Comment regarding the Rolling Harrier
The descprition above is good I just want to qualify one thing. Adding the control inputs early
(feed in left rudder and about the same time down elevator )
works, actually the next input is more early than at about the same time, to do a rolling harrier circle. Effectively what is happening is the rudder and elevator are alternating duties. 1/2 of the time the elevator is acting as the rudder and vice versa.
Too Add.
Straight Line Rolling Hariers are similar but the control inputs have to be timed better so that you DO NOT input early or late. You have to hit the rudder/elevator inputs spot on to keep the airplaen going in a straight line. For me straight line rolling harriers were the most difficult of all to learn.