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Macgyver
6th May 2006, 17:16
Hey guys,

I'm having a bit of a brain-fart here. I understand the relationship between Va and weight (higher weight=higher Va). It seems intuitive to me that Va should also vary with altitude, however, I can't find any references to prove/disprove my assumption.

The way I look at it is that at higher altitudes, there is less aerodynamic dampening. Since there is less dampening, the a/c will be "easier" to accelerate up/down, and so it will reach its design limit load factor sooner than it would if it were at a lower altitude where the effects of dampening are greater. So, I'd imagine that Va would be lower at higher altitudes.

Any comments? Thanks in advance!

Mad (Flt) Scientist
6th May 2006, 19:27
Well, if you express Va in EAS it all takes care of itself anyway.

If you work in CAS or IAS you'll have some corrections to apply, but they aren't huge, and since Va isn't a critical operational number for most people I'd bet any published value in IAS or CAS is just the most conservative correction for the EAS value for the range of altitudes that matter.