Definition
The yellow arc on an aircraft airspeed indicator marking the range of speeds at which flight is permitted only in smooth air and with caution. The caution range lies between the maximum structural cruising speed (Vno) at the lower end and the never-exceed speed (Vne) at the upper end.
Plain English
The yellow band on the airspeed dial. You can fly at these speeds, but only when the air is calm and you're being careful. Turbulence at these speeds could damage the aircraft.
Context Anchor
Seen on airspeed indicator markings and in load factor discussions, especially when learning how speed affects the forces on an airplane.
Derivation
Caution derives from the Latin 'cautio' meaning heed or care; range indicates a span or extent. Together the term signals the specific speeds requiring attentive handling to avoid overload.
Why Pilots Care
Operating in this range without caution risks structural damage or loss of control in turbulent conditions.
Intuition Check
Do not read “caution range” as meaning the airplane is already unsafe. It means this speed range is acceptable only under the right conditions: smooth air and gentle control use.
Example Sentence 1
As the air grew bumpy, the pilot eased back on the throttle to bring the airspeed needle out of the yellow caution range and into the green arc.
Example Sentence 2
During the preflight, the instructor pointed out that the caution range begins above the normal cruise speed for this aircraft.