Capn. B
I started to respond but finger trouble and other activities got in the way. Chesty has partly covered what I intended.
Your claim that, in FLCH you have no control over V/S is totally erroneous. In FLCH you have total control over V/S, but not as “a set and forget”.
On a short descent (2-2.5 minutes rings a bell, but I would not swear to it), the auto throttle will reduce to accommodate as far back as idle. Once it gets to idle, or if the descent is going to be for a longer period, the auto throttle, as designated on the FMA, will go into HOLD. This means “I can no longer achieve what you want with my limited parameters, you sort it out and I will stay in standby” i.e. “your thrust levers”. When approaching the selected altitude, the autopilot will raise the nose in an ALT CAP mode and the auto throttle will wake up and set the appropriate power for the selected airspeed.
During the descent, which will have the IAS nailed, you may vary the ROD by use of ; increased speed if you have no limitations or by increased drag from the boards if you are speed limited.
I reiterate, you have total control of both airspeed and V/S, but you have to control it, no fancy dial to set.There are many places outside the free open spaces of Western Australia, where speed control is paramount. Places where if you fail to adhere to speed restrictions you will massively screw up the traffic flow. c.f. LAX “reduce to 210 knots THEN descend to……….”
Try running over designated speed into any one of dozens of busy places and you run the risk of immediate sanctions, such as spitting you out into a hold.
Speed in a lot of places is paramount. But that all relates to my first post.
You claim that my second post is indefensible and “a stupid idea period”.
As you don’t identify which you think is indefensible lets look at it point by point.
Why would you reset to missed approach altitude before you have captured G/S?
Well, why would you? If you have a clearance to an altitude, and a clearance to conduct the ILS, the altitude is a hard limit until you have established on the G/S. Is it not a prudent thing to do, to set the limiting altitude until that limit is removed by intercepting the G/S? If you don’t there is a possibility that you will bust the altitude restriction. I reckon there is a pretty good chance that your FCOM will tell you that this is the way to do it.
Why would you ignore the flight director without making some compensation for what is inevitable?
If you want to go manual fine, I would encourage it, (too much reliance on misunderstood automatics). But once off auto, for pity’s sake fly the aeroplane. If the Flight director is giving a cue, why not assess it as a valid data input, to be assessed along with all other inputs. There are occasions when it is valid and appropriate to look through the F/D but in doing so you must keep situational awareness, when the F/D says to you “you are not doing what you asked me to do” do you really want to go down this path’?
Why would you not invoke airmanship and awareness?
Another indefensible statement???
Is it not a reasonable assumption that, before disengaging the autopilot, the brain should be engaged?
Indefensible ? As Mr McEnroe said “you cannot be serious.
The problems with automatics arise when people try to do things differently to that which was designed, and/or, do things with little or no understanding of how it works.
For a lot of that, our training organisations and regulators must take a lot of the blame.The good part of it all is that in most circumstances, if you follow the FCOM you will be safe.
But you already know that so why the aggressive response.
BTW, do you still have an IAS hold on the 717? Genuine question.
Maui