A question for jet boys and girls
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Join Date: Sep 2002
Location: Australia
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A question for jet boys and girls
This is a question I have been wondering about for quite some time, Sometimes while im flying and listening to ML/BN centre frequencies I hear the controller give a requirement such as "Virgin/Qantas/Jetstar 123, requirement to Cross waypoint X at time X"
Is this time requirement programmable into the FMC's of jets or is it a case of working out how much speed you need to gain/lose to meet the requirement in your head.
Cheers!
Is this time requirement programmable into the FMC's of jets or is it a case of working out how much speed you need to gain/lose to meet the requirement in your head.
Cheers!
Join Date: Mar 2000
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Not sure about other fleets but;
744 FMC Progress page 3, RTA (Req Time of Arrival). Just punch in the waypoint and time Zulu followed by nothing (exact time), 'A' (At or after) or 'B' (By or before) and there ya go! The page will generate the required Mach or IAS and you either let VNAV fly the speed you just executed or manually control the autothrottle.
744 FMC Progress page 3, RTA (Req Time of Arrival). Just punch in the waypoint and time Zulu followed by nothing (exact time), 'A' (At or after) or 'B' (By or before) and there ya go! The page will generate the required Mach or IAS and you either let VNAV fly the speed you just executed or manually control the autothrottle.
Nunc est bibendum
767 can't work like the 744 and just tell the a/c what time you want to be there. We need to crunch the numbers ourselves to programme a descent speed which will meet the required time of arrival. We do this by plugging in a mix of cruise and descent speeds which show on the FMC as the required arrival time. With experience you work out that you can lose two minutes by going from a 300 knot descent (which we don't do anymore) to a 250 knot descent. More than that requires a slower cruise speed.
Depending on when they let you know, you can lose up to five or six minutes without too many dramas. Much more than that and the ATCO will have to do some work with vectors.
Depending on when they let you know, you can lose up to five or six minutes without too many dramas. Much more than that and the ATCO will have to do some work with vectors.
quick ROT to get you started before jumping in to the FMC (if you have one),
for every second to lose or gain, change your G/S by the same amount and hold for 6 mins; or 1/2 the change for 12 mins and so on.
for every second to lose or gain, change your G/S by the same amount and hold for 6 mins; or 1/2 the change for 12 mins and so on.
Join Date: Aug 2002
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767 can't work like the 744 and just tell the a/c what time you want to be there.
I gave a B767 a 2 minute lose the other day from 200+ before the 'feeder fix' and they said, couldn't do it; I thought to myself, what a crock, at 250IAS on the drop you'll be late. It's all becoming clear...
Of course me being beligerant (infered by pilot) at the time; busy with the sequence I vectored and then gave 300IAS and had a lovely string of dots each going 300IAS after 6 got vectored; but no missed gap in a sequence of 13 jets.
PS, the A332's get way too slow and low for a practical sequence; had one at 300IAS 80NM from touch getting 'killed' by a 737 nearly 12000 feet higher at 250IAS at 105NM from touch. Poor 737 and subsequent sequencies had to be vectored to keep the gaps.
