Garmin GNS430 not acquiring sats

gkainz

gkainz

Final Approach
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Greg Kainz
Looking for any ideas on our Garmin GNS430 not acquiring satellites. Installed ~6 months ago in our Dakota, reports from club members now that it recently started occasionally not acquiring satellites. Last report was "GPS failed to acquire satellites - intermittent at first, then continuously" (I assume that was with multiple reboot/restarts).

It just got back from a shop check where they said:
"Unit checks out good on the bench"
"A/C components (antenna, cables, etc) check good in the shop"
"Unit performs normally installed in the aircraft at the shop"

Club member picked it up from the shop yesterday (after hours) and reported no sat acquisition again on the taxi back to the hangar.

Further questioning about performance differences between engine running or not says doesn't matter (thinking maybe vibration induced problem?)

Perhaps unrelated (or maybe not) - Mode C reported as intermittent occasionally - mostly leaving the airport, usually reported ok on return, or after recycling, or sometimes after selecting "TEST" and releasing. Altitude encoder replaced a couple of weeks ago and no further reports of errors, until the same flight that reported the GPS issues.

Thoughts?
 
Thanks - will follow up. Interesting on the ELTs, however, we upgraded to the 406 at annual in March.

Edit - beechtalk requires a login. I've signed up, but says activation could take up to 24 hours. I guess I'll be patient ... 24 .... 23 ....
 
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Is the airplane hangared or tied down on a ramp? We ran into a similar issue with our GNS530 when the airplane was out on the ramp for a long period of time. I think we narrowed it down to moisture in the antenna but we couldn't confirm that because the issue went away after we started hangaring the airplane.
 
Hangared. However, the failures were noted by a club pilot returning from an XC trip. No idea from where or if it sat thru some rain.

However, the beechtalk threads have some interesting failures noted - WAAS antenna failures that cause sat dropouts due to interference from 1) other gps 2) 121.5 ELT or near freq transmissions, 3) cell phones ...

I'll quit rolling my eyes at the FAs nagging about "cell phones OFF OFF OFF" now ...

from one of the beechtalk threads:

"And, as part of your troubleshooting, be certain that all cell phones are off. It has been well known since 2003 that certain cell phones can cause 430/530s to loose all the satellites. First discovered by an avionics shop at PDK, then verified in the lab by NASA.

See http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040040193_2004035943.pdf

Here is an excerpt from the introduction of the NASA tech report:

"In July 2003, it was reported to the Federal Aviation Administration (FAA) that a cellular phone when turned on simultaneously interfered with three different aircraft GPS receivers, causing complete signal loss. The three GPS receivers were using three separate antennas, and were installed on a small aircraft. The phone was on, however, calls were not made during the incidents and subsequent tests.

In an email message to the FAA, the company who owned the airplane reported the subsequent tests taken to prove a clear and convincing direct relationship between the phone being in ON-mode, and interference with the three onboard GPS systems. The company verified several times, in multiple flights over different days, that the interference problem could be recreated reliably in the air by having the phone turned on. The interference disappeared when the phone was turned off or covered behind a metal object, and re-appeared when turned on or brought into the open again. In addition, the company conducted tests at two different places to ensure that it was not dependent on location, and were able to reproduce the interference effects at both. The interference occurred when the plane was in the air, but not on the ground. Tests using other phones did not create interference problems on the same aircraft and systems. "
 
Thanks for posting that Greg. I usually turn my phone off because the lightspeeds pick up some interference. Now I'll make sure pax turn their's off too.

The new 430w in the frankenkota is nice and I'm finally figuring out how to use it some. But it seems to have lost the airspace rings in the latest nav update. Anybody know what's up with that?
 
Which nav update? On my last flight, I "think" I noticed the airspace rings were not displayed at certain range selections when I expected them to be - I zoomed in a couple clicks and saw them again. Didn't think about it after that.
 
Probably just didn't zoom down far enough. Still learning the 430. It's the June database.
 
Our newest database always goes into the Bonanza and Saratoga. The Dakota gets the dregs. I haven't flown in 30 days or so, so not sure which db the 'kota has now - most likely it was the March or April db when I last flew.
 
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