Rear stabilisers produce lift not downforce
I heard a story that I'm still not sure I believe despite the fact I want to.
if you look at a stabiliser on most ac it is rigged at a positive angle of attack. It produces lift not downforce. The story instructors tell about downforce on the tail plane is a convenient way to explain longitudinal stability.
When we draw the lift weight couple it shows the net lift from both surfaces ( main and tail) together not separately. If you draw them separately the main lift is forward of the weight and the lift from the tail stabilises it.
I've never seen a diagram of this and it was so contrary to what I was taught I was in serious denial at the time. However I can't look at aircraft and see negative stabiliser pitch.
This came to me from David Schouler so I'm thinking there's some truth in it. However if I heard it wrong in a fug of classroom overload I apologise for bringing it up.
Anyone else heard this theory?