EC REVIEW

Taking stock of EC

Share the air. Sense all others, be seen by all others. So say the CAA’s slogans for the future of airspace in the UK. Ian Fraser reports

Atheme common to many recent CAA publications (CAPs) concerning the future of airspace in the UK is ‘sense all and be seen by all’. It is about Electronic Conspicuity (EC), a system in which all aircraft automatically transmit their GPS derived position via radio beacons and we will all (including ATC) have a ‘radar’ display and warning device, using this data, to alert us to potential traffic conflicts.

That couldn’t be clearer, and there is affordable technology available today that could do it. With this technology, the airspace modernisation programme planners can harness the data, confident that it has high integrity and will allow a reduction in the amount of controlled and restricted airspace. Commercial and GA traffic could share the air safely, and the UK would become a much more aviation-friendly place to be.

Successful EC is absolutely fundamental to the CAA’s lower airspace modernisation strategy (CAP1734) and must happen. But will it?

One of the key requirements for the CAA’s vision of EC is that all the devices must be (in their words) ‘interoperable’. To me, that means that there can only be ONE standard for all beacon transmissions and the same standard for all receivers.

In various CAPs, the CAA say that they will start to Below The CAA CAPs and the SkyEcho 2. mandate EC for choke points by 2023, and several regional airports are already planning airspace change in response to their modernisation initiative. Is EC ready for that? No, it is not. Currently there are four incompatible conspicuity technologies in use in the UK – ATC Radar, Mode S ES (ADSB), FLARM and Pilot Aware (PA).

Incompatibility

Much has already been written on the problems of, and incompatibility between, these technologies, so I won’t repeat much of it here. It’s a bit like current politics where every standard has its champions who claim they are right and that everyone else is completely mad and wrong. In fact, each of the technologies has strengths and more seriously, weaknesses.

This article was supposed to be an annual technology update on the EC world, but since my last one in February 2019, very little new technology has appeared. Nothing is happening because the market is waiting for the CAA’s decision on an affordable way ahead for EC technology.

To date, the CAA and EASA have been very careful not to take any decisions. In most of their documents they carefully explain that they are not favouring any technology, but they do appear to prefer the traditional transponder band, 1090Mhz, and to continue to use

Mode S ES (ADSB), so I shall focus on this. As well as being expensive and old technology, it’s single channel’s capacity to handle the level of radio activity EC could precipitate is in some doubt. CAA’s own preferred low-cost uncertified technology (defined in CAP1391) is also a 1090Mhz ADSB device and thus vulnerable to the same channel capacity problems.

Unfortunately, it is severely limited in the ‘seen by all’ role too, due to its incompatibility with Radar interrogation systems, which means it will be invisible to most ATC radars and many aircraft equipped with TCAS. It is also banned from controlled airspace as it is uncertified (CAT 3) transmitting equipment (why I don’t know, because radio waves don’t honour airspace boundaries). One of the manufacturers of a CAP1391 device has already said it would be simple to make their device respond to interrogations, but until the CAA permit that, CAP1391 remains seriously flawed with respect to the ‘seen by all’ objective.

FLARM and PA are not visible to any ADSB in device, so no certified aircraft or ATC can sense them. They are currently hamstrung by the radio frequency band they use (around 860Mhz), which is a European low power public radio band shared by many other users in both the UK and Europe. Their choice of band limits them to very low power (= low range) and is outside the authority of the CAA or EASA to either protect it or do anything about it. The CAA’s own Airspace Modernisation programme could resolve this when old technology such as DME is removed and replaced with GPS. This could free up many of the 126 channels available in the 1 GHz aviation band, which in turn could be allocated to FLARM or PA. This would render them serious contenders. It would be comparatively simple for the current devices to make this change and an option for the CAA or EASA as an alternative to Mode S ES ADSB. But only they, not PA or FLARM can make that decision.

Of course, the CAA could just revert to the existing Mode S ES transponder devices, ignoring the risk of 1090MHz channel saturation and have its customers swallow the cost and inconvenience. But will that work? Actually, it has its own technical problems, too. I have been flying with an ADSB In /Out system from a well-known Avionics manufacturer for some time now.

I have noticed that some ADSB transmissions that I know are there, and indeed are detected by various other receivers and ground-based systems, are conspicuous by their total absence from mine. Is it a SIL 0 setting or an antenna issue we asked? No, they say it’s not, the receiver is SIL 0 compatible. The manufacturer has spent some time investigating this anomaly, both in the aircraft and on the bench, but to no avail. They still can’t explain it, although their investigation has exposed several other problems, in particular with other manufacturer’s ADSB Out settings and interfaces. Despite its maturity, mode S ES ADSB is still a fragile technology and no more ready to support ‘sense all others’ than any of the alternatives. The CAA’s strategy is clear. ‘Sense all others’, not just some others, be seen by ‘all others’, not just a few others. This is in line with my original article that I wrote back in December 2017 and with the LAA’s policy on EC, that the immediate focus should be on developing compatibility and interoperability of existing, installed systems rather than the CAA mandating the carriage of any specific equipment type. Two years on I have little confidence that any of the technologies will get anywhere close to this aspiration, let alone meet the CAA’s ‘seen by all’ objective (which needs a quantised performance target too). For such a system to be of any use to their airspace modernisation visions, it must work effectively and reliably in all aircraft from airliners to drones.

The trouble with EC is that nobody seems to know how well any of the available devices actually work together as a system. To realise their vision, I think the CAA must take a system wide view including receivers, displays and human factors as well as beacons, and produce a proper system specification that will ensure interoperability. Only then will industry stand a chance of giving us a solution we can trust and afford.

Above The PilotAware Rosetta.

Available options

There are several options available to the CAA, and indeed they have consulted the aviation world on the matter. The result of their consultation (CAP1837) seems to me to be inconclusive, so the community is not going to help them.

It is up to the CAA to make a decision, not us. If they expect us to equip them with EC, they have to make that decision now to give us – and industry – time to implement their solutions and gain whatever approval is required by 2023. Before we depend on this equipment to keep us safe mixing it with other aircraft, we all need some confidence that the chosen technology will work.

Meanwhile, I attended one of several airspace modernisation workshops run by local commercial airports (Bristol in my case). When I asked how they intended to incorporate EC into their strategy they replied ‘nothing to do with us, it’s up to the CAA’. Because of what I have said in this article, I understand their point, but how can the CAA possibly expect an organisation to plan airspace change without taking into consideration one of their fundamental principles of lower airspace modernisation – EC? Despite all the promises in the various documents, it still looks as if Mode S ES is going to be imposed on us whatever the utopian dream says.

Watch this space, and please provide any feedback to the LAA forum. ■