Ok ....pitch main control is the elevator(you use the control column).
Stabiliser is used by automatics or manual to relieve force on the elevator.
Stabiliser is used by the speed trim system to allow speed stability and elevator is used at higher mach number for speed stability and avoid mach tuck.
The stabiliser is the back up for elevator jam,elevator is back up for stabiliser jam.
Easy no?
Dont over trim is the main point,thrust can be used to reduce load,and avoid over trimming.
Some system helps the trimming (STS)and during every t/o ,a nose down trim,to force pilots to trim up at a certain height(about 400 feet or so)just in case an engine fails,so aircraft is a nose up trim.(system is part of mach trim).
Once again,go arounds require very little trimming and so do any other maneuver..flying manually needs also only very few clicks on the stabtrim here and there,normally while banking,1 or 2 clicks NU or when selecting flaps,intially would require nose down,(lift increase),but manul elevator enough,then when stable in speed,1 or 2 click of NU.
Selectionof flaps 40 for example on AP will command a significant trimming about 3 secs or so because the AP is reacting to drag and speed decay,pitching the ND, while on manual flight, not reducing thrust as much as the automatics would before/during selecting flaps 40,would require much less stab trim.
Pilots know in advance what will happen based on their input,,AP are only REACTING to an input.
Last edited by de facto; 29th Mar 2016 at 13:45.