Chesty Morgan
Bsieker, if the Q400 wasn't prone to deep stalls then would it still be fitted with a stick pusher?
To prevent a "normal" stall, obviously. That's bad enough already. The difference is that you can recover relatively easily and quickly from a normal stall, whereas recovery from a deep stall, if possible at all, requires patience, a lot of experience and a huge lot of altitude.
I recommend again "Handling the Big Jets" to understand "Stall" vs. "Deep Stall":
Amazon.com: Handling the Big Jets: An Explanation of the Significant Difference in Flying Qualities Between Jet Transport Aeroplanes and Piston Engined Transpor: David P. Davies: Books
[EDIT: nonsense deleted.]
Bernd