Matronics Email Lists Forum Index Matronics Email Lists
BBS Forum Interface to the Matronics Email Lists
 
 Get Email Distribution Too!Get Email Distribution Too!    FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

ADS-B compliance question

 
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> RV10-List
View previous topic :: View next topic  
Author Message
dan(at)syz.com
Guest





PostPosted: Thu Feb 08, 2018 3:46 pm    Post subject: ADS-B compliance question Reply with quote

Hi everyone.

I have a Dynon SV-XPNDR-261 and Garmin GTN650 to meet the US mandate to be ADS-B out equipped by 2020 (I'm Canadian, so a UAT doesn't make a lot of sense, which is why I went for 1080ES).

I did a flight to the US about a month ago and recently stumbled across the Public ADS-B Performance Report Request tool (https://adsbperformance.faa.gov/PAPRRequest.aspx). So I put in my info to see how my equipment and installation did.

Generally speaking, it seemed to do well with very few errors, and for the most part failures for missing elements, integrity, accuracy, etc. were substantially <1%. However, one element flagged red (the only one flagged red) which was my Geo Alt. It reported:

% Fail: 3.70%
Max dT: 00:00:21
MCF: 8

First, is the failure percentage accurate? The flight duration was about 2.5 hours (total reports 15616, processed reports 8320), and from the documentation I read, max dT is "Total time during flight the message element failed performance assessment.". 21 seconds out of 2.5 hours isn't 3.7% (more like 0.24%). And another category on my report (NACp) has a Max dT also of 00:00:21 with MCF of 2 and does report a %fail of 0.25%.

I presume this happened when my GPS just lost a 3D solution (which of course, all GPSes do from time to time). Does someone who understands ADS-B compliance think this may be a cause for concern? I don't want to be flagged as a non-compliant ADS-B out aircraft.

Thanks for any help any of you can provide!

Dan
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
Kellym



Joined: 10 Jan 2006
Posts: 1517
Location: Sun Lakes AZ

PostPosted: Thu Feb 08, 2018 4:14 pm    Post subject: ADS-B compliance question Reply with quote

How your transponder performs for altitude will depend on altitude
source. It is supposed to have a barometric source, such as an EFIS or
blind encoder, as well as a GPS altitude source.
I found with my Dynon Skyview that I needed to adjust my ADAHRS reported
altitude down about 40-50 ft to get it spot on. I am using the same
transponder and GPS source as you are and got a clean performance
report. You also need to be certain that your transponder has firmware
2.09 or higher, and your GTN has firmware from within the past couple
years, so that both are set for ADS-B+ communications protocol.

On 2/8/2018 4:43 PM, Dan Charrois wrote:
Quote:


Hi everyone.

I have a Dynon SV-XPNDR-261 and Garmin GTN650 to meet the US mandate to be ADS-B out equipped by 2020 (I'm Canadian, so a UAT doesn't make a lot of sense, which is why I went for 1080ES).

I did a flight to the US about a month ago and recently stumbled across the Public ADS-B Performance Report Request tool (https://adsbperformance.faa.gov/PAPRRequest.aspx). So I put in my info to see how my equipment and installation did.

Generally speaking, it seemed to do well with very few errors, and for the most part failures for missing elements, integrity, accuracy, etc. were substantially <1%. However, one element flagged red (the only one flagged red) which was my Geo Alt. It reported:

% Fail: 3.70%
Max dT: 00:00:21
MCF: 8

First, is the failure percentage accurate? The flight duration was about 2.5 hours (total reports 15616, processed reports 8320), and from the documentation I read, max dT is "Total time during flight the message element failed performance assessment.". 21 seconds out of 2.5 hours isn't 3.7% (more like 0.24%). And another category on my report (NACp) has a Max dT also of 00:00:21 with MCF of 2 and does report a %fail of 0.25%.

I presume this happened when my GPS just lost a 3D solution (which of course, all GPSes do from time to time). Does someone who understands ADS-B compliance think this may be a cause for concern? I don't want to be flagged as a non-compliant ADS-B out aircraft.

Thanks for any help any of you can provide!

Dan
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213







- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD
Back to top
View user's profile Send private message
rleffler



Joined: 05 Nov 2006
Posts: 635

PostPosted: Thu Feb 08, 2018 4:24 pm    Post subject: ADS-B compliance question Reply with quote

A couple questions........

What EFIS do you have? Is it a Skyview or AFS? Your EFIS should be providing the 261 pressure altitude. GPS altitude is only used as a backup. I believe that both are transmitted as part of the ADSB out.

I can't tell you how to debug the Skyview, but on the AFS there is the ability to dump data from the serial ports to an ascii file. It may be tedious, but you can look through this output and see if there is any issues with the EFIS transmitting pressure altitude to the 261. I'm sure that you can do something similar on the Skyview. Unfortunately I don't have that experience.

How close was the nearest ADSB tower? Sometimes there are errors during initial climb out and on descent. Especially if the ADSB tower is nearby or on the field. I know that some folks were advised for the ADSB rebates to leave everything turned off until they hit 3K agl to minimize these errors.

Have you had the 261 certified yet? They should be able to see if there are any issues with the transponder and its data feeds. Although many shops have older test rigs.

If these weren't failed as red, I wouldn't lose any sleep over it. Generate another PAPR the next time you're In the US.

I have AFS 5500s, GTN650, 261, and a 472. The later two were just installed over the holidays. I was able to get a clean PAPR on the first flight with them a couple weeks ago.

Bob
--


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Bob Leffler
N410BL - Phase I
http://mykitlog.com/rleffler
Back to top
View user's profile Send private message
Kellym



Joined: 10 Jan 2006
Posts: 1517
Location: Sun Lakes AZ

PostPosted: Thu Feb 08, 2018 5:06 pm    Post subject: ADS-B compliance question Reply with quote

The Skyview under setup(ADAHRS section IIRC) lets you input an altitude
offset, so that you can ensure that the static system reading matches
the calibrated test set for pressure altitude. That eliminates any
errors from rounding in reported altimeter settings at the local field.
As I said, I wound up using an offset of about 50 ft, but had gotten a
report before I had the static system IFR certified, and everything passed.

On 2/8/2018 5:23 PM, Bob Leffler wrote:
[quote]

A couple questions........

What EFIS do you have? Is it a Skyview or AFS? Your EFIS should be providing the 261 pressure altitude. GPS altitude is only used as a backup. I believe that both are transmitted as part of the ADSB out.

I can't tell you how to debug the Skyview, but on the AFS there is the ability to dump data from the serial ports to an ascii file. It may be tedious, but you can look through this output and see if there is any issues with the EFIS transmitting pressure altitude to the 261. I'm sure that you can do something similar on the Skyview. Unfortunately I don't have that experience.

How close was the nearest ADSB tower? Sometimes there are errors during initial climb out and on descent. Especially if the ADSB tower is nearby or on the field. I know that some folks were advised for the ADSB rebates to leave everything turned off until they hit 3K agl to minimize these errors.

Have you had the 261 certified yet? They should be able to see if there are any issues with the transponder and its data feeds. Although many shops have older test rigs.

If these weren't failed as red, I wouldn't lose any sleep over it. Generate another PAPR the next time you're In the US.

I have AFS 5500s, GTN650, 261, and a 472. The later two were just installed over the holidays. I was able to get a clean PAPR on the first flight with them a couple weeks ago.

Bob


--


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD
Back to top
View user's profile Send private message
dan(at)syz.com
Guest





PostPosted: Wed Feb 14, 2018 6:35 pm    Post subject: ADS-B compliance question Reply with quote

Quote:
On 2018-Feb-08, at 5:23 PM, Bob Leffler <bob(at)thelefflers.com> wrote:



A couple questions........

What EFIS do you have? Is it a Skyview or AFS? Your EFIS should be providing the 261 pressure altitude. GPS altitude is only used as a backup. I believe that both are transmitted as part of the ADSB out.

It's an AFS system I have.

Quote:

I can't tell you how to debug the Skyview, but on the AFS there is the ability to dump data from the serial ports to an ascii file. It may be tedious, but you can look through this output and see if there is any issues with the EFIS transmitting pressure altitude to the 261. I'm sure that you can do something similar on the Skyview. Unfortunately I don't have that experience.

I'll try to do a serial port dump the next time I go flying to see if there are any inconsistencies. Thanks for the suggestion!

Quote:

How close was the nearest ADSB tower? Sometimes there are errors during initial climb out and on descent. Especially if the ADSB tower is nearby or on the field. I know that some folks were advised for the ADSB rebates to leave everything turned off until they hit 3K agl to minimize these errors.

I'm not sure - and likely throughout the flight hopped between several towers. The report didn't give me much info other than just saying that there were some errors with Geo Alt. For all I know, it might have just been on the ground when the GPS was still getting a lock on the satellites and didn't know altitude yet. But in any case, I can't figure out why a total outage of 21 seconds worth of data came to a reported 3.7% fail rate, when in reality the failure rate should have been 15 times less by my calculations.

Quote:

Have you had the 261 certified yet? They should be able to see if there are any issues with the transponder and its data feeds. Although many shops have older test rigs.

The "traditional Mode C" side of the transponder was certified a bit less than a year ago. Though the equipment used didn't have the ability to dig deep into the ADS-B data other than to just see that it was generally sending valid packets.

Quote:

If these weren't failed as red, I wouldn't lose any sleep over it. Generate another PAPR the next time you're In the US.

The Geo Alt. section (under missing elements) was flagged as red. But none of the "exceptions" section (NIC, NACp, NACv, SIL, SDA) or anything else. Just the Geo Alt.

Others have suggested potentially inputting an altitude offset to ensure barometric altitude matches closely with GPS altitude (unless the reference is to adjust the GPS altitude, though I've already set my antenna height above the wheel base accurately). But I thought the "Missing Elements" Geo Alt failures were "standalone" where the GPS didn't provide altitude data. I didn't think it was flagging that it didn't compare favourably against barometric altitude. My Baro Alt, Baro Alt Delta, Geo Alt, and Geo Alt Delta under the Kinematics section all read 0 errors and 0% failure rate.

In any case, how could they actually compare the two, since baro alt for the transponder is standardized at 29.92 and geo alt isn't affected by the local air pressure. Plus, even if they recorded nearest station altimeter readings to make the appropriate corrections, even then comparing the two assumes an ISA atmosphere, which is rarely the case. From my understanding, that's why, for example, even if altimeters are set perfectly, if the weather is cold, cold temperature corrections are necessary to find true height above sea level otherwise you're flying lower than you think. The GPS altitude wouldn't reflect any of this.

I'll double check the firmware for the transponder and GTN as well, to make sure they're all up to date.

Regardless, I'll try doing a serial dump the next time I fly, though since I don't fly in the US that often, it might be some time before I can compare it against another PAPR.

Thanks again for the suggestion!

Dan
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213


- The Matronics RV10-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?RV10-List
Back to top
Display posts from previous:   
Post new topic   Reply to topic    Matronics Email Lists Forum Index -> RV10-List All times are GMT - 8 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Powered by phpBB © 2001, 2005 phpBB Group