EC REVIEW

Electronic conspicuity – and how to use it!

Neil Fraser explains EC’s foibles and advises plans for when you have a potential conflict…

Ihave been investigating, using and reporting on Electronic Conspicuity (EC) for nearly four years and have notched up more than 150 hours air use of various gadgets. My experience of the traffic information from my EC has on the whole been good, and I have even experienced a couple of real traffic alerts. However, while they have woken me up, they also demonstrated to me that I was not as familiar with my traffic display as I should be, and I had no real plan of how to deal with the more challenging traffic conflicts it may identify. So, in this article I take a more in depth look at EC displays and possible pilot reactions to traffic alerts from them.

The CAA says it is embracing EC for the future of airspace Below The CAA’s latest Clued Up publication. management. It has published several brochures, which include slogans such as ‘see and be seen and share the air’, the latest of which is Clued Up future vision (Picture 1) which can be found on its website as CAP2000 and was handed out at the LAA Rally. In it, the CAA encourages us all to equip ourselves for our own good but talk about ‘sharing the air’ without any explanation of what this might really mean to us in terms of freedom or restriction. My own expectations of EC and indeed the CAA’s future vision, if taken literally, depend on EC devices working effectively together as a system, not individually.

Before EC can really contribute to a safe and capable aviation infrastructure that permits ‘sharing the air’ the CAA must resolve the interoperability challenge of the disparate standards – ADSB, PAW and FLARM – about which they currently sit firmly on the fence. However, the politics and difficulties over beacon (EC out transmitter) standards have been debated interminably elsewhere, so let’s move on.

Traffic avoidance only becomes a serious problem when two aircraft try to occupy the same piece of airspace. Thankfully such events are few and far between, but it is a risk we all take when we fly. As an American pundit put it, ‘today we depend on big sky and small airplanes for our air traffic safety’. However, as the public airports in the UK continue to grab more of our airspace (seemingly unaware of the CAA’s ‘share the air’ and EC policy), that big sky is getting smaller and the traffic density higher. The CAA, it’s procedures, regulations and our training as pilots, address avoidance of traffic conflict to try to minimise this hazard, but are they moving with the times? With the advent of Electronic Conspicuity many of us have invested in EC devices to reduce the risk further, and it certainly adds another string to the bow of collision avoidance. Is it just a question of putting a beacon in your aircraft to be able to ‘share the air’ safely, or is more required to reduce the risk?

Conflict prevention: The Skyway Code

To help us avoid conflict the CAA has published rules condensed into a readable form, the Skyway Code (CAP1535). This includes (VFR) rules for avoiding and resolving traffic conflict including directions of flight at altitudes above 3,000ft, flight along line features (roads / rivers etc.), priorities and procedures around aerodromes, passing and conflict avoidance manoeuvres. Mutual compliance with these rules goes a long way to mitigate the collision risk, but maybe now is the time for it to include EC.

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Above FLARM LED display / Power FLARM receiver showing traffic 0.5 miles ahead.

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Above SkyDemon display / Sky Echo receiver showing aircraft landing at Gloucester. First stage of warning (Yellow). Own Aircraft at airfield perimeter.

Detection and avoidance: Pilot training

As trainee pilots we were taught to look out and to scan the sky for traffic, and were advised that peripheral vision (in healthy eyes about +/- 60°) may alert us to high contrast or moving objects without having to look straight at them. Even if our eyesight and scan is perfect, does what we can see from our cockpit scan cover all the directions from which conflicting traffic may arrive? The answer is: No. How much you can see will depend on how you scan, your peripheral vision, glasses, aircraft structural clutter, the sun and even your hat. My normal visual awareness seems to be about +/- 90° from side to side, and +/- 30° up and down except directly in front of the aircraft which is limited by the panel to near horizontal. That gives me less than 25% coverage of the total sphere around me. That’s for me and my RV-6, but all pilots and aircraft types will vary.

EC: No blind spots

Effective EC can eliminate the blind spots, but to benefit you need to be equipped with EC-in, which consists of an EC receiver and an EC display. Sometimes the receiver is part of a beacon (a transponder or other EC-out device), sometimes separate. The display can be part of your portable navigator (often connected by Bluetooth or Wi-Fi), in a panel instrument, or embedded in your glass cockpit display. The EC-in device measures your own position, height, speed etc., then compares it to the received position data from other aircraft. For those aircraft that are transmitting EC in a format that you are equipped to receive, they can’t hide – there are no blind spots. But, if their beacon is not compatible with your EC receiver, your EC-in will not detect them (this situation will remain until the interoperability issue is resolved). If, however, it is interoperable, does EC-in change our approach to traffic avoidance? Below Garmin Aera 660 / GDL50 receiver showing traffic in circuit around Henstridge airfield. Own Aircraft just landed.

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EC displays, what do they tell us?

Alert

Firstly, EC-in can alert us of a potential traffic conflict. Some devices generate an audio alarm for traffic within a predetermined time or distance range. This is by far the best way as you don’t distract yourself or become fixated with an extra scan item. Others place a traffic message on the EC display screen that needs a (albeit basic) scan to pick up. Traffic is represented by symbols or pointers and that which may become a problem is often highlighted by a change of colour. Others are reliant on you interpreting the traffic display as part of the scan to spot a potential conflict. Traffic displays

Although most traffic displays have some unique individual features, they fall into three general categories. • The clock display (Picture 2), comprising illuminated compass points indicating the horizontal direction of the closest or most threatening traffic. These are augmented by other information including the height (here presented as angular) and range of the traffic relative to you. Good for initial alert and guiding visual scan, but less good at providing spatial awareness of conflicting traffic and its relative motion to aid resolution. • Map displays (Picture 3) superimpose traffic on a navigation map in the form of symbols or pictograms augmented by text and arrows. Traffic status or possible conflict can sometimes be indicated by symbol colour change and augmented by a warning message either on the screen or in audio form. The display can be either north up or track up depending on your navigator map setting. Maps in north up mode are not very intuitive when used to determine avoidance manoeuvres and, regardless of orientation, the clutter of other map symbology detracts from their effectiveness. • Radar or PPI (plan position indicator) (Picture 4) displays are normally tracked up and have an otherwise uncluttered screen. They display symbols or icons representing the position of nearby traffic and often include other information such as aircraft id, height, direction and climb / descent trends. It is also possible on some to adjust the range and height band to further declutter the screen. I find these the easiest to interpret. As usual in the chaotic EC world, not all symbology depicting an item is the same and not all displays are compatible with all the EC-in receivers, resulting in confusion and variation in effectiveness of use. However, in its Clued Up brochure, the CAA has at long last started to recognise this. In its short section on human factors, it emphasises the need to understand the limitations of your EC device. This is currently a very

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important statement hidden away in an obscure paragraph and I wonder when that is going to get into the Skyway Code or training syllabus…

Display, its capabilities and limitations

First, it is important that the text and symbology you will use to identify, and perhaps resolve, a conflict is large and uncluttered enough to read and interpret in the active cockpit environment. For me, many of the display devices fall at this hurdle but, if you can see and read it clearly, are you fluent with what the display format, symbols, colours, arrows, pointers, numbers, and text actually mean? Much symbology is built around FAA TIS B Icons (Picture 5).

Others use aircraft outlines, triangles etc. to represent traffic. Colour or filling often denotes proximity, range or threat level, with yellow the normal threat warning. However, each product seems to have its own interpretation of which details are a subject in their own right, and many symbols have annotations providing further information. For example, height data is relative to you and is generally (but not always) in hundreds of feet + if above, and – if below.

Accuracy

All of the above possibly sounds comforting, but how accurate are EC displays? For EC to work properly, all EC devices must use the same height standard for both their receiver and beacons – but they don’t. While most devices use pressure altitude (1013.2 hPa), some use GPS altitude. If, for example, an EC-in receiver used GPS altitude, but the

Left top (pic 5)

Typical TIS B style symbols. The white arrow outline represents an aircraft travelling in the direction of the arrowhead. If filled, it is the first warning of ‘concern’ and the yellow circle the second. The square is an aircraft on the ground

Left (pic 6) A traffic icon with trend data. The target aircraft is depicted flying north but due to the combined motion, its relative position is moving to the southwest. The dotted line is a position trend, not a heading.

Position error. The RV-6 is obviously close at two o’clock, slightly high, but look carefully at the EC display in the RV-8 (bottom left) which shows it at five o’clock below. At short range position information is not reliable, even with good GPS data.

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beacon in the other aircraft used pressure, and QNH was 990 hPa, the reported traffic height separation could be incorrect by 800ft!

At the moment EC-in devices don’t seem to recognise and report the difference, so there is no way of knowing if both aircraft are using the same altitude standard but even with compatible standards, certified altitude encoders are allowed a +/- 200ft tolerance and certified GPS +/- 300ft, so there still could be cumulative errors of as much as 400-600ft. A target reported as -3 (300ft below) may indeed be below and therefore no threat, or could well be at the same height and a collision risk, you just don’t know for sure. Normally the height data within the same standard is quite accurate but be cautious with how you interpret such information and apply a tolerance before you use it for an avoidance manoeuvre.

Position data for EC is always derived from GPS but is also subject to errors. Data from some GPS devices and EC Beacon messages include accuracy information on the position message, but it’s what an EC-in traffic receiver and display does with that data that is important. Most do nothing and display the position as transmitted, however erroneous. Some do suppress really close data (that could be misinterpreted due to position errors) but on what basis is not obvious. The position accuracy of a certified GPS receiver can be +/- 0.05 nm (300ft) and as always with two measurements (one for each aircraft) the worst-case cumulative error must be considered. In other words, the position you have displayed for the traffic could be as much as 600ft away from where it is indicated to be – an aircraft that looks as if it is going to pass close by on the right could well do so on the left. Accuracy is a key limitation to be considered when using EC displays particularly when monitoring close or level traffic (Picture 6) where a small position error could be fatal. Be cautious.

Understanding if traffic is climbing, descending or horizontal manoeuvring is vital in managing conflict. Some displays have information to help you identify this (Picture 7). For example, a symbol annotated +7 might indicate 700ft above descending, safe at the moment but an impending level conflict. Some displays include vectors (direction of travel), but make sure you understand exactly what they are depicting. Some may be the last reported GPS heading of the traffic, others are averages of the last few minutes and of course, the aircraft may be manoeuvring (e.g., gliders). Some also have a similar-looking relative position trend display – it is displaying the relative motion of the two aircraft but is tagged onto the other aircraft and it predicts how the two aircraft will move relative to one another over a given short period. It is easy to misinterpret if you are not on the ball.

One of my biggest disappointments is user handbooks. Many lack clear data on exactly what displays are showing. How can we be expected to interpret displays if we only discover some functions in the air (as I have done, and I was looking for them)? This problem includes some major equipment manufacturers which should know better. So, look at the actual display and check that you understand all its features before you have to depend on it.

Traffic conflict resolution: Should we use EC data to help?

This is aviation and we are safe because we follow well-thought-out and tested procedures, don’t we? If we have an EC traffic advisory message, audio warning or have discovered a potential conflict in our scan, and we have assessed where it really could be, what do we do? We are told (mostly in the device manufacturer Ts&Cs) that EC is

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Above ‘Catchup’ (on a clock display) showing traffic 0.2 miles behind and level. The red LED indicates it of concern, but no more information can be gleaned from this display.

just an aid to the visual scan and, once alerted, to look out visually for the reported traffic. Once we have it in sight, the Skyway Code tells us that if we need to manoeuvre to avoid it, we do so to the right. Well, that covers 25% of the big sky, what do we do if, for example, EC flags up traffic catching up from behind? (Pictures 8 and 9). It’s not simple. We need to have thought it through and prepared a reaction before it happens.

We are told not to use EC data as primary data for manoeuvre decisions so, do we ignore warnings of traffic we can’t see because of a legal caveat in the handbook, or do we do something about it? Before you condemn this as an unlikely scenario, have a quick look at CAP 707 which contains deconfliction advice for air traffic controllers who are managing just such catchup / climb / descend conflict situations routinely. It points out the final responsibility for aircraft safety lies with the pilot. These days GA is a mixture of 40-140kt aircraft all following narrow routes around and between various chunks of restricted airspace. We are following VFR corridors, VRPs, or are transiting choke points, so catchup is an increasing hazard. If the crew of the catching aeroplane see you, they should follow the Skyway Code and pass you to the right. If they haven’t seen you and don’t, (Picture 10) there is a collision risk. If you turn right, as implied in the Skyway Code, you could jeopardise their avoidance manoeuvre if they make one, and a simple procedural situation has just become dangerous. So, do you just sit there, do nothing (as convention implies) and hope

Above top (pic 8)

‘Catchup’ (on a radar display) shows traffic .5 mile behind. The yellow dotted trend line indicates it is closing fast on a conflict course due to intercept in just over 30 seconds.

Above right (pic 10)

‘Caught up’ shows an alarming situation of impending conflict, but picture 6 shows what actually happened, a pass to the right. It could equally have been a collision, you just can’t tell from either display type. As well as position errors, the scale of the symbols is misleading. You have no idea whether the pilot behind has seen you. What would you have done? they miss you or do you turn left (or climb or descend)?

That is something that may stand a better chance of getting you out of the way intact but risks the wrath of the Skyway patrol. Who knows? Will we ever get well-thoughtout and tested advice or procedures for flying with EC?

Don’t hold your breath. In this risk averse world, I don’t think anyone is going to be prepared to accept the liability for providing such advice. It’s up to you, the pilot, what you do with your EC. Are you prepared?

EC alert plan

For your own preservation, when you get an alert or find a conflict, it is important that you have thought it through and planned what to do next. Perhaps you should develop a small EC warning procedure and ask yourself, ‘where is the threat and could I see it? Yes or no?’ If yes, look for it, if you see it forget EC and follow the Skyway Code. If no (e.g. it’s from behind catching, above descending or below climbing) don’t bother looking for it visually, that is survival time wasted. Have a plan or strategy and react to the potential conflict as soon as you 10 can, rather than waiting to see how it develops.

In deciding what to do, remember the accuracy issue. Is the traffic exactly where it is reported by your display? Think through a few examples and prepare your plan. What you definitely shouldn’t do is have this quandary during the minute before potential impact. If you have EC, plan and prepare for such eventualities in advance.

The real point of this article is to suggest that if EC is to be successful, we all need to think through what we will do if we encounter a traffic conflict. We should prepare ourselves to react smoothly and efficiently to our EC traffic warnings, however they are presented, rather than have to react as a crisis looms with no plan.

EC is no longer just a cockpit toy, but an important safety tool and it is going to become more important whether it is for sharing the air, avoiding UAVs, allowing access to some future airspace or just as an extra pair of eyes. As the CAA says, it is important that we all understand its capabilities and limitations rather than fly around kidding ourselves it is a super accurate radar. It is not and using it as such is not safe.

This article is not intended as a tutorial or product review but more to prompt thought and perhaps debate. Let’s have some feedback on this through the LAA forum under Electronic Conspicuity. (https://phpbb. lightaircraftassociation.co.uk) All the instrument illustrations are real, captured in the air. Thanks to Ruth Kelly, Clive Davidson and Patrick Carruth for help with the flying and photographs. ■