Originally Posted by
Midland63
So what assumptions as regards the portion of the flight over which it will be vectored does the FMC assume when calculating T/D? For example, do published approaches to airports say something like "anticipate vectors for X-Y track miles from waypoint ABCDE ..." or something like that?
Midland..they might do, they might also publish a full procedure to cater for a radio failure but as an example of the real world at places like Heathrow shortly after you've left one of the holds on a vector ATC will tell you your landing runway and tell you your track miles to run....that varies from one approach to another at LHR depending on how they are fitting you in with preceding or following traffic..
Some days you'll get a "snatch" other days you flog downwind for miles. LHR are also very keen on you flying a continuous descent pretty much from leaving the hold to touchdown for noise abatement reasons.....most folks I fly with stop using VNAV at or before entering the hold and switch to something like Vertical speed or Flight Level Change.
At other airports VNAV might well be appropriate until closer in.