Airspeed & Turbulence: Easy Adjustments

The airspeed indicator always has been one of a pilots most useful tools for measuring aircraft performance. Its colorful, with white and green, maybe a pair of red lines and a blue one, and maybe some yellow. And theres that big white needle we use for bragging rights. Early on, we were taught some of the most important speeds we need to know and use arent marked on it. One of them is the airplanes design maneuvering speed (VA), sometimes confused with the turbulent air penetration speed, which perhaps is better known as design speed for maximum gust intensity (VB).But is there a difference between VA and VB? What is it, and when do you use them? Why? Which should we be concerned more with as a pilot, and when? And airplanes are stressed to lower negative-G limits than their positive G-load limit-what about negative-G encounters in turbulence? Lets look at the operational reality of airspeed and G-load control in turbulent air.

Tom Turner

Friday, December 11, 2015 at 12:00 AM ET

Verified

Key Takeaways:

Design maneuvering speed (VA) is for safe abrupt control inputs, ensuring a stall occurs before exceeding positive G-limits during pilot-induced maneuvers; it is weight-dependent. Maximum gust speed (VB), if defined by the manufacturer, is for turbulence penetration, ensuring the wing stalls before structural damage from gust loads.
Aircraft have lower negative-G load limits than positive-G limits, and these can be the true limiting factor in turbulence, making it vital for pilots to understand the full maneuvering envelope.
To prevent overstressing the airframe, pilots must proactively slow down to a target airspeed significantly below the weight-adjusted VA or VB (e.g., 20-25 knots less) *before* entering suspected turbulence, providing ample margin against both positive and negative G-loads and accelerated stalls.

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The airspeed indicator always has been one of a pilot’s most useful tools for measuring aircraft performance. It’s colorful, with white and green, maybe a pair of red lines and a blue one, and maybe some yellow. And there’s that big white needle we use for bragging rights. Early on, we were taught some of the most important speeds we need to know and use aren’t marked on it. One of them is the airplane’s design maneuvering speed (VA), sometimes confused with the turbulent air penetration speed, which perhaps is better known as design speed for maximum gust intensity (VB).

But is there a difference between VA and VB? What is it, and when do you use them? Why? Which should we be concerned more with as a pilot, and when? And airplanes are stressed to lower negative-G limits than their positive G-load limit—what about negative-G encounters in turbulence? Let’s look at the operational reality of airspeed and G-load control in turbulent air.