Electronic Conspicuity: the FLYER test

The CAA offer of a £250 rebate towards EC kit means there’s never been a better time to make the aircraft you fly more electronically visible, but there’s a lot to think about. Ian Seager gets airborne with the kit you might be considering… [first published in FLYER December 2020]

Let me get straight to the point, well, several points. First, there’s funding available to help you with your Electronic Conspicuity solution. That’s very good news. The Department for Transport (DfT) should be thanked and if you qualify (most of us do), you should take advantage to make the aviation world a better place.

Second, there are great solutions available right now but there’s no one-box solution that will do everything. It doesn’t exist, it may never exist and while doing nothing while you wait for it to exist is always an option, I don’t think it is a particularly good one.

Third, I know that PilotAware has some concerns about my own preference for ADS-B giving bias to this feature. If you want to know what I think personally, then read my column here. As far as this review is concerned, I’ve dug out my extra straight bat, and I’ll be using it, metaphorically, throughout this article.

There’s an Electronic Conspicuity thread running on the FLYER forum that has 1,063 posts – over 71 pages. It’s had 42,883 views and, as with most long forum threads, it’s a mixture of fantastic technical information, informed views and great summaries alongside entrenched positions (with forum posters stuck on transmit), and a sprinkling of comments that might make you want to poke your eyes out with a sharp stick.

This article is not a rehash of those arguments. This article is about a group of normal, everyday pilots who wanted to find out about Electronic Conspicuity in real aeroplanes in the real world.

eelectronic conspicuity test aircraft
Our three aircraft for this Electronic Conspicuity real world test: Cessna 182, Jodel and Van’s RV-8 Photos: Ed Hicks

We gathered four aircraft and some great friends of FLYER together with a selection of EC kit, both fitted and portable, and went flying. Our collection of emitting options totalled:

  1. Two fixed ADS-B solutions, one fully certified and one in an RV-8
  2. Two SkyEcho 2s with one putting out ADS-B (the other only acting as a receiver)
  3. A PilotAware Rosetta, putting out its proprietary P3i
  4. FLARM
  5. Our transponders, all of which were Mode S.

We figured that was a pretty good selection for the types of traffic that everyone would generally find, and of course, being a half-decent day, there were also some aircraft flying around that weren’t part of our test. In terms of receiving traffic information and displaying it, we mainly used portables, with a mixture of iOS and Android tablets and phones, all of which were running SkyDemon.

We were able to compare the various systems in flight in real time, recording results on phone and tablet

Target aircraft

Rather than all four aircraft getting airborne at the same time, we ran through the various combinations one on one with the ‘target’ aircraft running up and down a line feature with it on their left, and the spotter aircraft doing the same at an appropriate distance. This gave the opportunity for converging and diverging traffic. The target aircraft then moved its track through 90°, and flew back and forth perpendicular to the line feature (the Westbury to London railway if you’re interested). We repeated this a couple of times, taking recordings of the tablets and phones, and stills of the certified traffic display on the 182’s GTN 750 moving map, which was being driven by Garmin’s certified GTS 800 Traffic Awareness System.

The first flight saw the Jodel depart with Rosetta on board and ADS-B out via its SkyEcho 2. Sitting on the ground in the 182, waiting for the pre-briefed gap to form, it was comforting to be able to track the Jodel on my iPad thanks to its ADS-B signal (the Rosetta in the Jodel was putting out a P3i signal and that can only be read by another PilotAware unit). We took off and set up to start our head-to-head runs (separation assured by us each being on different sides of the railway line). Ed Hicks was with me in the Cessna, and we watched the Jodel, a few miles away, begin its turn towards us. Then it disappeared.

An instance where PAW Rosetta did not display the head-on traffic until the very last minute

And so, just a few minutes into the first flight, the trend was pretty much set for the whole day. I know it doesn’t take a genius to figure out that the positioning of aerials on portable units is important, but it ruddy well is, and I think too many people ignore that.

The SkyEcho 2 was vertical (important) and in an elevated position in the Jodel. For an internal device its placement was pretty optimum. In the Cessna, the SkyEcho 2 was attached to the windscreen on the P1 side of the aeroplane. Not as good as the Jodel’s placement but about as good as it gets in a Cessna. Portable units with internal aerials mean that there will be occasions when emitting traffic is invisible, thanks to things like bodies, engines, carbon fibre etc.

RV-8 antenna
The upper FLARM antenna in the RV-8 – it’s paired with a lower external blade on the bottom of the aircraft

Detect and Display

And the first trend perfectly illustrated the next trend. As Dave White, pilot of the SkyEcho-equipped Jodel pointed out, EC really has four different elements: Detect, Display, Alert and React. The temporarily vanishing Jodel grabs your attention and, if you’re not careful, the process stalls after Detect and Display. Looking back at the screen recordings of that first flight I was shocked at all the other traffic that was shown, and that I’d missed when flying, because I was fixated on the Jodel, which of course reappeared once the aerials were no longer blanked.

With the two aircraft closing, SkyDemon played its part by alerting, both visually and aurally. The Jodel’s symbol turned from green to yellow and finally red, but even more impressive was SkyDemon’s audio alert, stating ‘Danger, Aircraft ahead, 1.5 miles, same level, reciprocal heading’.

Next up was the RV which is pretty well equipped, being able to do both ADS-B and FLARM in and out through installed aerials. ADS-B out is transmitted through an aerial on the belly, and FLARM via an aerial on the topside of the fuselage (but inside the canopy). Unsurprisingly, the RV remained (electronically) in view for pretty much 100% of the time. In a turn its ADS-B signal would disappear only to be instantly replaced by its FLARM signal. This particular RV is about as conspicuous as it gets and the SkyEcho 2 mounted inside the Cessna had no problem picking up either of the signals.

Cessna 182 PAW antenna
Antenna placement, unsurprisingly, is critical and has a huge effect on efficiency. This is the PAW unit mounted on the coaming on the C182

Blanking issues

For the final two-ship flight of the day we put the PilotAware Rosetta in the 182 where we placed it on the panel’s coaming with the best view we could manage. It was linked to an iPad, while the SkyEcho 2 was linked to my iPhone. Target ship was the RV-8.

There was an inexplicable (to me) anomaly when sitting on the ground. The SkyEcho was picking up both the RV and a Cub that also had a SkyEcho, while PilotAware was only showing the Cub. Presumably it was some kind of aerial blanking issue.

In flight the units both worked well. There were times when the situation on the ground at Lydeway (our base air strip) was reversed and Rosetta saw SkyEcho 2 equipped traffic, while our SkyEcho 2 didn’t. Again, an aerial issue I suspect. Rosetta did however pick up traffic that we believed to be another PilotAware equipped aircraft as it wasn’t visible to either SkyEcho or the Garmin GTS 800 (so it wasn’t transponder equipped).

PAW Atom Grid
PAW’s Atom Grid base stations in the south – there’s a bit of a gap where our test took place, south of Chippenham, so we went looking for stations

PilotAware makes a big thing of its Atom Grid base stations, essentially a network of transmitters set up by volunteers that rebroadcast traffic including FLARM and what’s referred to as Mode S/3D. Through multilateration, the position of otherwise bearingless traffic is known and broadcast to be received by aviating PilotAware users.

During our flights we didn’t see any Mode S/3D or FLARM traffic through Rosetta. Keith Vinning of PilotAware had warned us that we were in an area of poor coverage, so we enabled the software to show ground stations and flew to our closest. From a height of 1,500ft we had to fly within 1.5km before we could pick up the station. Flying an orbit to allow for a very directional antenna issue on the ground, we lost the station at something just over 2.5km.

Later that day, and unwilling to rely on such disappointing results, we took off again and headed for The Park gliding site, where we picked up the ground station from just over 3.3nm away, another surprisingly short range.

Note: Since this feature first appeared we have bene in touch with Lee Moore from Pilot Aware. Lee analysed our track data from which he also recreated our flights. The data shows that we did receive some Mode S/3D traffic, and were visible to/could receive from a distant station. As soon as we can fly again, we plan to take another look at ground stations, their coverage areas and the information uplinked from them. IS


Sporadic data

Thinking about this, I had to conclude that the coverage provided by the ground stations is insufficient for traffic data and that the extra traffic PilotAware talks about is going to be sporadic at best. I also knew that my conclusion would be unpopular, even disbelieved, so I decided to fly again to see if I was right, or had been unlucky.

There’s no available list of ground stations, nor way of knowing just how many there are, although we have been told that, “The target is 300 stations by the end of 2021, 400 stations by the end of 2022. The addition of a further 200 stations within the next two years will provide increased coverage, greater range and redundancy.”

However, we’d heard of one in Bath and knew there was one at The Park gliding site. I took off from Lydeway, with PilotAware Rosetta on the 182’s coaming and linked to my iPad. The Bath station became visible at 3.8nm, a significant improvement. Better still, while The Park again became visible at just over 2nm to the north, it remained visible when I turned for home 10nm south.

In trying to understand this I have spoken to three different people who run ground stations. They all asked to remain anonymous but said things like ‘still needs the antennas put outside, they are at present in the roof space… so the range is not great’ and ‘trees in the vicinity cause problems with range’. Two of them also spoke of software crashes.

Undoubtedly the available range will vary on antenna placement, and while owners of Permit aircraft can permanently install PilotAware with well-sited external aerials, renters or people with certified aircraft cannot.

For me, the bottom line is that while a network of volunteer-built and operated ground stations might be a rapid and low cost way to build a network, the coverage is not predictable or widespread enough to be a viable way of transmitting traffic to the General Aviation fleet. Sorry.

Returning to Lydeway, neither the iPad (Rosetta), nor my phone (SkyEcho) were showing any traffic but the Garmin had picked something up and was showing a target on the GTN 750 at the same level on a reciprocal heading. Just as we both saw a C42 coming straight at us, the GTS 800 called the traffic perfectly. A great illustration that not all traffic will appear on every system and some traffic won’t appear on any system.

Traffic spotted
This C42 wasn’t picked up by either PAW or SkyEcho but Garmin’s GTS 800 traffic system spotted it, below

Training community

Making yourself electronically conspicuous is a very good thing, being able to see other participating traffic is great, but it’s very, very easy to get distracted or even fixated. Perhaps, as Dave White suggested, maybe the training community should be considering a syllabus to ensure the systems can be used to best effect.

With thanks to… It was a fascinating day and would not have been possible without very generous help from Steve Ayres, Mark Collett and Dave White who provided their time, aircraft and patience in return for no more than a cup of tea and a chocolate biscuit or two. Thanks also to Nigel Charles who allowed us to use Lydeway as a base.

Battle of the portables…

SkyEcho 2
SkyEcho 2

SkyEcho 2

What we like The SE2 feels like a high quality piece of consumer electronics. While you wouldn’t want to throw it at a wall, you would expect it to live a long and happy life in a pilot’s bag. The built in battery charges through a USB-C port, and a full charge will outlast pretty much all pilot bladders and most of their fuel tanks too.

It’s supplied with a RAM mount and a simple quarter turn fitting, and should be mounted vertically for best reception. This makes it very easy to live with if you rent aircraft, or swap between several different ones. There’s a simple on / off button and three lights, battery to show there’s charge, ADS-B to see if it is set to transmit (you can disable this if you are already doing ADS-B) and GPS so that you know it’s found itself.

The SE2’s internal GPS allows the SIL value to be set to 1, and while SDA currently remains at 0, that too should change when the CAA gets around to amending CAP1391 (see: Unavoidable tech talk boxout)

It has two receivers, one for ADS-B on 1090MHz and the other for ADS-B transmissions on 978MHz. The latter is used in the US for uplinked data which can be FIS-B and / or TIS-B (weather or traffic respectively). There have been a few trials in the UK (and one last year in Germany) along with persistent rumours of more to come. Should that happen, and should it ever roll out nationwide, the SE2 will be ready and waiting. Right now, it is possible to go into the units settings and change the second receiver to pick up FLARM transmissions. You’ll have to pay another £30 to your nav app provider, but the unit will then be able to see FLARM traffic in addition to ADS-B traffic.

What we don’t like We mentioned very early on that the placement of antenna is critical, this is particularly true if you are considering a fixed installation where you can take some time and care to place them to best advantage. Sadly, the SE2 has no external sockets, so the antenna are going to be wherever you mount the unit. Right now, the choice to receive FLARM transmissions is simple, that other receiver is doing nothing anyway, and it’s definitely worth £30 a year to spot all of those cross-country gliders. However, when and if (we can dream can’t we?), TIS-B or FIS-B or both become available in the UK we’ll have to choose between them and FLARM.

PilotAware Rosetta
PilotAware Rosetta

PilotAware Rosetta

What we like Wow. Talk about innovation and ingenuity. What started as a self-build (and originally, solder) kit has been transformed into a box that arrives almost ready to fly. The small team of developers and volunteers constantly develop the product with features added regularly.

The aerials have external mounts, so if you’re working on a fixed install you can run cables and put the aerials in the best place possible, and that should increase the range at which you see traffic, or the range at which you can pick up ground stations. Rosetta puts out a P3i transmission that will be picked up by other Rosetta users. There’s an annual subscription of £14.40, which we think is a low cost for upgrades and improvements.

What we don’t like The build and feel is not fantastic and I doubt that it would have a very long life if treated in the same way as the other electronics in most pilots’ flight bags. This is accentuated by the aerial mounts, and if the antenna are left on, it makes the connections even easier to damage. My first classic unit met its end when the aerial mount snapped off.

The literature is very clear in saying that the battery / power supply is critical for trouble-free use, so it’s a shame that there’s no internal battery, and that you have to buy an external battery and the lead to plug it in. This doesn’t make portable use any neater. Adding power to Rosetta turns it on, and removing it turns it off, there’s no switch which seems a bit strange. Equally, there’s no light to indicate that it’s being powered. We tell a lie, there are a couple of lights, but they are inside Rosetta’s case, and you have to peek through the cooling slats on the side to see of they’re on. Some people are emitting P3i as their EC transmission. They can only be seen by other Rosetta/PilotAware users.

What we think Both units need to improve. SkyEcho has an app in both Apple’s App Store and Google Play. PilotAware has an app in Apple’s App Store. With SkyEcho you can easily change several parameters, and with Pilot Aware you can easily update the firmware. Both of these things are good.

What’s not so good is that to do certain things for either unit you have to join its WiFi network and log in to it via a browser by entering its IP address. No. No. No. I might be able to do it, you might be able to do it, but the widespread voluntary adaptation of EC needs to be geek-free and friendly from the user’s point of view.

Garmin GTS 800
Garmin’s GTS 800 traffic system

Unavoidable tech talk – CAP1391, SIL and SDA

Once upon a time anything to do with aviation had to be fully certified. This is a good thing for wing spars and structures etc, but it also acts like a prophylactic. It keeps us safe from many nasties but gets in the way of the next generation.

The CAA’s CAP1391 document on Electronic Conspicuity devices sets out to make a nationally regulated hole in the end of the condom, which has meant that we now have access to much lower cost systems. General Aviation doesn’t fly in a vacuum, and we do interact with other traffic, so some conditions were put in place to guard against unwelcome surprises should that super cheap GPS dongle you found on eBay doesn’t quite do what’s expected (yes, I know, most do.)

Airline and business jets tend to fly with expensive TCAS systems and a fair few General Aviation aircraft fly with active traffic systems like Avidyne’s TAS600 and Garmin’s GTS 800. These fully certified systems, by regulation, have to ignore emissions that have a Source Integrity Level (SIL) or System Design Assurance (SDA) value of less than 1, and that means much of the equipment flying thanks to CAP1391.

Today, an ADS-B transmission that uses PilotAware for its GPS location data, or one that is being sent out by uAvionix’s SkyEcho 2 will not be seen. Any transponder using PilotAware for its position source should have both SIL and SDA set to 0, and SkyEcho 2 has SIL set to 1 and SDA to 0.

In response to a question from FLYER, the CAA said, “We do plan to update CAP1391 to make it more of a universal standard for more airspace users. In the immediate future we are considering an option of following the CASA (Australian) approach that would ask manufacturers to declare that they meet some of the certified aspects of a TSO.”

uAvionix has stated that it is capable of meeting the requirements for SDA = 1, so a small and promised paperwork change should make SkyEcho 2 emissions visible to much more traffic. Come on CAA, get it done!

What regular users say…

Paul Kiddell and his fellow Eurostar group members are avid PilotAware users: “Like many UK microlighters, we’ve utilised PilotAware for some years, and since 2017 we’ve flown 1,100 hours with PAW and found it an exceptionally valuable and reliable tool.

“Our Rosetta is a permanent fit with internal power, and uses external underside aerials.  Our PAW provides GPS to our Trig TT21 transponder to enable ADS-B out (albeit with SIL=0).  All very straightforward and being a Permit aeroplane, we undertook all the work ourselves.

“PAW/ADS-B out has made touring in large groups effortless. Using SkyDemon, we can always see each other, which has cut down on radio chat.

“We regularly meet en route in flight and have no trouble rejoining after staggered departures. With external aerials, we enjoy excellent range on PAW and ADS-B airborne targets and generally 20-30 miles on OGN-R stations.

“Indeed, the extensive FLARM rebroadcast network proves very useful, allowing us to reroute to avoid glider concentrations, while also giving us a heads-up of RAF Grob activity. Bearingless targets can be a mixed bag but on one notable occasion encouraged me to look for traffic only to find a Cessna 152 very close and descending towards me from the rear of my aircraft.

“Like all EC devices, PAW is not a panacea for collision avoidance but I do feel it provides excellent and affordable additional situational awareness. Combined with a transponder to give ADS-B out results in a fantastic all-round EC package.”

Dave White has been using SkyEcho 2 since July 2019: “Our Jodel group bought SkyEcho to provide ADS-B out since our Mode S transponder would not allow that. We also added the optional FLARM reception for £30/year from SkyDemon.

“The unit needs charging typically only after every three to four flights unless it has a been a long multi-hour trip.

“The firmware has been updated a couple of times using the clear instructions on the uAvionix website. Still some wifi dropouts, but rarely a practical issue.

“We have tried a few positions in the aircraft – suckered to rear window, windscreen etc – but the Perspex flexes sufficiently inflight to sometimes pop it off the screen so it’s now attached to a mechanical clamp above and behind my head.

“We are a wood and fabric Jodel, yet even so some receiver antenna blanking is noticeable, particularly from the engine and a fuel tank behind the rear bulkhead, but otherwise coverage seems fairly good all round. Traffic does appear/disappear from the screen at times but if close enough to be a hazard I am fairly confident it will show up. From what others say, transmit blanking from our aircraft seems less of an issue.

Bearingless targets

Bearingless targets

If you want to be able to electronically see where Mode C and Mode S targets are, sadly the £250 government grant is not going to get you there. You’ll probably need to spend in the region of £10,000 on an active traffic system (you might also need to spend more on a display if you don’t already have something suitable), and that’s a punchy number for any aviator. Last year I overhauled the avionics in the FLYER Cessna 182 to include Garmin’s GTS 800 active traffic system which displays on the GTN 750 and gives aural warnings. It is frankly amazing and I feel naked without it, but it’s not for everyone.

Other systems such as Rosetta pick up Mode C and Mode S and are able to provide bearingless targets, above. These are shown as dynamic circles around your aircraft. A threat that is estimated as being close yields a smaller red circle instead of a larger yellow one. The calculation of distance is done on the strength of the transponder signal.

Like many other things related to EC, opinions are polarised. None of the people helping us out liked bearingless targets or found them useful. The traffic could be in your field of view, or it could be lurking in the large blindspots that inevitably accompany most aircraft. The people we spoke to found them a distraction, meaning the Detect, Display, Alert, React sequence was often stymied.

So what should you do?

Electronic Conspicuity is about seeing and being seen. The CAA’s preferred technology is ADS-B on 1090MHz, and pretty much every single Electronic Conspicuity device I can think of is capable of receiving ADS-B on 1090MHz. The right thing, the collective thing, the thing with the most benefit to most people is to spend your grant money on putting out ADS-B.

First choice would be to use a suitable transponder and an approved GPS source, like Trig’s TN72, that allows you to set SIL and SDA = to 1, (see, Unavoidable tech talk – CAP1391, SIL and SDA for why SIL=1 and SDA=1 is important).

If you jump between multiple aircraft, or if you rent a club aircraft, then portable ADS-B out is the next best solution, and right now that means SkyEcho 2 (which, when the CAA gets a wiggle on, should also add SDA=1 to its SIL=1 capability).

Once you have taken care of your own conspicuity, you will want to consider your options for being able to see others. Pretty much everything sees ADS-B and the more people who equip to do ADS-B out the better.

The elephant with long soaring ears in this room is FLARM. On busy days there can be hundreds of gliders airborne and they’re notoriously hard to see. In an ideal world you’d be able to see FLARM. This is possible with SkyEcho 2 and a £30/yr payment or with Pilot Aware if you are flying in range of an uplink station. Personally, I’m hoping that the cross-country soaring community uses this opportunity to equip with ADS-B out.


  1. Great article, very informative. I have a PAW Rosetta and Trig TT21 transponder fitted to my aircraft and would like to link them to give me adsb out, is there a cable available to achieve this?

Leave a Reply

Your email address will not be published. Required fields are marked *