Originally Posted by
Negan
FL210B means you want the aircraft to be at or below that altitude. You're basically telling VNAV you want s continuous descent as long as you're using VNAV. VNAV will calculate the profile for you to follow down and tell you if you're high or low on it.
Same goes for speed like usually we put 180B for speed inside the 10NM range of the airport and VNAV will calculate your slow down points and show you in the navigation display your decel points.
If you programme VNAV correctly it works really well for descent management and planning and doesn't require any mental math to be on profile like your 3 times altitude.
Usually I set 220 knots below for a downwind leg and 180 knots below for base and follow the VNAV profile down.
A magenta.bug will appear much like an ILS glideslope sort of to tell you how high or low you are on profile in descent.
Even if you're not using VNAV for descent you can still follow the pathing information if gives you, you don't need to be in VNAV for the path to be accurate.
It's always a good reference to use as long as you programmed the FMC correctly. You need to keep updating it if you're not in VNAV and updating your speed in the FMC if you're not following the speed you selected because if you have a path of 260 knots set and you're actually doing 300 knots in descent it's not accurate for you and can catch you out.
Always update your speed in the FMC if you're not following it for extended periods.
rubbish.
Refrain from reprogramming the fmc unless you get a new runway, star or waypoints below 10.000ft. or in congested airspace. Even as PM. Keep things simple. Type type type is poor airmanship In the Terminal area, and when I see this on linechecks, you will get a comment on it.
if you get a different speed, deal with it, do your mental maths, the vertical profile indicator will still give you your position compared to the original programmed path, and will continue to do so. Otherwise, learn to interpret the 3x rule, learn how to interpret the speed/altitude/distance for your type and get to know how your aircraft behaves using your instruments and maps, instead of overrelying on a computer.