— By James Ferrier, Director, Aviation Operations, COPA

Last week COPA highlighted the first concern around the lack of regulatory authority of NAV CANADA to announce an ADS-B mandate on behalf of the State. This week COPA would like to explore its second concern about how a decided course of action can be announced when trials are still ongoing, and the results of those trials have not been made public for review, consultation, or challenge.

NAV CANADA’s ADS-B “Mandate”?

In 2019 NAV CANADA, with UK NATS, first implemented space-based ADS-B over the North Atlantic. We know significant trials were conducted, operational data and results reviewed and accepted by the international community before use of ADS-B over the North Atlantic was implemented.

Based on the information from the successful implementation in North Atlantic airspace, use of ADS-B above FL290 was introduced in Canada’s domestic airspace for suitably-equipped aircraft. The evidence of the oceanic trials validated the extension of use between suitably-equipped aircraft but still recognized the need for other aircraft not equipped to operate based on current regulation and using traditional separation standards. ADS-B-equipped aircraft were given an operational benefit, but others were not excluded.

Moving forward and quoted from NAV CANADA’s website, “NAV CANADA is conducting a trial within specific airspace below FL290 in Montreal Flight Information Region beginning December 10th, 2021, followed by Edmonton FIR in early 2022. This trial represents the first time ADS-B data is used below FL290. The trial will help evaluate performance, gather air operator, air traffic controller and flight service specialist feedback, and address any potential technical issues prior to the mandate going into effect.”

This last statement raises the question and concern that needs to be addressed. The quote itself states this is the first-time space-based ADS-B is used below FL290 and is to evaluate performance, gather feedback and address technical issues. If this is the case, then the trials are not complete, the performance, procedures of the system are not validated and the evidence to decide to implement the use of ADS-B below FL290 is just not complete. How can a defined course of action be decided if trials are not complete?

Aside from the obvious contradiction of declaring a course of action without validation from trials, there are also technical questions that COPA understands need to be answered before implementation of ADS-B in low-level airspace. The main question is to be whether space-based ADS-B can perform in high-density, congested airspace? As early as 2008, the FAA (Federal Aviation Administration) was concerned about congestion on the 1090 MHZ frequency and the ability of surveillance systems to handle traffic. This was a contributing factor in deciding to implement a two-frequency system to manage bandwidth. If this was a concern with a land-based ADS-B system one can only assume a space-based system would face similar, if not greater, challenges with congestion. While not officially confirmed, COPA believes there is some concern about this problem and there is the possibility that ground-based ADS-B units may be needed to help manage data congestion in high traffic airspace. Knowing this may be a problem it is confusing why ongoing trials are being done in lower volume airspace versus busy airspace where potential problems could reasonably be expected to be encountered?

Understanding there may be a challenge with congested airspace one must look at the current state of surveillance. We know currently Secondary Surveillance Radar (SSR) systems provide land-based data which is combined with space-based ADS-B and provides surveillance redundancy in busy airspace. This combined data is merged in ATC displays and should be able to be filtered by source to reduce the amount of data processed and displayed and allow systems to manage data congestion. It is also known SSR are high-cost systems that ANSPs are looking to replace in the future with lower costs systems like ADS-B.

From a business perspective, it does make sense to reduce ANS costs but if current SSR capabilities are to disappear in the future what could be used to filter data and be the redundancy factor, or backup? It makes sense that redundancy would be maintained with some form of ground-based ADS-B system which could provide surveillance data should space-based data become unavailable. Knowing there is current surveillance technology available in busy airspace and, a likely, future ground-based backup to space-based ADS-B why do users need ADS-B capability in the near term and more importantly why is there a requirement for antenna diversity or ability to broadcast ADS-B Out to space-based receivers.

Considering that trials are admittedly ongoing, and the future structure of surveillance has not been decided (at least not publicly), the question remains on how a Mandate can be announced with a determined course of action? Has the verdict been decided before all the evidence is available?

Representing the single largest group of Canadian airspace users, COPA reasons that the concerns and questions identified in this article need to be addressed, answered, and explained, publicly, before this “Mandate” can be imposed, in less than one year.

Next week we will look at airspace access questions and the costs to users of implementing the ADS-B mandate as currently defined.

(Image: Aireon, YouTube)