Why Does Maneuvering Speed Increase With Weight?

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Aircraft maneuvering speed, increases as the airplane gets heavier. It’s a simple fact that most pilots are either blissfully unaware or simply take for granted, and I’ve honestly never given it much thought. But then one AskACFI user posed the question – why does maneuvering speed increase with weight?

 

I think the best way to understand maneuvering speed is to look at how it is determined, and for that we need the VG/VN diagram.

This is a really useful tool that shows the theoretical accelerated stall speed for a given load (how many G’s you’re pulling).

For this airplane, we can see that the normal stall speed at 1G is about 64mph and increases as we pull more G’s.

Look at the chart and suppose you were flying at 90mph when you suddenly yanked back on the stick. How many G’s could you load before stalling the airplane?

Just follow a line up from around 90mph to the red “Accelerated Stall” line, then read the load factor to the left. I’m getting about 2G’s. So VS is 90mph with a load of 2G’s.

The chart also shows some hard limits. Notice that the caution box for structural damage starts at +4.4G’s. If you pull harder than that, you risk damaging the airplane. On the slow side of the chart, it is impossible to put the airplane at risk because we’ll stall first – in theory. But at the fast side, you can see that it’s easy to load five, six, seven or more G’s!

But something interesting happens right at 136mph. Stall speed is equal to the structural load limit of 4.4G’s. This is the absolute limit, where the airplane is supposed to enter an accelerated stall right at the load limit. This speed is known as maneuvering speed.

Maneuvering Speed = VS at +4.4G

Now think about the question: Why does maneuvering speed increase with weight? Recall that stall speed increases with weight. Since maneuvering speed is really just a stall speed at a higher G load, then maneuvering speed will also increase with weight!

You’ll notice I never used the notation VA, more on that later.


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About the author
Pat Flannigan is a professional pilot and aviation blogger. He has been flying for fifteen years and is currently working as an airline pilot in the United States.

3 Replies to Why Does Maneuvering Speed Increase With Weight?

  1. skipper44 says:

    Another way of saying it is that maneuver speed is a speed derived by adding a margin to the stall speed, this margin provides adequate leeway for the increased stall speed (plus some) during normal maneuvering. Sometimes the final figure is also adjusted so as to provide a modicum of fuel efficiency.

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