De Facto,
I know it's not Boeing procedure but this is the tech forum and I wouldn't mind knowing why the difference, as opposed to just the pat answer of 'because it's not Boeing procedure'. I won't do anything other than that written in the QRH and I'm not suggesting we should. I would just like to know why one procedure has you disconnecting the A/T, whereas the other doesn't. In both cases the A/T system is working properly and in both cases you have the same pitch guidance on the FDs. I'm not going to lose sleep over not getting an answer but it came about because it's slightly relevant to this thread.
I suggest the argument for disengaging the A/T is because you don't want it doing strange things to you at an inopportune moment. You tell me I shouldn't be concerned if the automatics are working properly and that we don't disconnect the A/T in auto flight but do in manual flight because it's procedure. Hardly an answer to ponder as I hit F2 to get my gear down.
Finally you tell me I'm worried about G/A mode reducing thrust on me, suggesting I don't have a clue what I'm talking about. Fair enough with your assessment of my knowledge but let's take a possible scenario: you're happily established on an ILS at 1000' with all the automatics in and a missed approach altitude of, say, 4000' in the MCP. Up pops Windshear, so you do your stuff. I say you press the TOGA buttons once because the windshear logic will give you max N1, you say twice. I won't argue at this point because we've got a windshear warning, so go ahead and press it as many times as you like and back into the sky we go. We're climbing at a hefty rate; max N1 and 15 degs nose up and what happens next? Even though we're only at 3000' we're climbing quickly and Alt Cap. The speed window is open at your present speed. Ahhh, says Mr A/T I'll drag back the thrust to keep the speed, even though we've still got 1000' until that MCP alt. Now, I would suggest I don't want the A/T reducing power on me during a windshear escape manoeuvre but you're saying it's Boeing procedure that we don't disengage the A/T in auto flight. I know it is but why, especially as this wouldn't happen in manual flight?
Am I worried? No. Despite your suggestion that my system knowledge is sadly lacking, can I conceive a realistic scenario where the QRH actions could mean more, unnecessary, work for me on the day? I think I can.
Sadly, the modern Boeing 'tech' manuals are sorely lacking detail and rather economical in the way they are written. I've looked in the books for my Boeing types and none of them make specific reference to the way in which the A/T functions in a windshear G/A situation. I accept 100% the way in which it works normally, with 1 or 2 presses of the buttons but it is only through empirical evidence that I can write about the differences in G/A logic.
I've just got off the phone to a trainer mate of mine. Now, it could be that we're both wrong and, without getting in the sim, we're not going to be guaranteed the absolute, no s%4*t, 100% truth but he has suggested the same as me i.e. that the windshear warning being generated changes the logic of the G/A and 1 press will give max N1. The QRH doesn't help because it only talks about ensuring 'GA power' is set, rather than max GA but this is the same script for all the Boeings in my logbook, so rather unspecific.
Anyone going to the sim soon?