# Why don't rudders stall at 30 deg deflection, as they don't have downwash to reduce local AOA like flaps and horizontal tails do?

Why don't rudders stall at 30 deg deflection, as they don't have downwash to reduce local AOA like flaps and horizontal tails do?

or do they?

I understand flaps and horizontal tails don't stall at 30 deg deflection as the downwash from the wing reduces the local Angle of Attack, so flaps and horizontal tails aren't seeing an angle of attack of 30 deg even though they are deflected by 30 deg.

However, there is no "vertical downwash" from the wing to help the rudder. Why don't rudders stall at 30 deg deflection when most classic NACA airfoils stall at about 15-20 deg?

• It's just a wing sticking up, so there is a "sidewash" no? Same thing pretty much. Aug 28 '19 at 0:10
• @Fred - Are you sure they don't? Aug 28 '19 at 0:27
• Are you talking about an all-moving vertical tail? Otherwise I don't see what AOA has to do with rudder deflection.
– JZYL
Aug 28 '19 at 5:49
• Why do you expect a trailing edge surface deflection to be comparable to the deflection of the entire airfoil? Aug 28 '19 at 5:50
• @RobertDiGiovanni not my point; a $30^o$ deflection of an aileron will not increase the $\alpha$ of the entire airfoil by anywhere near $30^o$, more like $15^o$ if the aileron takes about half the chord (for small angles, etc). Aug 28 '19 at 7:29

Deflect the rudder relative to the vertical tail and there will be sideslip $$\beta$$. In the situation in the drawing: deflect the rudder to the left, and it will be in line with $$\beta$$ but will have a deflection relative to the vertical tail.