Ask My Sky Mom. Aviation wit and wisdom.

Hey Mom,

With the recent Air France crash, there’s been some talk about the Airbus displaying the wrong airspeed, and flying at the wrong speed through the storm.  What is the best speed to fly through a storm, and why?

Thanks,

Feeling the Need For (the Right) Speed

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Hi Speedy,

The speed you’re wondering about is known as Va, or design maneuvering speed.  When flying in turbulent air (Yes, this would include flying anywhere NEAR a thunderstorm!), pilots should slow to an indicated airspeed at or below Va. Why?  At or below Va, abrupt deflection of the controls (pilot induced OR due to turbulent air) will result in a stall before structural damage can occur.  You’ll stall before you bend anything.  This is a good thing!  A very good thing indeed.  Every pilot has practiced stall recognition and stall recovery which should make this a manageable situation.  Structural deformation may not be…

Interestingly, maneuvering speed is one of the few airspeeds not marked on the airspeed indicator, and for good reason: it varies with aircraft weight.  Yup.  As aircraft weight increases, so does maneuvering speed.  This strikes some pilots as counter intuitive until you slow down to consider just why this might be.  A very light airplane is more susceptible to sudden changes in direction or velocity.  A quick change in wind direction or an abrupt control input has the potential to dramatically increase the load factor imposed on the wings and other load bearing surfaces.  A heavier airplane will be comparatively sluggish and won’t respond as readily to the turbulence around it, thereby decreasing the amount of load that can be suddenly imposed.

The long and short of it?  Whenever you plan to practice maneuvers that may involve abrupt control deflection (which sounds like most of them to me!), or you encounter turbulence, be sure to slow to Va for the duration.

Hope you’re feeling a little more up to speed on how to handle turbulence,

Mom

P.S.  Just a reminder-please don’t go flying anywhere near thunderstorms if you can help it, at Va or any other airspeed.  No matter who you are or what you’re flying, thunderstorms are just plain dangerous and should be avoided.  But you already knew that!

~ by myskymom on June 9, 2009.