How much do you trust your Garmin 530?

[Joe Larussa]

Just did two Rnav approaches into Ksac and same thing both times. Had Lpv all the way until right before the final approach fix. Lpv turned to yellow and after crossing the final approach fix it went to Lnav. Flew back to Klhm and all was normal on the Rnav 15. Somebody had suggested to flip to the satellite page and check reception.

[bradp]

I’ve had satellite reception issues in some circumstances that is geographically dependent - ie flying direcltynover downtown Richmond VA.  It seems like it may be Airport dependent?  Just KSAC?   There was a story about a delivery driver that used a gps signal blocker at the approach end at KEWR and caused a kerfluffle. 

[PTK]

42 minutes ago, Joe Larussa said:

Just did two Rnav approaches into Ksac and same thing both times. Had Lpv all the way until right before the final approach fix. Lpv turned to yellow and after crossing the final approach fix it went to Lnav. Flew back to Klhm and all was normal on the Rnav 15. Somebody had suggested to flip to the satellite page and check reception.

I don't think it's the equipment. I think it's as simple as the LPV, for some reason, downgraded to LNAV and it happened exactly as it should. When on the approach if VTF is selected or the FAF becomes the active fix and the green LPV turns yellow it downgrades to LNAV. In your case it happened right before the FAF. The yellow LPV color means that the criteria for a downgrade exist and if they don't improve it will downgrade. I remember reading somewhere that this is more common on the west coast.

[kortopates]

3 minutes ago, PTK said:

I don't think it's the equipment. I think it's as simple as the LPV, for some reason, downgraded to LNAV and it happened exactly as it should. When on the approach if VTF is selected or the FAF becomes the active fix and the green LPV turns yellow it downgrades to LNAV. In your case it happened right before the FAF. The yellow LPV color means that the criteria for a downgrade exist and if they don't improve it will downgrade. I remember reading somewhere that this is more common on the west coast.

It should really only happen at the fringe area of WAAS coverage. I've reported loosing LPV200 service on the west coast a couple of times but that hasn't happened since the temporary period when we were down to a single WAAS satellite. That was quite some time ago. These days the fringe area is generally well beyond the coast lines. You can see the current real time status here: http://www.nstb.tc.faa.gov/ with many options including historical data. Highly unlikely a it was normal to loose LPV at KSAC but possible. Yet you can even run a video that shows the status changing over time and see what was going on when you were in the air. 

[Joe Larussa]

Is it at all possible it has something to do with settings in the 530? About a month ago I did the adsb out upgrade to my 330 transponder. After of which my Gpss wasn't working. They had to reprogram something in the 530 to get it to work.

[Simon]

Are you close to any Military Training Routes?  I've lost GPS before along with several aircraft in the vicinity and it was explained to me by someone older and wiser that it was most likely the military.  At the time I was very close to a MTR.

[kortopates]

Just now, Joe Larussa said:

Is it at all possible it has something to do with settings in the 530? About a month ago I did the adsb out upgrade to my 330 transponder. After of which my Gpss wasn't working. They had to reprogram something in the 530 to get it to work.

Couldn't imagine so. I recall the only setting for the GPS is map datum year and antenna height. There are no interfaces to other equipment necessary for your GPS except for the anntena. Interfaces to other equipment are completely different and require ports to be configured properly for protocol and data format.

[Joe Larussa]

Does anyone know how far apart the Elt antenna and Gps antenna should be? Mine are 9" apart. Maybe a thing?

[kortopates]

35 minutes ago, Joe Larussa said:

Does anyone know how far apart the Elt antenna and Gps antenna should be? Mine are 9" apart. Maybe a thing?

The com antenna is a bigger concern but here is an excerpt from the GNS4xx install manual for what it calls out.

[Andy95W]

3 hours ago, Joe Larussa said:

Does anyone know how far apart the Elt antenna and Gps antenna should be? Mine are 9" apart. Maybe a thing?

Your ELT antenna doesn't radiate energy unless you crash, and after that you won't need your WAAS GPS signal.  

[M016576]

I had a problem with my 430W when I first bought my second mooney, in 2013.  I had shot a ndb approach down to minimums and was still 500’ above a licting fog bank and was on my way to my divert when my 430W went “dead reckoning.”  NBD... I had a 396 and an iPad running FlyQ.  But... they ALL lost GPS signal at the same time!  Turns out, the antenna on my 430W was bad- and the particular failure mode that disabled that antenna also emits a signal that is higher than the GPS threshold... basically every gps within about 15 feet of the failed antenna is disabled.  I ended up having to arc using an OBS to an ILS final, in IMC, and broke out at about 700’.  Turns out, that’s a known failure for some of the Garmin Waas antennas... I replaced the antenna and it’s good to go know.  Happy to be on an Avidyne IFD as well... but it’s still a Garmin antenna.

[Joe Larussa]

13 minutes ago, M016576 said:

I had a problem with my 430W when I first bought my second mooney, in 2013.  I had shot a ndb approach down to minimums and was still 500’ above a licting fog bank and was on my way to my divert when my 430W went “dead reckoning.”  NBD... I had a 396 and an iPad running FlyQ.  But... they ALL lost GPS signal at the same time!  Turns out, the antenna on my 430W was bad- and the particular failure mode that disabled that antenna also emits a signal that is higher than the GPS threshold... basically every gps within about 15 feet of the failed antenna is disabled.  I ended up having to arc using an OBS to an ILS final, in IMC, and broke out at about 700’.  Turns out, that’s a known failure for some of the Garmin Waas antennas... I replaced the antenna and it’s good to go know.  Happy to be on an Avidyne IFD as well... but it’s still a Garmin antenna.

Good Lord !!

[M016576]

Just now, Joe Larussa said:

Good Lord !!

Yeah... bad day- but a good flex of the old IFR muscles .  My wife and daughter had come down with the flu, as well and, no kidding, were both throwing up while I was shooting the approach.  No radar at TWF- so I had to do it the old fashioned way.  

[Cyril Gibb]

On 12/9/2017 at 1:39 PM, Piloto said:

Cable impedance does not change with cable length. Some cables are provided with the connectors attached and the installer just coils the extra length to avoid cutting and reinstalling connectors.

José

Jose is correct re: impedance, however from the GNS530 install manual: (cable length matters, italics and bold added for clarity)

GPS antennas in Table 1-3 require a cable loss between 3 dB and 7 dB.

The coaxial connectors and adapters, such as TNC to BNC, add additional loss to the cable and should be considered when computing the cable loss. A typical loss of 0.2 dB can be used for each connection. To maintain integrity of the WAAS signal, the GPS antenna coaxial cable must have a minimum of two shields (e.g. RG-400 or RG-142B).

If RG-142B or RG-400 is used, 1.5 dB equates to a length of approximately 6.5 feet of cable with a connector on each end. RG-142B or RG-400 cable can be used as long as the length is less than 35 feet. For longer lengths, use low-loss double or triple shielded 50 Ω coax.

For very short runs, where the loss is less than 1.5 dB, additional cable should be used to increase the loss to within 1.5 dB to 6.5 dB.

Edited December 10, 2017 by Cyril Gibb
clarifying that length doesn't change impedance but coax length still matters

[Joe Larussa]

Today I shot the same approach with almost the same result. Take a look at the video.

My_Video.mp4

[Joe Larussa]

Okay so video may be too large. What I noticed was I received a call from Atc. Two satellites briefly dropped out then the Lpv went to yellow. Soon as I switched to tower I lost most of the satellites for a second. This all happen prior to the final approach fix. Lpv went back to green and all was normal.

[kortopates]

24 minutes ago, Joe Larussa said:

Okay so video may be too large. What I noticed was I received a call from Atc. Two satellites briefly dropped out then the Lpv went to yellow. Soon as I switched to tower I lost most of the satellites for a second. This all happen prior to the final approach fix. Lpv went back to green and all was normal.

Video looks great for showing the issue. Sure looks like a signal loss/noise issue. Vnav requires that VFOM (vertical figure of merit accuracy) not go above 30 something feet from memory, but yours goes briefly to 46 and 66', and we see it go up and down makes it look like interference or signal loss. However, rather than assuming its an antenna or coax issue the fact that changing Com freq's appears to set it off (assuming this is repeatable) suggest it could be a noise issue internal to the box. I'd suggest calling the Garmin Tech support Monday morning and get some them to look at your video for their suggested next steps. I am sorta expecting they may want to check out your the 530W. But if changing freq's was purely coincidental I'd be looking for a signal loss external to the box but see what Garmin Tech support suggest.

[Brandontwalker]

Your ELT antenna doesn't radiate energy unless you crash, and after that you won't need your WAAS GPS signal.  

While technically accurate, the GPS frequency resonates on same frequency as a 121.5 ELT antenna. To troubleshoot my issue, my Avionics shop had me Fly a couple of approaches with the ELT removed from the airplane. Problem was immediately resolved. From there, all it took was a $35 filter in the ELT antenna.


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[thinwing]

On 12/9/2017 at 6:22 AM, Brandontwalker said:

I had the same problem with my GTN 650. My Avionics shop has me install a filter on the ELT because he said the ELT frequency can interfere with GPS reception. It has been rock solid since.


Sent from my iPhone using Tapatalk

Uh..that doesn't make a lot of sense considering your ELT is normally off

[Andy95W]

25 minutes ago, Brandontwalker said:

While technically accurate, the GPS frequency resonates on same frequency as a 121.5 ELT antenna. To troubleshoot my issue, my Avionics shop had me Fly a couple of approaches with the ELT removed from the airplane. Problem was immediately resolved. From there, all it took was a $35 filter in the ELT antenna.

So that would mean that the ELT antenna was absorbing RF at 121.5 MHz, and then somehow backfeeding it to the ELT so that it created interference with the GPS antenna and associated cabling.  I don't doubt it, the GPS signal is so weak it probably doesn't take much to interfere with it.  I learned something new here, thanks.  It's probably a rare occurrence, but troubleshooting it is definitely counterintuitive. 

[Piloto]

On the video I didn't see an RF problem related to the antenna or cable. Looks to me like a processor interrupt problem when the frequency switch was push. Suggest update the unit software.

José

[Joe Larussa]

8 hours ago, Piloto said:

On the video I didn't see an RF problem related to the antenna or cable. Looks to me like a processor interrupt problem when the frequency switch was push. Suggest update the unit software.

José

I'll check to see what software version I have. Two months ago I did the adsb out upgrade to my 330 transponder. I believe it did involve some programming in the 530.

[rbridges]

10 hours ago, thinwing said:

Uh..that doesn't make a lot of sense considering your ELT is normally off

I agree with you, but my friend was having static in his comms, and the avionics shop cut his ELT antenna.  They said it was too long and may be interfering.  

[Piloto]

1 hour ago, Joe Larussa said:

I'll check to see what software version I have. Two months ago I did the adsb out upgrade to my 330 transponder. I believe it did involve some programming in the 530.

Did the problem started after the upgrade? It may be related to the 530 programming.

[Joe Larussa]

On 12/9/2017 at 10:52 AM, Piloto said:

Verify your GNS 530W has the latest software. Latest revision address some of these issues.

https://www.garmin.com/en-US/aviationalerts/service-bulletin-1317-gps-400wgnc-420wgns-430wgps-500wgns-530w-series-units-software-upgrade-to-main/

José

 

Looks like I'm running 5.3