The A/P automatically disengages when any of the following occurs:
• pushing either A/P disengage switch
• pushing either Takeoff/Go-around (TO/GA) switch with a single A/P
engaged in CWS or CMD;
• below 2000 feet RA or,
• with flaps not up or,
• G/S engaged
• pushing either Takeoff/Go-around (TO/GA) switch with a single A/P
engaged in CWS or CMD above 2000 feet RA with flaps not up or G/S
engaged.
• pushing either TO/GA switch after touchdown with both A/Ps engaged in
CMD
• pushing an illuminated A/P ENGAGE switch
• pushing the A/P DISENGAGE bar down
• activating either pilot’s control wheel trim switch
• moving the STAB TRIM AUTOPILOT cutout switch to CUTOUT
• either left or right IRS system failure or FAULT light illuminated
• loss of electrical power or a sensor input which prevents proper operation
of the engaged A/P and mode
• loss of respective hydraulic system pressure.
Note: Loss of the system A engine-driven hydraulic pump, and a heavy demand
on system A, may cause A/P A to disengage.
From FCOM Chapter 4