Originally Posted by
HarryC
Not so, the rudder causes the same roll response no matter which way up the plane! You can, and I have often, fly a 3 channel model doing inverted circuits and the rudder behaves the same, right rudder means roll right. If the rudder's roll effect reversed at negative AoA then it would also reverse when upright and pushing well forward on the stick. Dihedral effect works the same whether AoA is +ve or -ve.
Think it through.. Apply left rudder and hold left rudder deflected.
Now freeze the plane inverted. When the plane is inverted and has negative G - (that is the key - negative G) the rudder is pointing to the right side (viewed externally)
Another way to think about it.. If you built a plane with a rudder underneath and an anhedral wing.. and you flew that aircraft normally.
Applying left rudder in this plane the rudder would move to the left. viewed externally.
But in our inverted scenario, the rudder was left (viewed externally, when upright, but when inverted, it is now deflected right, viewed externally) There is a difference.