Definition
The speed at which an aircraft is rotating about its vertical axis, expressed in degrees per second. The turn-and-slip indicator senses this rate gyroscopically and displays it as a needle deflection, which under coordinated flight corresponds to the rate of turn.
Plain English
How fast the nose of the aircraft is swinging left or right around a vertical line through the aircraft, measured in degrees per second.
Context Anchor
Seen in discussions of the turn-and-slip indicator, which shows how fast the aircraft is turning.
Derivation
Yaw originally described the unsteady side-to-side motion of a ship straying off course. Applied to aircraft, it describes the same kind of motion -- the nose swinging left or right -- and 'rate of yaw' is simply how quickly that swing is happening.
Why Pilots Care
It lets the pilot establish and hold a standard rate turn for timed instrument procedures such as holds and procedure turns.
Grounding Statement
If the nose is moving left or right faster, the rate of yaw is higher.
Intuition Check
Do not confuse rate of yaw with bank angle. Bank angle is how much the wings are tilted; rate of yaw is how fast the nose is turning left or right.
Example Sentence 1
The turn-and-slip indicator's needle deflects in proportion to the rate of yaw sensed by its gyro.
Example Sentence 2
During the holding pattern, the rate of yaw remained steady while the pilot maintained altitude with pitch and power.