How much do you trust your Garmin 530?

[Joe Larussa]

On too many occasions during practice approaches I have had either loss of signal or loss of glide slope. I have had the radio checked and antenna changed yet every now and then it happens. I'm starting to consider only doing ILS in actual from now on. Bummer sense it wasn't cheap to upgrade to Wass.

[kortopates]

Sounds like you must have a signal strength or signal loss issue in the form of coax to antenna or antenna problem. A change of coax was often required for the WAAS upgrade. But what you are describing is not at all normal. A good installation will never experience this. I much prefer the easier LPV over the ILS. Don't give up.

 

 

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[gsengle]

I have a 530 in the Mooney and 430s at work. This literally never happens.

One other thought, check the RAIM forecast for your location? Maybe you’re just in a bad spot?


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[rbridges]

I've got a 430W.  Fingers crossed, never had a single failure.  The only complaint is the occasional "sticky" button, but never any signal failure or shutdown.

[Bartman]

Never had a problem in over 10 years with my 430W, but I do have a King HSI coupled to it and I did have the KI 525 HSI rebuilt due to glideslope indicator issue. 

[flight2000]

Joe, agree with the others.  You need to have the entire wiring system checked.  I had a 430W in my Mooney for+ 8 years and a GTN750 in my Beech for 18 months and never had a drop or loss of signal.  I used to fly in your area a lot two years ago when I lived on the other side of the mountains from you (Reno).  Has to be a gremlin or two in there. 

Brian

[carusoam]

Definitely something wrong... box or installation, or the oddity of loss of raim.

Is Doing a raim test on your unit required prior to using it on the approach?  This is an aging standard for early GPSs.  See if your device has a raim Check procedure.

Self test idea... Is there a page that indicates all the satellites in view?  The more the better. If only a few, The box and antenna are probably not working together very well... GPS signals are so faint on a good day. Wiring and connections, and antenna placement can be a challenge.  Any other antennae close to the 530’s?

any new radios or antennae added before this issue appeared?

 

+1 On Getting The Issue Found....

 

PP thoughts only...

Best regards,

-a-

[rbridges]

9 minutes ago, carusoam said:

Definitely something wrong... box or installation, or the oddity of loss of raim.

Is Doing a raim test on your unit required prior to using it on the approach?  This is an aging standard for early GPSs.  See if your device has a raim Check procedure.

Self test idea... Is there a page that indicates all the satellites in view?  The more the better. If only a few, The box and antenna are probably not working together very well... GPS signals are so faint on a good day. Wiring and connections, and antenna placement can be a challenge.  Any other antennae close to the 530’s?

any new radios or antennae added before this issue appeared?

 

+1 On Getting The Issue Found....

 

PP thoughts only...

Best regards,

-a-

I may be wrong, but I didn't think raim checks were required on the waas units. 

[Bryan]

I had a GTN 750 installed this spring. I was losing GPS on the unit and took us a while to diagnose. We replaced the antenna, the head (unit) and finally found a connector issue in the back of the tray. The installer used a staring connector that was pushing up against a bulkhead that was causing the issue. We then changed to a right angle connection and it has been rock solid since. I would trust it all the way down to minimums in IMC EVERY time now.

As others have said, check your connections and coax.

[Cyril Gibb]

Is the coax double shielded (eg. RG400) as required in the install manual?

[Jerry 5TJ]

RAIM is calculated in the receiver itself so if you have an outage due to RAIM it would be annunciated. 

WAAS satellites in addition to sending their ephemerides also transmit GPS constellation integrity information (derived from ground-based integrity monitoring stations) to users so that RAIM calculations aren’t necessarily required.  

Legacy ILS uses two separate radio transmitters near the runway.  Two separate receivers in the plane process the localizer and glide slope signals.  Sometimes one part fails, so it is possible to lose the GS but still have localizer guidance.  

Integrity monitoring of ILS is done by ground based equipment.  If the self test fails, the Morse identifier is removed — that’s why we listen to the audio during an ILS approach.  You listen during every ILS approach, right?  Me either.  

RNAV GPS approach horizontal and vertical steering data are calculated in the receiver based on the aircraft and runway 4-dimensional location estimates.  (Except for aircraft carriers runway locations tend to be stable).  It’s not possible to “lose” only the GS portion on an LPV or LNAV+V approach.  

If the calculated z axis accuracy is reduced, generally due to GDOP, the receiver is required to step down from providing vertical guidance.  In that case it could annunciate LNAV instead of LPV at the FAF inbound.    

My long winded nerdy lecture done I’ll agree with others:  

Check the entire RF path from box to antenna. Look at the grounding under GPS antenna.  If your GPS coax is older than a decade replace it with the correct RG-400. Ensure the coaxial cable loss is within the limits specified in the install manual.  Consider a new GPS antenna and make sure it’s well located for sky view and distance from com antennas.  

The GPS antennas are the most important antennas on your plane:  Don’t be a CB on those vital parts. 

PS In a decade of flying with a pair of GNS530 and now  GTN750 I have never seen the two display disagreements—except inside the hangar where the aft GPS antenna on #2 is more blocked.  

[Brandontwalker]

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.


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[Piloto]

I mostly do LPV GPS coupled approaches and never lost the glideslope. Joe, is this on LOC or GPS/LPV, the antennas are different.

José 

[PTK]

Not certain how the GNS does it but I know my GTN750 monitors RAIM automatically during approaches and will warn me if RAIM is not available. So I may use a non-GPS approach. It also has a RAIM prediction function to help plan for a pending flight to confirm GPS operation during an approach. It predicts if GPS coverage is available at current location or at a specified waypoint at arrival date and time. It does not predict weather or not an LPV or LNAV/V approach will be available. That's done via NOTAM by the FAA. It only predicts GPS coverage.

[Joe Larussa]

1 hour ago, Piloto said:

I mostly do LPV GPS coupled approaches and never lost the glideslope. Joe, is this on LOC or GPS/LPV, the antennas are different.

José 

This is on GPS on the 530. It happens so random, you never know when it's going to happen.

[Joe Larussa]

Thanks for all the replys. They pulled the box and found no issues. They changed the antenna and the connector. Can't recall if the connector on the box was changed. The correct coax was already in the plane, so it is original, vintage 2001 I believe. There had been thoughts that the antenna was too close to the ELT antenna. Never had an issue until doing the Wass upgrade.

[DanM20C]

About 6 months after buying my last airplane my autopilot needed some work. I called the avionics shop that did the install originally with the previous owner.  When they looked up my N number they said they hadn’t finished the WASS upgrade to the 530 that the previous owner had started. He said the box was updated but I still needed the new coax and antenna.  I questioned why I needed new coax because I though coax was coax.  He said what they originally installed in 2005 was not compatible with WWAS.  I told him I hadn’t noticed any problems so far. He said there was a chance of having gps reception problems.  

I was under the impression all WASS upgrades required new coax. Was the correct coax available before WASS and I just had the cheep stuf?  

Maybe you need to replace the coax. 

Cheers,

Dan

[Joe Larussa]

7 minutes ago, DanM20C said:

About 6 months after buying my last airplane my autopilot needed some work. I called the avionics shop that did the install originally with the previous owner.  When they looked up my N number they said they hadn’t finished the WASS upgrade to the 530 that the previous owner had started. He said the box was updated but I still needed the new coax and antenna.  I questioned why I needed new coax because I though coax was coax.  He said what they originally installed in 2005 was not compatible with WWAS.  I told him I hadn’t noticed any problems so far. He said there was a chance of having gps reception problems.  

I was under the impression all WASS upgrades required new coax. Was the correct coax available before WASS and I just had the cheep stuf?  

Maybe you need to replace the coax. 

Cheers,

Dan

They did verify I had the correct coax. I was just thinking when I replaced the interior I remember that there was a lot of excess cable. Wonder if the cable length makes a difference. Either way I'm going to have it replaced asap.

[yvesg]

Here is a suggestion Joe: Find another aircraft owner having a 430W or 530W. Park near him and compare the satellites received (I don’t remember which page it is. ) If there is a significant difference report it to the avionics guys.

Yves

[DanM20C]

7 minutes ago, Joe Larussa said:

They did verify I had the correct coax. I was just thinking when I replaced the interior I remember that there was a lot of excess cable. Wonder if the cable length makes a difference. Either way I'm going to have it replaced asap.

 They installed excess cable in mine too. When I questioned it, because it looks sloppy to me, they said they needed a certain length to get the correct  impedance.  I think it’s normal to have excess.

cheers,

Dan

[Joe Larussa]

31 minutes ago, David Herman said:

Your description is unclear? You say you lose “glide slope” but then you say you’re considering ILS approaches only? Do you mean you lose vertical path guidance during GPS approaches? 

As mentioned, check that the coax to the GPS antenna was replaced ..

 additionally, some of the old G35 GPS antenaes experienced failures when they cracked and water shorted out the signal reception. This was hypothetically from over-tightening the bolts during installation. Garmin does nice “damage control” - that is minimizing the issue ... and keeping the talk about the problem to a bare minimum.  

We have a GNS-430W that has performed flawlessly. Love the LPV Approaches! 

RAIM problaby the wrong term ... RAFF is what we’re looking for nowadays 

Yeah I would have it down graded from Lpv to Lnav right after the final approach fix on the Rnav approach. I've had two antennas and same thing. Did a Rnav back into my home airport after the issue and it was fine.

[Piloto]

33 minutes ago, DanM20C said:

 They installed excess cable in mine too. When I questioned it, because it looks sloppy to me, they said they needed a certain length to get the correct  impedance.  I think it’s normal to have excess.

cheers,

Dan

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

[DanM20C]

Ahh, I was wondering if he made something up to keep him off his back.  

Dan

[Piloto]

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

 

[kpaul]

2 hours ago, David Herman said:

RAIM problaby the wrong term ... RAFF is what we’re looking for nowadays 

RAFF?