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Eobt and taxi time

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Eobt and taxi time

Old 23rd Apr 2019, 10:28
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Eobt and taxi time

Greetings.
I was part of a discussion regarding the window of an a/c to depart +-15 from EOBT and a longer taxi time than that window.
The main concern issued was what if the a/c starts at eobt and taxi time to said runway due to meteo and traffic is 20 mins. Normally a delay shall be issued (?) because it's impossible to depart in those 15 mins, but what if a SAM comes due to that delay?
I read in the ATFCM user manual that TRS from that airport will prevent SRM and SAM to come, but the TRS is a limited time window, what happens next?
How do AO at much busier airports with taxi times of 40 minutes due to traffic handle this? I can't believe you are number X for departure and get a SAM at some point because you got issued a delay.

Thanks for the help.
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Old 26th Apr 2019, 17:46
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For each airport there is a parameter TAXITIME . A flight without a slot if supposed to take off at EOBT+TAXITIME +-15 MIN . If it does not make it then a FLS message is sent. TAXITIME is set by ATC and does not concern the operators. An AO at a busy airport will file its plan with a EOBT which indicates that the plane is ready . CFMU computes the actual takeoff time taking in account TAXITIME. The delay message is only concerned with EOBT , not with what happens after startup.
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Old 26th Apr 2019, 17:57
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Originally Posted by cavver View Post
For each airport there is a parameter TAXITIME . A flight without a slot if supposed to take off at EOBT+TAXITIME +-15 MIN . If it does not make it then a FLS message is sent. TAXITIME is set by ATC and does not concern the operators. An AO at a busy airport will file its plan with a EOBT which indicates that the plane is ready . CFMU computes the actual takeoff time taking in account TAXITIME. The delay message is only concerned with EOBT , not with what happens after startup.
Thanks for the reply. I did read about taxitime also and that if needed, atco can change it according to the needs. But do atcos at very busy airports do that for every flight?
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Old 26th Apr 2019, 21:52
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TAXITIME is set for all flights. In case of a SLOT , when sending a ready message a different TAXITIME can be set. I do not work at a large airport so I cannot be sure what happens there , but an incentive ( slot adherence reports ) exists for ATC to set the correct global TAXI TIME in order not to give takeoff clearance out of CTOT interval.
The burden to be ready at EOBT stands with AO/ground ; the burden to get the aircraft airborne after startup in the correct time interval stands with ATC. Each has its own job .
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Old 27th Apr 2019, 05:08
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just a little clarification

Just a little clarification, if you are not yet airborne at ETOT (Estimated TakeOff Time) +16 , (where ETOT=EOBT + Taxi Time) the flight will be not suspended yet. The FAM (Flight Activation Monitoring) procedure start at 25 minutes after ETOT. from 1st of may wil be reduced to 20 minutes. Then recapping and considering us operating after 1st of may if you have an eobt 10.00Z and an airport taxitime of 10' you will be suspnded at EOBT + Taxitime + 20 = 1030z. Eurocontrol reduced the FAM windows from 30'to 20'in approximately 1 year (or little more) to avoid the situation of Flight/aircraft living in a "limbo"between needing a delay (after 15 minutes of ETOT) and not being suspended. now this period of time is reduced to 5 minutes.
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Old 27th Apr 2019, 06:03
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Originally Posted by elafrican View Post
Thanks for the reply. I did read about taxitime also and that if needed, atco can change it according to the needs. But do atcos at very busy airports do that for every flight?
Yes. When sending a RDY message we always send RDY + X minutes, where the X minutes is assessed on the basis of the predicted time that it will take at that particular moment to go from pushback to holding point.
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Old 27th Apr 2019, 06:18
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Originally Posted by redpassion View Post
Just a little clarification, if you are not yet airborne at ETOT (Estimated TakeOff Time) +16 , (where ETOT=EOBT + Taxi Time) the flight will be not suspended yet. The FAM (Flight Activation Monitoring) procedure start at 25 minutes after ETOT. from 1st of may wil be reduced to 20 minutes. Then recapping and considering us operating after 1st of may if you have an eobt 10.00Z and an airport taxitime of 10' you will be suspnded at EOBT + Taxitime + 20 = 1030z. Eurocontrol reduced the FAM windows from 30'to 20'in approximately 1 year (or little more) to avoid the situation of Flight/aircraft living in a "limbo"between needing a delay (after 15 minutes of ETOT) and not being suspended. now this period of time is reduced to 5 minutes.
But from Autumn 2019 it will be 15 mins insead of 20 and during winter for example, the taxitime for the runway furthest from the apron is 20 mins, but it's a first I hear about suspension from ETOT and not EOBT. Everything I read said from EOBT (i just looked at an internal announcement that its 20 mins from May and it says EOBT). I also read that a flight must take off 15 mins after EOBT (regardless of that FAM parameter), but don't quote me on that yet, I'll read up again today and paste it here, maybe I misread.
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Old 29th Apr 2019, 12:22
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Originally Posted by elafrican View Post
Greetings.
I was part of a discussion regarding the window of an a/c to depart +-15 from EOBT and a longer taxi time than that window.
The main concern issued was what if the a/c starts at eobt and taxi time to said runway due to meteo and traffic is 20 mins. Normally a delay shall be issued (?) because it's impossible to depart in those 15 mins, but what if a SAM comes due to that delay?
I read in the ATFCM user manual that TRS from that airport will prevent SRM and SAM to come, but the TRS is a limited time window, what happens next?
How do AO at much busier airports with taxi times of 40 minutes due to traffic handle this? I can't believe you are number X for departure and get a SAM at some point because you got issued a delay.

Thanks for the help.
Sorry but I am a bit confused. Should a/c start or depart in tolerans time +-15 according to EOBT? I am mentioning a flight without a slot.
For example:
EOBT: 10:00
Taxi Time: 10 minutes
1. A/C would start at 09:35 (EOBT-15-Taxi time)
2. A/C would start at 09:45 (EOBT-15)

Which one is true?

Last edited by oneo; 29th Apr 2019 at 12:23. Reason: Missed writing
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Old 29th Apr 2019, 14:49
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Aircraft should not start outside EOBT +/-15, BUT that still leaves a very wide range of take-off times. One day you could start within tolerance, taxi and be airborne in 5 mins ie EOBT-10, another day it could at the end of tolerance with a long queue at the runway and realistically be airborne at EOBT+45. ATFM thus has a possible airborne window of 55 minutes from which they need to model en-route airspace capacity. This is why the push for more predictability, networked airports and more accurate planned take-off times. Slow progress, but progress is there.
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Old 3rd May 2019, 09:48
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Join Date: Dec 2016
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Thanks a lot Dan Dare.
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