Regarding CDG (quite a busy airport I may say), two situations may occur :
- the pilots start reporting some tail wind, and the weather forecasters (who said fortune tellers ?
) tell us that it's not temporary and the wind is actually shifting ; then we'll wait for the end of the arrival peak if any and only afterwards perform the runway shift : it's easier to block departures on ground for 10-15 minutes during the shift than to keep 60 incoming aircrafts in the holding patterns while they weren't initially suppose to hold...
So, coordinating approach and tower, we decide of an hour for the shift, say 14:30. Around 14:15, 14:20, regarding to the traffic, the ground will start rerouting the departures to the new rwy holding point (well, not too close to avoid blocking the last arrivals vacating the rwy
)... At 14:15, the incoming arrivals will be hold in the stacks. At 14:25, the approach will release the first arrivals in the new configuration ; the last arrival should land at 14:30, just afterwards the take-offs start again...
- the wind shift is stronger, with aircrafts going around due to the back wind for example, or when a thunderstorm front has swept the airport. Then we have no choice but to act immediatly, everybody is stacking until the new runway configuration is available ! In case of a thunderstorm, it may happen that we need to shift twice in a row... I've seen once an Alitalia lining up, but refusing to take off due to the back wind... he was to be the last taking off facing West... "No problemo", he vacates the rwy, taxies to the other end, queues behind the other... but when it's about to be his turn... the wind has turned again, and we have to face West once again... so he taxies back to his initial holding point... and happens to be number 15 when he arrives there... When we've been able to start departing facing west again... we've allowed him to backtrack the rwy a short while to pass the others and to depart as #1 : he had been fair play all along, never complaining, we couldn't do less !
