ADS - CPDLC What can ATC see?

[EK380]

For ATCO's with ADS experience:

What exactly can controller see while on an ADS contract with an aircraft? I suppose that depends on the service and the contract.

I heard somebody mentioning the following:

1/Flight into AUS. Controller asked why the aircraft had setup the STAR and approach into the MCDU, before the clearance had been given...

2/On a NAT crossing. Crew advised by ATC that somewhere down the route the routing in the FMGS (FMS) was not correct. The error was not the next TO waypoint.


I had been under the impression, that ATC was only seeing the next TO and the FROM waypoint...

Anybody more info?:confused:

[Nautilus Blue]

1/ results from the a/c sending FROM, TO and NEXT, but I can't remember if is ADS-C or CPDLC. ADS-B gives only position and level, I think ADS-C is the same (but the reporting schedule is adjustable). CPDLC sends full position reports at each reporting point.

e.g. A/C has planned and has been cleared A B C DEST. In anticipation of the STAR, the crew set up A B X Y Z DEST, before they get to A. At A, A/C reports at A time, FLxxx, est B time, next X. ATC computer is expecting next C, recognizes the discrepancy and triggers an ARCW (something route conformance/compliance? warning) on the controllers screen.

I'm sure someone more familiar with the systems will be along shortly to clarify.

[Plazbot]

1. In OZ the controller would have received an alert called an ARCW or ADS Route Conformance Warning. I am guessing this was the DONYA arrival into Darwin late at night? Some carriers plan the arrival into the machine but ATC don't issue the STAR late at night usually.

2. As per 1

This also shows up when crews input weather diversions into the FMS to plan around cells. Pretty much, when you FMS does not show EXACTLY your flight plan*, the alarms go off.


*This means the flight plan held in the ATC system. Sometimes, it is not exactly the same as filed. Some carriers plan the STAR which is removed by the assistants as it gets rejected by the computer in ATC land.

[EK380]

Hi Plazbot,

You seem to be knowing what you talk about... thanks for the reply.

No it was not into Darwin, but Melbourne.

Can you please confirm once again that you guys can see whatever is in the FMGS, not only the TO waypoint and the next one ? The whole route including the STAR and the landing runway?

We teach our crews to enter the expected routing and landing runway in the box (FMGS) in the beginning of the flight, in order to have a realistic fuel remaining, time, etc... and to improve situational awareness. Needless to say that the arrival is then updated whenever the arrival clearance is received.

Do you guys have any problems with that?


Curious for your feedback,
EK380

[Plazbot]

There may be a limit on the look ahead distance and 3 waypoints rings a bell? It certainly goes beyond the TO and off memory, 3 does indeed 'look' right. When you plan WX diversions, we see your first off track, the last off track and the interception pont on the alert. Oceanic offsets also show up when you cross the line going to/from Indonesia. When you are on Radar, we can't see the ADS-C route so it will only show up in places where you are off radar, approaching the fringe and within the look ahead. Darwin and I am guessing into YMML/SY/BN from the Tasman would have the issue as well as into CS from the North/West/East. Perth too but noone cares about Perth ;)

Some carriers physically plan the arrival like I said above and I have always assumed that they input it into their FMS ausing the TAF conditions for the runway but the OZ procedure is to remove it from the flightplan then enter it into the ATC system. My memory is hazy but I recal something in AIP or a Supp that advises crews not to enter assumed STAR information into FMS before being cleared.

I would look it all up for you but am no longer in OZ and looking at your user name may be sharing the same neck of the woods now. There is sure to be someone else along soon. If not, I can try and put you in touch with the ADS guru in Brisbane 'unofficially' if you want to pm me an email address.

[EK380]

Thanks again Plazbot.

Just send you a PM.

[rab-k]

With an ADS Waypoint event contract we see your position reports in the same format as HF; waypoint/ata, level, next waypoint/eta, subsequent waypoint. If we "Demand" a report we see your ppsn/time, level, next waypoint/eta, subsequent waypoint. Also, if you should alter the route in the FMS the kit can also automatically send us a position report in the same format as the "Demand" report. Therefore if you deviate for weather, for example, we'll see what you're doing before you've even told us...:E

CPDLC we don't use for position reports in the Shanwick area for reasons I won't bore you with.

[max1]

EK380 and Plazbot,

I'll try and get our Oz Guru, (you know who I'm talking about Plazbot, AW) to get on here and talk to EK380.

For those who are just reading out of interest, the ADS-C part is the Automatic Dependent SURVEILLANCE- Contract (like radar) and the CPDLC is the Controller Pilot Data Link COMMUNICATION (like VHF or HF).

We (ATC) basically make an initial 'contract' with the aircraft about what we will see and monitor on ADS-C.
If the aircraft deviates differs from what ATC originally "contracted' to see we will get alarms that the aircraft has deviated from intended route/level/clearance etc.THis also has a designated look ahead component.

These are EVENT reports, e.g. if an aircraft deviates from its cleared level/s by +- 200ft this will trigger a message to the ATC, or when an aircraft crosses a compulsory position report.
There are also PERIODIC reports, i.e. an aircraft will automatically send a 'position report' at a set time.

Different aircraft Boeing and Airbus also have, or did have (it's been awhile), different formats for downlinking position reports.

It's a great piece of kit, vice HF.

[EK380]

Thanks Max1. Starts clearing up!

Especially interested if there are any problems from a controller standpoint to enter a expected STAR and expected approach in the FMGS before arrival clearance is received.

EK380

[hoboe]

Max, Plz, & EK, Im pretty sure that ARCW alerting (Oz ATC software compares acft FMS route with FDR route) is only based on the NEXT reporting point and NEXT+1.

However I still can't see how it would have alerted a controller for an acft arriving in YMML as ADS-C alerting is inhibited once an acft is painting on radar isn't it?

Edited: found a helpful link courtesy of Craig J.Roberts

ADS (http://members.optusnet.com.au/~cjr/ADS.htm)

[willadvise]

I can confirm that in Oz the computer only checks for next waypoint and next waypoint+1. These checks are inhibited when you are in radar or in ADS-B coverage. Most of the ADS-C guys have ADS-B now and just about the whole country is covered by ADS-B now. The advent of ADS-B has removed a safety net for the enroute guys as incorrect routes are picked up by the ARC-W before the aircraft flew on a different route. In ADS-B coverage incorrect routes are picked up only when the controller notices the aircraft diverging from route (hard to notice on the scale the big enroute sectors operate on) or when the RAM (Route Adherence Monitor) goes off when the aircraft is 5nm off track (I think that is the number, someone may correct me) The only places where you are likely to get an ARC-W coming into ML is if you are flying a southerly flex track (south of AD) or your ADSB is US.
I personally don't have a problem with you planning the STAR. The procedure that it generally followed if you do generate an ARC-W is that we will confirm with you your actual route (annoying before both us and the aircraft) or we will coordinate with the next sector that you are subject to an ARC-W and that you may fly the STAR without being issued it.

Question for you. In the advent of total comms failure what would you fly?

[EK380]

Thanks for the info willadvise! Great stuff...

Regarding the loss of comms, flying filed FPLN route and standard lost comms procedures would apply for us. Would you expect us to do something different?

One more question...What speed/Mach and Altitude do you guys see with ADS-B? Indicated Mach nr and Altitude and/or selected M and FL on the MCP/FCU panel?


Thanks again

[Quokka]

Regarding the loss of comms, flying filed FPLN route...

Is the anticipated STAR entered into the FPLN route when filed?

[EK380]

I guess not...!?

[willadvise]

I would expect you to fly the lost comms procedures but if we have seen an ARC-W we think you might fly a STAR. The problem is that some operators submit a flight plan containing a STAR which is deleted before entry into the flight data system. So to see what you have actually flight planned we have to ask the Flight Data Coordinators for a copy of the original plan. The plan may indicate a STAR for a non duty runway at the time.
For an aircraft subject to an ARC-W indicating the STAR, who has a comms failure we should check to see if you have filed the STAR in the original plan. If so I would expect you to fly the STAR. If the filed STAR is for the wrong RWY I don't know what I would expect you to do. If you haven't filed the STAR I would be left wondering are you going to fly the STAR or are you going to fly planned route. In any event you can be pretty certain that we would cover all options and keep everything out of your way . The chances of total comms failure is pretty remote in most modern jets(I would expect you to risk using a mobile phone if necessary) unless there is some other catastrophic failure in which case you would just be landing in the most expident manner.

One more question...What speed/Mach and Altitude do you guys see with ADS-B? Indicated Mach nr and Altitude and/or selected M and FL on the MCP/FCU panel?

We only see ground speed and mode C level. The ground speed is calculated by the system. We don't get to see any of the other goodies yet. I understand that we will get to see the other stuff at some unspecified time in the future with a software upgrade. We get your Mach Nr in a CPDLC position report which is useful in determining if we are going to have opening or closing speed between aircraft but because you only send one of these at the FIR boundary is not updated when you change speeds. Indicated Mach Nr would be useful for sequencing and in the enroute phase to stop those occasions where you wonder why your B744 is being flogged by a B762 and when you ask them the say they are at minimum because they are going to bust curfew at YSSY. Of more use would be the selected FL on the panel. This would reduce the number of IDDEs (Information Delivery and Display Error.. The term we use for incorrect information transmitted, failure to hear an incorrect readback or for entering incorrect information into the ATC computer) massively. Any hearback error or incorrect selection of cleared flight level (CFL) into the ATC computer, would be picked up immediately by a discrepancy between selected Fl on the panel and the CFL on the ATC computer.

[Chrome]

Plazbot Some carriers physically plan the arrival like I said above and I have always assumed that they input it into their FMS ausing the TAF conditions for the runway but the OZ procedure is to remove it from the flightplan then enter it into the ATC system. My memory is hazy but I recal something in AIP or a Supp that advises crews not to enter assumed STAR information into FMS before being cleared.

Great information here, thanks to the informative postings. But does anyone know of the said AIP or Supplement? Thanks.

[ollie_a]

The closest thing I could find is in AIP ENR 1.1.19.5:

SID/STAR details and instrument approach fixes/way-points for Australian airports must not be included in flight notification contents.