I take it you all mean BRASO when you speak of LOGAN? When LAM is full (up to FL170), aircraft are held at BRASO (FL180-FL240) and when BRASO is full they are then held at LOGAN (FL250+).
LOGAN holding is not a desirable situation to be in as it screws over TC East and Clacton but the main reason being that when Heathrow approach pull 4 aircraft out of LAM at the same time, it takes quite a while (relatively) to bash the LAM stack down so aircraft can be brought on from BRASO and descended so that aircraft can then be brought on from LOGAN to BRASO. It can only be described as an accordion effect and leaves a lot of sky being used up with not a lot of planes in there, whilst the outer holds are full.
With a skilled controller and a bit of tactical rule bending, the levels can be regained fairly quickly but this isn't always the case.
Swapping from LAM to BIG is
relatively easy providing that there aren't many aircraft at BIG. It's usually just a matter of TC East turning it left a bit and descending it, requiring a fairly standard co-ordination with TC South. LAM to BNN, however, goes into TC Capital's airspace and depending on the level, TC Midland's airspace too. If the traffic situation is fairly complex on NW Deps/BNN at the time, a swap from LAM can easily push it over the edge.
In answer to the thread starter, the reason that you still hold for 15 minutes at LAM after slowing down is that everyone else is slowing down too and I believe the delay calculation takes this into consideration (don't quote me on that though!)
It does seem to be a regular occurence where the delay screen is saying <10 mins yet aircraft are holding for 15 mins or on the flip side, the delay is showing as 15-20 mins yet aircraft are coming straight off. Another consideration to take into account is that if something happens to push the delay up, e.g. strong winds, it can take a considerable amount of time to get things back to normal. The winds may be long gone by the time you get there but the knock on effect is massive, especially during the busy periods.
There was one occasion last week when I was working BNN and a 744 had been holding for some time in BRASO and LAM and was eventually swapped over to BNN to make some room. As such, his EAT needed to be recalculated. They were quite tight on fuel and told me they could hold for about 10 minutes more before they'd have to declare an emergency as he was committed to Heathrow. The pilot kept asking me for the revised EAT but I must have waited almost 10 minutes before one was calculated. It was very frustrating for me and the pilot. He needed to know whether he'd have to declare or not and I needed to know if I was going to have to pull him out of the stack and drop him down. I felt quite bad as neither of us was in the picture and the pilot probably thought I was a bit of a numpty for giving him guesses rather than actual times!
I hope all that makes some sense!
