ATC slots

[JonF]

Just come back from Paphos. Flight was due to leave at 15.55 but after we'd boarded pilot said we'd been given a 16.30 slot by Brussels and that head office were attempting to get an earlier slot. Can someone in the know explain how this all works? Is Brussels the centre for all flight plans etc?

[Localiser Green]

Yes, Brussels is home to the Central Flow Management Unit (CFMU), which co-ordinates all European flights.

An airline's operations can attempt to negotiate an improved slot with Brussels, perhaps with a slight route adaptation or a different flight level.

[Trabbi]

Hi Jon...

a few words which might give you an insight look (most probably there are more experienced users out there which can give you more information on some details).
Every flight is controlled by a flightplan which is sent to Brussels (and Paris) where it is stored in a database and accessable by the ATC units.
If you fly on a route without any restrictions, you will not get a slot (which is a 15 minute gap where you have to depart from your departure point).
If a departure airport, an arrival airport or the route is restricted in any way (too much traffic, not enough controllers, strike, thunderstorm, military activity, no parking space, anything you can think of) your flight will receive a slot. If the restriction isn't worse, the slot will be "on time", so you need to depart on time (inside the 15-minute gap). If the restriction is heavier, the slot is later than your "published departure time".
Want to have a look what is going on in the sky and on the ground, then have a look here:
CFMU Network News (http://www.cfmu.eurocontrol.int/j_cia_public/cia_public/pages/msgAimlist.jsf) then click on Network News
The CFMU (Central Flow Management Unit) publishes it every day and estimates the upcoming delays. In your case, Cyprus and the UK - restricted nearly every day.

Greets,

Trabbi

[stansted_dan]

As others have rightly said, slots can be enforced by the Eurocontrol in Brussels due to various ATC restrictions. Most commonly the slots we incur are simply due to ATC capacity along certain routes, for example London-Ibiza/Majorca/Faro/Malaga during the Summer months. If it's expected that there will be too many aircraft on particular airways at a certain time, then aircraft will be given slots so as to stagger the departures. Another one is ATC capacity/congestion at certain airports, a good example in the Summer are the Greek Island airports. Most of them are very small and can only take 5 aircraft or so on the apron at a time. Therefore Greek ATC will notify the CFMU that they can only accept 5/6/7 arrivals per hour, and aircraft will then get slots to stop too many departing the UK or wherever at the same time.

You can get round some slots by re-routing sometimes. Last week there was a large radar failure in the London FIR, almost any aircraft departing/arriving or flying over the London FIR were getting huge delays. We had an aircraft waiting to depart from Corsica to Dublin which was given a 300 minute delay. With some careful flight planning we managed to send the aircraft around the outside of the FIR, and so instead of routing over the top of London it ended up flying West through France, over the Channel Islands and then directly North into Dublin. Once we re-filed the plan with this routing the slot disappeared and we were able to depart right away. It meant extra fuel burn, but it was better than having an aircraft and crew stuck in Corsica.

Sometimes you can also reduce slots by notifying Eurocontrol that you are ready to depart. Pilots or Operations can submit a ready message to CFMU and if at that moment in time they can fit you in then they will do their best to let you depart.

There's a whole lot more to it but that's about all I can think of in a nutshell!

[JonF]

Thanks for your replys, all very informative!!:ok:

[airman13]

and if you are given a slot, you may takeoff 5 minutes earlier or 10 minutes later, in respect of that slot, so if you are not able to comply, you will lost that slot, and you will be given other slot

[Fenders]

The important thing to remember is that is it easier to create/manage the separation of aircraft before they become airbourne rather than when they are flying. It avoids unnecessary bunching at "choke points" along the airways network and ATC is all about safety and separation. (Safe and expeditious flow is the term commonly used)

Everything above is correct and other issues also need to be considered. Weather on route and also weather at destination. There is little point in getting airbourne for a flight from for example Heathrow to Amsterdam when the reported weather is thick fog. You will only spend more time in the hold burning fuel and generating even more work for the Amsterdam controllers, and eventually diverting back to where you came from. Some aircraft/airlines can operate with different weather minima. So whilst one aircraft may land in fog of 200mts, another may not be allowed to because of the level of equipment on board, pilot training, etc.

Some flight levels are more desirable than others because of fuel burn, wind speed, etc, and so it is often possible to get a better slot if the crews agree to accept a different flight level.

On a similar vein mentioned previously, in the past the French ATC often would strike and so anyone wanting to fly from/ to the UK heading SE through to SW would be affected. For UK traffic bound for say the Iberian peninsula/ NW Africa/Canaries would be offered a re-route using oceanic routes via Lands End across Biscay thus avoiding France. If I remember rightly, these routes were T8 and T9. On these routes aircraft would be initially controlled by Shanwick and then on to the Portuguese (Santa Maria). Obviously, this then overloads these areas and so can generate bad slots.

A very complex subject which probably mystifies most passengers that are not in the industry.

[JonF]

To follow on what happens regarding flights that head out of europe i.e to US or far east??

[Fenders]

JonF

For trans Atlantic flights from Europe ( i.e. westbound) the crews will make contact with Shanwick for an oceanic entry time at a given fix.
For those that are departing from airfields close to the "ocean" this may mean obtaining their oceanic clearance before departure, otherwise those that are already airbourne will get theirs on route. Generally, the Atlantic track structure offers a series of routes that run parallel to each other. They are changed on a daily basis taking into consideration weather patterns, jetstreams and demand for certain destinations. There are 2 track patterns a day. Eastbound and westbound.

[chiglet]

I visited Scottish "Oceanic" a few weeks ago...it's like something out of Star Trek..
"Real Time" updated position reports [FANS, etc] All the tracks cascading. According to the Watch Manager, they can handle a lot more traffic than the Domestic guys can cope with, and they are getting new kit...the mind boggles