check
Do not read “southerly heading” the same way as “southerly wind.” A southerly heading means the aircraft is pointed toward the south; a southerly wind usually means wind coming from the south.
Example Sentence 1
Rolling out from a turn onto a southerly heading, the pilot stopped the turn past 180° to compensate for the compass leading the actual heading.
Example Sentence 2
With a southerly heading established, the airplane tracked directly toward the airport 20 miles away.