CPDLC vs. ADS-C Position Reports

Several months ago, in a blog on “Greater Than 2-Minute Revised ETA vs. ADS-C”, I described the effect of an active ADS-C connection on updating ATC with position reporting information. I think that pretty well settled the 2 vs. 3-minute question. The last portion of that blog touched on the idea of not using CPDLC and/or HF/SATCOM Voice to make position reports once ADS-C is active. If you missed it, here’s a link: "Greater Than 2-Minute Revised ETS vs. ADS-C"

Discontinuing normal CPDLC and/or HF/SATCOM voice position reporting when an ADS-C contract is active is true. Pilots are supposed to just trust the system that it is working unless notified differently. Like any good pilot, a tradition saying, “Prove it!” has been heard frequently.  Prove CPDLC and/or HF/SATCOM voice reporting in not required AND prove to me that my revised ETA got to ATC. Seems like fair and reasonable questions to me.

A Tale of Many... Books!

As of September 2016, there is not a “Back n’ White” answer to be found. The reference paragraph in GOLD is 5.6.3. This is the source document for all things data link. A similar paragraph is found in ICAO Document #4444, Paragraph

Here’s how the document trail works: FAA resource guides and AC documentation drive US operators into ICAO’s “GOLD” Document for data link answers. The GOLD document is then modified by a country’s NOATMs or AIP. When it comes to the issue of ADS-C vs. CPDLC position reporting, I found no difference to GOLD listed in #7030 for Asia, North America and the NAT regions. Only the differences to ICAO Annex’s’ are listed in ICAO Doc#7030, the GOLD document is not listed here.

Dated Information

In GOLD’s Appendix E, there are several FIRS’ that require a CPDLC position report at FIR crossing. My best guess is that these are old discontinued procedures. I cannot find a NOTAM or AIP requirement for CDPLC position reporting with an active ADS-C contract in the Canadian, Australia, Japan, China or Brazil AIP’s.

I did find a NOTAM from the Oakland OCA that has kept the FIR boundary position reporting alive with a twist. Basically waiting until the receiving FIR has accepted the handoff and is the “CDA” then CPDLC position report.

Standby for a new issue of GOLD anytime now, it has been approved by the team authoring it and is waiting ICAO’s release to publish. Meanwhile this creates some of the confusion for pilots operating in the regions with FANS connectivity.

A Human Factors Angle

Some operators will use FreeText to update ETA’s. With a Current Data Authority, CDA and an active ADS-C connection to the same FIR, this is a resounding “NO”.

If pilots choose to use this kind of position updating, it requires a manual input by the controller into the ATC computer systems. READ: Human error inducing.  To add to this uncertainty for the pilot,  there are plenty of documentation and ATC procedures that ask pilots not to call and confirm receipt of  automated position reports. This procedure would defeat the purpose of the automation and drive ATC into distraction.

I think that if an operator MUST have a record of action to update a revised ETA in a ADS-C active environment…use CPDLC FreeText and ask “Confirm Revised NEXT ETA”. This operation will not induce a human error into an automated system.

Let me clear, this recommended procedure is not specifically approved GOLD. This technique complies with the GOLD directive to use FreeText only when amplifying or explaining a previous message. This will also make it alot less stressful for a pilot to prove that you are keeping ATC advised of your revised ETA w/o the need for more voice communication.