737NG a/p disengagement techniques
Thread Starter
Joined: Mar 2012
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From: Europe
737NG a/p disengagement techniques
Hello to everyone!
This morning I was preparing our A320 sim for training and peeked into the cockpit of the 737NG where students were already flying. I saw a student disengage the A/P by pressing the CMD button and the CFI yelling at him that this was not a proper technique. I've heard of it many times, I understand that when you want to transition to manual flight, pressing the yoke A/P disc button is a better idea overall, but I decided to see what Mr. Boeing had to say. Having looked through FCOM and FCTM I couldn't really find any recommendation on this. There are instructions on how the A/P can technically be disconnected, but are there any recommendations on how to properly do this that I have overlooked? The only place I remember as a credible source is the 737 CBT. There, yes, it was mentioned that the proper technique is the yoke button, the disc bar is not the common way, but any docs?
Besides, is it really possible to disconnect A/P on a real 737 by pressing the CMD button for the second time? I realised I've never tried. FCOM doesn't list such a function in the description of the button.
This morning I was preparing our A320 sim for training and peeked into the cockpit of the 737NG where students were already flying. I saw a student disengage the A/P by pressing the CMD button and the CFI yelling at him that this was not a proper technique. I've heard of it many times, I understand that when you want to transition to manual flight, pressing the yoke A/P disc button is a better idea overall, but I decided to see what Mr. Boeing had to say. Having looked through FCOM and FCTM I couldn't really find any recommendation on this. There are instructions on how the A/P can technically be disconnected, but are there any recommendations on how to properly do this that I have overlooked? The only place I remember as a credible source is the 737 CBT. There, yes, it was mentioned that the proper technique is the yoke button, the disc bar is not the common way, but any docs?
Besides, is it really possible to disconnect A/P on a real 737 by pressing the CMD button for the second time? I realised I've never tried. FCOM doesn't list such a function in the description of the button.
Joined: Jan 2006
Aviation Qualifications: CPL
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From: Between a rock and a hard place
Besides, is it really possible to disconnect A/P on a real 737 by pressing the CMD button for the second time? I realised I've never tried. FCOM doesn't list such a function in the description of the button.
Joined: Mar 2001
Posts: 4,562
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From: I wouldn't know.
I started flying on 737-300/500s which had already the AP/CWS buttons and the disengage bar. Using that one could leave it in a position where it was ever so slightly displaced and prevented any autopilot engagement without it being an obviously visible cause. Therefore it was drilled into us not to use the MCP disengagement bar. The resulting mode confusion and then the resulting confusion why the autopilot was not working was simply too distracting for many pilots.
The NG initially had a similar setup until it was replaced by the updated MCP with a disengagement button instead of the bar that had to be pushed downwards. Of course, using the CMD buttons a second was always possible, but not used as a standard method either.
The NG initially had a similar setup until it was replaced by the updated MCP with a disengagement button instead of the bar that had to be pushed downwards. Of course, using the CMD buttons a second was always possible, but not used as a standard method either.
Thread Starter
Joined: Mar 2012
Posts: 9
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From: Europe
This is quite a surprise for me since every NG I've seen had the bar. However, as you say, I was taught that this bar was to be used only when other means haven't worked. I can see your point regarding the rest.
Joined: Apr 2004
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From: Planet Earth
Not flown the 737 but spent a couple of decades operating the 727, MD80, 757 and 767
Not sure why you’d ever want to disconnect the AP with the MCP switch, you really want to be holding the yoke and looking at the attitude indicator when you disconnect, and the yoke mounted disconnect switch makes that as easy as possible
Thats why it’s there, using the MCP switch would be an unnecessary distraction
Joined: Mar 2001
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From: I wouldn't know.
Joined: May 2002
Posts: 266
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From: U.K.
I agree that using the MCP button is in the ‘why would you want to?’ category and deliberately using the trim to disconnect isn’t a good practice. Either technique would probably be questioned, both on line or in the sim.
Re the disconnect bar, the -800’s I fly (mix of older NG’s and almost new) all have the bar. I seem to remember an internal report that a crew couldn’t engage the autopilot until they pushed the bar, which was fractionally out of place.
Anyway, heres one from a zoomed in bit of a photo I took a few months ago.
Re the disconnect bar, the -800’s I fly (mix of older NG’s and almost new) all have the bar. I seem to remember an internal report that a crew couldn’t engage the autopilot until they pushed the bar, which was fractionally out of place.
Anyway, heres one from a zoomed in bit of a photo I took a few months ago.
Joined: Feb 2000
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From: It's a secret
Hello to everyone!
This morning I was preparing our A320 sim for training and peeked into the cockpit of the 737NG where students were already flying. I saw a student disengage the A/P by pressing the CMD button and the CFI yelling at him that this was not a proper technique. I've heard of it many times, I understand that when you want to transition to manual flight, pressing the yoke A/P disc button is a better idea overall, but I decided to see what Mr. Boeing had to say. Having looked through FCOM and FCTM I couldn't really find any recommendation on this. There are instructions on how the A/P can technically be disconnected, but are there any recommendations on how to properly do this that I have overlooked? The only place I remember as a credible source is the 737 CBT. There, yes, it was mentioned that the proper technique is the yoke button, the disc bar is not the common way, but any docs?
Besides, is it really possible to disconnect A/P on a real 737 by pressing the CMD button for the second time? I realised I've never tried. FCOM doesn't list such a function in the description of the button.
This morning I was preparing our A320 sim for training and peeked into the cockpit of the 737NG where students were already flying. I saw a student disengage the A/P by pressing the CMD button and the CFI yelling at him that this was not a proper technique. I've heard of it many times, I understand that when you want to transition to manual flight, pressing the yoke A/P disc button is a better idea overall, but I decided to see what Mr. Boeing had to say. Having looked through FCOM and FCTM I couldn't really find any recommendation on this. There are instructions on how the A/P can technically be disconnected, but are there any recommendations on how to properly do this that I have overlooked? The only place I remember as a credible source is the 737 CBT. There, yes, it was mentioned that the proper technique is the yoke button, the disc bar is not the common way, but any docs?
Besides, is it really possible to disconnect A/P on a real 737 by pressing the CMD button for the second time? I realised I've never tried. FCOM doesn't list such a function in the description of the button.
