ADS-C question

[glennbb]

Hello

Does anyone know the update times of the ADS-C periodic contract.

Is there a default update time?

Thank you.

[FE Hoppy]

Not off the top of my head but it will be in GOLD which is free to download from ICAO.

[ahramin]

It is supposed to be set in function of the separation required. Recommended not shorter than five minutes. Theoretically it can be set between 1 and 4096 seconds (2^12) but RTCA DO-258A/EUROCAE ED-100A limits the minimum interval to 64 seconds. If the controlling ATSU does not specify, the aircraft will default to 304 seconds.

[ghw78]

It is largely dependent on the ATSU providers and what they set in each contract. There is all the usual identification of the aircraft and flight Number/Registration/Tail number as well as a time signal when the message (uplink or downlink is sent.

Most have a number of trigger events such as waypoint passage (WCE or Waypoint Crossing Event in ADS speak) and can set values to trigger Altitude excursions and amount of deviation off track. GOLD has a fair amount of detail of the functions that are available in the ADS C systems.

In terms of timing for a data downlink (generally position and currrent flight parameters) the common values as recommended for ATSU providers is not greater than 27 mins between updates in RNP 10 airspace and at intervals not greater than 14 mins in RNP 4 Airspace. It is up to the individual providers to set their own standards, in one of the RNP 4 airspace areas I know that the interval is set at 10 mins.

[underfire]

Interesting question, in regards to update times, I would look at the following...

With ADS-C, there are two lines here, basically the ground system and the aircraft system.

The ground system sends instructions to the aircraft with a list of reports to send, and how often to send them. The system on the aircraft automatically replies, if it can. Depending on the ground system sophistication, it may request very frequent response.

The ground system receives the reports, and based on the vendor, will interpolate between the received data points. Current ATC designs are using more frequent update requests and fewer interpolations.

There are a number of contract type as well, Periodic (ie every 'x' seconds) Demand (ie report requested from ground system) and Event (ie crossing a waypoint, altitude change, and lateral deviation change)

Some ground systems will ask for other data as well, but the ac is not required as of yet to comply, there is Predicted Route Group (next +1 position), Earth Ref Group with track extrapolation (ground speed, vert rate), MET Group with wind/temp, and Intent Group for route conformance.

As noted above, there are some basic minimums, depending on the routes.

[glennbb]

Thank you all for your answers.

[underfire]

This is from the FAA.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.faa.gov%2Fabout%2Foffice_org%2Fheadquar ters_offices%2Fato%2Fservice_units%2Ftechops%2Fatc_comms_ser vices%2Fsc214%2Fcurrent_docs%2Fversion_k%2Fmedia%2FPU-10_SPR-K_Chapter-6_ADS-C_1April2013.doc&ei=Q4ZqUrblAYGDjALXvIDACQ&usg=AFQjCNFmHOxbWxNVol5cKrYAMdrSXLscFg&sig2=1ZcrhPAFIcJ_p8ItsUJHOQ&bvm=bv.55123115,d.cGE