Loss of GPS during flight

John Pringle

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Sep 5, 2020
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54
Yesterday while on decent into El Paso Tx from the east to west I had a full loss of GPS on both SkyView pan as well as my Garmin that my flight plan was running on. The GPS for all devices came back on several minutes later about the time I was landing at KELP. I suspect that this may have occurred due to some sort of GPS jamming and not a problem with my system, maybe?
fortunately I was in clear VFR conditions when this happened because the behavior of both SkyView panels one showed the PFD and the other full maps basically began flashing lost GPS signal and then appears to show the terrain rapidly rising to put the PFD instruments going into the groun, now all of the flight instruments remain working fine it was only the map and synthetic vision that shows the terrain rising or the false impression that the aircraft is descending. This was only mildly annoying in VFR conditions but in one was in actual instrument conditions it could cause a horrible impression of what was not happening.
anyone ever have this happen?

Dynon this behavior should be reconsidered if it’s expected as it gives a false impression of rapidly rising terrain with GPS failur.
 

skysailor

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Oct 17, 2008
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Did you contact local ATC and say "Stop buzzer"? If the problem was jamming, this will cure it as jamming will be curtailed. Was there a NOTAM for GPS in the area?
 

GalinHdz

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Mar 3, 2008
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Yup. Here in NE Florida this happens once in a while. We are very close to big Navy facilities and they do operations off our shores. Most of the times the NOTAM comes out well in advance, but not always.

I was at the airport (KSGJ) one day when it was hard IMC and three different airplanes reported total loss of GPS. Two of them (business jets) went missed and landed using the ILS. The third (Piper Aztec) went off shore to descended then came in VFR.

Lesson is, GPS is great but not infallible. We civilians can use the GPS system as long as the "owners" (DOD) let us. "Stop buzzer" doesn't work with ATC since they are not the ones doing the jamming and it can take them a long time to find out who actually is. By that time the jamming has probably stopped. So make sure you have a backup plan at all times. Oh, and when they are jamming, they jam the entire GPS band so every system becomes unusable.

:cool:
 
Last edited:

John Pringle

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Sep 5, 2020
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54
Thanks Gent’s,

So no NOTAM on this one..and RAIM showed good to go. Never heard about the buzzer thing so I’ll keep it in mind. El Paso is right next door to a air force base and they have a lot of border operations on going as well as possible interference from Mexico so who knows where the outage came from? I’m glad I had this experience in VFR conditions first. Mostly so that I was able to experience what happens on the Dynon display and how after the GPS fail the synthetic vision begins to show the terrain rising. And a good reference as to why have that backup ILS plan ready is so valuable.
 

HFMan

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Aug 28, 2019
Messages
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Was likely GPS outage- I get frequent notifications from the FAA regarding GPS disruptions originating from White Sands/Holloman AFB, which is only about 75 miles north of El Paso.
 

TouchTheSky

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Jun 16, 2018
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Being the GPS "maintainer" in the Stratux project, this triggers a couple of comments/questions:
  • when talking about GPS, let's make sure that what we mean is rather GNSS which amongst GPS also includes GLONASS, GALILEO and BEIDOU (plus WAAS and EGNOS sats for local correction) which are all in full operation
  • which GNSS is used in the Dynon receiver besides GPS/WAAS? if only GPS (which I can't believe) then this would worry me
  • latest state of the art GNSS receiver chipsets like ublox M8, M9 or M10 (which we use in our Stratux project) receive at least 3 out of the 4 GNSS which offers significant redundancy - an ublox M9 receiver which receives all GNSS simultaneously in clear sky usually "sees" 25+ satellites
  • you probably did not use an iPad or something similar as such devices usually also receive multiple GNSS so it would really be interesting to understand what happened during your flight
  • a "GPS" outage would be something different that an entire "GNSS" outage which I doubt can happen
 

John Pringle

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Joined
Sep 5, 2020
Messages
54
Being the GPS "maintainer" in the Stratux project, this triggers a couple of comments/questions:
  • when talking about GPS, let's make sure that what we mean is rather GNSS which amongst GPS also includes GLONASS, GALILEO and BEIDOU (plus WAAS and EGNOS sats for local correction) which are all in full operation
  • which GNSS is used in the Dynon receiver besides GPS/WAAS? if only GPS (which I can't believe) then this would worry me
  • latest state of the art GNSS receiver chipsets like ublox M8, M9 or M10 (which we use in our Stratux project) receive at least 3 out of the 4 GNSS which offers significant redundancy - an ublox M9 receiver which receives all GNSS simultaneously in clear sky usually "sees" 25+ satellites
  • you probably did not use an iPad or something similar as such devices usually also receive multiple GNSS so it would really be interesting to understand what happened during your flight
  • a "GPS" outage would be something different that an entire "GNSS" outage which I doubt can happen
Thanks for the information, interesting, so I was on a flight from Abilene TX to KELP the second leg of my flight west from Arkansas to San Diego finally. The entire flight I used my Garmin GNC355 as the primary navigation source for my trip. I used the GNC355 source and had it displayed on my two Dynon SkyView monitors. This was a one time event during the entire trip that otherwise was uneventful.
while on visual approach about 5 miles to the east into KELP all GPS devices began to display warnings that there’s “NO GPS signal“ understandably all GPS Navigation reference was no longer viewable on ether the Dynon or Garmin devices. Within a few moments the dynon display shows the ground rising to the artificial horizon or what appears to be a controlled decent into the ground. That’s what gave me concern!
when on short final the GPS signal returns simultaneously to both the Garmin and Dynon and both screens return to what is normally displayed. There was not anything that indicated anything other than GPS was not available or had failed, can’t remember the exact terminology displayed on the screens.
 
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