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 denotes a "caution range" where the airframe's structural protection against gusts and abrupt control inputs is significantly reduced compared to the green operating range.
Specifically, aircraft certified for operation in the yellow arc are only required to withstand a 15 fps gust, which is half the 30 fps gust protection mandated for speeds within the green arc.
Consequently, operation within the yellow arc is only considered safe in exceptionally smooth air with minimal control inputs to prevent structural overstress, and is generally not recommended for descents or in suspected turbulence.

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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.