[luuckyy]

Ok,
if your aileron isn't properly aligned to any axis (I suppose this is the case) :

Hoping you know the distance you want between your axis vertices and the end line vertices (left and right ones).
Duplicate and extrude one of the right half circle triangle by normal by that distance ; you now have a vertice (the one from the extruded triangle that is aligned to your right axis vertice) at the exact location where your right end line vertice should be, so you just have to move it there (use the "move to" function), and delete the extruded object. Same applies for the left side.

HTH.