Adverse Yaw

[philo beddoe]

Consider the roll rate. Yes, there is arguably an upward component of relative wind as the wing lowers, which does increase angle of attack slightly, but the effect should be negligible.

Consider a point 10 ft out on the wing. The aircraft rolls into a 30 deg bank in the space of 5 seconds, for sake of argument.

The 10 ft reference point has traveled approximately 5 ft. (10x sin(30))
Yes, trig experts, I know that I should use the arc segment formula, but this is close enough.

The 10 ft point of the wing therefore travels 5 ft in 5 sec. = 1 ft per sec. This is around 1/2 knot. [Someone check my math here, just in case.] Vector addition gives us a .2 degree change in angle of attack.

 

[philo beddoe]

This profile drag increases on both wings when the ailerons are deflected, but the increase is equal when the ailerons are deflected by the same amount.

Not to be too picky, but wouldn't this only be true for a perfectly symmetric airfoil/aileron combination flying at relatively low angle of attack?

Wouldn't localized airflow also conspire to make profile drag slightly less than perfectly equal? I'm sure it is negligible, though.

 

[siucavflight]

You are correct. It would be more of a factor on a perfectly symetrical airfoil. But it still does come into play on any wing of any shape or size, just not as much of a factor.