WAAS GPS-ADSB

[flybuddy]

Got a Skyview with the 261 Transponder and 470 ADSB. Do not have a certified waas gps. For 2020 compliance purposes, can anyone suggest a relatively low cost method of gps waas ? Seems nuts to purchase a 430W or something similar just for the waas gps. Some lower cost units hitting market soon like L3 lynx, but would have to get a transponder system along with the waas gps which I'm not even sure would work with a mode S. Any suggestions appreciated

 

[dynonsupport]

There are no low cost units right now. The floor is about $2,500. However, you have 6 years to comply, and in the last 3 years the price has gone from $6,000 to $4,000 to $2,500. We'd suggest you wait.

 

[lolachampcar]

I posted this in another thread-
The Dynon version of the Trig transponder is the same and a statement from Trig to that affect would help with a Field Approval. The down side is the pressure encoder and ground/air portion. Even though there are no signal integrity elements to either of these, that fact will likely not stop the FAA from rejecting the idea.

This brings up an interesting question. Experimental aircraft have to use FAA approved transponders (TSO'd) equipment. Has anyone asked the question if Experimental aircraft will be required to have an FAA approved ADSB-out solution (combination of Txp, GPS, pressure and ground/air)?

It could very well be that the FAA will not accept transmission of positional integrity and latency compliance data from a combination of TSO'd txp and GPS components. They are not doing it for certified so it stands to reason that they will not do it for Experimental. Has anyone asked this question?

 

[flybuddy]

I was under the impression that the only thing lacking from the standard Dynon setup is that their Waas GPS is not certified. The transponder is TSO'd and we get recerts on static system/Xpndr/alt.

 

[lolachampcar]

This is why I bring the issue(s) up. In working through what I need to do to be 2020 compliant in a certified aircraft, I came across this whole notion that you can not just stick in a TSO'd transponder and a TSO'd GPS. The whole system (including antenna, electrical, mounting, air/ground switching, performance, etc.) must be determined to be correct and in compliance with the regs.

The FAA originally mandated STCs for certified aircraft which was nothing short of a joke. In my case, there is no company that will spend the time and money to do an STC for 50 gliders in the US of which only half are airworthy at any one point. They finally opened up the option of a Field Approval based on an existing STC. That is a joke as well if you consider the number of aircraft that need to be made compliant and the amount of time we have left. If everyone does Garmin, then it may be possible. If people need Field Approvals then there is simply not enough FAA to go around.

 

[dynonsupport]

We are always talking to the FAA about ADS-B and experimentals, and they are more than happy with our transponder in an experimental plane, when hooked to the GPS units we support.

It's a fuzzy world, since technically all ADS-B out installs must be STC'd. The tradeoff is that an STC is impossible on an experimental because it never had a TC to begin with. So in one sense, it's impossible to have a compliant ADS-B install on a experimental.

That was never the FAA's goal, and they realize this issue. They have said that they will accept any combination of equipment that has been STC'd in a certified airframe as acceptable in an experimental. Thus, the Trig transponder we use is acceptable if you use the Garmin or Freeflight GPS units we support, since those combinations have been STC'd. Technically, hooking up a random certified GPS is not OK until that GPS with that ADS-B out device has been STC'd somewhere. They have also accepted that the Transponder we sell is functionally identical to the Trig, and we have actually done test flights with them to verify that.

 

[lolachampcar]

How do they respond to your using (a Dynon algorithm based) air/ground switch as Garmin's complete ADSB-Out system is the only pitot/static based solution that has been accepted (so I am told)?

 

[dynonsupport]

Bill,
As you seem to have discovered, ADS-B OUT installations require the air/ground status to be automatically detected. Manual switching is not allowed. This is one of the things the STC of ADS-B out does in a certified plane.

The auto air/ground switching is inside the transponder and has been fully TSO'd and accepted by the FAA. SkyView does not make that decision, however it DOES source some of the data required to do this from the AHRS. So to be ADS-B compliant, you need our AHRS.

I can't comment on how Garmin may do it, but they aren't the only ones that can do it algorithmically. We have the paperwork that says we can too

As far as we are concerned, any experimental EFIS changing modes on a Mode-S transponder without the pilot directly requesting it is not acceptable, which is why we did this inside the transponder, not inside the EFIS. The algorithm is required to be redundant against single input failures, and it requires certain behavior in specific failure cases, so it uses a lot more than just airspeed or VSI or any single input.

 

[William_Ince]

We are always talking to the FAA about ADS-B and experimentals, and they are more than happy with our transponder in an experimental plane, when hooked to the GPS units we support.

It's a fuzzy world, since technically all ADS-B out installs must be STC'd. The tradeoff is that an STC is impossible on an experimental because it never had a TC to begin with. So in one sense, it's impossible to have a compliant ADS-B install on a experimental.

That was never the FAA's goal, and they realize this issue. They have said that they will accept any combination of equipment that has been STC'd in a certified airframe as acceptable in an experimental. Thus, the Trig transponder we use is acceptable if you use the Garmin or Freeflight GPS units we support, since those combinations have been STC'd. Technically, hooking up a random certified GPS is not OK until that GPS with that ADS-B out device has been STC'd somewhere. They have also accepted that the Transponder we sell is functionally identical to the Trig, and we have actually done test flights with them to verify that.

So what is on the horizon from Dynon regarding ADS-B equipment, besides what is available presently?

 

[dynonsupport]

Lots of questions in the past on Dynon's "plans" for a 2020 GPS. Note that overall, it's our standard procedure to not talk about any future product until it's imminently ready to ship. It doesn't do a customer or our business good to talk about things we might or might not do in the future.

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1390584132

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1411066154

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1408829117/13#13

 

[lolachampcar]

It sounds like Dynon has done A LOT of work on this subject with the FAA.  There should really be no surprise there given your approach on so many other tasks.

Now for the fun question....  If there is something approaching approved data for the air/ground element and the transponder element is TSO'd and STC'd in another application for certified aircraft, I may actually have enough to go for a Field Approval for a Skyview based 2020 compliant installation in my Stemme.  Would you be kind enough to provide the air/ground related data in support of this effort?  The Stemme maintenance manual allows for non-TSO'd displays so Skyview with FreeFlight just might yet work and set a precedent for a 2020 compliant Skyview installation.

I'll run it up the flagpole if you can provide the air/ground info

Bill,
As you seem to have discovered, ADS-B OUT installations require the air/ground status to be automatically detected. Manual switching is not allowed. This is one of the things the STC of ADS-B out does in a certified plane.

The auto air/ground switching is inside the transponder and has been fully TSO'd and accepted by the FAA. SkyView does not make that decision, however it DOES source some of the data required to do this from the AHRS. So to be ADS-B compliant, you need our AHRS.

I can't comment on how Garmin may do it, but they aren't the only ones that can do it algorithmically. We have the paperwork that says we can too

As far as we are concerned, any experimental EFIS changing modes on a Mode-S transponder without the pilot directly requesting it is not acceptable, which is why we did this inside the transponder, not inside the EFIS. The algorithm is required to be redundant against single input failures, and it requires certain behavior in specific failure cases, so it uses a lot more than just airspeed or VSI or any single input.

 

[lolachampcar]

I have a question regarding the barometric pressure information provided by Skyview and reported by the Trig Transponder.

How does Dynon meet the requirement in AC 20-165A that spells out-

3-4. Barometric Altitude Source. a. Equipment eligibility.
(1) Utilize barometric altitude from a barometric altimeter meeting the minimum performance requirements of:
(a) TSO-C10, Altimeter, Pressure Actuated, Sensitive Type, (any revision) or
(b) TSO-C106, Air Data Computer (any revision).
(2) If appropriate, utilize a digitizer meeting the minimum performance requirements of
any revision of TSO-C88, Automatic Pressure Altitude Reporting Code-Generating Equipment.

As I read this, the pressure sensor needs to either be TSO'd or meet the requirements of a certain TSO. Is this correct? Does the Skyview system meet these requirements?

 

[lolachampcar]

I'd like to add another question regarding Dynon's display of information from the ADS-B installation. Specifically, does Skyview provide the following support-

(1) System status.
The installation must have a method to display system operational status to the flight crew, which is consistent with the overall flight deck design philosophy. The system must display flight crew inputs such as Mode 3/A code, emergency codes, IDENT, and call sign. If an existing transponder is used to input Mode 3/A codes, emergency codes, and IDENT into the ADS-B system, the current transponder control interface is sufficient. The following two failure annunciations must be available to the flight crew.
(a) ADS-B device failure.
If the ADS-B equipment is unable to transmit ADS-B messages, the system provides an appropriate annunciation to the flight crew.
(b)ADS-B function failure.
TheADS-B system depends on a position source to provide the data to populate the ADS-B messages and reports. If the position source or its interface with the ADS-B equipment fails then the ADS-B system will not be able to broadcast the required ADS-B data. In this case, the ADS-B equipment has not failed but it cannot perform its function due to a failure to receive the position source data. TSO-C166b and TSO-C154c require this condition to be annunciated. The ADS-B system should distinguish between a position source or interface failure and an ADS-B equipment failure. The installer must provide documentation, in either an AFM or Pilot’s Guide, which explains how to differentiate between annunciation of an equipment failure and a function failure if the failure annunciations are not independent. The ADS-B function failure must not cause a TCAS II system failure.

 

[dynonsupport]

On the altitude encoder portion, the requirements are that a device MEET the requirements of the TSO, not BE TSO'd. We've been doing that for over a decade with our altitude encoders.

Also:

(1) The barometric altitude used for the ADS-B broadcast must be from the same altitude source as the barometric altitude used for the ATC transponder Mode C reply, if an altitude-encoding transponder is installed in the aircraft.

Our system is our transponder, so the altitude sent out by ADS-B is just the MODE-C altitude.

As for the next question, our ADS-B out is our transponder, so no additional interface is required. We annunciate loss of data to the transponder that will stop only ADS-B transmissions, as well as complete transponder failures.

 

[lolachampcar]

Thank you for the information. I addressed the altitude encoder issue here-
http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1412080332

 

[kastein]

We are always talking to the FAA about ADS-B and experimentals, and they are more than happy with our transponder in an experimental plane, when hooked to the GPS units we support.

It's a fuzzy world, since technically all ADS-B out installs must be STC'd. The tradeoff is that an STC is impossible on an experimental because it never had a TC to begin with. So in one sense, it's impossible to have a compliant ADS-B install on a experimental.

That was never the FAA's goal, and they realize this issue. They have said that they will accept any combination of equipment that has been STC'd in a certified airframe as acceptable in an experimental. Thus, the Trig transponder we use is acceptable if you use the Garmin or Freeflight GPS units we support, since those combinations have been STC'd. Technically, hooking up a random certified GPS is not OK until that GPS with that ADS-B out device has been STC'd somewhere. They have also accepted that the Transponder we sell is functionally identical to the Trig, and we have actually done test flights with them to verify that.

Great to hear - I've been worrying about this, and hadn't found an answer yet.

Somewhat related question that I haven't been able to answer searching the installation manual: If I install a Freeflight 1201, feeding an SV-XPNDR-261, do I need any other hardware in between (ARINC-429 module? RS232 level converters?) to do any translation, or will it Just Work connecting the 1201 serial output pin to the XPNDR-261 input on pin 3? If I do this, will the WAAS GPS data be forwarded on to the D1000 for use or do I still need to install an SV-GPS-250?

 

[Dynon]

No additional hardware needed. The 1201 has a serial output, and our transponder has a serial input. You set what format the transponder is listening for in SkyView setup.

That position isn't shared with SkyView - SkyView still needs its own source like the SV-GPS-250.

All of that said - the ADS-B position sources are in flux right now with the FAA's rule change. We hope that we'll have some clarity on what that means going down the road for experimental and LSA, but right this moment might be the time to hold off on purchasing a compliant position source until it's clearer what the paths going forward look like.

 

[lolachampcar]

and to respond to using the FF position source.... I'll reiterate some comments from Dynon defending their puck as an accurate, high resolution gps with a very good update rate. Their recommendation was to use the Dynon puck over the FF unit.