Definition
A phrase used in instrument scan technique describing the instrument the pilot looks at first to establish and check bank angle when starting a turn. In the context of timed turns, the turn coordinator (or turn-and-slip indicator) is the primary bank instrument initially, because it directly shows the rate of turn used to time the maneuver.
Plain English
It means the instrument you look at first to set and check how much the airplane is banking when you begin a turn.
Context Anchor
Seen in Instrument Flying Handbook timed-turn figures, where the panel instruments are labeled by what the pilot should use them for during each part of the turn.
Derivation
Primary' comes from the Latin primus, meaning first. In the instrument scan, the 'primary' instrument for a given task is the one that gives the most direct, accurate information for that specific job at that specific moment. 'Initially' simply means at the start of the maneuver, signaling that the primary instrument can change as the maneuver progresses.
Why Pilots Care
Rolling into the correct initial bank quickly lets the pilot reach a standard 3° per second turn rate without large corrections that waste time or overshoot the heading.
Intuition Check
“Primary” does not mean the only instrument to look at; it means the main instrument for that job at that moment. “Bank” does not mean money here; it means the airplane’s left-or-right wing tilt.
Example Sentence 1
When starting the timed turn, the turn coordinator is the primary bank instrument initially, so the pilot uses it to set a standard-rate turn.
Example Sentence 2
The primary bank initially gives a close standard-rate turn that is then refined with the turn needle.