Loss of GPS in flight

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curts63
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Loss of GPS in flight

Post by curts63 »

I was just leaving KRDG yesterday and shortly after take-off the GPS lost satellites. I lost my terrain and navigation for the remainder of the flight. Right after it occurred, I cycled the power off and back on, hoping to restart the system and have satellites again. It didn't work. I looked at the status page for both GPS 1 and GPS 2, there were no satellites locked in, only one or two showing wouldn't didn't lock on. The flight was short, about 20 minutes, but the GPS never re-established.

When I started the plane and during run-up, everything seemed to be working fine. Entered the destination, took off, turned to heading, climbed to 2500, and poof......

Anyone have any ideas what might have occurred? I'm do this week for my transponder, pitot/static inspection, but wanted to gain some insight before blindly turning my plane over to the avionics shop.

Thank you,
Curt
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Rick
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Re: Loss of GPS in flight

Post by Rick »

I can think of two possibilities. One is that there was some sort of GPS problem in your area. Typically those are predicted and NOTAMed in advance, but I suppose there could have been some sort of failure. Did you have a tablet or any other GPS device with you and notice if they were also having an issue, or anyone else on the frequency complaining of GPS issues?

The other thought I had is that there were a batch of bad GPS antennas back around the time your DA40 was built. There are some threads on this forum: one here, and another one here. Possibly you have one of these faulty antennas?
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curts63
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Re: Loss of GPS in flight

Post by curts63 »

It was such a short flight, I didn't hear many people on the radio to know. I also didn't have a handheld device operating. I read some of the previous postings that you pointed to. It would seem that a problem exists with one or both antennas?

Why would it be intermittent and not all of the time? I would think if something were cracked, it should fail all the time?

In an earlier post, someone had mentioned the same problem, did they resolve it and what was the resolution?
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Re: Loss of GPS in flight

Post by dgger »

I think you can tell difference between a loss of GPS signal and a loss of GPS receivers. Provided receivers are intact I would expect the Garmin to fall back into Dead Reckoning mode and initially show a Loss of Integrity as you can see below (any GPS derived data would be shown in yellow).

While have not had an actual hardware outage my expectation would be to see a red X immediately.

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Rick
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Re: Loss of GPS in flight

Post by Rick »

I had this problem on one of my previous DA40's. The problem was very intermittent - no problems on probably 9 out of 10 flights, but then I'd be flying along and suddenly no GPS signal. Both GPS's would go out at the same time, as one of the GPS antennas would go into some mode where it would somehow transmit, which then took out the other GPS receiver. The GPS page would show no errors, but also no satellites, as I recall. It DID fall into "dead reckoning" mode, I do remember getting that message, and there were no red X's, which makes sense because the receiver didn't really fail, just the antenna was blocking the signal.

It turned out that BOTH of the GPS antennas on my DA40 had serial numbers in the faulty range, so they replaced both of them. The faulty antennas were installed when the previous owner had added WAAS. I don't know all the particulars of what the actual antenna problem was, but I do know in my case it was intermittent, and the solution was to replace the antennas (no more failures after they were replaced).
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Re: Loss of GPS in flight

Post by curts63 »

I remember looking for information in the data fields for ground speed, time, or anything else. There were no numbers, not even yellow dead reckoning information. When I cycled the power, it said "terrain system test ok", Then immediately said "terrain system not available". My GPS Status screen looked just like the one above, 2 would show up on the constellation graph, but no signal strength below.

Is the antenna problem something that Garmin is standing behind, or is it another out of pocket expense?
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Rick
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Re: Loss of GPS in flight

Post by Rick »

curts63 wrote:Is the antenna problem something that Garmin is standing behind, or is it another out of pocket expense?
At the time, I believe Garmin supplied two new antennas without cost to replace the defective ones. I am pretty sure I paid for the labor to have them replaced, though.
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Don
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Re: Loss of GPS in flight

Post by Don »

I had the same problem on my 2010 Star. It turned out to be defective GPS antennas. Garmin replaced them at no cost but I had to pay for installation.
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Re: Loss of GPS in flight

Post by baldesk »

I saw this in flight in my 2011 DA40 once when I was charging an iPhone using a USB charging unit plugged into the cigarette lighter charger on the panel. I assumed the GPS antennas were bad, but I think the USB charger was injecting noise into the system interfering with my GPS antennas. I stopped using the cigarette charger and never saw the problem again.
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Re: Loss of GPS in flight

Post by curts63 »

I finally got the plane in for the 24 month inspection. I had them look at the GPS problem too. Turns out that both antennas were bad. While I'm glad they made the repair, I wasn't happy with the cost. Then again, this is the cost of flying certified aircraft.

Does anyone know if the antennas made around November of 2011, that Garmin was warrantying, are still being covered by that? Guess I can have the avionics shop ask for that?
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