Getting a/c out of the holding stack

[ferris]

How is it done where you work?

More to the point, how is it done accurately?

Have heard in London that approach owns the bottom two levels of the stack, and they take them out. True? Other places the a/c are given stack departure times, and do it themselves?

[Warped Factor]

In general terms for London area inner holds approach work 70-120 and the TMA 130 and above.

Approach instructs when to leave hold for sequencing purposes.

WF.

[HEATHROW DIRECTOR]

ferris.. To add to what my learned friend WF said, everything at London is under radar control and ATC calculates EATs, etc. It's extremely difficult to provide accurate EATs due to so many variables, eg a go-around loses us a slot on the approach which adds a couple of minutes to each subsequent EAT. We try to provide accurate updates but this is not always possible. Pilots accept this and stay in the holds until instructed to leave. We can take a/c off the holds way bove the minimum stack levels if necessary. The "accuracy" of getting traffic off the hold at a particular time is not relevant as we can adjust track lengths within the intermediate approach quite easily..

[Spitoon]

And to add a bit more. I'm not sure if this is what ferris has in mind but, depending on the other traffic in the sequence and how busy it is, I'll either tell the aircraft to turn onto a particular heading now or tell it next time over the fix leave on heading such and such.

[ferris]

Spitoon- yes, that is exactly what I am after. Have worked in different places where it is done differently, just wondering if there is a better way out there.

[HEATHROW DIRECTOR]

OK.. well there are lots of ways to fix an approach sequence and it all basically comes down to "delaying action" to achieve the required track distance to touchdown. The following are possibilities:

1. Speed control the a/c as it approaches the hold to prevent it actually having to hold and bring it straight off.
2. 1 above plus using a slightly delaying heading off the hold. Eg if the standard heading off is 270, you could use 200 for 3-4 miles to build in that extra track distance.
3. Get the a/c to carry out an orbit instead of a full hold.... and apply speed control if necessary in combination.
4. Snatch the a/c back half way down the outbound leg..
5. Tell the a/c to maintain its outbound heading until instructed to return to the hold and leave.. This is good if two a/c have to leave but they're one above the other - allows you to build in the required distance between them.

There must be a hundred other ways too..

[FWA NATCA]

Ferris,

Normally you unstack the holding pattern starting with the acft on the bottom, I've seen it done the other way but not without a few, eeks, ahhs, dropped pens (so the other controllers can say they didn't see anything) and holy mackerls.

Mike R
FWA

[HEATHROW DIRECTOR]

Well we sometimes have to unstack 'em at random levels to achieve the best final approach spacing and hence the best landing rate. Ie "First come, first served" doesn't always apply. By this method we can get all the Heavies together and juggle the other weights so we don't have too many big spaces on the approach.