Definition
A reference index on the turn coordinator or turn-and-slip indicator that shows the bank or deflection corresponding to a standard rate turn — a turn of 3 degrees per second, which completes a 360-degree circle in two minutes.
Plain English
A small mark on the turn instrument. When the indicator lines up with it, you are turning at the standard rate of 3 degrees per second.
Context Anchor
Seen on the turn rate indicator or turn coordinator during instrument flight training and timed turns.
Derivation
‘Standard rate’ refers to the agreed-upon turn rate of 3 degrees per second used in instrument flying. The ‘mark’ is simply the index line on the instrument face that shows where the needle or miniature aircraft sits when that rate is being achieved.
Why Pilots Care
It lets the pilot make consistent, predictable turns required for holds, approaches, and course changes under instrument conditions.
Intuition Check
Do not read “standard” as just meaning “ordinary” or “roughly normal.” Here it means a specific calibrated turn rate shown by a mark on the instrument.
Example Sentence 1
Rolling into the turn, the pilot banked until the wing of the turn coordinator aligned with the standard rate mark.
Example Sentence 2
During the procedure turn, the pilot held the needle on the standard rate mark for the prescribed time.