Originally Posted by
PaulisHome
Meikleour
Yes. If the aircraft is moving from an airmass moving at one speed, to an airmass moving at another, then inertia is an issue in the sense that it will take time for the aircraft to accelerate to recover its desired airspeed. That's what happens as we go through wind shear on approach.
Where that doesn't happen is if the aircraft stays in one airmass, whatever speed it is moving at relative to the ground. It's fairly easy to do the sums to demonstrate this, and it doesn't matter which frame of reference you use, the result is the same, though the algebra is a little trickier in one case than the other.
The Bernoulli/Newton reference (for lift from a wing) is not really a good analogy. They are both ways of explaining lift that pilots use, but neither of which actually explain what's going on. (Listen to John Finnemore's Cabin Pressure for a very funny sketch on this). Newton's laws of motion are hugely accurate, at least until you get to relativistic speeds, and I don't believe we're built an aircraft like that yet.
I went back and read your comment. Don't know is the answer, although if this was happening during the descent that would be entirely reasonable since you can get different winds at different heights (and then see my first paragraph above).
Good points both - I stand corrected. Thinking more about it, I suspect that gusts are quite a big issue, particularly when air may not be moving horizontally, thus seriously modifying the AoA. And it's gustier closer to the ground. But you can see this effect in when thermaling a glider at a high angle of bank close to stalling speed - it's not uncommon to find the glider starting to auto-rotate as one wing hits an adverse gust. Easily fixed with some forward stick and opposite rudder, but you really need to be able to do it from feel.
cats_five
Sounds sensible. For those of us that do mountain flying it's entirely possible to be turning within a low few hundred feet of the ground in rather gusty conditions. But I think the key is if you'r going to put yourself in a position where a spin is possible (ie slow, gusty, turning), then being high enough to recover might be smart. So we do the low turns quickly.
You will need to turn finals a lot higher than 500' to be able to recover a spin.