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Garmin Aera 660/GDL 52 bogus traffic alerts

kcameron

Well Known Member
In January 2019, I installed an all new Garmin ADSB in/out system in my RV4:
GTX 335
Aera 660
GDL 52R

I chose the Aera 660 because the Airgizmo mount fits in the same panel hole as my previous GPS 496. I chose the 335 and 52R because of cost (compared to GTX 345) and my desire to retain SiriusXM radio input. The 335 gets pressure altitude from my AFS 3400 EFIS (just like the GTX 327 it replaced). The Aera 660 provides navigation info to the EFIS and autopilot. The 660 also provides frequency settings to my SL-30 radio.

The installation and configuration went smoothly. Changing the transponder tray was the biggest job. Everything seems to communicate together as expected. The GTX 335 passed the ADSB out performance report and I got my $500 rebate from the FAA. ADSB-in seems to be mostly working as well. I get (real) traffic info and weather as expected.

The only real problem with the system is false traffic alerts. All too often I get the "Traffic!" audio alert when there are no other airplanes nearby. Mostly it's done this while I turn downwind in the pattern and the traffic display shows my position and tail number on the approach end of the runway. When doing touch-and-gos, it will give the alert almost every time. A few times, I've gotten the "Traffic!" alert while flying straight and level and the display shows a yellow dot directly on top of my position. The dot will stay with me for 10 or 15 minutes.

The false alerts add stress to what should be fun flights. Every time it happens, I am distracted from what I was doing. I have to divert my eyes to the display then crane my neck around to try and see if there might really be traffic nearby. I don't want to be habitualized into ignoring the alerts but I'm afraid that process has already begun.

I've opened a support ticket with Garmin but it's been frustrating. The technician seems to want to help. I've jumped through every hoop he's put up to try different configurations, etc. He even sent a replacement GDL 52R though it always seemed unlikely to be a hardware issue, IMHO. Also, he generally take days or weeks to respond after I email him so that's made things very slow.

So. Anybody here have ideas how to fix it? Am I expecting too much? How do others deal with it?
 
This sounds like the GDL 52 is "seeing" the ADSB-OUT from the GTX 335 and not knowing any better.

I haven't looked specifically at the GDL 52, but I know the GTX 335 has an external "suppression" input to disable multiple transmitter conflicts (DME, Transponders, ADSB??)

This is a question for Garmin tho -- they may have not considered a split ADSB-IN/ADSB-OUT in the same aircraft with GDL 52R. The GTX 345 + GDL 51R might have been the correct solution in this case -- ADSB-IN/OUT processing in one unit, and SXM weather via the GDL 51R.
 
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In January 2019, I installed an all new Garmin ADSB in/out system in my RV4:
GTX 335
Aera 660
GDL 52R

I chose the Aera 660 because the Airgizmo mount fits in the same panel hole as my previous GPS 496. I chose the 335 and 52R because of cost (compared to GTX 345) and my desire to retain SiriusXM radio input. The 335 gets pressure altitude from my AFS 3400 EFIS (just like the GTX 327 it replaced). The Aera 660 provides navigation info to the EFIS and autopilot. The 660 also provides frequency settings to my SL-30 radio.

The installation and configuration went smoothly. Changing the transponder tray was the biggest job. Everything seems to communicate together as expected. The GTX 335 passed the ADSB out performance report and I got my $500 rebate from the FAA. ADSB-in seems to be mostly working as well. I get (real) traffic info and weather as expected.

The only real problem with the system is false traffic alerts. All too often I get the "Traffic!" audio alert when there are no other airplanes nearby. Mostly it's done this while I turn downwind in the pattern and the traffic display shows my position and tail number on the approach end of the runway. When doing touch-and-gos, it will give the alert almost every time. A few times, I've gotten the "Traffic!" alert while flying straight and level and the display shows a yellow dot directly on top of my position. The dot will stay with me for 10 or 15 minutes.

The false alerts add stress to what should be fun flights. Every time it happens, I am distracted from what I was doing. I have to divert my eyes to the display then crane my neck around to try and see if there might really be traffic nearby. I don't want to be habitualized into ignoring the alerts but I'm afraid that process has already begun.

I've opened a support ticket with Garmin but it's been frustrating. The technician seems to want to help. I've jumped through every hoop he's put up to try different configurations, etc. He even sent a replacement GDL 52R though it always seemed unlikely to be a hardware issue, IMHO. Also, he generally take days or weeks to respond after I email him so that's made things very slow.

So. Anybody here have ideas how to fix it? Am I expecting too much? How do others deal with it?

Hi Kevin,

I have been flying with a GDL 52R mated to an Aera 660 and then to an Aera 760 for many years, and haven't had any trouble with ownship traffic indications or alerts.

Over the years I have flown with GTX 23ES, GTX 345R, and now GNX 375 1090ES ADS-B Out transmitters - all very similar to what you are using.

Garmin may have already told you to check this, but the first thing to check is that your GTX 335 is properly setup to tell the ground stations that your aircraft ADS-B dual frequency receiver is receiving traffic targets on both 1090 Mhz and 978 Mhz. This is how you do this on the GTX 335.

GTX335RxSetup.png

If this isn't setup properly, the ground stations could be re-broadcasting traffic targets (including yourself) with a delay. This is known as ADS-R (re-broadcast) traffic.

If you are fast enough and this delay is significant enough, the GDL 52R may be conservatively identifying one of these delayed targets as traffic instead of ownship due to the how far this delayed traffic is from your current position - especially when you are maneuvering, like in the traffic pattern.

Your system works best when ALL traffic you receive is air-to-air direct from the transmitting aircraft (including yourself) and no ground station is trying to help by sending you ADS-R traffic.

How far is your GDL 52R ADS-B antenna from your GTX 335 antenna? If they are too close, it is possible that the GDL 52R is having a hard time receiving directly from your "too powerful" GTX 335. I have not heard of this being a problem, but just trying to cover the bases since what you are seeing is unusual.

Do you have the latest software installed in your Aera 660/GDL 52R?

Is the GDL 52R connected to the Aera 660 using RS-232?

One more question. Is your Aera 660 receiving TIS-A traffic over RS-232 from your GTX 335? That would be undesirable if it is.

Steve
 
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Thanks for the input, Steve.

Garmin may have already told you to check this, but the first thing to check is that your GTX 335 is properly setup to tell the ground stations that your aircraft ADS-B dual frequency receiver is receiving traffic targets on both 1090 Mhz and 978 Mhz

The 335 is set up as you showed. Both 1090ES and UAT input capabilities are being reported.

How far is your GDL 52R ADS-B antenna from your GTX 335 antenna?

About 7' 4"

Do you have the latest software installed in your Aera 660/GDL 52R?

Yes and No. The Aera 660 is on the latest firmware (v3.70). The GDL 52R is on firmware version v2.12. The Garmin website states that firmware v2.14 has been released. However, GDL firmware is shipped as part of the Aera 660 firmware. Since GDL v2.14 was released after Aera v3.70, there's no way for me to update the GDL to v2.14. I had hoped they would rectify that when I got the replacement GDL but it came with v2.12. Very annoying. I complained to Garmin but they don't seem to much care.

Is the GDL 52R connected to the Aera 660 using RS-232?

Yes

Is your Aera 660 receiving TIS-A traffic over RS-232 from your GTX 335?

No
 
Somewhere in your Aera set up, or GDL, or both, is there a place to enter your N number and/or your hexadecimal ICAO address? Make sure that's set up correctly. A ground station may be sending your position to another aircraft (it could be 15 miles away, so unseen), and either your GDL52 or your Aera has to block/disregard that data.
 
I have 3 aera 660's talking to GDL 52's in three different airplanes (and also helped set one up with an aera 760 in a Bird Dog and a yet another with an aera 796 in a Mooney). No trouble with false targets from the "one ship". For reference, all of these aircraft use UAT out ADS-B. Three with GDL 82's, one with a FreeFlight Rangr and one with a uAvionix EchoUAT out with SKYFXExt GPS. I have never combined the 52 (or 52R) with a 1090ES "out" so perhaps the key here would be with the GTX 335 out.

Garmin has the GDL 5X(r) series update automatically through it's portable, a G3X Touch updates, or via Garmin Pilot app. So as far as the GDL 52R firmware update issue, you might see if Garmin Pilot has thenewer GDL 52 update instead of relying on an aera 660 update. If so, you could Bluetooth between Garmin Pilot and the GDL 52 and it will update the 52. If you don't subscribe to Pilot you could try a free 30-day trial.
 
Somewhere in your Aera set up, or GDL, or both, is there a place to enter your N number and/or your hexadecimal ICAO address? Make sure that's set up correctly. A ground station may be sending your position to another aircraft (it could be 15 miles away, so unseen), and either your GDL52 or your Aera has to block/disregard that data.

As far as I know, there's only one place to enter the tail number on the Aera 660. That's on the "Profile" page where you enter info for flight planning (speed, fuel burn, etc). Maybe the Aera sends the tail number to the GDL but who knows.
 
Garmin has the GDL 5X(r) series update automatically through it's portable, a G3X Touch updates, or via Garmin Pilot app. So as far as the GDL 52R firmware update issue, you might see if Garmin Pilot has thenewer GDL 52 update instead of relying on an aera 660 update. If so, you could Bluetooth between Garmin Pilot and the GDL 52 and it will update the 52. If you don't subscribe to Pilot you could try a free 30-day trial.

I hadn't thought about Garmin Pilot since I've never used it before. I'll give it a try.
 
Kevin,

You might also verify that your Aera 660 GPS fix is always 3D Differential, even when maneuvering and landing since your GDL 52R is using this lateral/vertical data in its ownship and traffic separation determinations in addition to pressure altitude from its internal sensor.

Your GDL 52R compares the GPS position and GPS altitude it receives from the Aera 660 to the same data in the ADS-B Out transmission it receives from the GTX 335 and tries to determine if they are one and the same.

If the Aera 660 mounted in the panel has a poor GPS fix that is something other than 3D Differential at all times, the GPS altitude determination could be in error enough that the GDL 52R is no longer certain that it is receiving a transmission from ownship and may declare that target (you) as other traffic to err on the side of safety.

I was thinking about the differences in my installation, and yours, and they are pretty significant since my aircraft is all Garmin. My G3X Touch system measures and gives pressure altitude data to both the GNX 375 ADS-B Out device and the GDL 52R. Additionally, the G3X Touch system is using GPS data from the GNX 375 ADS-B Out device and sending that GPS data to the GDL 52R. The GDL 52R doesn't use its internal pressure sensor or GPS receiver in this installation because it is getting better data from the G3X Touch system. Because of this tight integration, both the GNX 375 ADS-B Out device and the GDL 52R ADS-B receiver are using the identical pressure altitude, GPS position, and GPS altitude, so there can never be an error in ownship determination which provides high assurance that my system can never declare ownship as a traffic target (and it never does).

Not saying that your system cannot also work well, but the quality of the GPS data from the Aera 660 is very important in your system, where it is not at all important in my system.

Steve
 
Steve might be on to something with the quality of GPS position. I try to get an external antenna involved when there is an aera linked to a GDL 5X or GDL 39. And when I do I always use an antenna attached to the GDL rather than the aera for ease of insertion and removal of the aera without having to insert or attach the antenna lead in the side of the aera. So if your area or GDL 52R doesn't have an external antenna attached, you might consider adding one. You only need one because as Steve pointed out above, all the Garmin devices share GPS and some other data over their connections which is really nice. You only need one antenna attached to one device to feed all the others.

And based on Steve's insight again you might want to check to see if the PFD air data altitude reading matches the altitude sensor reading in the GDL 52R, under the assumption the GDL 52R is in fact using it's internal sensor as the pressure altitude source for the aircraft is not from a Garmin system. Since Garmin has swapped out the GDL 52R perhaps your PFD/EFIS should have an altitude correspondence check.

And as far as the installation, I also always try to hardwire the aera to the GDL 5X or 39 (or other external interfaces) using the optional Garmin bare data/wire cables. By reading your original post I would guess you have done the same. I like this rather thank a wireless data link. A good wireless link should be as good as wires but you know how that goes. Plus, that leaves the wireless channel on the area and GDL 5X free for other devices to link to them, like a second Garmin portable or EFB for the passenger(s).

Jim
 
Jim,

Good points, but I think you will see that anytime there is a Garmin portable or G3X Touch system connected to a GDL 5X/5XR, regardless of what antenna may be connected to the GDL 5X/5XR, the GDL 5X/5XR is using the externally supplied GPS data.

When the GPS Position says "Valid (External)", it is not using its internal GPS receiver.

You can confirm this on the Data Link Info page accessible from the Traffic page by pressing Menu, More Info.

Aera660DataLinkInfo.png

Steve
 
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You might also verify that your Aera 660 GPS fix is always 3D Differential, even when maneuvering and landing since your GDL 52R is using this lateral/vertical data in its ownship and traffic separation determinations in addition to pressure altitude from its internal sensor.
I hadn't thought about the possibility of GPS errors. I'll put up the GPS info screen next time I'm out and see if I can catch any deviations from ideal reception. I do know that the internal antenna on the Aera 660 is very good; certainly better than any other handheld GPS I've used. Sitting in my hangar with the metal door closed, I usually get 12-13 GPS satellites and 3-4 GLONASS satellites.

Your GDL 52R compares the GPS position and GPS altitude it receives from the Aera 660 to the same data in the ADS-B Out transmission it receives from the GTX 335 and tries to determine if they are one and the same.
Very perceptive. I should have mentioned it before but, as you surmised, I'm not using the 52Rs internal GPS but rather relying on the 660 for 3d position.

... the GDL 52R is no longer certain that it is receiving a transmission from ownship and may declare that target (you) as other traffic to err on the side of safety.
One thing I don't get about all this is why the 52R or 660 don't filter out traffic reports with my tail number. It seems like that would be an obvious thing to do and not difficult programming-wise.

I was thinking about the differences in my installation, and yours, and they are pretty significant since my aircraft is all Garmin. My G3X Touch system measures and gives pressure altitude data to both the GNX 375 ADS-B Out device and the GDL 52R. Additionally, the G3X Touch system is using GPS data from the GNX 375 ADS-B Out device and sending that GPS data to the GDL 52R. The GDL 52R doesn't use its internal pressure sensor or GPS receiver in this installation because it is getting better data from the G3X Touch system. Because of this tight integration, both the GNX 375 ADS-B Out device and the GDL 52R ADS-B receiver are using the identical pressure altitude, GPS position, and GPS altitude, so there can never be an error in ownship determination which provides high assurance that my system can never declare ownship as a traffic target (and it never does).
Yes. It sounds like your altitude system is better. My EFIS sends pressure altitude to the GTX 335 transponder but not to the 660 or 52R. I've been looking at the 335 installation manual. It appears it can output altitude in a Garmin format that may work with the 52R. Maybe I should feed that to the 53R's second RS-232 port. Is that how your 375&52R are wired? I've broached the altitude issue with Garmin tech support but they haven't said a word (3.5 weeks ago and counting).
 
Steve might be on to something with the quality of GPS position. I try to get an external antenna involved when there is an aera linked to a GDL 5X or GDL 39. And when I do I always use an antenna attached to the GDL rather than the aera for ease of insertion and removal of the aera without having to insert or attach the antenna lead in the side of the aera. So if your area or GDL 52R doesn't have an external antenna attached, you might consider adding one. You only need one because as Steve pointed out above, all the Garmin devices share GPS and some other data over their connections which is really nice. You only need one antenna attached to one device to feed all the others.
Interesting. It never occurred to me that the Aera could use position from the 53R's GPS antenna. I may try a temporary antenna connection to the 52R to see if it helps.

And based on Steve's insight again you might want to check to see if the PFD air data altitude reading matches the altitude sensor reading in the GDL 52R, under the assumption the GDL 52R is in fact using it's internal sensor as the pressure altitude source for the aircraft is not from a Garmin system. Since Garmin has swapped out the GDL 52R perhaps your PFD/EFIS should have an altitude correspondence check.
Per the Garmin technician's instructions, I've set the 52R to "pressurized" mode. I assume that means it only uses GPS altitude. Using cabin pressure seems pretty sketchy to me anyway since it can be pretty far off from true pressure altitude. Of course GPS altitude isn't very accurate either but at least it's not affected by airspeed, open vents, etc.

And as far as the installation, I also always try to hardwire the aera to the GDL 5X or 39 (or other external interfaces) using the optional Garmin bare data/wire cables. By reading your original post I would guess you have done the same.
Yes. All hard-wired.
 
One thing I don't get about all this is why the 52R or 660 don't filter out traffic reports with my tail number. It seems like that would be an obvious thing to do and not difficult programming-wise.

It does, but only when it can reliably determine what your ICAO address is from all the traffic targets it might be receiving. For example, let's say you and your buddy power up together on the ramp, and the GDL 52R receives his ICAO address first and says "hey, this is close, it must be me". You wouldn't want it to hold onto that ICAO address for the whole flight and give continuous traffic alerts for your GTX 335 output. Instead, it is constantly re-evaluating ownship to make the best decision.

Right or wrong, the decision for portables like the Aera 660 with GDL 5X is that they can be moved from plane-to-plane, so it is best that they not be given a fixed ICAO address (like your Mode S transponder does which never leaves your plane).

In a G3X Touch aircraft with a Mode S transponder (like GTX 23ES, 35ES, 335, 345, 45R, GNX 375, etc), the G3X Touch display tells the GDL 5X(R) what the ICAO address is of the aircraft's ADS-B Out transmissions, so the GDL 5X(R) doesn't have to ever determine what ownship is. This is another reason why a G3X Touch installation never falsely traffic alarms on ownship.

Yes. It sounds like your altitude system is better. My EFIS sends pressure altitude to the GTX 335 transponder but not to the 660 or 52R. I've been looking at the 335 installation manual. It appears it can output altitude in a Garmin format that may work with the 52R. Maybe I should feed that to the 53R's second RS-232 port. Is that how your 375&52R are wired? I've broached the altitude issue with Garmin tech support but they haven't said a word (3.5 weeks ago and counting).

The GTX 335 doesn't know how to communicate with a GDL 5X(R) and provide GPS and altitude data. This is done via the GDU 4XX display in my aircraft.

It never occurred to me that the Aera could use position from the 53R's GPS antenna. I may try a temporary antenna connection to the 52R to see if it helps.
It cannot. The Aera 660 is a standalone GPS navigator with its own high quality WAAS/GLONASS receivers and doesn't accept GPS data from any external device.

Steve
 
Right or wrong, the decision for portables like the Aera 660 with GDL 5X is that they can be moved from plane-to-plane, so it is best that they not be given a fixed ICAO address (like your Mode S transponder does which never leaves your plane).
I understand that they want to keep the software the same between all the units in the GDL 5X family but the GDL 52R is intended to be permanently mounted. [grumble]

Again, I appreciate all the good input, Steve.
 
Garmin has the GDL 5X(r) series update automatically through it's portable, a G3X Touch updates, or via Garmin Pilot app. So as far as the GDL 52R firmware update issue, you might see if Garmin Pilot has thenewer GDL 52 update instead of relying on an aera 660 update. If so, you could Bluetooth between Garmin Pilot and the GDL 52 and it will update the 52. If you don't subscribe to Pilot you could try a free 30-day trial.

I struggled for an hour trying to connect my 4.5 year old Samsung Galaxy S7 to the GDL 52R via bluetooth. It would act like it was connecting but the Garmin Pilot app wouldn't work and the 52R bluetooth setup page on the Aera 660 never showed "connected'. I guess I'll get a new Android phone. Has anyone here been able to get their Android phone to connect to a GDL 5x?

I borrowed my wife's Iphone and it connected easily and instantly. As soon as it connected, it offered to update my 52R to v2.14. Worked perfectly and I'm up-to-date now. The Garmin Pilot app surprised me with the amount of information it shows. Among other things, it allows one to see detailed ADSB-out info for all the airplanes it sees (at least a dozen with my plane sitting in the hangar with the door open). It's like having your own ADSB compliance tester. The ADSB status page has an "ownship" section which correctly identifies my transponder. If I can get a phone that works (or borrow my wife's for awhile), I'll see if there's any problem identifying ownship while flying sometime soon.
 
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Hi Kevin,
How far is your GDL 52R ADS-B antenna from your GTX 335 antenna? If they are too close, it is possible that the GDL 52R is having a hard time receiving directly from your "too powerful" GTX 335.
Steve

Since we're grasping at straws here....
Since the GTX335 is very close to the GDL 52R, I'd look at the coax and connector exiting the GTX335. Also check the grounding of the shield to the connector, and the connector to the airframe, at both ends of the 335 cable. While clearly the 335 is working, I wonder if its coax can be leaking enough (or reflecting enough) energy back into the cockpit to overload the GDL? Maybe even try moving the GDL's antenna as far to the side as possible, just to get it further from the transponder?
 
Since we're grasping at straws here....
Since the GTX335 is very close to the GDL 52R, I'd look at the coax and connector exiting the GTX335. Also check the grounding of the shield to the connector, and the connector to the airframe, at both ends of the 335 cable. While clearly the 335 is working, I wonder if its coax can be leaking enough (or reflecting enough) energy back into the cockpit to overload the GDL? Maybe even try moving the GDL's antenna as far to the side as possible, just to get it further from the transponder?

Thanks for the input, Bob.

The antennas are more than 7 feet apart which is within the published requirement so I wouldn't rate it high on the list of probabilities. It's possible there's some issue with the transponder antenna or coax. I'll check them as best I can.
 
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