ADS-B FAA Compliance Report

[paulrkuntz]

I installed a Dynon SV-XPNDR-261 Class 1 Mode S transponder and SV-GPS-2020 GPS receiver earlier this year. I had a local avionics facility perform a transponder check, then flew locally for a system check. I requested an FAA ADS-B Compliance Report, which came back reporting no exceptions. So far, so good. A few weeks later, out of curiosity after a longer interstate cross-country flight, I requested another Compliance report. This report came back reporting non-compliance for the NIC (Navigation Integrity Category) parameter. The NIC values in the non-compliant report were: % Fail 2.81%; Max dT 00:00:03; MCF 7; Avg 8.7; Min 0; Max 9. The FAA User Guide for the Compliance report says little regarding NIC other than a minimum NIC value of 7 is required, and that NIC values less than 7 will be flagged red in the report when the MCF (Maximum Consecutive Failures) threshold is exceeded. The NIC MCF for the first (compliant) report was 3, so apparently the MCF threshold for NIC is somewhere between 3 and 7. The average NIC value of 8.7 for the non-compliant report is better than the required minimum of 7, but the minimum value is 0, so I infer that I was squawking a NIC value of zero (or some value less than 7) for more than some unclear number of consecutive reports. I'm not sure where to go from here. At the moment I'm inclined to do nothing. I have one fully compliant report from the FAA that I can refer to if I'm challenged, and frankly, an MCF of 7 really doesn't seem all that bad. It means that at some point during the flight my position reporting was outside the required integrity level for up to seven seconds. I would be worried if the interim value were not compliant for tens or hundreds of seconds. Does anyone else have experience with diagnosing and resolving a similar ADS-B compliance issue?

 

[planecurious]

Likely you haven't updated to the latest SkyView and transponder firmware that corrects a number of issues relating to what you're reporting. "2020 compliance" has proven to be something of a moving target, and Dynon Avionics, to their credit, is responding rapidly with firmware updates to both the SkyView system and their transponder to address issues that the FAA identifies.

Check with the Dynon Avionics SkyView firmware pages to ensure that you are fully up-to-date. Be sure to read the notes about transponder updates, as that is performed AFTER the SkyView firmware update.

 

[paulrkuntz]

My software is current, so that's not the problem. After downloading compliance reports for other flights and thinking about it a bit, I have concluded that the very likely problem is that my GPS is being swamped whenever I transmit on my VHF radio. The length of the outages in the FAA compliance reports are consistent with that being the case, and I violated Dynon guidance for antenna placement when I installed the SV-GPS-2020 receiver puck. My original Dynon GPS receiver was only about 14 inches from the VHF antenna, but it worked fine, so I elected to simply swap it for the new GPS. That location is suitable for good Skyview Nav performance, but there are apparently GPS outages during VHF transmission that I don't notice, but are noticeable to the FAA system.
To test this theory, I flew a couple of days ago, and did not use the radio at all during the flight except to announce my takeoff and pattern entry. The compliance report for that flight came back with no exceptions.
So my next move will be to bite the bullet and move the GPS antenna further away from the VHF antenna.

 

[jdubner]

GPS is being swamped whenever I transmit on my VHF radio

That's a nice piece of detective work, Paul.  Good to know.

--
Joe

 

[swatson999]

Just FYI, the GNS-430W installation manual I have has a procedure which includes the frequencies which are likely to destructively interfere with GPS signals, and the process for testing the installation (selecting each frequency and keying up while watching the GPS signal strength page).

I suppose one could do the same with the Skyview, using the GPS satellite page, perhaps (I don't have the manual opened at the moment and am not at the hangar to see if that page includes signal strength indications). ETA: Yes, it does...thus, you can do the same thing for the SV GPS. I'll dig out the frquencies from the Garmin manual and post them.

There are a handful of frequencies which are at some odd harmonic of the GPS frequencies.

 

[swatson999]

OK, here's the GNS-400 series comm interference check:

1. View the Satellite Status Page and verify that at least 7 satellites have been acquired on the 400W Series unit.
2. Verify that the GPS “INTEG” flag is out of view.
3. Select 121.150 MHz on the COM transceiver to be tested.
4. Transmit for a period of 35 seconds.
5. Verify that the GPS “INTEG” flag does not come into view.
6. Repeat steps 4 and 5 for the following frequencies:
25 kHz COM Channel Spacing

• 121.150 MHz
• 131.225 MHz
• 121.175 MHz
• 131.250 MHz
• 121.200 MHz
• 131.275 MHz
• 121.225 MHz
• 131.300 MHz
• 121.250 MHz
• 131.325 MHz
• 131.200 MHz
• 131.350 MHz

 

[tespn]

I upgraded to Rev 14.2.1 with existing GPS250 and SIL/SDA set to 1.  FAA ADS-B report returned average NIC value of 6 on last flight with range of 6-6 and 100% NIC error. 

Prior to the upgrade, NIC value averaged 7 with a range of 7-0.  The failure rate was .11% with 3 MCF. 

Is the Rev 14.2.1 software set to transmit a max NIC value of 6 when using the GPS250 with SIL/SDA=1?   If not, any suggestions on how to correct?

 

[n456ts]

Did you also update the transponder?

 

[Dynon]

I think you're talking to our support team as well, but to answer publicly as well: We don't have an immediate explanation. We're pretty sure we didn't change anything on the way that the SV-GPS-250 is processed. Keep in mind that the SV-GPS-250 - no matter how good the lock is at any moment, won't qualify for 2020 compliance.

 

[madb1rd]

Yeah, the other thing that really messes up the NIC reporting is flying around upside down... It will be interesting to see how they try to process the legalities around this one.

 

[cbennet12]

Hi,

How long after the flight were you able to get a report?

I have not been able to get any feedback after two flights.

I'm selecting the Trig TT-22 transponder, what do I select for the GPS - the 250 is currently installed.

Craig

 

[dynonsupport]

Craig,
Are you using this site?:

https://adsbperformance.faa.gov/PAPRRequest.aspx

Dynon is listed as a manufacturer for both the transponder and GPS. You should be using that, not Trig.

The most likely reason for not getting a report is that you didn't fly in a ADS-B area. There's a map at the top of the request form showing those areas.

Second is if you are mis-configured. If your ICAO is wrong, then when they go to look it up it won't show up.

 

[cbennet12]

Craig,
Are you using this site?:

https://adsbperformance.faa.gov/PAPRRequest.aspx

Yes.

Dynon is listed as a manufacturer for both the transponder and GPS. You should be using that, not Trig.

This is what was odd. When I selected 1090es out, Dynon was NOT listed as an option. I tried it several times. I just selected Dual which DID show Dynon and when I changed back to 1090es out, Dynon was still available. Perhaps it was a browser caching issue.

The most likely reason for not getting a report is that you didn't fly in a ADS-B area. There's a map at the top of the request form showing those areas.

I was within the 30nm veil for LAX.

Second is if you are mis-configured. If your ICAO is wrong, then when they go to look it up it won't show up.

I'll recheck my transponder config again.

Craig

 

[swatson999]

Hi,

How long after the flight were you able to get a report?

I have not been able to get any feedback after two flights.

I'm selecting the Trig TT-22 transponder, what do I select for the GPS - the 250 is currently installed.

Craig

Just curious...why bother? The 250 doesn't get you sufficient SIL/SDA levels, and you'll just be alerting the FAA that you're flying around sending ADS-B signals out with too low of a level (IIRC, the report may include some notice to stop broadcasting ADS-B until you have a compliant system)...

 

[cbennet12]

For the $500 rebate. Why pay for the 2020 when it gets me nothing until 1/12020?

Craig

 

[swatson999]

Yeah, but I don't think the 250 qualifies...

"Avionics that are certified to FAA Technical Standard Orders and meet the program rules"

The 250 isn't certified to the appropriate standards level.

I could be wrong, in which case, have at it. But I thought the rebate only applied to equipment that met the 2020 standard.

 

[Raymo]

Steve,

You are correct. The equipment must be TSO'd and (IIRC) be installed by a certified shop, which means you'll spend way more than that $500 rebate to meet the requirements.

 

[swatson999]

Steve,

You are correct. The equipment must be TSO'd and (IIRC) be installed by a certified shop, which means you'll spend way more than that $500 rebate to meet the requirements.

Well, "way more" is relative, I guess. Upgrading from the 250 GPS to a 2020 is $590, so after the rebate, it's $90. That seems pretty inexpensive to me.

That's assuming you have a SV (or else, why would you be on this forum? ), and the Dynon (TT) XPDR, of course.

 

[swatson999]

Steve,

You are correct. The equipment must be TSO'd and (IIRC) be installed by a certified shop, which means you'll spend way more than that $500 rebate to meet the requirements.

Well, "way more" is relative, I guess. Upgrading from the 250 GPS to a 2020 is $590, so after the rebate, it's $90. That seems pretty inexpensive to me.

That's assuming you have a SV (or else, why would you be on this forum? ), and the Dynon (TT) XPDR, of course.

ETA: I don't believe it has to installed by a certified shop, though, but I expect Dynon Support will weigh in here shortly...

 

[cbennet12]

The 250 is valid until 1/1/2020. Dynon already confirmed this on a separate post. The unit is listed as a option on the FAA web site when you request the report.

Craig