ADS-B Traffic after 2016 and Dynon?s Solution
 

As many of you here at VAF may have heard, the FAA has recently announced that they will be turning off ADS-B based TIS-B and ADS-R traffic services for aircraft that are not equipped with GPS position sources that are of sufficient quality starting in early 2016. Details of these changes can be found in this document from the FAA, which also outlines the history of this change: TIS-B_Service_Change_Summary.pdf

Dynon has been involved in discussion with the FAA leading up to this, and we want you to know that the SkyView system has you covered. You will not see a change in traffic coverage in 2016 if you are using a SkyView system with the Dynon transponder.

Not ones to leave a statement like that and run, we also thought it would be helpful to resolve some of the questions that might still be out there for the E-AB and LSA communities in general about this upcoming change.

Does this affect me?

This change might affect you if you have an ADS-B IN device AND an ADS-B OUT device. If you don’t have ADS-B IN yet, you aren’t getting TIS-B traffic, so it will have no effect. If you have no ADS-B OUT device, even if you have ADS-B IN, it will also not affect you, as you are currently not receiving these services. If you have a 2020 compliant GPS, or a Dynon SV-GPS-250, you will also not be affected, and you will continue to see traffic as you do today.

I have ADS-B IN and OUT. What will change?

First, this only affects traffic. FIS-B weather services are broadcast continuously to all aircraft and are not and cannot be directed to individual aircraft. Any ADS-B based weather data you get today will not change no matter what system you are using.

What might change is how much traffic you receive. This depends on what kind of GPS you have on board.

If you have a 2020 compliant GPS, nothing will change. Your traffic coverage will remain the same as it is today.

If you have a Dynon SV-GPS-250 as your GPS source, and a SV-XPNDR-261/262, you will also see no change in traffic coverage.

If you do not have a 2020 compliant GPS, a Dynon SV-GPS-250, or another GPS of sufficient integrity, you will experience reduced traffic coverage.

What will I be missing without full traffic coverage?

The ground station will no longer consider you a client for TIS-B or ADS-R services and will not send you targets from the ground station. This means that the 90% of aircraft without ADS-B OUT on board will not show up, since they are sourced from ground radar systems. It also means that aircraft with ADS-B OUT which are on a different frequency than your ADS-B IN will not appear (978MHz vs 1090MHz).

You may still see targets at times, if there is an ADS-B OUT aircraft near you that is waking up the ground station. These aircraft get a “hocky puck” of traffic 15NM around them and 3,500’ above and below. You will be able to see these aircraft. However, this is a false sense of security, as the aircraft “waking up” the traffic could be 3,500’ above you, and then you could only see targets that are above you, not below, but with no way to know that you are lacking coverage below you. You may also not see the aircraft that is waking up the ground station in the traffic picture as it does not get transmitted back to itself.

Dynon’s SkyView systems annunciate this situation as “ADS-B PARTIAL” in the ADS-B status block, instead of "ADS-B FULL".

Do I need a TSO’d GPS to keep getting full traffic coverage?

No. You never need a TSO’d device for ADS-B, even for full 2020 compliance. Just one that meets the “performance requirements” of the TSO.

Even better, this change to traffic services does not require a device that is “2020 compliant.” ADS-B has multiple levels of integrity for position sources. This change is only turning off traffic services for aircraft with zero integrity (a SIL or SDA of zero which means “unknown”). To be a traffic client after 2015, you must have a SIL and SDA of 1 or higher. A SIL of one allows a failure every 1,000 hours. A 2020 compliant GPS has a SIL of 3 and SDA of 2, which represent a very high level of integrity, allowing a false or misleading position only once every 10,000,000 flight hours.

I have a Dynon SkyView system with Dynon’s Transponder. What do I do?

Dynon believes strongly that traffic display is an important safety feature for our customers. While not a replacement for the eyeball, cockpit traffic displays reduce workload and provide reliable warnings for possible collisions. It is important to us to make sure our customers do not lose this capability.

Dynon has been working to ensure that the SkyView system is compliant with the requirements in order to continue receiving traffic after 2015. A free software update for the SkyView system will be available before 2016 which will transparently make the changes required to ADS-B OUT so you can continue to be a client to the ground stations and receive the full traffic portrait. More specifically, after this update, a SkyView system equipped with an SV-GPS-250 will transmit a SIL and SDA of 1, which is the level that is required to receive traffic after the FAA makes their changes to the ADS-B system. You will need to be using Dynon’s SV-GPS-250 as the GPS position source to your SkyView system for this to work, and the SV-XPNDR-261/262 for your ADS-B OUT. This change will maintain traffic service for your aircraft no matter what ADS-B IN solution you are using.

How is Dynon doing this?

The regulations on ADS-B OUT are performance based, meaning that what matters is how well it performs in the real world. Dynon has analyzed the SV-GPS-250 as well as the whole SkyView system and determined that the system’s performance meets the requirements for a SIL and SDA of 1.

Does this mean SkyView with an SV-GPS-250 is 2020 complaint?

Unfortunately, no. The FAR has not changed, and after 2020 in order to fly in certain airspaces, you will still need a GPS that is compliant with the performance required in § 91.227. The SV-GPS-250 is not designed with this level of integrity in mind, and cannot be used for full ADS-B compliance. Thus, after Jan 1, 2020, you will either need to be equipped with a compliant GPS, or avoid airspace defined in § 91.225.

Take me through all of this again.

There are three ADS-B GPS position source categories:

“Unknown Integrity”. Will not wake up traffic services after early 2016. This is the majority of the integrated GPS units in non-certified EFIS systems today, and in standalone non-TSO’d ADS-B boxes. Transmits a SIL or SDA of 0.

“Low Integrity.” This is the category the SV-GPS-250 will be in after a software update. This has demonstrated integrity, but not to the highest level. Good enough to wake up ground stations and get traffic after the FAA makes their early 2016 change. Is not 2020-compliant, and is not good enough to allow access to all airspace after 2020. Transmits a SIL and SDA of 1 or 2.

“High Integrity.” A device which meets all the requirements of 91.227 and the performance requirements of the applicable TSO. Allows aircraft into all airspace in the USA after 2020. Does not need to be TSO’d. Transmits a SIL of 3 and SDA of 2. Can be a standalone GPS receiver, or an IFR certified panel-mount GPS navigator.

Configurations with no change to traffic data displayed in cockpit:

ADS-B IN with ADS-B OUT and 2020 compliant GPS: Full traffic data
ADS-B IN with SV-XPNDR-261/262 and SV-GPS-250: Full traffic data
ADS-B IN with no ADS-B OUT: Partial traffic data.
ADS-B OUT with no ADS-B IN: No traffic

Configurations with reduction in traffic data:

ADS-B IN with ADS-B OUT and unknown integrity GPS: Partial traffic data

Hope all of this helps everyone understand the changes and options going forward. Please ask any questions and we'll do what we can to help.

--Ian Jordan
Dynon Avionics

Ok. As I expected from Dynon, a good thing without a commitment to a much better thing in the future!

We are all well aware of your policy of not promising anything until it is ready to be shipped. You obviously we're around for the BD-12 fiasco.

I continue to expect a reasonably priced replacement for the GPS-250 well before 2020, I just have to wait for the suprise.

Thanks again.

dynonsupport: THANKS for explaining the updated ADS-B requirements in words we can understand.

:cool:

Dynon GPS
 

Ian,

Is the Dynon ultimate 2020 solution as easy as replacing the GPS-250 unit with a compliant one?

Or are there other major system issues in the rest of the Skyview components that need to be addressed?

Gil,
Dynon already supports fully 2020 compliant ADS-B out if you have a compliant GPS on board. It's legal, works, and many of our customers are already compliant and ready to go.

There are no system issues preventing us from being compliant with any other future GPS that can demonstrate a SIL of 3 and an SDA of 2.

Ian,

Thanks for the quick response.

Can you help us by detailing some of the technical difficulties in making a hockey puck antenna that does meet the 2020 accuracy (SIL and SDA) requirements?

Is it a production/traceability STC issue? ...or a more involved engineering design issue?

Thank you for posting these numbers. I've strongly suspected that the reliability requirements for compliant ADS-B Out were extremely high; this gives us numbers. Nice to know that the FAA considers reporting 3D position to within feet to be the single most important part of the aircraft (because I guarantee the engine, airframe/structure, and everything else on the airplane will fail long before 10,000,000 hours).

Out of curiosity (and perhaps to echo another poster), how much time/effort/money would saved by not having to do the full TSO paperwork, including all the FAA-required bureaucratic bookkeeping that doesn't affect the end product, and just meeting the technical performance part of the requirement?

Thanks Dynon for being the only industry representative to cry foul when the FAA presented this idea last year, and for coming up with a reasonable solution.

I do have a question about your 10,000,000 hour figure. I've seen a reliability requirement of 99.99999%. If you report position once a second, I believe that comes out to one false report every 2777 hours.

Thanks,
Paige

Paige,
Thanks for pointing out the statistical fuzziness I may have caused.

The TSO does define failure as 1x10^-X. It allows you to define this as per sample, or per flight hour, and that definition is actually broadcast over ADS-B OUT as well.

For level 3, this is 1x10^-7. This is 99.99999% as you mention.

However, the regulation requires this be per hour from a GPS. From DO-260B:

So, in reality, the requirement is that in any given hour, there is only a 1x10^-7 chance that you mis-report position. This, admittedly, does not directly translate to hours of error free operation.

It isn't as simple as 99.99999% of the one second samples you transmit needing to be accurate (2700 hours), but it's also not as simple as "only one failure per 10 million hours" as I over-simplified as well. It's a deep, wonky analysis that probably only 8 people in the world really understand.

--Ian