Mad (flt)scientist's observations concerning stick shaker trigger margins are quite correct.Stick shakers were introduced because some early jet transport wing sections produced little or no natural aerodynamic buffet prior to the stall and artificial warning became necessary. The stick pusher was introduced on some types, which lacked a natural pitch down at the stall, as a back up to the shaker. On highly swept wing, T-tail jets, where delayed pilot reaction to stick shaker warning could, due to pitch dynamics, let the aircraft enter a high attitude stall from which recovery was not possible, the pusher was essential. This was due to the disturbed airflow from the stalled wing causing loss of airflow over the tailplane and considerably reducing its effectiveness. As previously mentioned, A BAC 1-11 was lost due to this and also Trident G-ARPY during pre-delivery flight test. In the late 60's there we had no true flight simulator for the Trident, so all type rating exercises were flown on the real aircraft.Stall recoveries were always made at the stick shake, with no reliance on the pusher and there was an additional non-standard AoA indicator fitted to help avoid reaching critical pitch angles.