Loss of GPS during flight

[JP JR]

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]

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]

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.

 

[JP JR]

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]

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]

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

 

[JP JR]

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.

 

[CanardMulti]

Apologies for reviving this thread, but I'd like to get as firm as possible understanding of what I should expect to see on my Skyview screens in flight in a situation like this:

I just finished reading an article about a recent persistent GPS interference / outage event centered around the DFW airport that lasted more than a day. It was bad enough that it made it into the airport's NOTAMS. My understand is that as long as my pitot - static information is valid, my attitude / ADI function of the PFD will remain usable. Is that correct? Loss of Skyview navigation is a given, but what else is going to be lost, or worse, display invalid information?

Sure would appreciate a definitive explanation from the mothership.

 

[JP JR]

Apologies for reviving this thread, but I'd like to get as firm as possible understanding of what I should expect to see on my Skyview screens in flight in a situation like this:

I just finished reading an article about a recent persistent GPS interference / outage event centered around the DFW airport that lasted more than a day. It was bad enough that it made it into the airport's NOTAMS. My understand is that as long as my pitot - static information is valid, my attitude / ADI function of the PFD will remain usable. Is that correct? Loss of Skyview navigation is a given, but what else is going to be lost, or worse, display invalid information?

Sure would appreciate a definitive explanation from the mothership.

In my case I just lost all navigation references this included synthetic vision as well as all maps for any reference.. but fortunately all PFD information remains active. But if you loose all maps it’s going to make you consider have I also lost everything else.. fortunately it’s only been one case for about 10 minutes that I had to deal with it.. unfortunately for me it was also during a time when we were dealing with severe turbulence over El Paso so that wasn’t a fun add to the situation.. it’s good to know ahead of time though that this might happen and what to expect

 

[RV6-KPTW]

Thanks for reviving this thread. The current events in Texas give one pause.

TouchTheSky raised the question about what GNSS was used. I cannot find info in the pilots guide or install guide indicating anything other than ”GPS” is used. I’ll call Dynon if no one knows.

As to what Skyview will provide if GPS is not available, I see Pilots Guide, Page 2-4, Table 1 indicates that GPS is required to Synth Vision, winds, flight path marker, and ground speed. There is discussion of how Attitude is calculated if there are static/pitot issues but none if GPS is not available. WIll the functions noted above that rely on GPS fail out and display an error giving one a heads up?

Is there any documentation around how the system specifically reacts to GPS loss? I did not see any in the install or pilots guide. If none exists, this would be a worthwhile addition by Dynon.

I assume (yes, I can spell it) that Attitude will continue to be accurate (and Synth Vision must be ignored) unless one has inaccurate airspeed due to a static/pitot issue. This condition should display “CHECK PITOT HEAT” which is pretty good but not great clue to look to the backup AI. Mine is a D2. Argh… What GNSS does it use and how is it affected by a loss of GPS? More research to do.

Thanks

 

[CanardMulti]

Back before EFIS, many pilots learning to fly IFR found that flying 'partial panel' was one of the toughest skills to master. Instructors often advised students to carry devices - anything from special 3" suction cups to something as simple a pad of 'sticky notes' - to cover up instruments that had actually failed. With a well developed instrument scan habit, it becomes exceptionally difficult to repeatedly ignore the incorrect display from a failed instrument even though you KNOW the information is bogus, especially an attitude indicator that has rolled over and died.

I think I may practice shutting down synthetic vision in flight some VFR day and see how it goes. If it seems do-able w/o too much fuss I might build a checklist to put in the back of my checklist binder. Ignoring some bogus values is one thing, but a synthetic vision background wandering all over the entire PFD would probably drive me nuts in short order.

Another question for which I'd sure like an official Dynon answer: With external GPS signal loss in flight that results in the PFD failing down to just attitude and pitot static information, would the autopilot heading and altitude hold functions still work? I simply don't know enough about what talks to what internally, and under what circumstances, to dope out a solid answer.

 

[Marc_J._Zeitlin]

With external GPS signal loss in flight that results in the PFD failing down to just attitude and pitot static information, would the autopilot heading and altitude hold functions still work? I simply don't know enough about what talks to what internally, and under what circumstances, to dope out a solid answer.

So my GUESS is that altitude hold and heading hold would still work. You could test this by disconnecting the GPS antenna from the system, go up for a flight and see what works and what doesn't. Maybe Dynon will tell us, but it would be easy enough to test it on a nice day over the home airport.

Synvis can easily be turned off in the PFD Tools menu.

 

[swatson999]

So my GUESS is that altitude hold and heading hold would still work. You could test this by disconnecting the GPS antenna from the system, go up for a flight and see what works and what doesn't. Maybe Dynon will tell us, but it would be easy enough to test it on a nice day over the home airport.

Synvis can easily be turned off in the PFD Tools menu.

Doesn't SV "turn off" synthetic vision *anyway* if it has no GPS, and simply revert to a PFD with blue for sky and brown for ground? It's what my screen looks like on start-up in the hangar for a few seconds before it acquires GPS (which it does remarkably well, if the hangar doors are open, WAY faster that the 430W, which may not acquire at all in this situation).

Maybe one could verify that in flight by going into the configuration menus and setting GPS input to use a different serial line (an unused one).

 

[RV6-KPTW]

I spoke with support yesterday. I asked how what happens in Skyview when GPS is lost. I don’t think this support person appreciated how many of us use Skyview in IFR. He suggested that I write an email requesting guidance / clarification on the Skyview mode on loss of GPS, similar to the discussion of how Attitude is calculated if there are static/pitot issues in the Pilots manual.

I’ll get that email out today and report back.

 

[RV6-KPTW]

Don Jones/ Dynon Support answered my email.

If the system loses GPS from jamming or something, it will still have the primary flight instruments, but all navigation will be lost of course. The primary instruments are GPS aided, but loss of GPS will not stop them from working, they may just be slightly less accurate in some situations.

He also stated that the synthetic vision will revert to the standard brown and blue colors as well as Messages should occur such as NO ADSB-OUT, GPS LOST errors and others.

Seems pretty straight forward but not easy to test.

I also asked about my backup AI, D3 - he states that the D3 will completely X out and be completely unusable, as it heavily relies on GPS for the primary display.

The worst case for me would be IMC with GPS outage coupled with something that takes out Skyvision (pitot static, electrical loss). This is a fringe case but realistic and occurs. I’d want my backup AI to keep me upright regardless.

I am now in the market for a backup AI that does not rely on GPS.

 

[airguy]

D

The worst case for me would be IMC with GPS outage coupled with something that takes out Skyvision (pitot static, electrical loss). This is a fringe case but realistic and occurs. I’d want my backup AI to keep me upright regardless.

I am now in the market for a backup AI that does not rely on GPS.

You're postulating a triple failure case here - GPS constellation is down or jammed, plus electrical failure, plus pitot/static failure. I doubt you would find ANY aircraft design that takes that into account.

 

[GalinHdz]

I am now in the market for a backup AI that does not rely on GPS.

Hence the reason I installed a D6 as the backup to my SkyView panel. It does not use GPS for anything.

 

[RV6-KPTW]

If I only had room for a D6…. I looked into the Foreflight / sentry combo and it should still provide attitude should all go to heck in a handbasket.

 

[CanardMulti]

If I only had room for a D6…. I looked into the Foreflight / sentry combo and it should still provide attitude should all go to heck in a handbasket.

That's one of the reasons I chose a G5 for my standby attitude indicator. Virtually every other candidate available at the time - including the D10 - would not fit in the space available. Some of the newer round choices that live within a 3 1/4" hole cram a lot of information into a *very* small area, resulting in numbers that are just too small for aging eyes to read easily. At night. In turbulence. The G5 screen is just enough larger to make a significant difference, to my eyes at least. YMMV.

While it can use its own GPS to add ground speed and track, it functions just fine as an attitude indicator + pitot static information without it. It can accept steering info via RS232 from pilot's choice of VHF NAV or an IFR GPS. Cost is reasonable. It has a 4 hour back up battery. And, for me at least, the fact that it exists in a 100% different software ecosystem is also a plus.

Also, many thanks for making the effort to reach out to the mothership for a definitive answer.

Ken

 

[Rhino]

I'm looking at the AV30 for pretty much the same reasons.