Definition
The range of airspeeds within which the wing flaps may be safely extended and operated, marked on the airspeed indicator by a white arc. The arc extends from the power-off stall speed in the landing configuration (VS0) at its lower end to the maximum flap-extended speed (VFE) at its upper end.
Plain English
The band of speeds where it is safe to use the flaps. Below this band the airplane will stall with flaps down; above it the flaps could be damaged by the airflow.
Context Anchor
Seen on the airspeed indicator color markings and in discussions of when flaps may be extended during approach and landing.
Why Pilots Care
Using flaps outside this range can cause structural damage or sudden loss of lift.
Intuition Check
Range does not mean distance here; it means a band of airspeeds. Operating does not mean the flaps must be used throughout that band; it means they may be used within that band if appropriate.
Example Sentence 1
On final approach, she kept the airspeed inside the white arc so she could safely lower the flaps to full.
Example Sentence 2
In the traffic pattern the airspeed remained within the flap operating range while the flaps were lowered in stages.