V-speeds & ASI markings
V-speeds mark an aircraft's limits and best-performance points. Several are painted on the airspeed indicator as coloured arcs and lines, each running from its slow end at the bottom to its fast end at the top:
- White arc, flap operating range: Vso (landing-config stall) to Vfe (max flap-extended).
- Green arc, normal operating range: Vs1 (clean stall) to Vno (max structural cruising).
- Yellow arc, caution range: Vno up to Vne, safe in smooth air only, because above Vno a sharp gust could overstress the airframe.
- Red line: Vne, the never-exceed speed.
Not on the dial: Va (design manoeuvring speed, below which a full control input or a gust won't overstress the airframe; lower at lighter weight, because the wing then stalls before it reaches limit load), Vx (best angle of climb, most height per distance), Vy (best rate of climb, most height per time).
Trap: the neighbours. Vno vs Vne (top of green vs the red line), Vso vs Vs1 (stall flaps-down vs clean), Vx vs Vy (angle vs rate).
Source note: TP 1102 defines Va, Vne, Vx and Vy. The colour-arc marking set and the Va weight-effect are standard airworthiness (not in TP 1102), and every actual speed is aircraft-specific, so your own POH/AFM is the authority. No numbers are given here on purpose.
References
- TP 1102 (Flight Training Manual)
- Aircraft POH/AFM (ASI markings)