Some great discussion going on in here! Although the original question seems to have been answered I'll throw in my 2c.
The way the sequence works in my neck of the woods is that the outer (ex) procedural sectors are responsible for for setting FF estimates into MAESTRO at around 350-400nm out, this starts to stabilise the system and then these controllers can give an expectation of delay and a Mach # slowdown when it hits a certain size. I'm not entirely sure what the process is for East Coast sequences re locking into MAESTRO, but for PH early stabilisation and slowdowns were what was requested by industry and works best for us due to the nature of the traffic patterns (no inbounds for 3-4 hours at a time, then a sudden sequence of 30-40 when all the mining traffic turns around at the same time). That's the reason that we have the outer sectors responsible for that stage.
The next sectors (250nm out) are responsible for issuing the actual FF times, making sure MAESTRO has put aircraft the correct order (remember the original sequence is built off pilot estimates.. Which is why MAESTRO often tries to put the cheeky bugger in his F100 ahead of the 737 even though he's 20nm behind and 20kt slower).
Even at this stage your 'expect a 6-7 minute delay' may have blown out to 15 mins due to 3 departures from nearby aerodromes. I guess the reason these departures aren't all allotted times in the sequence before departing is that if they don't get away on time then there will be holes in the sequence and everyone gets punished as a result... Similar to when pilots give an unrealistic estimate for JULIM, become number 1, then despite getting direct and pushing 310 on the descent to JULIM they end up 2 mins late and every behind gets shafted...
From 250nm to 160nm pilots have the chance to let us know how close they can get to the issued time and this info helps the inner centre controllers figure out the most efficient way to achieve the rest..
The last 12 months, with the implementation of MAESTRO and the consolidation of the GDP, has seen a decent increase in the number of aircraft being able to achieve the delays without our intervention. We've gone from 20-30min delays + holding the majority of traffic twice a day, every Tuesday/Wednesday/Thursday to occasionally having 15-20 minute delays and maybe holding a couple of aircraft a week.
But to go back to the original post there are still some instances where we will have to hit someone with 10 or so minutes on short notice.. People have discussed go arounds, medevac, rwy changes etc.. But occasionally it will also just be a case of taking a little longer than usual to pick up the delay. An example is: at 400 miles you give your estimate which puts you in your own sequence.. No one in front of you for 4-5 mins and no one behind you for the same time. Procedural sector locks this in, sees no delay in maestro and moves on to their next job. You get transferred at 250miles, get your STAR, and still no delay in MAESTRO, and no one near you so your time at the fix is not pertinent. In the next 6 minutes 3 departures get away from 2 aerodromes within 100 miles, and someone finishes airwork and is ready to return. These aircraft all need to be sequenced and some will end up in front of you.. Chances are you are coming in from the north and all these departures came from the south so it's a different controller looking after them. Someone who is all over it will be aware of what's going on in surrounding sectors, assessing Maestro making sure all times are up to date, but it does happen occasionally that as per this example an aircraft might run through to 160 odd miles before the inner controller picks up that what was originally a sequence of 1 has become a sequence of 4 and your dreams of scooting through the terminal before the rush are shattered.
Last edited by WhisprSYD; 25th May 2015 at 05:43.