ADS-B in Canada and equipment recommendations

[charrois]

Hi there. I'm currently building an RV-10 and am in the process of closing up some floor sections which is causing me to make some decisions on placement and existence of various antennas. That, in turn, requires me to decide on some of the equipment in general I will be installing.

I intend to equip the aircraft for light IFR, and to that end will be installing a GPS 430W, or perhaps GTN 650 if budget allows. But I've run into some uncertainty over the best choice for transponder.

Most of my flying is in Canada, though I do periodically take trips to the US (and possibly elsewhere in the future). At issue is ADS-B, and its mandated requirement in US airspace starting in 2020.

The problem really roots to Canada's sluggish deployment of ADS-B services. I have no intention of flying over the Hudson's Bay any time soon, and any schedule I've seen seems to avoid mention of any deployment at all in Southern Canada, where ATC is already served by radar. But I like the idea of the possibility of in-cockpit traffic and weather information. However, TIS-B and FIS-B broadcasts only exist in the US, and apparently require UAT equipment. UAT has all kinds of advantages of course, but Mode S 1090ES implementation is more commonly used to implement ADS-B around the world, and Canada's deployment so far seems to be with Mode S. Of course, in such a system, we'd never be able to receive broadcast weather in the cockpit.

So I'm appealing for advice to those familiar with the technology. From my understanding, ADS-B at its core does provide air-air traffic information at least for other traffic with similar ADS-B equipment, without need for a ground infrastructure. However, I suspect that UAT equipment and Mode S are incompatible systems (they use different frequencies and protocols), so one would only see traffic with one system or the other without a ground network to rebroadcast at both frequencies (and presumably add non-ADS-B radar contacts as well). Is this true? And if so, with the majority of US general aviation using UAT, they'd be invisible to 1090ES equipment, right? Yet, ADS-B in Canada only operates with 1090ES.

I'm at something of a dilemma here. The first option is to do nothing to support ADS-B at all and wait for the situation in Canada to improve. But this means that after 2020 (which will come all too soon), I won't be able to fly into the US without an equipment upgrade. Since I have to buy a transponder anyway, do I spend the extra now for a Mode S vs. Mode C transponder so that ADS-B is easier to implement with 1090ES? Is there any benefit for me doing so now, for flight within Canada? I presume I'd be able to receive air-air traffic information from other aircraft with 1090 ES hardware, right?

Or do I consider a UAT, which would only report on other traffic with UAT hardware unless close to the US border where I could pick up broadcasts from their ground network? UAT provides more functionality (in particular, I hate the concept of monthly subscriptions to receive something like weather - I'd rather pay a lump sum once and then be done with it). Does anyone know of any rumours of Canada planning to extend ADS-B service and/or building a UAT ground network as the US is doing?

Ultimately, though I'm still a bit away from getting the radio hardware, it's going to be much easier to install things like an external UAT antenna now if I'm going to go that route. I'm going to need a transponder antenna regardless of whether I choose a Mode C or Mode S, but I'm trying to establish for myself a game plan.

I've been involved in the tech industry long enough to know it nearly pointless to try and guess the direction of new technologies, but at the same time want to try and future-proof things as much as is reasonable, and am looking for the advice of those who have some experience on its practical implementation in Canada.

Any advice, on this or other equipment suggestions, is greatly appreciated.

Thanks! Dan

[Stephen Szikora]

American builders are just as confused about what equipment to install as you!

http://www.vansairforce.com/community/a ... 86903.html

Since you'll have a certified GPS with either Garmin option, I would pony up for the Mode S now. A GTX 330 with the 430W or a GTX33 remote mount with the 650 if you want to stick with Garmin.

Here's a good explanation of the issues you raise from the Trig website:

What equipment do I need?

To support ADS-B “Out”, the aircraft must have a GPS receiver as the position source, and a datalink transmitter to actually send the ADS-B data.

The datalink transmitter that most aircraft will use is a Mode S transponder, using a feature called “Extended Squitter”. The Mode S transponder with Extended Squitter is the international standard for ADS-B output. Specific to US airspace – and not approved elsewhere – is the UAT datalink transmitter as an alternative to the Mode S transponder. UAT transmitters may only be used on GA aircraft flying at lower altitudes in the USA.

The GPS receiver used must be an IFR certified receiver. Although that GPS is not required to be WAAS capable, that may be a moot point. Many legacy GPS receivers that were designed before ADS-B was planned do not include the necessary calculation of integrity and accuracy that ADS-B needs to operate. It is unlikely that these older devices can be upgraded, and therefore a new GPS receiver would be required. Most new GPS products today are WAAS capable.

Should I use UAT or Mode S?

If you are flying outside the USA, there is no choice – the only approved solution is Mode S. That is also true for large aircraft and high altitude aircraft in the USA – you must use Mode S. If however you are flying a GA aircraft in the US, you may instead elect to use a UAT solution.

A UAT solution will almost certainly be more expensive than a Mode S based solution, because the Mode S ADS-B solution is built into many existing ATC transponders, whereas the UAT solution is a separate datalink radio. Although there is some hot debate on the subject, you also still need a transponder if you install UAT. That raises the obvious question – why would anyone use UAT?

The key difference between the two solutions is that UAT has spare uplink bandwidth, whereas Mode S Extended Squitter only has the capacity for ADS-B position reporting. That means that a UAT radio can receive additional data streams, in addition to the traffic information. The FAA is providing a weather reporting function using the spare datalink bandwidth of the UAT radio, and the FAA is hoping that this “added value” feature will encourage GA operators to install ADS-B equipment sooner that they otherwise might.

What about ADS-B In?

An aircraft with ADS-B “In” would be able to hear position reports from all the other nearby aircraft – independently of ATC. Such a facility would drive what is called a “Cockpit Display of Traffic Information”, or CDTI. In practice this kind of display is often integrated with a Multi-Function Display or moving map GPS display.

To support ADS-B “In” obviously requires a datalink receiver, in addition to the datalink transmitter that is providing the ADS-B “Out” function. Most UAT based ADS-B solutions will include a datalink receiver as well as a transmitter – as already mentioned the key advantage of the UAT system is the ability to uplink other information, so there’s a limited opportunity for a transmit-only UAT system. Mode S transponder based solutions today do NOT include the datalink receiver. Instead, the Mode S based ADS-B receivers are generally packaged as a separate system. At the high end, these are usually integrated with TCAS systems. For GA aircraft a separate ADS-B receiver is used.

It is worth pointing out that in the US, because the FAA infrastructure will rebroadcast information between Mode S and UAT systems, it is possible to install a mixed solution – using Mode S for ADS-B Out and UAT for ADS-B In.

Unfortunately, the answer you seek is not obvious.

[ahramin]

Let's think about your requirements. You won't need any ADS anywhere in the world that an RV is going to fly until 2020 at the soonest. If the ADS-B requirement does happen in the US in 2020, there are already relatively cheap drop in solutions that would work with your existing avionics plan. I imagine there will be far more solutions by the time 2020 comes around. When will a single engine aircraft require mode S and ADS in Canada? Probably not in your lifetime. We don't have the traffic density that they have in the US, or the airspace congestion problems.

I would suggest that for now, do nothing. Whenever you want to add ADS-B you will be able to do so with a UAT solution for very little extra money. In the airspace you fly, you aren't going to need mode S for a very long time, if ever.

[CID]

If you go the transponder route, make sure you get the ES (Extended Squitter) model.

If I were you, I would wait a while. There is a good chance that things will change significantly before the mandate arrives. There have already been changes in the specifications for ADS-B. If you have ADS-B that works in the Hudson's Bay, it may not work in the US as the HudBay ADS-B is to an older standard.

[charrois]

Thanks for the responses!

As nice as it would be to have UAT functionality in Canada, it doesn't appear as though it's going to happen any time soon, if ever. So supporting ADS-B at all here would require a mode S with extended squitter.

For now, that means my antenna choices (which is why I'm visiting this issue now) are simple - drop the thought of a UAT antenna, and just go with a regular transponder antenna. In a year or so when I'm actually at the point of getting a transponder, if I can get a good quality second hand Mode C one for a reasonable price, I think I'm leaning in that direction - it will tide me over until 2020 until the US requires ADS-B. But considering how long I've been working on the plane, 2020 isn't all that far away. So if I can't find a used Mode C for a good price, I'd rather not pay full fare for a Mode C that will become a boat anchor in 7 years, so I'll go the Mode S with ES route.

By 2020, I do need a solution that will work in US airspace - when I travel down there, it is always to the bigger airports and busier airspaces. Good thing I still don't have to commit to a transponder yet - a lot can happen between now and when I'm actually ready for one. But the antenna choices I have to make now are pretty clear.

Thanks for all your help!

Dan

[RatherBeFlying]

I'm looking at an invoice for my Trig 22 Mode S transponder:

$2575 + $300 for internal antenna, harness and antenna cable. You can wire up your own harness if you're into that fiddly stuff. For a metal aircraft, you will need an external antenna.

For ADSB today, you need to plug in an expensive certified GPS WAAS receiver.

[Capt. Chaos]

The Garmin GTX 330 transponder also doubles as a control head for the Garmin GDL UAT boxes. It meets the single point of entry requirement in the US.