Originally Posted by
maui
FLCH cannot command a V/s
You make this point a few times and yes it's of course true... for the pitch channel. But we're talking about the throttle channel.
There is no potential interference there because the THR is out of it until some other input occurs viz Alt cap or physical intervention such as mode change. This is so ‘cos thrust is either at HOLD or full noise until an intervention. And it will be telling you that with HOLD or THR annunciations on the FMA.
If we're descending and it's in HOLD, then it's not in THR (other than the transient few seconds it's pulling back to HOLD) so there's no question of how it acts in THR. Clearly, the question of how it acts in THR is only meaningful when we're in in that mode (i.e., climbing).
If climbing outside of 125 seconds then yes it's in full noise. Inside of 125 seconds, the FCOM's "THR - The autothrottle applies thrust to maintain the vertical speed required by the pitch mode" seems to apply, and in doing so contradicts your categorical "the THR will not respond because it is on the limit set by FLCH and it is thinking about getting to altitude, not how rapidly it will get there."