Definition
Color-coded arcs and lines on the face of the airspeed indicator that show the operating speed ranges and limits for the aircraft. The standard markings are: a white arc (flap operating range, from stall speed with flaps extended at maximum landing weight up to maximum flap extended speed), a green arc (normal operating range, from stall speed with flaps retracted up to maximum structural cruising speed), a yellow arc (caution range, to be flown only in smooth air), and a red radial line (never-exceed speed, VNE).
Plain English
The colored bands and lines painted on the airspeed dial that tell the pilot at a glance which speeds are safe, which require caution, and which must never be exceeded.
Context Anchor
Seen on the airspeed indicator during preflight cockpit checks, takeoff, approach, landing, and any time the pilot is monitoring aircraft speed.
Why Pilots Care
The markings let a pilot instantly recognize safe speeds and avoid exceeding structural or aerodynamic limits without looking up numbers.
Analogy
They work like the colored zones on a car’s temperature gauge: one range is normal, one warns you to be careful, and one marks a limit you should not cross.
Intuition Check
Do not treat the markings as decoration or rough suggestions. On an aircraft, the colored arcs and lines show real operating ranges and limits for that airplane.
Example Sentence 1
During the preflight briefing, the instructor pointed out the airspeed indicator markings and reminded the student to keep the needle out of the yellow arc in turbulence.
Example Sentence 2
Before lowering the flaps, the pilot verified the airspeed was within the white arc shown on the airspeed indicator markings.