Overlapping Datablocks (in stacks)

[cancel_mayday]

How do you effectively control in stacks with multiple a/c?
Do they all fly standard patterns or each plane is given a heading?

Thank you.

[Roffa]

In the London TMA we use vertical stack lists on the Heathrow approach positions and adjacent TMA sectors with it being rolled out to the other approach sectors soonish...

http://www.levelbust.com/images/vertical_stack_list.gif

All the a/c fly a standard racetrack pattern, the VSL just gives much better situational awareness. Aircraft are radar vectored out of the hold for intermediate and final approach.

[eyeinthesky]

Question (since it's a while since I used the LTCC MATS II):

Is there still a rule in the MATS saying you must not use SSR info in the stack for vertical separation, or has this been rescinded with the advent of the VSL?

[anotherthing]

eyeinthesky

you can use ssr for separation in the stack, regardless of VSL (which is Heathrow only at the moment).

How long ago are you talking about, as it has never been a rule that I have known of??

[cancel_mayday]

Some colleagues goggle at screens, others try not to forget numerous headings to a/c in stacks while managers say that our 30-year old system can work for another decade... Vertical stack lists is what we miss, Porco Rosso.

[Radarspod]

Not that anyone should be using the Vertical Stack List for maintaining separation or control purposes - thats what the strips are for :}

[cancel_mayday]

We don't use strips for many years :ouch:

[cancel_mayday]

We don't use strips for many years :ouch:

[mocoman]

A query re the VSL.

I can see that the system 'knows' what FL/altitude the aircraft are maintaining but how is 'cleared level' information validated to the system?
Who 'tells' the system what the cleared FL is?( And how?)

F'instance, in the screenshot above the EIN152 is cleared FL110 and is passing FL119 descending but the system still shows FL110 in the hold as vacant whereas I would consider it as being imminently occupied.

I assume that there needs to be some operator input somewhere but am just curious as to how this occurs.

Cheers

[threemiles]

The "cleared level" is interrogated by the Mode-S radar sensor from the airplane. It is usually what you have turned in on the MCP. It is a part of the mandatory enhanced surveillance capabilities of the Mode-S transponder.

http://www.eurocontrol.int/msa/public/standard_page/modes_pol_aircraft_aircraftList.html

Also worth to know is that IAS is interrogated, too, and any deviations from a mandated speed are now subject to comments from ATC.

[coracle]

No input required.

When EIN152 passes FL116, then it has left FL120 and will then move down into the vacant FL110 slot, thus leaving the FL120 slot vacant for the next aircraft, in this case BMA7KD.

If EIN152 moved straight into the vacant FL110 slot as you suggested, then there would be a danger of descending an aircraft to a level not vacated as in this example EIN152 was only passing FL119 and thus has yet to vacate FL120.

[cancel_mayday]

Reading the three last messages I caught myself at a thought that I attend at a talk of another Galaxy's inhabitants. :confused: So large the generation gap is...

[mocoman]

coracle and threemiles:
Thanks for the answers, I had a feeling that Mode-S would come into it somewhere. However I didn't realise that the VSL was so tightly linked with the aircraft and MCP settings.
Also worth to know is that IAS is interrogated, too, and any deviations from a mandated speed are now subject to comments from ATC.
Does the system get data on instantaneous IAS or does it return the speed set in the MCP?
When EIN152 passes FL116, then it has left FL120
Of course, the old 'will be deemed to have vacated a level when the altitude indicates 400ft below the vacated level'. At that point I assume the EIN would drop into the FL110 slot.
So, what would occur on-screen if say 7KD reads back FL120 but puts FL110 in the MCP thus putting itself in potential conflict with the Shamrock? Is there any in-built STCA in the VSL?
Thanks

[Scuzi]

Does the system get data on instantaneous IAS or does it return the speed set in the MCP?
So, what would occur on-screen if say 7KD reads back FL120 but puts FL110 in the MCP thus putting itself in potential conflict with the Shamrock? Is there any in-built STCA in the VSL?
Thanks

The Mode S data shows the instantaneous IAS.

At present there is nothing to indicate two aircraft with the same selected flight level in the holding stack, apart from the controller noticing of course. The normal STCA works and will flash in the stack list too. There is a feature being implemented some time soon which will highlight aircraft with the same SFL which are populated in the same stack list. It's quite a clever feature too, as from what I remember from the presentation, if for example an aircraft at FL120 selected FL90 which is vacant and there happens to be an aircraft at say FL100, it will detect the conflict and highlight it in the stack list.
I'm not sure when it is being implemented though.

[mocoman]

Scuzi;
if ... an aircraft at FL120 selected FL90 ... and there happens to be an aircraft at ...FL100, it will detect the conflict

It all sounds very 'intelligent' but still reliant on the system knowing where the aircraft is in space.

I don't quite understand how the VSL sub-system 'knows' that BAW123 is in the BNN hold and thus adds it to the displayed hold list. Is position information not an ADS_B-only feature?

Does the software rely on position information from existing radar technology and then integrate that with the extended MODE-S information to create a 'picture'?

[Scuzi]

Each stack has what's called a 'capture volume', a defined area around the stack in which aircraft with the appropriate intention codes (in this case LL or WU) will be populated in the stack list. The system adds the aircraft to the stack list when they enter the capture volume, based on position information from the radar.
I'm sure the technicalities are a bit more complex than that but that's how they tell us it works!

[foghorn]

Should add to Scuzi's post: the capture volume is based upon processed radar data, not mode-S downlinked data, so even mode C squawking a/c are included in the VSL (but without the SFL).

[REVOLUTION]

Scuzi;
It all sounds very 'intelligent' but still reliant on the system knowing where the aircraft is in space.
I don't quite understand how the VSL sub-system 'knows' that BAW123 is in the BNN hold and thus adds it to the displayed hold list. Is position information not an ADS_B-only feature?
Does the software rely on position information from existing radar technology and then integrate that with the extended MODE-S information to create a 'picture'?
Every Aircraft has an individual registration/signature number. Similar to the ones on cars. So when a particular aircrafts Mode S is interrogated you get the correct info.
This is coupled with the capture area around each holding stack.
You can also individually 'hook' an aircraft and see IAS, magnetic heading, climb and descent rates.