Garmin 530 - WAAS losing satellites

AuntPeggy

AuntPeggy

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Ever since our WAAS upgrade, we've been losing the GPS satellites about half of our flights. Hubby phoned Garmin & they said to have the mechanic install a loaner. On the flight back after installing the loaner, the GPS went completely black and he lost the comms as well as display.:hairraise: After a restart, everything was back again.

We are just about to do a transcontinental flight in our C-172 and hope the loaner becomes more reliable.

Anyone else having similar experience with the WAAS upgrade? We NEVER lost the GPS before the upgrade.
 
AuntPeggy said:
Ever since our WAAS upgrade, we've been losing the GPS satellites about half of our flights. Hubby phoned Garmin & they said to have the mechanic install a loaner. On the flight back after installing the loaner, the GPS went completely black and he lost the comms as well as display.:hairraise: After a restart, everything was back again.

We are just about to do a transcontinental flight in our C-172 and hope the loaner becomes more reliable.

Anyone else having similar experience with the WAAS upgrade? We NEVER lost the GPS before the upgrade.
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Oh Crap! This has happened to me twice since my upgrade. About a 3 - 5 second loss of satellite. I asked my avionics guy and he thought maybe a bad antenna connection, we were going to pull it and check. If you're seeing the same thing, I wonder. :mad:

James Dean
 
This afternoon, my Garmin Nuvi took 10 minutes to get a satellite lock when it knew where I was, an the lock is usually really fast.

I wonder if they've sent a lot of sats to the war zone.
 
SCCutler said:
Mike:

Tell me you're joking.
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About what? GPS sats are not stationary.

Take a look at which and how many sats your Garmin sees. Try again a few weeks and see how the picture changes.

The DOD moves the sats to give better nav where needed.

http://www.gpsinformation.org/dale/theory.htm

The GPS satellites also carry nuclear detonation detectors, which form a major portion of the United States Nuclear Detonation Detection System

http://en.wikipedia.org/wiki/Global_Positioning_System#Techniques_to_improve_accuracy
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GPS satellites are moved, but only to put them more precisely into their preprogrammed orbit, since orbits are not perfect. They are NOT moved in the same way as Keyhole and other surveillance platforms, so there's no "adjustment" to give better coverage to specific areas of the world.

As for the nuclear detectors, it doesn't suprise me, but that technology is on lots of platforms up there, including some "private" communications satellites.
 
TMetzinger said:
GPS satellites are moved, but only to put them more precisely into their preprogrammed orbit, since orbits are not perfect. They are NOT moved in the same way as Keyhole and other surveillance platforms, so there's no "adjustment" to give better coverage to specific areas of the world.
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Bingo. The amount of fuel it would take to move them, say, over Iraq would be insane - You'd have to boost them to around double their current altitude, that's another 11,000 miles or so, to get them to stay in one place like that. The sats are constantly moving (watch your GPS info page and you can see them "rise" and "set") and your receiver is constantly grabbing and losing signals from various satellites.

In addition, if you moved them up to a geostationary orbit, the signal levels would probably be so low they'd be useless. They're already pretty faint in the grand scheme of things.
 
AuntPeggy said:
Anyone else having similar experience with the WAAS upgrade? We NEVER lost the GPS before the upgrade.
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Haven't lost the satellites entirely. I think I got a RAIM warning once. Maybe this problem is specific to the 530W, ours is a 430W.

The one problem I do have is the display "flashing" white once in a while which really sucks at night.

Then there's the inop E6B, which is a known problem and may have been fixed in a software update already.
 
O/T, but mildly relevant to the newly-creeped topic- I lost RAIM in the middle of an approach yesterday, first time flying a GPS App w/ a KLN94. Glad it was just under the hood!
 
kent is right, would take tons of fuel (probably literally) to make a big difference in the orbit. i guess iraq is pretty close to equator so it would be possible to hang a couple in geo stationary overhead. but it would be horribly difficult to do so while in flight. would be much better to place it in that orbit, or nearby, at launch.
 
Back O/T. This is why I am in no hurry to upgrade. Never buy serial #1. Or serial #100 for that matter.
 
SCCutler said:
O/T, but mildly relevant to the newly-creeped topic- I lost RAIM in the middle of an approach yesterday, first time flying a GPS App w/ a KLN94. Glad it was just under the hood!
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Interestingly enough, I lost RAIM on the approach on 6/24 too. Only mine WASN'T under the hood. I had to do a real missed and come back for the VOR-A. I was flying with a KLN89B.
 
tonycondon said:
kent is right, would take tons of fuel (probably literally) to make a big difference in the orbit. i guess iraq is pretty close to equator so it would be possible to hang a couple in geo stationary overhead. but it would be horribly difficult to do so while in flight. would be much better to place it in that orbit, or nearby, at launch.
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I spoke to an expert on these satellites. He said that the GPS satellites are in low orbit so that they are more accurate. Less distance means more accuracy. Geo-synchronous satellites are in high orbit. So, GPS satellites orbit the earth and cannot be sent to Iraq.
 
AuntPeggy said:
I spoke to an expert on these satellites. He said that the GPS satellites are in low orbit so that they are more accurate. Less distance means more accuracy. Geo-synchronous satellites are in high orbit. So, GPS satellites orbit the earth and cannot be sent to Iraq.
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GPS satellites are in 12 hour polar orbits because that's the best way to keep 4 or more satellites in view everywhere on Earth below 25 degees lattitude.

AFaIK the GPS satellites can be moved into a different orbit once or a few times. That's to allow a spare to replace any SV that fails.
 
Do you have 108.5 on your G/S dialed in? This one's a notorious interference generator....
 
One thing to note about the WAAS units is that there is no traditional RAIM alarm. There is an Loss of Integrity annunciation (LOI) which is based upon the required accuracy for the particular flight operation.

The LPV approaches require 50 meters or less of accuracy both horizontally and vertically.

If the data stream from the WAAS geo synchronus satellites is not available there cannot be vertical guidance on approach. At that point the system will revert to a fault detection and exclusion mode which will provide a more traditional RAIM alarm. But that's only outside of WAAS coverage.
 
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