737-800 A/P disconnection
Thread Starter
Joined: Jun 2002
Posts: 3
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From: Wor Yerm
737-800 A/P disconnection
I have searched, maybe not long enough, but I'll still ask anyway. What are the events that would trigger an automatic A/P disconnection in flight, ie. one NOT commanded by either pilot?
Thanks in advance.
PM
Thanks in advance.
PM
Joined: Mar 2004
Posts: 470
Likes: 0
From: Oxfordshire
I'm not familiar with the 737 but in general there are a host of things which will cause auto disonnect, here's some from the top of my head:
AP reaching it's authority limit
Computer failure
System failure (feedback from servo's etc)
Hydraulic system failure
Manual input to stick (possible involuntary input by leaning on it)
Bus failure
Transient gremlins!
AP reaching it's authority limit
Computer failure
System failure (feedback from servo's etc)
Hydraulic system failure
Manual input to stick (possible involuntary input by leaning on it)
Bus failure
Transient gremlins!
Joined: Jan 2010
Posts: 132
Likes: 0
From: The moon
I had a strange incident a few months back in the -800. We were in the descent somewhere in the FL200's with the speed brake fully extended at flight detent. As I slowly retracted the speed brake while we were in a shallow enough turn the autopilot disconnected, then the aircraft banked to 40 degrees and we got the 'Bank Angle' warning. I would guess that with the speed brake not fully retracted it caused the high roll rate, just as the book says however it was still a bit frightening as the aircraft really snaps into the roll. Another theory is that it was a strange aircraft as we had a generator failure on the next flight
Joined: Apr 2008
Posts: 111
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From: Sand on the Rocks !
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.
• 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.
