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ADS-B not picking up UPS aircraft

roadrunner20

roadrunner20

Well Known Member
This evening, I was departing Clearwater(KCLW) under the 3000' veil of the Tampa Class B.
Heading east bound at 2200', at my 10 o'clock a UPS cargo 757 was descending into St Pete/Clearwater(KPIE) around 3000'.

My ADS-B was reporting 5 stations & this aircraft DID NOT show up on my display. All other traffic in the area was rendered on my EFIS. (That I'm aware)

Why not this aircraft?
I'm using Navworx IN/OUT ADS-B on a GRT EFIS.
 
Dan, maybe you could identify the ups flight number look him up on say flight aware and see if he was actually tx a code or adsb signal. I would think so but you never know. Missed you at Tripl e tree this year. I was ther only on friday.
 
I've found ADS-B traffic to be very spotty (I am equipped with ADS-B out). I've visually acquired traffic (GA, airlines, and military) well within the ADS-B traffic "puck" that did not show up on the display.

If TIS-B shows traffic, it's probably there. If it shows nothing, however, that doesn't mean that something isn't there. Because of that, I think it is of dubious value at best.

Weather is nice however.
 
DennisRhodes said:
Dan, maybe you could identify the ups flight number look him up on say flight aware and see if he was actually tx a code or adsb signal. I would think so but you never know. Missed you at Tripl e tree this year. I was ther only on friday.
Click to expand...

Hey Dennis,
Would have loved to be at TT. Probably next year.

Since I was picking up other traffic & generally all the big iron coming into Tampa & St Pete, I thought UPS might have their transponder on standby or not squawking.
I talked to Tampa FSDO looking for their opinion & they were inclined to believe that was the case.
I wasn't able to get a tail number as they flew right over the top of me. Too close for my comfort.:eek:
 
What might be happening here are missing ADS-R (R=Rebroadcast) messages from the ground station. ADS-R is a capability of the ADS-B ground station to relay ADS-B messages from one link (e.g 1090ES) to the other link (e.g. UAT) to accommodate aircraft with single-link receivers. The UPS fleet is 100% ADS-B equipped (1090ES). ADS-B ground stations do not include ADS-B equipped aircraft in the TIS-B data stream. TIS-B data is composed of transponder (non-ADS-B) aircraft only. This is to prevent dual targets for the same aircraft. The ground station assumes that you will receive traffic info from ADS-B aircraft "air-to-air", at least if you are equipped with a dual-link ADS-B receiver. If you have a single-link receiver, the only way to receive traffic information from an ADS-B aircraft on the other link is via ADS-R.

IIRC, the NavWorx has a single-link UAT receiver. In order to enable the ADS-R cross-link, or have the 1090ES ADS-B messages relayed to you on UAT, you must have the proper capability bits set in your ADS-B "Out" messages. There are capability bits in your ADS-B "Out" message that tell the ADS-B ground station what type(s) of ADS-B receiver(s) you have. If you have done the FAA ADS-B performance test (https://adsbperformance.faa.gov/PAPRRequest.aspx), you will find the "In Capability" in the third section of the "Operation Summary" of the report. It should state "UAT". If not, then the ground station is getting an incorrect capability bit (or bits) from your ADS-B "Out" messages. I'm not familiar enough with the NavWorx to know if that can be improperly configured during the installation setup, but something you might check.
 
tprevost said:
What might be happening here are missing ADS-R (R=Rebroadcast) messages from the ground station. ADS-R is a capability of the ADS-B ground station to relay ADS-B messages from one link (e.g 1090ES) to the other link (e.g. UAT) to accommodate aircraft with single-link receivers. The UPS fleet is 100% ADS-B equipped (1090ES). ADS-B ground stations do not include ADS-B equipped aircraft in the TIS-B data stream. TIS-B data is composed of transponder (non-ADS-B) aircraft only. This is to prevent dual targets for the same aircraft. The ground station assumes that you will receive traffic info from ADS-B aircraft "air-to-air", at least if you are equipped with a dual-link ADS-B receiver. If you have a single-link receiver, the only way to receive traffic information from an ADS-B aircraft on the other link is via ADS-R.

IIRC, the NavWorx has a single-link UAT receiver. In order to enable the ADS-R cross-link, or have the 1090ES ADS-B messages relayed to you on UAT, you must have the proper capability bits set in your ADS-B "Out" messages. There are capability bits in your ADS-B "Out" message that tell the ADS-B ground station what type(s) of ADS-B receiver(s) you have. If you have done the FAA ADS-B performance test (https://adsbperformance.faa.gov/PAPRRequest.aspx), you will find the "In Capability" in the third section of the "Operation Summary" of the report. It should state "UAT". If not, then the ground station is getting an incorrect capability bit (or bits) from your ADS-B "Out" messages. I'm not familiar enough with the NavWorx to know if that can be improperly configured during the installation setup, but something you might check.
Click to expand...

Since he said that he was getting "other big iron" (which would be on 1090 only) I presume that the above is not the case.
 
I have had many cases that my ADSB pick up an aircraft only to disappear for some time (either short duration or long). Just last weekend, I was flying with a friend and I was seeing him for most of the one hour trip but for about 10 minutes he was not on my screen anymore while other aircraft were still on the screen and connected to a good number of ADSB ground station. I have never found a reason for these cases.
 
tprevost said:
What might be happening here are missing ADS-R (R=Rebroadcast) messages from the ground station. ADS-R is a capability of the ADS-B ground station to relay ADS-B messages from one link (e.g 1090ES) to the other link (e.g. UAT) to accommodate aircraft with single-link receivers. The UPS fleet is 100% ADS-B equipped (1090ES). ADS-B ground stations do not include ADS-B equipped aircraft in the TIS-B data stream. TIS-B data is composed of transponder (non-ADS-B) aircraft only. This is to prevent dual targets for the same aircraft. The ground station assumes that you will receive traffic info from ADS-B aircraft "air-to-air", at least if you are equipped with a dual-link ADS-B receiver. If you have a single-link receiver, the only way to receive traffic information from an ADS-B aircraft on the other link is via ADS-R.

IIRC, the NavWorx has a single-link UAT receiver. In order to enable the ADS-R cross-link, or have the 1090ES ADS-B messages relayed to you on UAT, you must have the proper capability bits set in your ADS-B "Out" messages. There are capability bits in your ADS-B "Out" message that tell the ADS-B ground station what type(s) of ADS-B receiver(s) you have. If you have done the FAA ADS-B performance test (https://adsbperformance.faa.gov/PAPRRequest.aspx), you will find the "In Capability" in the third section of the "Operation Summary" of the report. It should state "UAT". If not, then the ground station is getting an incorrect capability bit (or bits) from your ADS-B "Out" messages. I'm not familiar enough with the NavWorx to know if that can be improperly configured during the installation setup, but something you might check.
Click to expand...

Incredible reply.
I should have you talk to our FSDO as you are certainly more informed on the system.
FWIW, I did get a compliance reporting verification from the FAA when I initially set up my Navworx box.

Thanks for the info.
 
Bavafa said:
I have had many cases that my ADSB pick up an aircraft only to disappear for some time (either short duration or long). Just last weekend, I was flying with a friend and I was seeing him for most of the one hour trip but for about 10 minutes he was not on my screen anymore while other aircraft were still on the screen and connected to a good number of ADSB ground station. I have never found a reason for these cases.
Click to expand...
I too have had instances where I had traffic disappear. Usually only for < 60 secs though.
 
roadrunner20 said:
Hey Dennis,
Would have loved to be at TT. Probably next year.

Since I was picking up other traffic & generally all the big iron coming into Tampa & St Pete, I thought UPS might have their transponder on standby or not squawking.
I talked to Tampa FSDO looking for their opinion & they were inclined to believe that was the case.
I wasn't able to get a tail number as they flew right over the top of me. Too close for my comfort.:eek:
Click to expand...

Sounds like you got your answer already, so I'll just comment on the statement about the UPS guys squawking standby or not squawking at all while inflight-highly unlikely, IMO, unless there was a problem with the unit.

Doing so defeats the mandated TCAS systems all 121 carriers have installed (it's controlled thru the XPNDR control head) not to even bring up the entire "IFR flight without a working transponder" discussion...especially in RVSM airspace. Verboten, for practical purposes.

I've had ATC ask me to recycle or switch to the second unit if they are getting bad data, but never turn it off...and I've never not had at least ONE of the two installed operable in almost 30 years of 121 ops. They are exceedingly reliable.

Most of us flying 121 are pretty addicted to using the TCAS scope to assist us in looking for traffic, especially as we get into the terminal environment...it's a great SA tool. I know I'd be pretty uncomfortable without an operable TCAS...and darn sure wouldn't tolerate someone turning it off right when the threat is highest...

Probably more info than you wanted to know...
 
roadrunner20 said:
I too have had instances where I had traffic disappear. Usually only for < 60 secs though.
Click to expand...

When there are other AC close by, 10 seconds may seem like 10 minutes :)
So I can't really say for what period of time but it does happen time to time.
 
I too have seen some big iron not show up on my ADS-B and/or others disappear then re-appear. (I have UAT out & dual in). Honestly, it doesn't appear to be all that reliable of a system and the FAA is banking on this system to compact traffic.... and they are all concerned about position accuracy to a hand full of inches.... (Navworx debacle). IMHO, the FAA is delusional over the minute to minute functionality of ADS-B. They are splitting hairs over a system that at times can't see the broadside of a barn.
 
Dan,
Wondering if you have the 'ghost' option selected on in the setup menu. I use that when flying formation to prevent nuisance warnings. I think it's supposed to prevent getting a traffic warning from your own transponder. If he was close and you had this selected, you might not see him on your EFIS.
 
Dan,
Does your display system show if the ADS-B system sees you as a TIS-B client? Missing traffic is expected if the ground station is not specifically telling your aircraft that it is fully covered, and it's up to the cockpit display to communicate this to you.
 
dynonsupport said:
Dan,
Does your display system show if the ADS-B system sees you as a TIS-B client? Missing traffic is expected if the ground station is not specifically telling your aircraft that it is fully covered, and it's up to the cockpit display to communicate this to you.
Click to expand...

My system reports the number of stations reporting & it was reporting at the time. Normally, in that area I can see 4 to 8.

To answer Scott, I don't recall a "ghost" mode so I suspect I don't have the option or it was not set.

BTW, 2 weeks ago, my hangar neighbor Ron S went on a flight to do approaches at a neighboring airport. He also has the Navworx 600 exp. He fell off my display for up to 3 minutes at one point. I knew where he was flying so I was really attentive on his location. I tried zooming in & out to see if that made a difference. It did not.
When he appeared on my display, I suspect it was accurate as I knew his approximate location & his position reports confirmed it.
 
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If an aircraft has a dual band, 1090 & 978, ADS-B-IN receiver, then it should display all ADS-B-Out equipped aircraft that are within range, regardless if a ground station is within range or not. If every aircraft were equipped with ADS-B-Out, then ground stations would not be needed, except to relay aircraft positions to ATC.
One possible explanation for disappearing traffic is that the aircraft aluminum skin could be blocking the line of sight signal. To solve that problem, more expensive ADS-B units have two antennas, one on top and one on the bottom of the aircraft.
 
roadrunner20 said:
My system reports the number of stations reporting & it was reporting at the time. Normally, in that area I can see 4 to 8.
Click to expand...

This is not the same thing. The towers send your specific ICAO code back to you if they know about you and are providing full traffic. You can easily be in a place where you can "see" 8 towers yet not have full traffic coverage. Traffic coverage is based on if the ground radars can see you. In the Dynon displays, this is the "ADS-B FULL" or "ADS-B Partial" status, and in a Garmin this is the little icon that shows a radar antenna.

Also, many displays filter out traffic for various reasons, any chance your display was doing that?
 
dynonsupport said:
This is not the same thing. The towers send your specific ICAO code back to you if they know about you and are providing full traffic. You can easily be in a place where you can "see" 8 towers yet not have full traffic coverage. Traffic coverage is based on if the ground radars can see you. In the Dynon displays, this is the "ADS-B FULL" or "ADS-B Partial" status, and in a Garmin this is the little icon that shows a radar antenna.

Also, many displays filter out traffic for various reasons, any chance your display was doing that?
Click to expand...

No filtering. I have not defined any distance or altitude filtering.

In this area, I usually fly under the 3000' veil of Tampa Class B and normally see overhead traffic. Do I see it all? apparently not.

Thanks to all for your comments & insight.
Let us not get too complacent with ADS-B & forget to look out the windscreen for traffic.
 
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