Definition
Turns flown using only the magnetic compass as the heading reference, without the aid of a heading indicator or directional gyro. Because the magnetic compass swings, lags, and leads during turns due to magnetic dip and acceleration errors, the pilot must apply specific roll-out lead or lag corrections, which vary depending on whether the turn is to a northerly or southerly heading.
Plain English
Turning the aircraft to a new heading using just the magnetic compass, while accounting for the fact that the compass doesn't read accurately during the turn itself.
Context Anchor
Seen in instrument flying, especially during partial-panel practice or when the normal heading display is unavailable or unreliable.
Why Pilots Care
Allows continued safe flight and navigation when primary heading references are lost in instrument conditions.
Grounding Statement
In a compass-only turn, the compass is useful, but it is not a steady, exact pointer while the airplane is actually turning.
Intuition Check
Do not assume “compass-only” means you can simply watch the compass and stop exactly on the number you want. In a turn, the compass can lead or lag, so the pilot must make an allowance before rolling out.
Example Sentence 1
After the instructor covered the heading indicator, the student practiced compass-only turns to assigned headings.
Example Sentence 2
She timed the bank angle carefully and watched the compass card to complete the 180-degree compass-only turn.