Originally Posted by
DaveReidUK
The published plan for operation of a 3-runway Heathrow shows one runway being used for departures, one for arrivals and one for both (mixed mode), with their respective roles alternating through four different permutations.
Perhaps you should have a word with them.
You will need to alternate (technically not mixed mode, as you are not using the gap between two arrivals for a departure) one runway to balance daily capacity if you have three runways. It also works better with arrival and departure peaks (AMS uses this). As a departure runway has more capacity than one used for arrivals, departure mode will need to be used less often than arrival mode. This does not work as well for closely spaced parallels (for example CDG, LAX and ATL 08/26 + 09/27) as departures can only be released after the arrival on the parallel has touched down due to the possibility of missed approaches / go arounds.