Definition
A heading that points the aircraft toward or near magnetic north (approximately 360°/000°). In the context of compass turns, headings near north are significant because the magnetic compass exhibits its largest turning errors when the aircraft is on, rolling out on, or rolling away from a northerly heading in the Northern Hemisphere.
Plain English
A heading where the nose of the aircraft is pointed roughly north on the compass. This direction is important because the magnetic compass behaves badly when you turn to or from it.
Context Anchor
Seen when practicing or reading about turns using the magnetic compass, especially in the Instrument Flying Handbook section on compass turns.
Derivation
‘Northerly’ comes from ‘north’ plus the suffix ‘-erly,’ meaning ‘in the direction of.’ So a northerly heading simply means a heading in the general direction of north — not strictly 360° exactly, but the band of headings near north where compass errors become a practical concern.
Why Pilots Care
Northerly headings produce the strongest turning errors in the wet magnetic compass, requiring pilots to lead or lag the rollout to avoid overshooting the desired heading.
Intuition Check
Northerly does not mean a wind coming from the north here. It means the aircraft itself is pointed roughly toward north. Also, heading means where the nose points, not necessarily the exact path the aircraft travels over the ground.
Example Sentence 1
When rolling out on a northerly heading, the pilot stopped the turn early to compensate for compass lag.
Example Sentence 2
On a northerly heading the magnetic compass showed the greatest lag during a standard-rate turn.