What is it exactly in the PF3 programming that triggers ATC to ask for the user a/c to start its descent? I thought it was always at the waypoint prior to the T/D, which is why I always try to find a waypoint close before and close after the TOD in my flight plan, but I am often asked to descend earlier.
The problem is, PF3's T/D and the aircraft's T/D do not always coincide; they can be many miles different. If I am still well short of the T/D and PF3 asks me to descend (and I do so), this can rather mess up a managed descent (where the a/c will respect all the waypoint speed constraints), as you are well below the T/D (i.e. cruise) altitude by the time you get there.
I seem to have the choice of either not descending when ATC tells me (unthinkable!!) and waiting until the a/c FMC shows me to be at the T/D before doing so, or just letting the a/c manage things when it finds itself a lot lower than expected when you start the managed descent (really talking about Airbuses here of course). Neither very satisfactory.
Ideally, you'd need to find a way of getting the PF3 T/D (where ATC gives descent instructions) as close as possible to the aircraft's calculated T/D, but since the a/c's calculated T/D isn't known until you are in the sim setting up the FMC, that's not really feasible I suppose.
What's the best way to set this up? Anything I can do in the waypoint altitude adjustment page?
Thanks.