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  #1  
Old 02-19-2015, 06:30 PM
KTOA KTOA is offline
 
Join Date: Aug 2010
Location: SoCal
Posts: 36
Default GPS Antenna Failure(s)

Earlier this week I flew into Hailey, ID (KSUN) late one night. It's essentially tucked into a valley with high mountainous terrain on three sides surrounding it.

While on the visual approach 10 miles out, all three of my GPSs lost their signal. This includes the 530W, 430W, and the 696 which is mounted on the panel with velcro. Surprised...yes. Fortunately we were VFR and landed without issues.

On the ground, all three GPSs regained their signals. OK. Great. Intermittent problems are always easy to troubleshoot...

The next night, on approach into Willows, CA (KWLW), we again lost all three GPSs. Landed without issue in VFR conditions.

To get to the end of the story, the 530 antenna went south with a vengeance. It ended up sending out some kind of 'signal' that blanked out the other two antennas.

Could this have been an issue while on an approach while IMC? A strong YES. I have never heard of this scenario before so I'm just trying to get the word out of this being a possibility.

The antenna was approximately four years old from when we upgraded to WAAS. The avionics shop that made the repair had seen this scenario once before in a King Air. All the other approximately 30 antennas they have seen had just 'died' and stopped working.

Be careful out there.
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  #2  
Old 02-19-2015, 06:42 PM
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grubbat grubbat is offline
 
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Default Test

Check NOTAMs to see if GPS outages expected in that area. Sometimes govt conduct tests which play havoc to GPS. Having vor/ILS backup is nice sometimes.
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  #3  
Old 02-19-2015, 07:00 PM
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scrollF4 scrollF4 is offline
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Default

The NOAA Space Weather observations only showed R0, S0, and G0 level activity over the last several days, so it doesn't look like a solar radiation event.
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  #4  
Old 02-19-2015, 07:26 PM
KTOA KTOA is offline
 
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Default NOTAMS

The first thing I checked after each landing was any NOTAMS that I may have missed (yes I do read the NOTAMS prior to flying...). There was nothing published, including all the FAA/GPS/DoD sites I could find/check.

The offending 530W antenna was the root cause. Verified.
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  #5  
Old 02-19-2015, 07:37 PM
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Brantel Brantel is offline
 
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Default

Please contact Garmin with your issue. I had similar issues and Garmin went out of their way to fix my problem. I am sure they are tracking these issues and would love to have all your details first hand.

Since they fixed me up and I later upgraded to the GTN650 (same antenna), all has been well.

This and other forums show a history of this issue going back several years with similar failure modes like you describe. Last I was told, it was mostly isolated to a certain range of antenna serial numbers which makes sense because reports of issues with the newer units are scarce.
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Last edited by Brantel : 02-19-2015 at 07:42 PM.
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  #6  
Old 02-19-2015, 07:57 PM
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SmilingJack SmilingJack is offline
 
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Any details on the model of GPS antenna?
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  #7  
Old 02-19-2015, 09:08 PM
KTOA KTOA is offline
 
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I did call Garmin tech and will report what they say.

Antenna
Model: GA 35
Garmin P/N: 013-00235-00
D.O.W: 07/10

I have the antenna in my possession. I did a quick attempt at opening it. No joy - denied. I strongly suspect it will be epoxied. Not that I have a clue of what I would be looking at. I will hold off in case Garmin wants it.
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  #8  
Old 02-19-2015, 09:13 PM
kaa kaa is offline
 
Join Date: Dec 2013
Location: Oakland
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This happened to me once too. Surprisingly of all of the GPS receivers that I had in the aircraft only the one built into an iPad survived.

How did you verify that it was the 530 antenna? Is there a way to trigger the problem if it is intermittent?
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  #9  
Old 02-19-2015, 09:29 PM
KTOA KTOA is offline
 
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The avionics shop needed to identify the problem antenna because the 530 & 430 antenna are adjacent to each other.

They covered the antenna with aluminum. That allowed the other antennas to see the satellites. After that, I covered the antenna with my hand and that had the same result. I should try the same hand covering experiment now that the new antenna is installed.

During each event my Blackberry (I know, I know) and my friend's Iphone GPSs were fully functional.
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  #10  
Old 02-19-2015, 10:55 PM
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RVG8tor RVG8tor is offline
 
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Location: McKinney, TX
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Default Same issue

I had the same issue but it was intermittent at first then became more frequent. One way I used to isolate it was to turn off GPS items one at a time, when you turn off the culprit you will see the signal strength on the other GPS units jump.

There seems to be some idea that people are tightening the antenna mounting screws too tight. I installed mine and I know they were torqued correctly. After trying all kinds of trouble shooting, Garmin replaced my antenna. So far so good and I have not had any issues.

Cheers
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