Sky Wave, a really neat summary of the whole back track/ line up issue
. To add to your info...
We can, most of the time, replace the 2 mins by 5nm, slightly reducing the 120 second seperation.
Even better:-
ON 26, a "BPK" following a CPT or OLY can be reduced to 1 min or 3nm. (On 08 a CPT or BPK following an OLY, an OLY following a BPK, or a CPT following a BPK
) -multiple line ups or intersection departures are useful here.
A multiple line up can work really well even with the 2 minute/ 5nm split depending on the position of the inbound (If inbound is around 10-12nm). Even if the backtracker has to sit on the threshold for a good minute or so waiting for the intersection to roll, get airborne, etc, the crucial time saved by having an aircraft lining up whilst one is backtracking gets 2 away instead of 1.
I will always try and ask crew if they can accept an intersection departure if I spot such an opportunity.