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.