CTOT -5+10 ownership
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CTOT -5+10 ownership
Hi!
I recently had a discussion with a friend of mine who is a controller at a norwegian airport. The question at hand was with regard to a situation about a conflict that had come up, when an aircraft with CTOT was denied push from gate because he would not make his CTOT. The Captain argued that he was pushing from gate within his -5+10 min of his CTOT and should therefore be given his clearance. The controller argued that even though he was within his CTOT at gate he would not, because of airport congestion, be able to TOF within his CTOT limitation. We of course both agreed that a discussion over the RF should not have occured, but the discussion turned more towards who ownes the -5+10 minutes around the CTOT. My opinion is that this time is owned by the crew since everybody who has ever flown comercially know that blocking off exactly according to schedule or CTOT is not easy. There are simply too many factors to consider (Ground handling, traffic coordination, ATC + + + ). My friend argued that the time limit is for ATC to control with regard to other trafic at the airport, since the crew does not have the big picture on this traffic. But where can I find official information about this ?
Does anybody have an opinion on this ?
Best regards FJ
I recently had a discussion with a friend of mine who is a controller at a norwegian airport. The question at hand was with regard to a situation about a conflict that had come up, when an aircraft with CTOT was denied push from gate because he would not make his CTOT. The Captain argued that he was pushing from gate within his -5+10 min of his CTOT and should therefore be given his clearance. The controller argued that even though he was within his CTOT at gate he would not, because of airport congestion, be able to TOF within his CTOT limitation. We of course both agreed that a discussion over the RF should not have occured, but the discussion turned more towards who ownes the -5+10 minutes around the CTOT. My opinion is that this time is owned by the crew since everybody who has ever flown comercially know that blocking off exactly according to schedule or CTOT is not easy. There are simply too many factors to consider (Ground handling, traffic coordination, ATC + + + ). My friend argued that the time limit is for ATC to control with regard to other trafic at the airport, since the crew does not have the big picture on this traffic. But where can I find official information about this ?
Does anybody have an opinion on this ?
Best regards FJ
StandupfortheUlstermen
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From a UK persepctive, I'm not sure where you will find 'official information' on the subject, but all the ATCOs I know will tell you that the -5/+10 belongs to us for some of the reasons you have stated among others.
It's not easy for us to get an aircraft off the ground dead on time, so we are allowed a tolerance by flow to enable us to get the aircraft airborne. Crews know this but are reluctant, probably due to economic pressure, to delay flight plans in case they get a CTOT which can up to 3 hours later than their planned EOBT. However, this is not our fault, as we in ATC have to work within the rules. A handling agent (at least at the airport I work at) is responsible for informing the flight deck of any CTOT. The flight deck should then keep the handling agent informed if they can make the slot. If not, then the flight plan should be delayed.
We don't make the rules, but we have to stick to them.
It's not easy for us to get an aircraft off the ground dead on time, so we are allowed a tolerance by flow to enable us to get the aircraft airborne. Crews know this but are reluctant, probably due to economic pressure, to delay flight plans in case they get a CTOT which can up to 3 hours later than their planned EOBT. However, this is not our fault, as we in ATC have to work within the rules. A handling agent (at least at the airport I work at) is responsible for informing the flight deck of any CTOT. The flight deck should then keep the handling agent informed if they can make the slot. If not, then the flight plan should be delayed.
We don't make the rules, but we have to stick to them.
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Agree with Standard - CTOT is for the aircraft, -5/+10 is to give ATC some flexibility in how we sort them out (I've had 3 aircraft with the same CTOT before - it's down to me to decide in which order they go, not the pilots).
If it's patently obvious the aircraft won't make the tolerance then you have two options:
1) Aircraft has to file a DLA and then ATC / Handling send a ready to see if they can improve on any slot given.
2) ATC speak to the Flow man at the ATCC - sometimes you can get an extra 5 minutes on top (and sometimes you can't, in which case option (1) above applies)
(Top tip - DON'T file a DLA unless we ask you to - just in case we've got you that extra "5" on your previous plan & CTOT)
Don't forget - CTOT stands for Calculated Take Off Time - it's the airborne time that counts, not the time you push back from the gate. The Captain should have known this (it's hardly rocket science after all). I've had crews try the same thing with me, thinking they can push back, start, taxi and be airborne in 4 minutes (It takes about 8 where I work) and are obviously annoyed when they get told they won't with a grudging "I suppose you know better".
Them's the rules - learn them, abide by them.
If it's patently obvious the aircraft won't make the tolerance then you have two options:
1) Aircraft has to file a DLA and then ATC / Handling send a ready to see if they can improve on any slot given.
2) ATC speak to the Flow man at the ATCC - sometimes you can get an extra 5 minutes on top (and sometimes you can't, in which case option (1) above applies)
(Top tip - DON'T file a DLA unless we ask you to - just in case we've got you that extra "5" on your previous plan & CTOT)
Don't forget - CTOT stands for Calculated Take Off Time - it's the airborne time that counts, not the time you push back from the gate. The Captain should have known this (it's hardly rocket science after all). I've had crews try the same thing with me, thinking they can push back, start, taxi and be airborne in 4 minutes (It takes about 8 where I work) and are obviously annoyed when they get told they won't with a grudging "I suppose you know better".
Them's the rules - learn them, abide by them.
UK AIP ENR 1.9.7.2 says:
In order to comply with a CTOT, Aircraft Operators need to plan the departure of a flight so that the aircraft will be ready for start up in sufficient time to comply with a CTOT taking into account the taxi time shown in the Slot Allocation Message (SAM).
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All airports have a variable Taxi time allocated to them and any slot issued will take that into account. Taxi time = the time taken from EOBT to get to the runway, therefore the crew must request start accordingly to meet the CTOT.
The tolerance is solely there to assist ground controllers in getting that aircraft from A to B in times of peak demand/WIP on the airfield.
The tolerance is solely there to assist ground controllers in getting that aircraft from A to B in times of peak demand/WIP on the airfield.
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My opinion is that this time is owned by the crew since everybody who has ever flown comercially know that blocking off exactly according to schedule or CTOT is not easy.
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BOAC - I somehow doubt you will find a definitive list of Taxi-times anywhere. As I said before, they are variable and can change by the hour at some airports i.e AMS. The max permitted I believe is 40 minutes.
Standard time for most smaller airfields is 10 minutes but that goes up to 25 mins for larger/busier/more complex airfields i.e LHR/LGW etc
LGW for example has 20 mins as standard for runway 26 and 25 mins when 08 is in use.
Obviously not all aircraft will take that amount of time to taxi as it will depend on location of parking stand/weather/complexity/holding/wip etc, but it is a good average from which the CTOT will be based.
Example - XXX123 FILED EOBT 1200 from LGW means the earliest possible CTOT that can be allocated will be 1220 when on 08. This gives a zero delay. A CTOT of 1230 gives a 10 minute delay.
Standard time for most smaller airfields is 10 minutes but that goes up to 25 mins for larger/busier/more complex airfields i.e LHR/LGW etc
LGW for example has 20 mins as standard for runway 26 and 25 mins when 08 is in use.
Obviously not all aircraft will take that amount of time to taxi as it will depend on location of parking stand/weather/complexity/holding/wip etc, but it is a good average from which the CTOT will be based.
Example - XXX123 FILED EOBT 1200 from LGW means the earliest possible CTOT that can be allocated will be 1220 when on 08. This gives a zero delay. A CTOT of 1230 gives a 10 minute delay.
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QWERTY9
When I worked at Gatwick the taxi times were the same for both runways at 20 mins in the summer and reducing to 15 mins in the winter period. Therefore in your example the earliest slot available for a 1200 EOBT (should a slot be required) would be 1220 in the summer and 1215 in the winter. Giving ealiest time for departure of 1215 in the summer and 1210 in the winter.
When I worked at Gatwick the taxi times were the same for both runways at 20 mins in the summer and reducing to 15 mins in the winter period. Therefore in your example the earliest slot available for a 1200 EOBT (should a slot be required) would be 1220 in the summer and 1215 in the winter. Giving ealiest time for departure of 1215 in the summer and 1210 in the winter.
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SilentHandover - The LGW times changed a couple of months ago I think, to what I quoted before. I believe ??? it was partially to do with a section of taxiway which narrows directly adjacent the tower which can cause particular problems for certain aircraft types when taxiing to 08.
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QWERTY9 is correct with the new Gatwick taxi-times. 20mins for 26L and now 25 mins for 08R in the summer. I can't remember what was decided for the winter.
Rather than due to a narrow taxiway, it was suggested and agreed by ATC that when busy, especially in the summer, it was sometimes difficult to get a/c airborne before the end of the slot tolerance during 08R ops due to the length of taxi.
An extra 5 mins taxi time was therefore added, and seems to be working, with fewer slots missed.
It is also worth pointing out that even if a pilot calls ready for start at CTOT minus published taxi time, in busy traffic ATC will sometimes deny start due to congestion and request a DLA message to be sent.
Some of the more 'helpful' controllers will let pilots know when they request clearance that it is busy and give them a time they may need to be ready by to make good the slot.
Rather than due to a narrow taxiway, it was suggested and agreed by ATC that when busy, especially in the summer, it was sometimes difficult to get a/c airborne before the end of the slot tolerance during 08R ops due to the length of taxi.
An extra 5 mins taxi time was therefore added, and seems to be working, with fewer slots missed.
It is also worth pointing out that even if a pilot calls ready for start at CTOT minus published taxi time, in busy traffic ATC will sometimes deny start due to congestion and request a DLA message to be sent.
Some of the more 'helpful' controllers will let pilots know when they request clearance that it is busy and give them a time they may need to be ready by to make good the slot.
Taxi Times
http://www.cfmu.eurocontrol.int/cfmu...taxitimes.html
This Eurocontrol page gives the taxi times declared to CFMU
This Eurocontrol page gives the taxi times declared to CFMU
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Not only that - but if the slot ends in 20 mins and there is 21 mins of traffic at the holding point then there is no way the slot can be made, which may have been the case there.
And the -5+10mins is mine!!!!
louby
And the -5+10mins is mine!!!!
louby
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I've had crews try the same thing with me, thinking they can push back, start, taxy and be airborne in 4 minutes.