GNS530W dead reckoning failure

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John Collins

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I have heard of a few incidents with the 430W/530W where all GPS navigation capability was suddenly lost. I had one instance of this on a recent flight. In my case, I have a 530W as my #1 and a KY197 as my #2 Com. I found that if I transmitted on the frequency of 120.9 on #2 Com, all the satellites would instantly disappear on the 530W and I would get a dead reckoning message. I have since been unable to reproduce this. I have heard of others who have dual 430W/530W installations would lose all GPS when one of them was on. Turning off the offending unit, resolved the interference with the other unit. I have heard that the WAAS antennas can go into oscillation and transmit, thus killing reception. All this is anecdotal and seems to be an intermittent form of problem. If you have experienced this kind of failure, can you report your information, Garmin may have a problem they don't recognize and with some data, it might point them to a resolution.
 
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My single 530W has gone belly up like that maybe three or four times since installation three years ago, with no apparent common situation. However, it's not 120.9 because that's Lancaster Tower's freq, and I've never seen it happen there. It always comes back in a few minutes.
 
I have not experienced that with my 430W since it was installed a little over one year ago. I did have it happen with a KLN89B once, while IMC on a GPS approach. But I was never able to reproduce it.
 
Another data point: I've never seen that at all with our 430W. Maybe it's 530W-specific.
 
The interference between the comm section and GPS reception is supposed to be addressed during installation. If you are consistently getting interference on a particular frequency, see an avionics shop. If they give you a glassy-eye when you describe the symptoms, find a better one.
 
We had some similar isolated incidents with a Garmin 530 (non WAAS). We tried a comm filter which you may want to try the next time you visit the avionics shop, but that didn't do it for us. It didn't seem to be affected by transmitting or receiving certain frequencies (radio related) but rather, it was completely random. We figured it may have been some moisture build up in the antenna which evaporated after we started using the aircraft (it sat for almost 3 years with the previous owner) since we haven't been able to recreate the issue in almost 12 months time.

Try asking your local avionics shop about a communication filter. It is a small rectangular box that screws into the back of the 530 com antenna jack.
 
TMetzinger said:
The interference between the comm section and GPS reception is supposed to be addressed during installation. If you are consistently getting interference on a particular frequency, see an avionics shop. If they give you a glassy-eye when you describe the symptoms, find a better one.
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Tim,

Your advice is sound, but I am not looking for advice at this point. What I am looking for is similar incidents to see if there is a pattern. Having owned and operated an avionics shop, I am very familiar with Com frequency interference between a Com unit and a GPS or an ELT re-radiating. What I saw had different characteristics than normal Com frequency interference. It was instantaneous loss of all GPS satellites as opposed to reducing amplitude over a 5 to 20+ second period and it was on a frequency that is not called out as being one that has harmonics that can interfere. What triggered me to post the inquiry was that I have gotten two other phone call reports within the last week of situations where one 430W GPS was interferring with another 430W GPS and turning off the offending unit was the only way the remaining unit would function. All the incidents resulted in instantaneous loss of all satellites and going into dead reckoning mode.

It may be maintenance related or there can be a design issue. Garmin does a poor job of managing incidents like this and is slow to acknowledge design issues. They don't correlate reports to see if there is a trend, so in cases where the problem is of sufficient low frequency, the individual support people will say they haven't heard that before, which can be true as they have several in their support staff and don't record incidents on a common search-able database.

I have used this technique twice before to gather data and present it to Garmin, all at once. In both cases, they were able to reproduce the problem and make software corrections to problems that they did not recognize thru the normal reporting system.
 
John Collins said:
Tim,

Your advice is sound, but I am not looking for advice at this point. What I am looking for is similar incidents to see if there is a pattern. Having owned and operated an avionics shop, I am very familiar with Com frequency interference between a Com unit and a GPS or an ELT re-radiating. What I saw had different characteristics than normal Com frequency interference. It was instantaneous loss of all GPS satellites as opposed to reducing amplitude over a 5 to 20+ second period and it was on a frequency that is not called out as being one that has harmonics that can interfere. What triggered me to post the inquiry was that I have gotten two other phone call reports within the last week of situations where one 430W GPS was interferring with another 430W GPS and turning off the offending unit was the only way the remaining unit would function. All the incidents resulted in instantaneous loss of all satellites and going into dead reckoning mode.

It may be maintenance related or there can be a design issue. Garmin does a poor job of managing incidents like this and is slow to acknowledge design issues. They don't correlate reports to see if there is a trend, so in cases where the problem is of sufficient low frequency, the individual support people will say they haven't heard that before, which can be true as they have several in their support staff and don't record incidents on a common search-able database.

I have used this technique twice before to gather data and present it to Garmin, all at once. In both cases, they were able to reproduce the problem and make software corrections to problems that they did not recognize thru the normal reporting system.
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Thanks, John. That's a little more information, and helps make sense of why you're asking the question. More data = Good Things! :)
 
John, posted the below to another thread and then saw this one. You could probably use the info and I could use any available help.

"Re: dead reckoning on 530/430
Bit late to this thread, but glad I found it...thought I was going bonkers. I am flying a helicopter with 2 430's with WAAS antennas. I will list the following symptoms, actions taken and results. Hopefully someone has some help.
1. When they decide to, both 430's go "DEAD RECKONING". This happens about 15% of operations.
2. On multi-leg flights, DR might occur on 2d or 3d legs but not the first.
3. Checking satellite signals during DR occurrence reveals all signals are absent, upper right message says "ACQUIRING" but signal is never acquired in flight regardless of how long you wait
4. Even though 430's indicate "DEAD RECKONING" menu fields to the right of the screens indicate some accurate aircraft movement if a waypoint and Direct To were selected before failure.
5. Turning off the 430's and then turning them on in any combination of On & Off has no positive effect on the problem.
6. Satellite signals usually return 60-75 seconds after landing and accurate position is revealed. However, position and satellite signals are lost very quickly on a subsequent takeoff (the helo has not been shut down). This problem seems to be related to aircraft movement.
7. One antenna was changed but that did not fix the problem. We are now going to replace both antennas.
8. Garmin Tech Support was contacted and tried to help but troubles have continued.

Anyone else figured out the solution(s)?:dunno:"
 
Another data point...

Friday, Oct. 29 and Thursday, Nov. 4 2010 at approximately the same time (~0730 lcl), altitude, and distance from my home airport (northwest and north) I experienced a similar anomaly on my 430w. My handheld GPSmap 96 did not lose satellite signal during either episode. The 430w resumed normal operation after approximately a minute and a half of an "integrity" warning. I remember the time and location distinctly because I made a comment to ATC about it to see if they had any other similar reports in the area after the second episode.

The only correlation I infer from the two episodes is they seemed to appear at approximately the same elapsed time from unit power up (~10-15 minutes). Since the handheld never lost satellite signal I have to assume the fault was internal to the 430w.

I put ~2hrs on the plane between the two episodes and 18 since with no other instances. The unit has about 350 hrs since installation.

I had forgotten about this thread until the previous post.
 
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Don't know if it's related but I just read on another forum that Garmin found a problem with some or all of their WAAS IFR GPS unit's software and has suspended updates and repairs.
 
stickhog said:
You could probably use the info and I could use any available help. ...
Anyone else figured out the solution(s)?:dunno:"
Click to expand...

I fly a composite experimental with a Garmin 430W and a 396. I had multiple though infrequent and erratic loss of GPS integrity on BOTH the 430 and 396. I had concluded it must be a static issue because it only seemed to happen after a few hours of flight and (just like a previous post states) I got signal back just a minute or two after landing. Feedback from Aeroelectric list led me to believe it may be related to radio interference.

It took 3 long cross country flights before I found the problem. Before I made ANY frequency change, I switched 430 to the GPS signal page. Made the frequency change and watched. I found that my DME was wiping out the GPS on at least one frequency (JOT - Joliet, Chicago). Dial in JOT and INSTANT loss of signal. Also found that if I located the 396 puck antenna in back of the plane, the 396 would maintain lock while the 430W lost signal - even on the bad channel. This was due to location issues related to the DME antenna.

My issues with the 430W have amplified my base Luddite instincts. I NEVER use just GPS. That said, the DME is now placarded INOP and the breaker is pulled. Figure if I really lose GPS for another reason (say the military decides it needs to go), I can always push the breaker and have my DME back.

Hope this helps someone - I lived with the problem for a few years before finally figuring it out.
 
gismo said:
Don't know if it's related but I just read on another forum that Garmin found a problem with some or all of their WAAS IFR GPS unit's software and has suspended updates and repairs.
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Oooh. I wonder if that includes the 480?
 
gismo said:
Don't know if it's related but I just read on another forum that Garmin found a problem with some or all of their WAAS IFR GPS unit's software and has suspended updates and repairs.
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Lance,

Where did you see that posted?
 
My antenna failed in my Garmin 530W and it effectively jammed my Garmin 396 handheld as well. The failure wasn't hard; rather, it occurred a couple times for very short duration, say 15 minutes. Several months later it happened again. On the third incident I was able to watch the satellite signal strenght fade to zero over about 30 seconds then 10 -15 minutes later pop back up only to repeat the cycle. Once I figured out what was happening I could turn off the GNS530W and the 396 handheld would instantly pop back up. The shop replaced the antenna and all troubles are gone.
 
Steve said:
Another data point...

Friday, Oct. 29 and Thursday, Nov. 4 2010 at approximately the same time (~0730 lcl), altitude, and distance from my home airport (northwest and north) I experienced a similar anomaly on my 430w. My handheld GPSmap 96 did not lose satellite signal during either episode. The 430w resumed normal operation after approximately a minute and a half of an "integrity" warning. I remember the time and location distinctly because I made a comment to ATC about it to see if they had any other similar reports in the area after the second episode.

The only correlation I infer from the two episodes is they seemed to appear at approximately the same elapsed time from unit power up (~10-15 minutes). Since the handheld never lost satellite signal I have to assume the fault was internal to the 430w.

I put ~2hrs on the plane between the two episodes and 18 since with no other instances. The unit has about 350 hrs since installation.

I had forgotten about this thread until the previous post.
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I have essentially the same issue. Single 430W installation with a 496 as well. About 17 minutes into each flight the 430 loses the satellites. When I go to the satellite page, they are all blank. After a minute or so, they begin to come back. This happens only once during the flight. One time, I had to hold for a while for an IFR release (about 17 minutes to be exact) and the satellites dropped while on the ground.

Somebody on the Red Board had what looked to be the exact same issue. He was under warranty and Garmin swapped out the board inside the 430W and he's been trouble free ever since.
 
From other radio knowledge in my head...

The transmission triggered failures sound like interference or worse, a harmonic of the transmission frequency "hitting" clock frequencies of data busses, etc. Relatively high power RF rectified into nearby comm busses (e.g. Inside the GPS section of the box) can be due to poor RF shielding design, bad grounding, and even the wrong choice of RF bypass capacitor on the inputs from the outside of the unit.

Time-based failures (the 17 minute thing) sound like heat-related (dead or non-existent avionics fan) problems or software bugs.

A good avionics shop can probably find these, but it's going to be a lot of labor if they have to go theory by theory. Best to involve Garmin immediately so at least if they have seen similar cases they can "hint" to the avionics shop what to look at first.
 
denverpilot said:
From other radio knowledge in my head...

The transmission triggered failures sound like interference or worse, a harmonic of the transmission frequency "hitting" clock frequencies of data busses, etc. Relatively high power RF rectified into nearby comm busses (e.g. Inside the GPS section of the box) can be due to poor RF shielding design, bad grounding, and even the wrong choice of RF bypass capacitor on the inputs from the outside of the unit.

Time-based failures (the 17 minute thing) sound like heat-related (dead or non-existent avionics fan) problems or software bugs.

A good avionics shop can probably find these, but it's going to be a lot of labor if they have to go theory by theory. Best to involve Garmin immediately so at least if they have seen similar cases they can "hint" to the avionics shop what to look at first.
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That's my plan. Already working on Garmin. I wanted to make sure I could document the circumstances of enough incidents to take it anywhere. I was not looking forward to a conversation with the avionics guy that was along the lines of "I don't know, sometimes it drops the satellites". That sounds expensive to me -- with the distinct possibility that a few AMUs later they say "well, it worked for us"
 
denverpilot said:
Time-based failures (the 17 minute thing) sound like heat-related (dead or non-existent avionics fan) problems
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I would say that a heat-related problem is unlikely. Heat problems will generally have a slightly variable onset time depending on the surrounding temp, and there will be ongoing problems after the initial problem, until power-down and a cooling-off period for the unit. In this case, it sounds like the onset is like clockwork and the problem goes away and does not recur, neither of which sounds like a heat problem.

I'd guess a software/firmware thing, though the timing still seems... Interesting. I would expect such a problem to crop up a little earlier, as you can execute an awful lot of instructions in 17 minutes! Plus, I would expect repeats of the issue after the first 17 minutes.
 
flyingcheesehead said:
I would say that a heat-related problem is unlikely. Heat problems will generally have a slightly variable onset time depending on the surrounding temp, and there will be ongoing problems after the initial problem, until power-down and a cooling-off period for the unit. In this case, it sounds like the onset is like clockwork and the problem goes away and does not recur, neither of which sounds like a heat problem.

I'd guess a software/firmware thing, though the timing still seems... Interesting. I would expect such a problem to crop up a little earlier, as you can execute an awful lot of instructions in 17 minutes! Plus, I would expect repeats of the issue after the first 17 minutes.
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GPS frames are 30 seconds, so allowing for initial acquisition time that's 32 to 34 full frames before loss of signal. Powers of two are a good reason to suspect firmware issues (probably with some other contributing factor, since this doesn't seem to be a universal problem).

I've seen similar behavior with a 530W, but can't say for sure what the timing is. The last time it happened was probably just about 17 minutes from startup though. I'll note the timing the next time it occurs and report back. It would be a good idea to note the affected firmware revision(s) too.
 
In any event, Garmin seems to agree that sending it back in to them is the right course of action.

Thank you for contacting Garmin International,

You are correct, I would have your dealer remove this unit and return for repair.

With Best Regards,

George K.
Field Service Engineer
Garmin Aviation Product Support
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fszczerba said:
GPS frames are 30 seconds, so allowing for initial acquisition time that's 32 to 34 full frames before loss of signal. Powers of two are a good reason to suspect firmware issues (probably with some other contributing factor, since this doesn't seem to be a universal problem).

I've seen similar behavior with a 530W, but can't say for sure what the timing is. The last time it happened was probably just about 17 minutes from startup though. I'll note the timing the next time it occurs and report back. It would be a good idea to note the affected firmware revision(s) too.
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The frames begin repeating again after 12.5 minutes. So, it seems like this issue is probably not related to the nav messages received. Also, I assume the Rx got lock prior to the 17 minute meltdown, which would mean the Rx locked on to enough satellites before it received the entire almanac via the nav messages.

Here is the GPS SV to User interface controlling document:
Warning it is an engineering level doc, so don't expect a light duty treatment of the GPS nav signal. Also it includes new civil signals which are not yet operational (L1C and L2C).
www.navcen.uscg.gov/pdf/IS-GPS-200D.pdf
 
garmin has had problems with there antennas. If it is less then 2 years old they will send new one. They are shorting out killing all GPS reception within 100 feet.
 
Vernjr said:
garmin has had problems with there antennas. If it is less then 2 years old they will send new one. They are shorting out killing all GPS reception within 100 feet.
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I had the exact problem in a mooney. Had the antenna replaced a few months ago. Problem is resolved.
 
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