The Yellow Arc

Tuesday, November 22, 2022 at 10:52 AM ET

Verified

The two main airspeed presentations found in piston-powered airplanes are shown: a generic “round-dial” airspeed indicator with a prominent yellow arc and a zoomed-in image of a Garmin G1000’s airspeed tape.

Key Takeaways:

The yellow arc on a piston aircraft's airspeed indicator is a "caution range" (between VNO and VNE) where the airframe's protection against overstress from turbulence is significantly reduced, certified for only half the gust intensity (15 fps) compared to the green arc.
Operating in the yellow arc is only safe in exceptionally smooth air with minimal control inputs, as the aircraft can be overstressed and damaged by moderate turbulence or abrupt maneuvers before a stall occurs.
Repeated exposure to speeds within the yellow arc may contribute to cumulative airframe fatigue over time; turbine aircraft utilize a dynamic VMO ("barber pole") system and do not have a fixed yellow arc or a comparable reduced protection range.

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Look at an airspeed indicator or vertical speed tape, as below, in a piston-powered airplane and you’ll see a yellow range of indicated speeds. This is called the “caution range.” Since typical piston airplanes can’t cruise in this speed range under most circumstances, we often don’t spend a lot of time learning how very different the airframe overstress protection scheme is when operating in the yellow arc instead of the green one. It’s not like the FAA decided to spice up airspeed indicators with a splash of color: There is a very real reason for the caution range of the airspeed indicator.