L says that at slow speed the yaw in the case of banking only with the aerilon can be so severe as to cause the plane to turn in the opposite direction. Has anyone been able to verify that?
Yes, can be. Needs to be an aircraft with more than the usual amount of adverse yaw, probably without differential ailerons. Several older types of glider exhibit this behavior, the slingsby tutor for example. The greater the aspect ratio the more noticeable this is, usually. One microlight I have flown will do this, the X-Air, and probably others. Anyone fly a luscombe here, I seem to remember a fairish amount of adverse yaw? You do need to be flying pretty near the stall to make this happen, though.
Backpacker, quite right
Even in a 60 degree, 2g steep turn at 100 knots the radius of the turn is still 125 meters. This is still less than 5% speed difference between the wingtips, and maybe 2.5% speed/lift difference across the whole wing.
Think about the airflow on the whole a/c. Unless you have a banana shaped fuselage there will be a sideways lift on the fin and rudder and of course the fuselage, which will have far more effect than the tiny speed difference between the wings. A very small number squared is still a very small number
