When talking about stall, we must remember that not only the wings can =
stall. The stabilizer can also stall, and because it normally produces =
negative lift, the result will be stabilizer up - nose down. Nasty !  A =
common cause of stabilizer stall is ice buildup on the stab. The effects =
of that ice are often not obvious until you extend flaps or something =
when you are about to land, with not enough altitude to recover... So =
don't extend flaps if you have ice on the stabilizer :-)

Deep stall is even more complicated. Often seen on jets with T-tail and =
all engines aft, like BAC 111, DC-9.  Wings go into stall, and the =
attack actually blocks the airflow around the stabilizer at the same =
time. With that engine placing there's no slipstream around the =
stabilizer either... and thus the elevator doesn't do what it is =
supposed to. Difficult to recover from. I think they crashed the first =
BAC111 prototype that way .

Regards

Attila - SM4RAN

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.