AndrewMcAllister
30th Aug 2005, 22:58
Was sitting at Beauvais the other day and the captain explained that we had missed our slot and would have to wait for 30mins until we could start the engines. Can anyone tell me why this is? There were no other aircraft in the vincinity although it was about 11pm.
PPRuNe Radar
30th Aug 2005, 23:18
The aircraft will fly through many 'parcels' of airspace, or sectors as we call them, on it's journey. Each has a declared capacity for safety reasons and when that capacity is reached for any individual sector then any excess demand has to be regulated by slots.
Your flight had a slot allocated which would meet with the capacity figures for the sectors along its entire route, which it missed. Because of that, all the other slots would already be filled and effectively your aircraft then has to go to the back of the queue to obtain the next free one. It would not be fair to delay other aircraft who have met the requirements placed upon them just because your aircraft could not meet its allocated slot (for whatever reason). Hence you will probably find a further delay being allocated.
The slot window is relatively generous, a 15 minute window when ATC can depart the aircraft. But as we all know, that can be easilly eroded by passengers staying in duty free, lost bags, lack of pushback tugs, etc, etc.
The flow managers at the various units all along the way, plus the overseers of the whole system which is located in in Brussels, do try and change things tactically to allow the most aircraft possible through each sector. So quite often you will find a 30 minute delay will come forward or perhaps even disappear. It is for this reason that operators board aircraft at the planned time in case any improvement is issued.
ATC certainly don't delay just for no reason. It is to keep the traffic flows in a safe and orderly fashion.
This is a simplistic description but I hope it helps.
AndrewMcAllister
30th Aug 2005, 23:20
Exactly what I wanted to know, nice one!