Definition
On an electronic flight display, the primary bank instrument is the one that gives the pilot the most direct and immediate indication of the aircraft's bank angle for a given flight condition. In straight-and-level flight and in standard-rate turns, the primary bank instrument is the attitude indicator on the Primary Flight Display, supplemented by the heading indication and the turn rate indicator.
Plain English
The instrument the pilot looks at first to check whether the wings are level or how steeply the aircraft is banked into a turn.
Context Anchor
Seen in instrument flying when deciding which part of the electronic flight display to trust first for keeping the wings level or controlling a turn.
Derivation
"Primary" comes from the Latin primus, meaning "first." In instrument flying, the primary instrument for a flight characteristic is the one consulted first because it shows that characteristic most directly.
Why Pilots Care
Proper use maintains coordinated flight, prevents heading drift, and supports accurate turns without excessive load factor.
Intuition Check
Primary does not mean the only indication you may look at; it means the main one for that moment. Bank does not mean money or a river edge here; it means the airplane’s sideways tilt.
Example Sentence 1
Once established in the standard-rate turn, the pilot returned to the attitude indicator as the primary bank reference and cross-checked the turn rate indicator.
Example Sentence 2
After leveling the wings, the pilot verified primary bank showed zero to confirm straight flight.