Originally Posted by
John Citizen
The bus actually has an RTA function which works quite well in my opinion. (Within 30 seconds, and designed to keep you within 30 seconds I think).
However you often have to tweak it during descent if you really want to meet the exact time.
This is not a system flaw but perhaps just because the descent winds might be different to forecast.
Also once on descent, the FMS gives priority to maintaining descent profile compared to meeting a fix at a certain time.
I have flown with old school pilots who openly crunch numbers on the way down (ground speeds, time and distance, miles per minute etc ..without a calculator or a whizz wheel....geeze they really are so smart) as they think out aloud (or to show me how smart they can be be without the FMS) but it really is not necessary.
The people who say it (the RTA function) doesn't work just don't know how to use it.
Fair enough, whatever works best for you.
The RTA is okay for giving you an indication of what’s required without letting it do the job. However it’ll bring you right back to green dot if you let it take over which sometimes isn’t appropriate. Especially in a smaller airbus with higher wing loading. Not so critical in the bigger ones. I use the RTA with a selected speed to initially see what it will require in the cruise. Then I’ll select that plus 10 knots and work the rest out with descent speeds.
It it really is a piece of cake. If you can’t make the time at this point, you advise ATC and they give you vectors. Or you drop to a lower level and slow up. Green dot is a knot higher for every 1000 feet over 20. So you can get some good speed reductions down low. Especially east bound out of the jet.
Anyway, stick with it son.