Definition
On an electronic flight display, the instrument that gives the most direct, immediate, and accurate indication of the airplane's yaw condition during a specific maneuver. For coordinated flight, the slip/skid indicator (the trapezoid or ball beneath the bank pointer on the attitude indicator) is the primary yaw instrument, showing whether the airplane's nose is aligned with its flight path.
Plain English
The one instrument the pilot looks at to see if the airplane is flying straight through the air rather than skidding sideways. In a glass cockpit, that's the small indicator just below the bank pointer that shows whether the airplane is in coordinated flight.
Context Anchor
Seen in instrument flying when using the electronic flight display to maintain coordinated flight without outside visual references.
Derivation
"Primary" comes from the Latin primus, meaning "first." In this context it identifies the first instrument a pilot should reference for yaw information — the most direct source. "Yaw" refers to rotation of the airplane around its vertical axis (nose left or right).
Why Pilots Care
Keeps the airplane coordinated and prevents unwanted yaw that can lead to heading deviations or unusual attitudes.
Grounding Statement
If the airplane is not moving cleanly through the air, the primary yaw indication helps the pilot notice it and correct it with rudder.
Intuition Check
Primary does not mean the yaw itself is most important in every situation. It means this is the main display cue used for yaw control in this part of the instrument scan.
Example Sentence 1
During the climb, the pilot kept the slip/skid indicator centered, since it was the primary yaw reference on the electronic flight display.
Example Sentence 2
When entering a turn, the pilot adjusted rudder pressure while watching the primary yaw display.