CTOT -5+10 ownership

[Fokker-Jock]

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

[Standard Noise]

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.

[Chilli Monster]

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.

[Gonzo]

If an a/c doesn't call ready for push at or before COBT (CTOT minus the airfield taxi time), ATC are justified in holding it and waiting for a new slot.

[perusal]

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).

[QWERTY9]

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.

[BOAC]

Where - please, are these 'standard taxi times' published? It would be useful for us to know.

[Frunobulax]

They are shown in Slot Allocation Messages anytime you get one. Who calculates the taxitime - I have no idea.

[ElNino]

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.

It's not easy, but the -5,+10, while definitely "owned" by ATC, does give you a fairly flexible window. While an ATCO is perfectly justified in holding you on stand if you won't be airbourne by +10, obviously he/she's not if you would be. This +10 is of course so often the difference between staying or going. However, if you miss your slot, tough luck. Them's the rules.

[Gonzo]

The taxi-times are declared to CFMU by each airfield's ATC.

[QWERTY9]

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.

[SilentHandover]

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. :cool:

[Gonzo]

When I worked at Gatwick.......

I hope you haven't been saying that too often in the past few months! :E:ok:

[QWERTY9]

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.

[Ratatat]

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.

[perusal]

http://www.cfmu.eurocontrol.int/cfmu/opsd/public/standard_page/operational_services_taxitimes.html

This Eurocontrol page gives the taxi times declared to CFMU

[loubylou]

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

[SilentHandover]

I withdraw my previous comments in that case, humble pie humble pie humble pie. :ok:

[Standard Noise]

I've had crews try the same thing with me, thinking they can push back, start, taxy and be airborne in 4 minutes.

Yep, we get those as well. I have seen it done (using 09!) by a certain lo cost from the Emerald Isle. Mind you, they are a bit on the impatient side that lot!

[BOAC]

Thanks all, particularly 'perusal' - amazing what is 'squirrelled' away!

[Gonzo]

Yes, perusal, very interesting. It says EGLL's taxi time for runway 23 departures is 20 minutes! They might have to wait slightly longer than that! :}

[perusal]

Don't bite me, I didn't write it. I'm just the messenger! :)

Need to get them to add Runway 05 :ok:

[routechecker]

Quoting from the CFMU's ATFCM users manual

4.3. Slot Adherence
Aircraft Operators and ATC are jointly responsible for slot compliance at departure
aerodromes.
4.3.1. Aircraft Operators
In order to comply with a CTOT, AOs 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 taxitime shown in the SAM.
Aircraft Operators shall inform themselves of and adhere to:
a) General ATFCM procedures including flight plan filing, strategic ATFCM measures and message exchange requirements.
and
b) Current ATFCM measures (e.g. specific measures applicable on the day in question, such as ATFCM slot or flight suspension).
4.3.2. ATC
a) ATC is responsible for departure slot monitoring at departure aerodromes. The exact procedures to be followed will depend on the way that ATS is organised at each aerodrome.
b) States shall ensure that an ATFCM slot, if applicable, be included as part of the ATC clearance. ATC shall take account of an applicable slot or flight suspension when a clearance is issued.
c) ATC units responsible for departure slot monitoring shall be provided with the necessary information concerning the restrictions in force and slots allocated.
d) ATC is also required to provide all possible assistance to AOs to meet a CTOT or to coordinate a revised CTOT.
e) A slot window of –5’ to +10’ is available to ATC to optimise the departure sequence.
f) ATC may deny start up clearance to flights unable to meet their slots until coordination with the FMP/CFMU has been effected and a revised CTOT issued.

rgds

[Chilli Monster]

b) States shall ensure that an ATFCM slot, if applicable, be included as part of the ATC clearance.

There are certain ATC units who could do with taking that one on board.

[hangten]

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.

Not quite the case anymore, just been altered slightly. 15mins is still the case wintertime but as of this year (technically still a trial at the moment) the 08 taxitime is helpfully 25mins, 26 is still 20mins.

This Eurocontrol page gives the taxi times declared to CFMU

Which doesn't seem to match the information here, even close; which is a shame because the effective from date is so recent. I wonder how often they request the information?

CTOT -5+10 ownership

mine mine mine!!!

[jangler909]

In the Finnish controller's handbook we have an instruction saying "when aircraft has received its start-up approval, a minor taxiing delay should not prohibit its departure". Reading this thread has given me an impression that this is a unique rule for Finland, or am I wrong? I find the rule rather amusing, because otherwise accurate and formal book has such inexact definition as "minor".

[His dudeness]

And thats the next step:
A0962/07 NOTAMN
Q) EDGG/QFAXX/IV/B/A/000/999/
A) EDDF B) 0704240200 C) PERM
E) NEW DEP MANAGEMENT SYSTEM (DMAN) IN OPERATION. REFER TO AIC IFR 2, 15 FEB 07 FOR PROCEDURES.
TARGET TIMES FOR START-UP APPROVAL (TSAT) AND OFF-BLOCK APPROVAL
(TOAT) ARE GENERATED. TOAT IS PUBLISHED IN THE AIRPORT INFORMATION
SYSTEMS. START-UP IS TO BE REQUESTED AT TSAT, (5 MINUTES BEFORE
TOAT), PUSH BACK OR TAXI IS TO BE REQUESTED AT TOAT. PILOTS SHOULD
ADHERE TO THE ASSIGNED TARGET TIMES.
SMS SERVICE IS AVAILABLE UNDER +41 76 3337777. SEND SMS WITH KEYWORD TOAT AND FLIGHT NUMBER (E.G. TOAT XY123) FOR INFORMATION ABOUT TARGET OFF BLOCK APPROVAL TIME (TOAT). YOU WILL RECEIVE INFORMATION ANDUPDATES AUTOMATICALLY.

The system is driving me crazy. But I´m just a lowlife executive pilot.
Another 25 years before pension.
:{

[A7700]

What says ICAO DOC 4444 :
7.8 CONTROL OF DEPARTING AIRCRAFT
7.8.1 Departure sequence
Note 2.— For aircraft subject to ATFM requirements, it is the responsibility of the pilot and the operator to ensure that the aircraft is ready to taxi in time to meet any required departure time, bearing in mind that once a departure sequence is established on the taxiway system, it can be difficult, and sometimes impossible, to change the order.
About variable taxi time ( "a concept" buildt by the CDM experts..) a very simple equation :
EOBT + variable taxi time = Variable take off time....Is it what we are looking for ?
At a large HUB airport, just a passenger missing can move a flight n°5 in a line of 5 wide bodies A/C which need to push in a row, instead of N°1 on standard schedule. The taxi time ( I think it would be more appropriate to use taxi "duration" and include push back and waiting time at Apron) will be increase by may be 15/20 minutes compared to a normal taxi "duration" if N°1 in the row.
So if the "variable taxi time" is 20 minutes, + or - 15 minutes, do'nt expect any improvement...:*

[goddammit]

of course, some uk places have a more relaxed attitude to CTOT tolerance and just get the aircraft airborne within a reasonable period, so it doesn't really matter who owns it.

[Legs11]

of course, some uk places have a more relaxed attitude to CTOT tolerance and just get the aircraft airborne within a reasonable period, so it doesn't really matter who owns it.

How unprofessional can you get!:ugh:

UK and European airspace is a finite resource and as such needs to be managed efficiently. Flow management by the application of CTOTs helps to optimise ATC capacity by ensuring the mose effective use of ATC resources.

That CTOT is given for a reason - somewhere up the line is an enroute sector or airfield that may as a consequence of this 'more relaxed attitude' find itself in an overload situation or worse.:ouch:

Before taking the above thoughtless action ATCOs need to ask themselves the question - "Do I know what I might create downstream if I do this?"

[goddammit]

I have to agree.
The pilots want to get airborne, atc want to please the airline, nobody puts a stop to it.

[LN-ATC]

FJ,
You will find the CFMU ATFCM Users Manual online here (http://www.cfmu.eurocontrol.int/cfmu/gallery/content/public/userdocs/docs/handbook_atfcm_11a.pdf). Page 27.
It seems like a few Scandinavian companies could need a brush up on CFMU procedures...

[niknak]

Very professional response Legs.:ugh:

If it's a matter of a couple of minutes, stuff what happens down the line, I would have thought that even you could understand that en route weather, traffic etc means that the aircraft may be delayed or expidited en route, and, more often than not, given a direct routing to assist and reflect the "real time" situation.
Fortunately,anyone with common sense, (that's the majority of us) would consult the flow manager if there was going to be an over run of 5 minutes or more, or let it go anyway if there was less.

[Ops and Mops]

Cue the can of worms just opened by niknak......

Many units have pilots that try and take the p1$$ by requesting start AFTER CTOT saying things like "well can't you get us an extension?" or "we will only be a couple of minutes late!", or "don't we have +10?!" In this case, the onus is on the company to contact the Flow peeps to re-negotiate. ATC should NOT delay the FPL EOBT as that prevents FMP making tactical, real time decisions!

The flip side of the coin is that if the aircraft has requested P&S in good time to make it's CTOT but is held up in a queue AT the hold, FMP normally recognise this and don't mind anything up to CTOT +15 getting airborne (in my experience). Clearly if the delay is going to be more than a couple of minutes, it would be professional courtesy to contact FMP to check before launching, as you, sat at an airfield many miles away, do not know what the impact of the regulation will be to other airfields, en-route sectors and TC holds.

The phrase "stuff what happens down the line" doesn't fill any pilot or controller with confidence. There is a reason for everything in aviation with an associated consequence. I would hope that we are not so insular as to realise this!

[mcdhu]

From the operator's point of view, the simplest way out of this jungle is to own up to delivery, tell them your situation and ask for the latest time they will grant push/start with regard to the prevailing traffic to/at the various holding points/positions.

Works well with the welcome cooperation of the guys and gals in the twr at Lgw - for which, thanks.
Cheers,
mcdhu

[CAP493]

This Eurocontrol page gives the taxi times declared to CFMU
Not quite the full picture as some airfields e.g. Luton, have enhanced taxi times during declared peak hours (in this case 15 minutes during two two-hour windows morning and late afternoon/evening) and further enhanced taxi times during Category 3 conditions (in Luton's case 20 minutes off-peak and 25 minutes peak-time).
Although not yet operational within the UK, when (if ??) Eurocontrol's Flight Activation Monitoring (http://www.cfmu.eurocontrol.be/cfmu/public/standard_page/cfmu_systems_evolutions_etfms_fam.html) is extended to UK airspace, flights that are not airborne within their CTOT or (EOBT if unregulated) tolerances will be subject to an automatically generated CFMU 'flight suspension' message. This happens if the SSR of the flight in question is not activated within the CTOT or EOBT tolerance (+ whatever additional time [measured in seconds] is allowed for the en-route radars to process the flight's SSR return). :8

[squak]

It would be interesting to know if you have checked the CFMU handbook lately. I think that the text below from the handbook is very clear about the "ownership" of the 15 minutes windows;

"A slot window of -5 to + 10 minutes is available to ATC to optimise the departure sequence"