Slot or EAT

[SATCO Biggin]

Here is the scenario. I have aircraft 'A' waiting to start for a positioning flight to Heathrow.

Frequent CB's and thunderstorms have caused a backlog of traffic going into Heathrow so a flow rate had been imposed. Over the last hour CFMU had issued aircraft 'A' with four different slot times and he was going to start in accordance with the latest revision of 1840.

I co-ordinate the start up with the next ATCU who inform me that Heathrow cannot accept the aircraft before 1915. If thats what the controllers at the coalface want then fair enough and I will go along with that time.

Now I have to explain to the aircraft that although he has a slot time from Flow Control it actually doesn't count for anything and we have to wait for the later time. Technically I have to 'slot bust' what CFMU want, which of course would normally lead to a slap on the wrist.

From where I am sitting on the outside it would appear that both the guys at CFMU and the guys at Heathrow are acting totally correctly so why the difference in slots? The only reason I can come up with is that the flow rate that CFMU were operating to could not be matched by those doing the job at the customer service end.

Must be confusing to the aircraft operator to have a 'runway slot' allocated by the BAA, a 'slot time' issued by CFMU, and an EAT issued by ATC that all differ.

Who decides flow rates through busy sectors?

[5milesbaby]

Slots and EATs are different things though, so I would expect them to be different. If all LHR inbounds are getting slots, its to make sure that they all don't appear at once. However 20 minutes delay can be expected as 'no delay' so the EAT is quite possibly departure time(slot time) + flying time + 20 minutes. If your a/c is on the ground at EGKB (guessing from your name!!) then TC would prefer to keep it on the ground and soak up delay there, rather than going in circles at BIG for 20 mins. This means your a/c departs BIG and goes straight into LHR without holding as the delay has been used on the ground, this makes it easier for TC as if the a/c had got airboune, it would be holding at min stack and all those before it need vectoring away before descending through it.

This only works for airfields close to the destination where the slot is issued due to the final sectors of the flight being busy (ie. holding occurring), I know it has been used occasionally from Manston into Stansted.

[AlanM]

Pete,

The option as I explained last night was:

Get airborne and hold OUTSIDE countrolled airspace at OCK at 2.4A (or in your circuit!) or take the delay on the ground and have a virtual straight in approach (actually it made just a few orbits at OCK)

If I remember correctly, the flight plan was to join CAS on a standard SDR, which is why I guess you got a slot as ALL EGLL inbounds were subject to a delay. That was why, I guess, that CFMU gave you a slot of 1840Z. If you had got airborne at that time, you would then have joined the queue and be given an EAT (which were +30mins of stack entry!)

Seems pointless to get it airborne, burn loads of fuel and put a strain on a busy sector if you can sit on the deck and relax.

Yesterday was also a particular bad day as a lot of the bad weather around that time was between the holds and the airfield. So even though TEAMing was in force (Left and Right for landings) it was physically impossible to get an aircraft 3 miles behind the previous as they were all requesting strange headings just before base leg, resulting larger gaps on final.

In terms of the "slot" bust - well that is to protect the sector of course. As there was only one sector involved, that sector and it's Traffic Manager didn't want the jet in the system too early.

A twr person can help me here, but a LHR landing slot time is an approx time only. It certainly doesn't relate to the current ATC delay.

A trying day for all - and it was slotted in as soon as it was airborne. I can assure you that people were working their butts of trying to reduce the delays, and the LTMA almost ran out of holding areas for the traffic (Some were holding at FL240!)