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Takeoff not permitted before EOBT?

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Takeoff not permitted before EOBT?

Old 11th May 2007, 14:58
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Takeoff not permitted before EOBT?

Hi,

It happened to me a while ago in Spain:
Startup was requested and approved at EOBT-15 minutes.
When I then arrived at the holding point, ready for departue, at EOBT-5, I was told that I would not be allowed to takeoff before my filed EOBT according to procedure described in the Spanish AIP.

I looked it up and the Spanish AIP (ENR 1.10-17) does indeed mention:
"To acquire the appropriate data coherence and consistency
of traffic demand, which allow an optimum application
of airspace capacity and flow control measures,
even if the AOBT may be advanced in 15 minutes, take
off shall not be permitted before the EOBT. (The Taxi-time
can never be negative)."
This does not seem to be applicable in other countries, where apparently you can takeoff as soon as EOBT-15 minutes.
I think the Spanish CAA is misinterpreting some ICAO directive.

What's the procedure in other countries?
Any reference to an ICAO directive?

Thanks,
Sabenaboy

Last edited by sabenaboy; 12th May 2007 at 09:01. Reason: link to aip changed to english version. (free) registration required.
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Old 11th May 2007, 15:01
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I think the Spanish CAA is misinterpreting some ICAO directive.
Or they've interpreted it correctly, and have filed a difference with ICAO.
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Old 11th May 2007, 21:59
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Probably time for you to educate an unknowledgeable here, but isn't it something to do with flow control? As flow works in 15 minute segments, and assuming (possibly wrongly) that most flights will have a 15 minute taxy time built in, then if you get airbourne before your EOBT then you are actually getting airbourne more than 15 minutes earlier than expected so should re-file the new EOBT and see if any flow should be applied. I only ask this as a few years ago I had quite a severe overload during a "free flow" period, and when the traffic count was looked at 2 entered the sector more than 15 minutes early and 7 entered more than 15 minutes late, the worst was 95 minutes late. I know that following this 2 airlines were contacted and threatened. All the aircraft were slot free due to their filed EOBT and none had updated when running early/late as they should. I do know that this has caused further overloads since but not to the severity of mine, there were other factors contributing in the later ones.
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Old 12th May 2007, 05:52
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Probably time for you to educate an unknowledgeable here, but isn't it something to do with flow control?
No, the AIP chapter that I mentioned is about flight plan filing and this rule is apparently applied to all flights, even if they didn't receive a slot.

I can understand that you have to wait with starting up until EOBT-15, but I can't understand why you then have to wait until your EOBT to takeoff. (I don't blame the ATCO. He's just following the rule as per spanish AIP)

So here are the questions again?
1. Do other countries have the same rule? (YOUR country?)
2. Can someone tell me if there is an ICAO/JAA guideline about as from which time a non restricted flight can startup, taxi and take off?

Regards,
Sabenaboy
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Old 12th May 2007, 07:21
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As far as we interpret the rules, provided you have no slot you should be able to start/takeoff EOBT+/- 15 min.
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Old 12th May 2007, 07:44
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even if the AOBT may be advanced in 15 minutes, take
off shall not be permitted before the EOBT. (The Taxi-time
can never be negative)
It's rather odd because the CFMU phrase "taxi-time" is used, and indeed it cannot be negative. But taxi-time is a planning parameter that affects the earliest possible CTOT if a slot is issued. It is not related to ATOT or AOBT as is implied in parenthesis.
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Old 12th May 2007, 08:20
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Sabenaboy - This maybe applicable to Spain only, unless they have interpreted it incorrectly.
I know of no other country that would operate in this manner.

5milesbaby
The UK may work in 15 minute segments on its own system but CFMU work in 20 and all flow capacity measures are based on the CFMU system.
Taxi Times are variable and range from 0-40 minutes. Most airports in the UK have 10 mins as standard.
It has nothing to do with flow control directly, it's to do with flight planning, but i suppose you could say that flight planning will affect flow control.

Last edited by QWERTY9; 12th May 2007 at 08:43.
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Old 12th May 2007, 11:07
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Thanks, starting to understand a bit more, but knew there was something about 15 minutes from the P time and a re-file was needed.

Sabenaboy:
No, the AIP chapter that I mentioned is about flight plan filing and this rule is apparently applied to all flights, even if they didn't receive a slot
All flightplans enter the system and still show up on flow control charts, so depending on what times are entered for the departure/FIR boundaries depends on whether you get a slot or not. If you don't get a slot then it means that based on filed times a slot isn't needed, all a slot does is limits the30 mins gap to a 15 mins gap so we can be slightly more accurate in when you're going to arrive. At Swanwick every supervisor position has flow charts that show block graphs in 15 minute segments (although not very accurate) and when "peaks" start appearing in a 15 minute gap then they look to whether the sector can be split and if not, apply a form of flow control to regulate the movements. This ranges from basic flow (slots), Minimum Departure Intervals (MDI's) applied to a particular airfield thats going to deliver most of the a/c whereby rather than one every 2 mins on a route, it'll be increased to delay some traffic. Also level caps can be applied to vertically split sectors, in London to protect the London Upper Sectors (S1/S2) some a/c will be hand picked to descend below FL310 and transit through the Middle sectors (S25/S26), normally those going to Manchester/Liverpool from the south.

Have had another thought - could it be to do with the Spanish ATC system? If it has a pending time entered for an a/c and then gets airbourne early then the sector may not be expecting it and therefore have no details, is there anyone from Spain who could confirm or deny this?
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Old 12th May 2007, 12:11
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Thanks, starting to understand a bit more, but knew there was something about 15 minutes from the P time and a re-file was needed.
Any non-regulated flight has up to time EOBT+15 to start. After that, a DLA message needs to be sent to update the EOBT. This is so that the ATFM measures can be updated with more accurate timings.
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Old 12th May 2007, 13:43
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5miles -
The 'not very accurate' UK system you refer to is the envy of many of your european counterparts. Rather arrogant to use that term when you admit you're not very knowledgable in these matters. Maybe you should become a little more educated in the system before knocking it.
It's not exact, no system of this nature is in ATC, but it's very accurate based upon the information supplied within a flight plan. It's not a crystal ball !
Other ANSP's are looking at this system closely and I wouldn't be too surprised if some of your nearest neighbours find themselves with it sooner rather than later !!
To answer another of your thoughts - The CFMU system picks up live radar activations so regardless of pending EOBT, the system does know the flight is airborne and enroute centres will know to expect it. This will not be the case though for flights originating from the USA/ASIA etc.
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Old 12th May 2007, 22:03
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Not arrogant at all, that "not very accurate" system can probably be partly to blame in at least half the overloads that occur at Swanwick - I've witnessed several of these by either being involved, taking over from the distraught controller, or sitting alongside helpless. Yes, it has some excellent properties that are fantastic for us to use, but why anyone would envy the system as a whole will always amaze me.
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Old 13th May 2007, 10:33
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Ah ! Blame the equipment which is only as good as the information provided by the operators.

The system cannot cause overloads, but interpretation of the data can, incorrect data being input into it can, slot busting can, the 30 minute window afforded to EOBT's can, controller ability can, traffic complexity can, pilot error can, emergencies can etc etc....most of those have human interaction !!

The reason it may amaze others is because of the equipment they have to work with in many cases being inferior.

To state that at least 50% of overloads are caused by it at Swanwick is absolute garbage and you know it. If that was the case it would have been withdrawn from operational use a long long time ago. I suggest you get yourself educated before talking such utter nonsense.
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Old 13th May 2007, 18:30
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To state that at least 50% of overloads are caused by it at Swanwick is absolute garbage and you know it.
I stand by every word I've typed here, which incidentally was "can probably be partly to blame".

The system is limited, the supervisors/flow use it to decide if flow should be implimented, they used it, flow was decided that it wasn't needed, sector gets overloaded - so how's that a system that is envied?

I stated I wasn't knowledgeable with the free flow tolerances, and thanks to Gonzo am aware its a delay message or ready message that should be sent when an a/c is early/late - I know the basics, just not the technicalities. I know all about TLPD or what ever name they want to give it this week, and I've witnessed first hand its limitations.
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Old 13th May 2007, 19:00
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5miles,

A bit more background for you..... Slotted traffic is straightforward to predict (and thus flow), given that there is a 15 minute window for its airborne time. Vagaries we are all aware of, such as; short cuts/direct routes; weather; different speed profiles on departure etc etc make the current flow system a blunt instrument.

The problem comes when aircraft going through, say, CLN sector between 0900 and 1000 are regulated, but the aircraft in the hour 0800-0900 are not regulated, as the demand is well below TSF. Now, if a few of the aircraft scheduled 0800-0900 are running late, but the EOBT is not kept up to date, they could get airborne to fly through CLN between 0900-1000 but CFMU system is 'not aware' of them, thus causing (possibly) an overload.

By keeping the EOBT up to date, and not allowing any a/c to start after EOBT+15, then those aircraft running late will be now be given slot times and will be factored in to the flow for that hour.

Measures such as the 250kt trial in the TMA was partly to increase the accuracy of flight time estimates to aid flow.
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Old 13th May 2007, 19:48
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Cheers Gonzo, that all makes sense and is what I thought/knew as well. Many of us ATCO's at Swanwick are becoming more aware of the flow charts we get, know their inaccuracies and rarely trust them. I haven't heard any supervisor NOT say that they don't trust the data they are provided and often split earlier or at times when its not needed. But its those times when one segment shows no traffic right up to its start time, grows during the 15 minute active time span, and shows the overload fully around 10 minutes after its passed through. I'm baffled that there isn't equipment around to counteract some of the reasons for this happenning. Or is it just another case of cost.....
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Old 13th May 2007, 22:29
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When you've a little more experience under your belt and when you actually understand how systems like this work you may just change your tarnished way of thinking !! Those who have been in the job longer than 5 minutes have a little more respect !
I suggest if your concerns are so grave about the system you have to work with you make some form of official representation and voice your concerns as it is clearly a safety issue to you and your colleagues.

Last edited by QWERTY9; 13th May 2007 at 22:47.
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Old 14th May 2007, 06:40
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Don't worry 5miles, we have a more or less similar opinion of the flow forecast data we get from our machine (TACT/CHMI). I've certainly been caught out by bandboxing GMC when the figures predicted a quiet hour.
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Old 14th May 2007, 08:34
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Gentlemen,

Would you please be so kind to return to the topic or create a new topic yourself to continue this little private conversation?

(No hard feelings though )

Regards,
Sabenaboy
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Old 14th May 2007, 17:51
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Understood Sabenaboy, hope that through the bickering that you are getting some useful stuff. You'll be glad to know that I've been in the job for "longer than 5 minutes" so do have some clout to what I say, at least I give the details and facts I know and state when I'm unsure and hope that someone will correct me if I'm wrong without getting childish about it, shame its an anomynous forum then we could settle this with a little "lake dunking"
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Old 16th May 2007, 11:45
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Sabenaboy.
I believe the ICAO documentation says that a FPL is only valid for the period ETOT + 30 minutes.
When you file a FPL it is checked against route closures, danger areas, military activity, conditional availabilty and so on for the period of vailidity.
If you depart outside the validity of the FPL you could find yourself arriving at an airway that is closed.
The Spanish rule would appear to be enforcing observation of the FPL validity. I would be intersted to know if they have a similar rule forbidding departure at ETOT +30.
It seems to be common sense really.
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