Originally Posted by
LEOCh
[...] FAA 25.203 describes (and forbids) what can happen to an aircraft loaded to static instability in the stall, the tail operating at higher AoA stalling before the wing causing pitch up.
No, not at all. This has nothing to do with the tailplane stalling under positive lift. If the tailplane were so heavily loaded (with an inconceivably far rearward CoG) that it might be close to stall under positive lift, the aircraft would be completely uncontrollable, and not be able to even start any certification tests. Or even take off, for that matter.
What is the most common reason for aircraft to pitch up during the stall is that swept wings tend to stall first at the wing tips, which are further aft than the wing roots, increasing pitch up moment. It is a common trait of many modern highly refined and efficient transonic wings.
Unless it was designed by Dr. William Christmas (look up "Christmas Bullet"), it is inconceivable that an aircraft would be built which, even under the most adverse weight and balance configurations and then some, would have a positively highly loaded tailplane. The only situation, in which a tailplane can stall is in severe icing or with an unbelievably forward CoG at low speeds and violent pitch-up maneuvers (early Cessna 177 Cardinal models suffered from that), and then it would stall under
downward "lift", result in an aircraft nose-
down moment.
Bernd