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 abrupt control inputs, not primarily turbulence, and must be adjusted downwards for lighter aircraft weights.
Maximum gust speed (VB), or a weight-adjusted VA if VB is undefined, is the recommended speed for turbulence penetration, designed to ensure the wing stalls before structural damage occurs.
Aircraft have significantly lower negative-G limits than positive-G limits, which often become the critical factor for structural integrity in turbulent encounters.
Pilots must pre-emptively slow down to a target speed (e.g., 20-25 knots below adjusted VA/VB) *before* entering suspected turbulence to provide sufficient margins against both positive and negative G-load exceedances and accelerated stalls.

See a mistake? Contact us.

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.