I just did a turn round a walk back to edit post because I am talking rubbish.
I was trying to say that because the Elevator is sitting in relatively stable flow of air and that it is attached to not the worlds greatest trim system. It can be upset relatively easily compared to lower types with all the prop wash.
It could be completely the oppersite to what i originally said and its actually the low pressure on the rudder face which is sucking the elevator down. I suppose it could still be air migrating just depends on where the elevator pivot point is in relation to the air movement.
And to answer the question on what you term conventional tail plane the wash from the prop is going alot faster than the arflow over the wing, think about that picture in thom of the big arrows wrapping around the plane. This supplys a constant source of energised air. Means you can do short field takeoffs, grass field or act the idiot lifting the nose wheel up at relatively low air speeds. Where as in the tommy and other t planes you cant really lift the nose until you have enough airspeed which maybe 30 knots more than a pa28.
And the reason for the span migration of air along the rudder just think of the rudder as a swept wing some will have it more than others depending on there profile etc. You can see the vortex's spilling off the tip the fin of large jets in the right conditions
Last edited by tescoapp; 5th Nov 2007 at 09:05.