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  #31  
Old 10-03-2018, 05:36 PM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by greghughespdx View Post
How close was he to you when he was not showing on the screen? Within 15 miles? And just to be sure, do you have ADS-B Out working in your aircraft?
Approach called him at 3 miles, 1 O'clock, same altitude. He was well within the "hockey puck". Yes, I have a Garmin GDL-82. It seemed to me like there was a ~10 minute latency before the ground station decided to send me the target. I really can't trust this system.
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  #32  
Old 10-04-2018, 06:55 AM
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In thinking this over, I didn't "see" the target because either I wasn't an ADS-B "client" or he wasn't a "target". After the flight, I requested a "performance report" and my TIS-B client percentage was only 11% for some reason. That had to be because I wasn't in contact with the ADS-B ground station, I wasn't in radar coverage, or something else? The C-172 only became "visible" on my screen when he climbed from 4,500' to 6,000'. It's hard to know whether the problem was mine or his because Foreflight/Stratus doesn't make use of the "Service Status" messages being broadcast which confirm whether your aircraft is a client. Garmin displays an icon on the screen that indicates you are a TIS-B client. It's very disappointing that Foreflight doesn't do this. As a result, when using Foreflight, I never know whether I am seeing the whole traffic picture. From Source: http://adsbforgeneralaviation.com/wp...1_20111024.pdf
Quote:
The SBSS [Surveillance and Broadcast Services System] control station monitors the ADS-B received reports to identify TIS-B Client aircraft. In order to be considered a TIS-B Client, an aircraft must be ADS-B-OUT, must have produced valid position data (see 3.3.1.2.5) within the last 30s to a SBS ground station, must be under surveillance of at least one secondary radar and must be ADS-B-IN on at least one link. Two key safety benefits for requiring TIS-B Clients to transmit ADS-B-OUT is spectrum conservation by the SBS [Surface-Based System? - Ground Station?] system and the provision of the TIS-B Service Status message by the SBS system to indicate service availability for specific aircraft.
That 3.3.1.2.5 (above) requires that your ADS-B (out) position be verified by another source, usually radar. This is why you have to be both in contact with an ADS-B ground station AND within radar coverage to become a "client". Strange, but true. I guess I need to call the TRACON and query them on radar coverage in the area in which I was flying.
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  #33  
Old 10-04-2018, 03:19 PM
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Default More info

I called the AVL TRACON this morning and had a productive discussion with one of the senior controllers. She told me that radar coverage was "problematic" below 5,000' in the area where I had been flying. I am convinced that is why I was an ADS-B client for only 11% of the flight. She also mentioned that the only ADS-B ground station in our area is very unreliable and is out of service every couple of days. Maybe that could be a contributing factor as well. I flew again today (in a different area) and my client percentage was up to 38%. I guess that's progress /sarc
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  #34  
Old 10-05-2018, 05:39 AM
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I've been flying with ADSB for 5 years. Up until recently, there was no TIS-B traffic data in the Asheville valley. The traffic had to be at or above the mountains to our south or southeast in order for TIS-B to work. Obviously a radar line of sight issue.

I have noticed TIS-B data in the valley recently but I agree it is flakey as of yet.

My last social visit to the tower included them showing me the 'Fusion' system screen in the approach room that was due to go online soon. My understanding is that new system will better use ADSB info.


ALSO. I have seen a few comments about the size of the TIS-B data airspace 'puck'of 15 NM. I commonly see data from craft that are 50 miles away such as the buzz of craft in KCLT Class B as I pass by outside the B, or targets near KGSO when that is 80 NM into the future.

Sup wit dat?
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Last edited by rzbill : 10-05-2018 at 05:51 AM.
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  #35  
Old 10-05-2018, 05:55 AM
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Quote:
Originally Posted by rzbill View Post
...the 'Fusion' system screen in the approach room that was due to go online soon.
That's some good information right there. When I spoke with Kim yesterday, she mentioned "new equipment". Maybe that's what she was talking about. I think you're right about the spotty radar coverage over the mountains, but I have a plan to confirm whether that's the source of my problem. Today I'm flying over the SE practice area again, but at 7,000' this time rather then 4,500'. Hopefully I'll see some TIS-B targets but it doesn't really matter. When I get home I'll request a Performance Report and see what my Client % was. (Aside: When I flew to GMU at 5,500' yesterday, my Client % was 48%.)

As for the distant targets you're seeing, Foreflight has an option to "Hide Distant Targets". You probably have something similar in whatever software you're using.
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Last edited by snopercod : 10-05-2018 at 05:58 AM.
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  #36  
Old 10-05-2018, 11:06 AM
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Default Q.E.D.

I went up today to the same area as two days ago but flew at 7,000' vs. 4,500'. My TIS-B client percentage was 69%, up from 11%. So as far as I'm concerned, the low-client-percentage mystery is solved. To get better TIS-B, you need better radar coverage. While up there I asked Approach if his "Fusion" system was operational and he said it was. He can now see ADS-B information on his screen as well as radar. He told me as far as he could tell, my ADS-B was working normally. I don't know exactly what his screen shows, but I'm happy now. I should have asked him if he could tell whether I was a Client or not.
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Last edited by snopercod : 10-05-2018 at 11:30 AM.
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  #37  
Old 11-08-2018, 02:53 PM
rcoleman-10 rcoleman-10 is offline
 
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Default ADS-B Test Report

Good afternoon,

I submitted to the FAA for the test report and looks like i have passed all but two areas in the Integrity and Accuracy category. I know that's an important section but I was wondering what is the resolution?

The report came back with:

Avg:

NIC = 9.0
NACp = 10
NACv = 2.0
SIL = 0.0
SDA = 0.0


The red are the failure points.

I know what the definitions of SIL and SDA are but do not know what would be done to correct the issue and pass those two areas.

my setup is a GTN650 and the GTX23

Any ideas?

Ron
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  #38  
Old 11-08-2018, 04:20 PM
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Quote:
Originally Posted by rcoleman-10 View Post
Good afternoon,

I submitted to the FAA for the test report and looks like i have passed all but two areas in the Integrity and Accuracy category. I know that's an important section but I was wondering what is the resolution?

The report came back with:

Avg:

NIC = 9.0
NACp = 10
NACv = 2.0
SIL = 0.0
SDA = 0.0


The red are the failure points.

I know what the definitions of SIL and SDA are but do not know what would be done to correct the issue and pass those two areas.

my setup is a GTN650 and the GTX23

Any ideas?

Ron
Hello Ron,

Since you have a GTX 23ES transponder, you must have a G3X or G3X Touch system.

Make sure that the Position Integrity is set to "IFR GPS 1E-7" on the transponder configuration page if you are using your GTN 650 as the position source for the GTX 23ES. Also, make sure your transponder type is set to GTX 23ES, not GTX 23.

Thanks,
Steve
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  #39  
Old 11-08-2018, 06:31 PM
rcoleman-10 rcoleman-10 is offline
 
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Quote:
Originally Posted by g3xpert View Post
Hello Ron,

Since you have a GTX 23ES transponder, you must have a G3X or G3X Touch system.

Make sure that the Position Integrity is set to "IFR GPS 1E-7" on the transponder configuration page if you are using your GTN 650 as the position source for the GTX 23ES. Also, make sure your transponder type is set to GTX 23ES, not GTX 23.

Thanks,
Steve
Thanks Steve,

You are right....It is the GTX 23ES and the transponder is set to that. And yes, it is the G3X non-touch to the GTN650.

I will check the transponder configuration page to ensure it is set to "IFR GPS 1E-7".

Thank you for the guidance.

Ron
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