Quote:
One effect of doing a low level turn is that your lower wing can be in air moving at a different speed to the air in which your upper wing is moving - due to wind shear. That can cause one wing to stall, followed by a spin and an impact with the ground.
I think I may now have seen it all........
It's real, though, doing the sums, probably not very big. There's a bigger effect due to the wings doing different speeds due to the geometry of the turn.
Take an aircraft with 20m wingspan doing 25 m/s (50kts) in a 45 degree turn.
Radius of turn = 63.7m (v^2/1.g = 25^2/9.81)
Difference in height between wingtips, and also difference in turn radius between wingtips = 20/1.4 = 14.3m
If we have a wind at height of 40 kts, and a 30% reduction across 300 ft due to the wind shear (4kts/100 ft or a little over 1 kt between the wing tips for our aircraft above). So not huge. But that 30% is representative of relatively flat smooth country. In rougher areas (mountains for example), it would be more.
However, the difference in turn radius between the upper wing and the lower wing is responsible for about 11 kts difference between the two tips (the top wing is doing a turn of radius 63.7+14.3/2 m in the same time as the lower one is doing a turn of radius 63.7-14.3/2 m).
So adding the two together if the aircraft is doing 50 kts, one tip can be doing 56 kts and the other 43 kts. That really is enough to make a difference.
Then into that, we can add gusts from various sources.
All of which says speed is your friend close to the ground (but it's still nothing to do with inertia).
Paul