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Thread: Navworx ADS-B & Unapproved Parts?

  1. #11

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    Quote Originally Posted by cub builder View Post
    The Navworx letter is interesting. All the vendors selling ADS-B equipment had to comply with the change and were notified ahead of time that the FAA would stop responding to ADS-B out with the lower integrity GPS units. NavWorx was far from the only vendor to get screwed by the FAA on that one. The vendor I was dealing with offered a prorated trade in with their older units of 50 - 100% credit towards a new unit with the higher integrity GPS. A number of pilots, myself included, had to upgrade or buy new equipment after the FAA decided to change the specs for the GPS integrity. Some are still saving their pennies for the upgrades and no longer receive TIS-B Traffic.
    This is interesting. I have an FAA Performance Report on mine that was done on 10/05/16 and it passed everything, including the "Integrity & Accuracy" section. So if I fly another test I can expect to fail?

  2. #12
    MEdwards's Avatar
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    Quote Originally Posted by tmcquinn View Post
    This is interesting. I have an FAA Performance Report on mine that was done on 10/05/16 and it passed everything, including the "Integrity & Accuracy" section. So if I fly another test I can expect to fail?
    No. I think cub builder is talking about the change that happened last January, when the FAA changed ADS-B to not send traffic to units with "low integrity" GPS position sources. I thought that was intended to rule out portable ADS-B Out units, I had no idea it involved any NavWorx units.

    The ADS-B Out unit transmits a flag called SIL, Source Integrity Level, which is set by the manufacturer basically to specify the "demonstrated accuracy" (my words, probably not the FAA's) of the GPS position source. SIL is not set dynamically based on any real time test or measurement. SIL=3 or greater means it "meets the spec." SIL=0 means the integrity of the GPS is unknown or unproven. Portable units are required to transmit SIL=0, as I understand it. If your unit transmits SIL=0, basically you get nothing back for your investment in ADS-B Out. NavWorx -0012 and -0013 units transmit SIL=3 and have since early 2016. It appears that fact is the source of the shouting match between somebody in the FAA and NavWorx. Somebody in the FAA says it should transmit SIL=0, NavWorx says their testing, and what they interpret as an FAA approval, allows them to transmit SIL=3. Until something requires NavWorx to update the unit's software to transmit SIL=0, your NavWorx unit should function normally.

    According to one source I read, an upgrade to a "demonstrated" higher integrity GPS (as described by cub builder) is not a short term option in NavWorx' case. i have not heard that from anybody officially associated with NavWorx, however.

  3. #13
    cub builder's Avatar
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    Quote Originally Posted by MEdwards View Post
    No. I think cub builder is talking about the change that happened last January, when the FAA changed ADS-B to not send traffic to units with "low integrity" GPS position sources. I thought that was intended to rule out portable ADS-B Out units, I had no idea it involved any NavWorx units.
    Good explanation of the details I left out. Only one correction. Portable units can have high integrity (SIL=3) GPS units. In fact, my Skyguard unit is a portable that reports itself as SIL=3 and successfully passes the FAA's Performance Report. However, it is limited to use in Experimental and Light Sport Aircraft.

    I was making the point that the FAA suddenly obsoleted a lot of vendor equipment when they surreptitiously chose to no longer respond to ADS-B Out units reporting a GPS System Integrity Level of [0]. That included some Garmin equipment that is now useless and a bunch of Dynon Skyview units that will need to have the GPS source upgraded. Navworx was far from the only vendor to get hosed, but ultimately, we as pilots got screwed by the FAA withholding potentially critical flight safety data because the FAA decided to tighten the specs after many vendors were already actively selling their products believing they were in compliance with the PMA specs.

    -Cub Builder

  4. #14
    MEdwards's Avatar
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    Point well stated. I agree. Thanks for the correction on the portable units, a subject I didn't follow closely after I decided to go with an installed unit in a certificated aircraft.

    Mike E

  5. #15

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    Well, I'm slowly getting up to speed on this. The Van's forum has a pretty good explanation of the history and SIL 0 stuff.

    I'm looking at my report and my unit seems to be broadcasting SIL = 3, as expected. So I guess the issue with mine is whether or not the TSO-C154c certification, which is printed on the case, holds up. I'm still hoping for a good outcome.

    I am struggling to understand why the FAA is taking this stance. As mentioned previously, if the goal is traffic separation, why is it acceptable to allow the same hardware in EAB? Do experimentals just bounce off of Boeings harmlessly now?

    In a year when cash is very tight, I managed to get ADS-B installed for half of what any avionics shop quoted me. Just once I would like to think something is too good to be true and be wrong!

  6. #16
    cub builder's Avatar
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    Really good explanation of this issue in AvFlash this morning. Apparently Navworx made a software change to have their units report SIL[3], but the FAA says that was unauthorized and that their GPS unit does not meet the standards for SIL[3]. Navworx says their GPS units do meet the standards for SIL[3] and that the FAA has not shared any instance of one of their units reporting an inaccurate position. SIL[3] is a block reported in the ADS-B out where the unit reports it's System Integrity Level, meaning the designed accuracy of the WAAS GPS receiver. This is a software bit that is set in the software according to the testing of that GPS design, not an actual test of accuracy of that specific unit. The answer as to whether the Navworx GPS receiver meets the standard for SIL[3] should be easily established with testing.

    In July of 2015, the FAA announced they had changed the TSO standard to require SIL[3] GPS receivers and to encourage pilots to upgrade, would stop responding to units broadcasting SIL[0] in January 2016. This was a sudden change thrust upon vendors with little time to react. The units they had already sold and many on the shelf were about to become instantly obsoleted and would stop reporting traffic. A number of vendors tested their units and issued software updates to change the SIL to [3] in their units. Otherwise the units they had just sold would no longer report traffic, which would make for a sales and PR disaster that was really not of their making. I knew then it would only be a matter of time until someone reprogrammed the SIL block on their units to make them comply without actually upgrading the GPS receivers. That is not to say Navworx did anything wrong or that their GPS receivers don't meet the TSO standard to report SIL[3]. Navworx and Dynon are two of the vendors that released software patches to change the SIL reporting to [3], but it is entirely possible that their GPS receivers already met that standard. Most of the ADS-B Out vendors were in that boat. The FAA is claiming, at least in the case of NavWorx, that their GPS receivers don't meet the standard to report SIL[3], and that the software patch to change the SIL reporting to [3] is unapproved.

    The FAA performance testing that is available gets even more interesting. The FAA sends you a copy of the data blocks reported by your ADS-B out, as well as the accuracy of your unit. The way they derive the accuracy is to compare your reported position against what radar was reporting as your position at the same time. Any errors in position are reported as errors in your unit. So, which do you think is most accurate? Your WAAS GPS unit, or the FAA Radar returns from 100 miles away? Early on when one emailed the FAA folks to ask for testing, they showed my unit as failing because I had <2% of my position reports not an exact match to center's radar, with a couple of meters of error. A few days later I got an unrequested ADS-B performance report from the FAA with a note from the tech that created the report saying that he saw my N number pop up again, so pulled a second report, again showing a very small number (<1%) of inaccuracies vs radar. In his note, he stated that in his opinion, my unit was reporting properly, but the inaccuracies were due to my distance from Center's radar and that I was in a mountainous area, which apparently also induces some small inaccuracies to their radar.

    Dynon is another vendor that sent out a software patch to change the SIL reporting without upgrading the GPS. But, since those Dynon units were almost all in Experimentals, there is darned little the FAA can do to force them to change or upgrade their GPS if the FAA decides to claim the Dynon software patch was also unauthorized. That is not to say the Dynon GPS units either did or did not meet the SIL[3] standard. But I do recall having a discussion with a Dynon rep in Sep 2015 where he stated that they would be sending out patches for many of their units to change the SIL reporting to [3].

    Anyway, the Navworx saga is going to get interesting and has the potential to expand to include other vendors that got caught in the same situation by the FAA's surreptitious change.

    -Cub Builder
    Last edited by cub builder; 10-21-2016 at 03:46 PM.

  7. #17

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    Thanks for that, cub builder. In a more perfect world I would hope for a software patch to broadcast SIL 1 or 2 for the time being and a deadline of 2020 for the warring parties to flesh out a solution.

  8. #18

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    Quote Originally Posted by cub builder View Post

    (snip) ... Dynon is another vendor that sent out a software patch to change the SIL reporting without upgrading the GPS. But, since those Dynon units were almost all in Experimentals, there is darned little the FAA can do to force them to change or upgrade their GPS if the FAA decides to claim the Dynon software patch was also unauthorized. That is not to say the Dynon GPS units either did or did not meet the SIL[3] standard. But I do recall having a discussion with a Dynon rep in Sep 2015 where he stated that they would be sending out patches for many of their units to change the SIL reporting to [3].

    Anyway, the Navworx saga is going to get interesting and has the potential to expand to include other vendors that got caught in the same situation by the FAA's surreptitious change.

    -Cub Builder
    This is a confusing situation, to say the least! As I understand it, the proposed AD also lists ADS600-EXP Model # 200-8013 as one of the affected units. This is the model intended for installation in experimental/EAB aircraft. I thought AD's were mandatory only for certified aircraft or their components. The ADS600-EXP is typically installed in an EAB aircraft. So, can the AD (if it is approved) be ignored when the NavWorx ADS600-EXP 800-2013 is installed in an EAB???

    If the AD can be ignored, I know there is the argument that the FAR's still require we operate our EAB's in an airworthy and safe condition. As I understand it, the FAA has not actually cited an instance where the specified units were inaccurate. So, if the AD became rule and we wished to ignore it but "addressed" the safety issue by having demonstrated and documented a satisfactory ADSB Performance Test report, haven't we resolved the safety/airworthy question?

    I hope this is all theoretical, of course! I'm confident that either NavWorx will work this out with the FAA or, if the AD stands, offer a revision mod to make all this moot!
    Last edited by jaustinmd; 10-30-2016 at 08:31 AM.

  9. #19
    Puertoricoflyer's Avatar
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    Quote Originally Posted by jaustinmd View Post
    This is a confusing situation, to say the least! As I understand it, the proposed AD also lists ADS600-EXP Model # 200-8013 as one of the affected units. This is the model intended for installation in experimental/EAB aircraft. I thought AD's were mandatory only for certified aircraft or their components. The ADS600-EXP is typically installed in an EAB aircraft. So, can the AD (if it is approved) be ignored when the NavWorx ADS600-EXP 800-2013 is installed in an EAB???
    You are right, aircraft AD's do not apply to ELAS or EAB. But this is not an aircraft AD, it is an equipment AD. It applies to the specific equipment indicated not to an aircraft. That is why the proposed AD states:

    "This AD applies to the following NavWorx, Inc., Automatic Dependent Surveillance-Broadcast (ADS-B) Universal Access Transceiver units (unit) installed on aircraft certificated in any category:
    (1) Model ADS600-B part number (P/N) 200-0012;
    (2) Model ADS600-B P/N 200-0013; and
    (3) Model ADS600-EXP P/N 200-8013."

    We experimental guys don't get a pass on this one if it becomes an AD. We have to comply.

    Last edited by Puertoricoflyer; 10-30-2016 at 11:14 AM.
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  10. #20

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    Quote Originally Posted by jaustinmd View Post
    I thought AD's were mandatory only for certified aircraft or their components.
    an AD applies to everything listed in the applicability section.

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