London FIR
Stack Management
There are two stacks for Gatwick - TIMBA and WILLO, both to the South. In order to work Gatwick efficiently, you should have a good knowledge of management of stacks.
Both the stacks are over Intersections:
| TIMBA | Inbound heading 310/R Turns |
| WILLO | Inbound heading 287/L Turns |
Holding in the stacks takes place from the minimum stack level (MSL) to FL150 at both TIMBA and WILLO. When stacks become full, enroute holding further down the STAR takes place - "Stack swap" procedures could also be put in force (See arrival routes section).
It is important that you keep the stacks laddered down so that levels can be freed up. In the stack, you can only clear an aircraft down to the next level when the previous aircraft has vacated the previously occupied level. There are two ways of doing this. 1) Ask the pilot to report leaving the level 2) When the mode C readout shows +/- 400ft from the assigned level, we can assume the aircraft has left the level. During busy periods, option 2) is the better one, to reduce RT transmissions.
In the hold standard holding speeds apply:
Up to FL140 |
220kts |
Above FL140 |
240kts |
Ultimately, it is the pilots responsibility to ensure that he enters the stack at 220kts. To help him out, as he approaches the stack, if you want him to enter the hold bring his speed back early (By doing this, as he reaches the stack you may then realise he doesn't need to hold because the reduction in speed has created enough of a delay)
Aircraft should be informed of the length of delay expected in the hold. The usual phrases used are "Less than 5 minutes", "5 to 10 minutes", "10 to 15 minutes" and "15 to 20 minutes". If the delay is going to be over 20 minutes, Expected Approach Times must be passed to aircraft.
Stacks are usually operated on a first come, first serve basis. The aircraft at the bottom of the stack is the first one to come out, and each aircraft above then follows in turn. It may be tactically beneficial to bring a higher aircraft out first, if there could be a vortex issue on final approach for example.
Coordination between the TMA (or LACC sectors if applicable) is very important to ensure that aircraft are released descending to the next available level in the stack. The worst thing that could happen would be an aircraft transferred to you descending to FL80, only to find that FL100 is the next available holding level.