Anyone know why my ADS-B test failed?

[RobertE]

To get the rebate (and, maybe, just be legit) we have to pass a flight test per AC20-165B.  It's a neat system whereby you input your date of flight, equipment, name and email address and  minutes later you get an email with the test results, including the code to claim the $500 rebate. 

Well, my report came back with a note "the Performance Monitor could NOT validate that the flight operation consisted of at least 30 minutes in the defined airspace.... Please ensure the flight meets Program requirements for flight time..."  But the report shows total flight duration of 90 minutes, I was in an area of ADS-B coverage and generally complied with all the rules defined in the AC.  BUT, the two exceptions were that although I complied with the requirement of a total of 10 minutes of maneuvering flight I didn't do the prescribed 2 left and right 360 degree turns and, although my cruising altitude was 7,500, it might have been 6,900 AGL, not the 7,000 AGL prescribed.  Could either of these deficiencies explain the failure?  Any other ideas?

Thanks.

[jrwilson]

Class e for "rule airspace " for the test is over 10k.  Go up above 10k, do the turns, go north south east and west over the same fix, etc and you will be set.  Remember to do some climbs also.  Maybe a block from 10.5 to 12.5k

Edited November 25, 2016 by jrwilson

[Piloto]

I personally think these tests should be performed on the ground with ADS-B out test equipment (already available) in the same manner as the biennial transponder/altimeter check. An ATC radar does not measure many of the parameters that ground test equipment does (ie. power and frequency). For a fleet operator with 100 B737s and B747s this becomes a very expensive test which may need to be repeated with no finding of the problem. While a ground test will quickly diagnose the problem. Notice that the air test was never required for mode C or mode S transponders. This tells me the FAA has some lack of confidence on the ADS-B out implementation concept. Can you imagine GE having to fly test every engine before is shipped out.

José

[takair]

15 minutes ago, Piloto said:

I personally think these tests should be performed on the ground with ADS-B out test equipment (already available) in the same manner as the biennial transponder/altimeter check. An ATC radar does not measure many of the parameters that ground test equipment does (ie. power and frequency). For a fleet operator with 100 B737s and B747s this becomes a very expensive test which may need to be repeated with no finding of the problem. While a ground test will quickly diagnose the problem. Notice that the air test was never required for mode C or mode S transponders. This tells me the FAA has some lack of confidence on the ADS-B out implementation concept. Can you imagine GE having to fly test every engine before is shipped out.

José

Jose

As of right now, this test is only linked to getting the rebate.  I don't think the FAA has mandated it beyond that.  I know that the OEMs are not flying this test with any of the production aircraft (at least the ones I work(ed) for.  The basic data is validated on the test aircraft and then the accuracy is based on the basis that the aircraft installs are duplicates.  The 91.411 and 91.413 test does not go away, so you still need to do that for the basic transponder that is still required.  Our part 23 aftermarket installs have more variation, so I think this is a semi-econimical way for us to validate the integration with the GPS.  Their are a number of dynamic parameters that are difficult to represent, even with the best equipment.  

[Piloto]

Just now, takair said:

Jose

As of right now, this test is only linked to getting the rebate.  I don't think the FAA has mandated it beyond that.  I know that the OEMs are not flying this test with any of the production aircraft (at least the ones I work(ed) for.  The basic data is validated on the test aircraft and then the accuracy is based on the basis that the aircraft installs are duplicates.  The 91.411 and 91.413 test does not go away, so you still need to do that for the basic transponder that is still required.  Our part 23 aftermarket installs have more variation, so I think this is a semi-econimical way for us to validate the integration with the GPS.  Their are a number of dynamic parameters that are difficult to represent, even with the best equipment.  

As per  AC20-165B par. 4.3 the air test is required and there is no refund for it. The only way an ATC radar can cross check ADS-B position is by mode C interrogation and this is affected by slant range and antenna beam width. The only way to insure dynamic accurate positioning is by using a TSO approved GPS.

José 

[Marauder]

17 minutes ago, Piloto said:

As per  AC20-165B par. 4.3 the air test is required and there is no refund for it. The only way an ATC radar can cross check ADS-B position is by mode C interrogation and this is affected by slant range and antenna beam width. The only way to insure dynamic accurate positioning is by using a TSO approved GPS.

José 

I often wondered if these airborne tests are as much as testing their ground based system as it is testing the stuff we install.

[Skates97]

Heard an interesting conversation when I was flying to Phoenix from CA a couple weeks ago. I was on flight following and it was fairly quiet. A guy asked control if they had time for a question. They said yes and he said that he just had ADS-B Out installed and wondered if they could tell him if they were picking it up. The controller responded that he really didn't have any way of knowing, that they (ATC) could have switched it off in the system and he wouldn't have any way of knowing if he wasn't piking it up because it wasn't working or if it was because it was off on the controllers end. The pilot then asked if TRACON would be able to tell and the controller responded that they weren't using it yet.

[Piloto]

22 minutes ago, Marauder said:

I often wondered if these airborne tests are as much as testing their ground based system as it is testing the stuff we install.

You are right. There are some issues on the ground side when relying on ADS-B.

For mode C/S surveillance ATC radar uses a high directional rotating antenna with a power gain of at least 100 (20db). The transponder reply and the ATC antenna are line up for signal reception. But with ADS-B the transponder transmission are not in sync with the ATC antenna bearing. So the ADS-B signal will be attenuated by a 100 20db or more F/B. To overcome this a monopole omni directional antenna of 3 to 6db gain is used. Due to the lower gain and no directionality ATC reception is degraded by longer range, weather and other traffic interference. A plane at 30,000 feet and 300nm will be pick up on mode C but not on ADS-B until at 100nm or closer. And this assuming there is no weather and no traffic interference. Not to mention that ADS-B is more susceptible to intentional interference.

José

Edited November 25, 2016 by Piloto

[JKeeth]

53 minutes ago, Piloto said:

As per  AC20-165B par. 4.3 the air test is required and there is no refund for it. The only way an ATC radar can cross check ADS-B position is by mode C interrogation and this is affected by slant range and antenna beam width. The only way to insure dynamic accurate positioning is by using a TSO approved GPS.

José 

takair is correct; the flight test is only required for the $500 rebate. However, the FAA encourages installers and users to request an ADS-B Performance Report to validate the performance of the newly installed ADS-B Out equipment. Not a requirement, but recommended. The flight for the performance report can be accomplished in any airspace where ADS-B coverage is available. However, the flight for the rebate must be accomplished in rule-compliant airspace as per FAR 91.225. I believe the OP's error was not flying in the rule-compliant airspace that is required for the rebate. 

AC20-165B is for the initial airworthiness approval of an STC. Once the STC is approved, the installer follows the manufacturers instructions using the prior approved STC data. The installer doesn't follow the AC, only the STC. 

Jim Keeth

L-3 Aviation Products

[carusoam]

There is also another thread around here where a pilot has had a similar question.  The rule airspace was also discussed to be a challenge to understand prior to flying...

Best regards,

-a-

 

[Piloto]

10 hours ago, JKeeth said:

takair is correct; the flight test is only required for the $500 rebate. However, the FAA encourages installers and users to request an ADS-B Performance Report to validate the performance of the newly installed ADS-B Out equipment. Not a requirement, but recommended. The flight for the performance report can be accomplished in any airspace where ADS-B coverage is available. However, the flight for the rebate must be accomplished in rule-compliant airspace as per FAR 91.225. I believe the OP's error was not flying in the rule-compliant airspace that is required for the rebate. 

AC20-165B is for the initial airworthiness approval of an STC. Once the STC is approved, the installer follows the manufacturers instructions using the prior approved STC data. The installer doesn't follow the AC, only the STC. 

Jim Keeth

L-3 Aviation Products

You are right Jim. But since FAA ADS-B approved equipment is indicated on the 337 form wouldn't be easier to get the rebate with just a copy of the 337 form. And then what happens if the flight test fails, are you illegal flying in class B? May as well don't do the flight test. 

José

[cnoe]

takair is correct; the flight test is only required for the $500 rebate. However, the FAA encourages installers and users to request an ADS-B Performance Report to validate the performance of the newly installed ADS-B Out equipment. Not a requirement, but recommended. The flight for the performance report can be accomplished in any airspace where ADS-B coverage is available. However, the flight for the rebate must be accomplished in rule-compliant airspace as per FAR 91.225. I believe the OP's error was not flying in the rule-compliant airspace that is required for the rebate. 
AC20-165B is for the initial airworthiness approval of an STC. Once the STC is approved, the installer follows the manufacturers instructions using the prior approved STC data. The installer doesn't follow the AC, only the STC. 
Jim Keeth
L-3 Aviation Products

Good info Jim. Another thing to consider for those not seeking the rebate is that without a successful Performance Report your installation may not be in compliance with the 2020 mandate. The installers cannot verify your compliance; you must do this yourself with an aerial test. I suggest doing this right after installation so that the installer might have some sense of obligation to remedy any deficiencies. As an early adopter (34 months ago) it took my (Garmin certified) installation shop 3 tries before my Performance Report came back okay.


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[Piloto]

9 minutes ago, cnoe said:

 

Good info Jim. Another thing to consider for those not seeking the rebate is that without a successful Performance Report your installation may not be in compliance with the 2020 mandate. The installers cannot verify your compliance; you must do this yourself with an aerial test. I suggest doing this right after installation so that the installer might have some sense of obligation to remedy any deficiencies. As an early adopter (34 months ago) it took my (Garmin certified) installation shop 3 tries before my Performance Report came back okay.


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What was wrong on the previous 2 tries?

[cnoe]

IIRC the first time was a configuration error which didn't fix it. After further investigation Garmin indicated that the position source provider (GNS530W) had to be updated before the data was usable by the ADS-B Out unit (GTX330-ES). Hopefully by now the shops are familiar with the whole setup. I thought it was silly that they couldn't test it before I flew away but they basically said "try this".


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[JKeeth]

4 hours ago, Piloto said:

You are right Jim. But since FAA ADS-B approved equipment is indicated on the 337 form wouldn't be easier to get the rebate with just a copy of the 337 form. And then what happens if the flight test fails, are you illegal flying in class B? May as well don't do the flight test. 

José

The FAA has always been concerned about approved, or non-approved, pairings between the GPS receiver and the ADS-B out equipment. So while a form 337 would list the equipment used, I don't believe it would necessarily ensure that the GPS position source has the right software and/or accuracy requirements, which is probably why the FAA encourages a performance check. Of course pairing issues aren't a concern with transponders or UAT boxes that contain internal GPS, so in that regard you bring up a good point about simply submitting the 337 for the rebate. 

Also, test equipment such as the Aeroflex IFR-6000 is more than adequate for testing ADS-B out on the ground to ensure a system is valid, except for the pesky "air on ground" issue that has been a problem for some installs. 

[FoxMike]

Just to give you some hope.  I installed a 750+345 two weeks ago and after completion flew up to Steamboat Springs at 12.5K.  Made a couple of heading changes and started an instrument approach.  Based on that I got a positive report from the FAA and filed for the rebate which has been approved.  I have not gotten the check yet.  I hope it is before inauguration day.  If you download the Public ADS-b Performance Report it seems to be useless information except any failures are coded red.  If you pass that test you need to download a GA Incentive Requirements Status Report and use the number on it to claim the rebate .  A lot of hassle for a the equivalent of a tank of gas.

[DVA]

For those who are interested ...

Here is the FAA ADS-B Compliance Report User Guide.  It contains the info you need to request an airborne report, as well as how to interpret the data.

DVA

ADS-B ACR User's Guide (2-16-16).pdf

[mooneyflyfast]

I passed the test Fri. making a regular 250 mile cross country flight at 11,500. Made only two turns-- one 75 degrees and one 65 degrees--neither in Rule airspace. 

[RobertE]

On ‎11‎/‎24‎/‎2016 at 4:07 PM, jrwilson said:

Class e for "rule airspace " for the test is over 10k.  Go up above 10k, do the turns, go north south east and west over the same fix, etc and you will be set.  Remember to do some climbs also.  Maybe a block from 10.5 to 12.5k

Victory!!  Thank you, Mr. Wilson.  I would never have thought (silly me) that "rule airspace" was "the airspace where by 2020 you gotta have it".  I was thinking of rule airspace as that airspace in which our transmissions are observable.

This forum is so very helpful.

[jrwilson]

Glad I could help

[carusoam]

The power of MS is awesome...

How else would we know what rule airspace is..?

Best regards,

-a-

[JohnB]

On 11/25/2016 at 11:39 AM, JKeeth said:

The FAA has always been concerned about approved, or non-approved, pairings between the GPS receiver and the ADS-B out equipment. So while a form 337 would list the equipment used, I don't believe it would necessarily ensure that the GPS position source has the right software and/or accuracy requirements, which is probably why the FAA encourages a performance check. Of course pairing issues aren't a concern with transponders or UAT boxes that contain internal GPS, so in that regard you bring up a good point about simply submitting the 337 for the rebate. 

Also, test equipment such as the Aeroflex IFR-6000 is more than adequate for testing ADS-B out on the ground to ensure a system is valid, except for the pesky "air on ground" issue that has been a problem for some installs. 

That's exactly what I have, just did my test and got the Air on Ground test portion failed where all other tests passed with flying colors. Do you or anyone know what this pesky error is likely due to?  Will have my avionics shop look into it,

[carusoam]

John, I think Somebody covered that answer here somewhere...

It may be in the other thread..?

Might have been something to do with the on the ground switch.  Airspeed or squat switch depending on what you have and if it is wired properly.

best regards,

-a-

 

[JKeeth]

10 hours ago, JohnB said:

That's exactly what I have, just did my test and got the Air on Ground test portion failed where all other tests passed with flying colors. Do you or anyone know what this pesky error is likely due to?  Will have my avionics shop look into it,

What ADS-B out equipment do you have, and is the GPS providing the in-air and on-ground logic, or is that being done with an external airspeed or squat switch?

The reason the FAA's system failed the "in-air on ground test" is because your airplane was reporting that it was in air mode while sitting on the ground (duh!), and in my experience this tends to happen most often after landing rather than prior to take-off. If your airplane reported that you were still in-air after you taxied off the runway, then that would cause the failure of the "air on ground" test. Of course, this would only happen at an airport that has coverage from an ADS-B ground station. If no ground station coverage, then your ADS-B OUT will never be received into the ADS-B system and therefore not see the "air on ground" discrepancy.

Fixing this depends on the ADS-B system in your airplane. For the Lynx NGT-9000, for example, GPS groundspeed is used to determine when to go from air mode to ground mode, and the groundspeed value is configured into the unit during installation. If the groundspeed is set too low then your airplane could be outputting air mode while taxing after landing, and in that case, increasing the GPS groundspeed would be the corrective action. Generally, the GPS groundspeed setting should be 70% of Vso.

[RobertE]

What I've witnessed from my system is that as soon as I'm moving about 5 mph I start receiving signals.  I assume I'm sending them at that time as well.  From what has been said about the proper speed setting being 70% of Vso it sounds like mine is set way too low but I happen to like it.  It's handing to see while taxing what aircraft are in the vicinity.