Loss of GPS in flight

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John Collins

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I have been asked to collect any information on GPS outages and how it affected the flight. GPS outages can be due to Interference, Jamming, GPS/WAAS System failures, Military Tests, or GPS RAIM/Integrity issues.

If you have had a GPS in flight failure, please post a response. When and where did it happen? What was going on at the time, were you enroute or on an approach? Did you determine the cause, if so what was it? How did you deal with the loss at the time, were you able to use other navigation capability or radar?

Thanks in advance.
 
I've had several while doing practice multi- and single-engine approaches recently. It must be caused by an on-board failure, because I had RAIM every time. Basically, whenever I'd load an approach or direct-to a point, noting would change on the display. The most notable was when doing the GPS 36 @ KRCM. I knew I was 6-8nm south of the IAF (BEJCY), but when I activated the approach to begin from there, it sent me on a heading of 186*. Since I knew that wasn't right, I re-checked RAIM and re-loaded the approach. Still doing the same thing. About 2 minutes later, the CDI flipped and all the info changed to the correct values. Weird. Still haven't figured out exactly what happened.
 
Are you interested only in failures in IMC, or more generally? I've yet to fly my airplane in IMC, but have had several LOI incidents and one or two complete position losses in the past year. Every time it was in the northern part of Detroit and suburbs, generally within a few nm of a line from KDET to KPTK. This summer it was the rule to get at least one LOI in the pattern at KVLL, especially downwind-base-final for rwy 9.

The only time a loss of satellites has affected a flight was once when I was shooting approaches at KDET. I was dialing in the RNAV 15 when it happened, so I asked for the ILS instead, and then was able to come back and do the RNAV about 20 minutes later without incident.

Other pilots based at KVLL have reported similar problems so I suspect there is some ground based interference involved, perhaps something from the multiple broadcast towers 5-6 nm S and SW of VLL. It's very concerning, as the RNAV 9 is the only straight-in approach at KVLL. These failures don't just knock out WAAS-based vertical guidance, but make course guidance unreliable as well (at least in terminal and approach modes, not sure about enroute).

FWIW my GPS is a CNX-80 (aka GNS 480), with the latest software update if it matters.
 
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Both my 430's lost their screen over the last couple years. It was an age thing, they were old 430's. Garmin fixed them for their flat rate. They failed at separate times while enroute and I have 2 so I just used the other one. No big deal....
 
Have had some issues on longer cross countries with getting satellites and quality HERR/VERRs. Probably more an issue with the almanac data that was loaded (this has always happened immediately after start up in the acquisition phase), and a couple cases of crypto keys not being loaded and/or up to date. Can't think of an example where it has just poo pood itself with an otherwise 4.0 system.
 
Funny thing.....aside from a software problem I had with a Garmin 296 (would occasionally crash and shut down), I can't say that I have experienced a loss of a commercial GPS.

On the military side, I have lost count of all the times my mil-grade GPS units have crapped out on me or reported my position incorrectly and that is not counting intentional GPS jamming exercises.
 
Jan 22, 2012... VFR flight from Jackson Wy to Dell Mt. 1:20 flight time. I left at 1630 and arrived at 1800. I Had a 196 bean bagged to the top of the panel and the panel mounted GPS in the local rental 172, don't remember the brand off hand. Both units were programmed to navigate me to 4U9 = Dell.. That part of the world has featureless terrian. Both units didn't show any flags for bad signals, both units steered me straight to Red Rock Mt, a spot directly between Dell =4U9 and Dillon = KDLN. I knew they were giving bad readings but flew to the ghost waypoint just to see what would happen. They both displayed that I had arrived at my destination around Red Rock. I saw the rotating beacons of both airports so I knew to make a left at I-15 and head south a few miles... Landed at Dell, took back off 3 minutes later and flew directly back to Jackson. Both units navigated perfectly on the way back..... It was WEIRD for sure. YMMV...
 
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The first flight I ever took to an unfamiliar field after I got my PPL, my 430W went dark en-route.

Being a newbie pilot, I had planned my flight the same way I did during training, and had identified multiple en-route nav milestones and scribed my route on a paper sectional chart.

So I flew the VOR needles and used pilotage to find the field, and also to get home. No biggie.
 
Loss of GPS in CAVU conditions :hairraise:

I'd say squawk 7700, call in a mayday, total loss on situational awareness, I mean how to you know where you are or where you are going without GPS (jk)
 
NineThreeKilo said:
Loss of GPS in CAVU conditions :hairraise:

I'd say squawk 7700, call in a mayday, total loss on situational awareness, I mean how to you know where you are or where you are going without GPS (jk)
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:rofl: Sadly, I know a few of those type. Seems to be that the local pilot factory flight school teach only the minimum necessary, and nothing more. Flew with one of them, and when we had a "GPS failure" (I might have turned off the screen :wink2:), we ended up 8 miles off course about halfway through a 54nm flight. Then they remembered that nifty new invention called VORs.
 
HighFlyingA380 said:
:rofl: Sadly, I know a few of those type. Seems to be that the local pilot factory flight school teach only the minimum necessary, and nothing more. Flew with one of them, and when we had a "GPS failure" (I might have turned off the screen :wink2:), we ended up 8 miles off course about halfway through a 54nm flight. Then they remembered that nifty new invention called VORs.
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Since many I know, that fly these nice high performance "experimentals"...........

A lot of us just don't waste the money installing those 60+ year old inventions known as navigation radios for VORs.

They can still get rid of them all, for all I care. Never worked well in mountain country (line of sight)..........anyway.

One thing about it.............my kids & grandkids will always be faster texting than I will. They'd probably pick up the fine points of glass panels, a lot faster too!

In other words, I'm not impressed with clicking the GPS off, and proclaiming VORs as the national bag of pilot skills. They're just old technology, who's time has passed.

L.Adamson

Oh yes, for this thread............lost signal for a few minutes back in 1994. Have owned five Garmin moving map portables, and one Lowrance, since that time.
 
HighFlyingA380 said:
:rofl: Sadly, I know a few of those type. Seems to be that the local pilot factory flight school teach only the minimum necessary, and nothing more. Flew with one of them, and when we had a "GPS failure" (I might have turned off the screen :wink2:), we ended up 8 miles off course about halfway through a 54nm flight. Then they remembered that nifty new invention called VORs.
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One more thing.........

Looking into the near future, it will be interesting to compare the rate of new students using GPS, to old timers who "unexpectingly" ended it on the side of a granite wall. I have a feeling...........that new tech will come out the winner on the safer side of things. So much for that classic invention, known as VORs.

L.Adamson
 
Not saying that sometime in the future the technology will be reliable enough to rely on it 100%. I mean, look at past technologies, such as MLS and NDB, that have come and gone once something better was established. What I am saying is that while VORs are one of the most prominent navigation methods, they should be learned. The GPS is not as robust as we would like, and it does fail. That's where just about everyone, IMHO, should be versed in their use. It'd be a shame to lose a plane because the GPS failed and the pilot didn't know how to navigate otherwise.
 
These GPS threads crack me up sometimes? l.Adamson is quite right, if you want a thread with 100 pages of comments, ask if anybody has lost VOR signal or found themselves in a "zone of confusion". GPS is the way to go.....
 
jbarrass said:
These GPS threads crack me up sometimes? l.Adamson is quite right, if you want a thread with 100 pages of comments, ask if anybody has lost VOR signal or found themselves in a "zone of confusion". GPS is the way to go.....
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What cracks me up is comments like yours that seem to imply that unlike other methods, GPS is free from error. It IS a better system, but it is far from perfect.

The military created the GPS system to put warheads on foreheads and in the last 2 weeks I have personally seen my gps tell me I am 500 yds away from my correct position (verified by visual fix).

And it was telling me I had a FOM 1 (as good as it gets) the whole time.
 
I would appreciate those that want to discuss the topic to use another thread as it is not helpful in gathering information. Please do your thread drift elsewhere.
 
HighFlyingA380 said:
:rofl: Sadly, I know a few of those type. Seems to be that the local pilot factory flight school teach only the minimum necessary, and nothing more. Flew with one of them, and when we had a "GPS failure" (I might have turned off the screen :wink2:), we ended up 8 miles off course about halfway through a 54nm flight. Then they remembered that nifty new invention called VORs.
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Please take your comments to a different thread.
 
jbarrass said:
These GPS threads crack me up sometimes? l.Adamson is quite right, if you want a thread with 100 pages of comments, ask if anybody has lost VOR signal or found themselves in a "zone of confusion". GPS is the way to go.....
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Please take your comments to a different thread.
 
Fearless Tower said:
What cracks me up is comments like yours that seem to imply that unlike other methods, GPS is free from error. It IS a better system, but it is far from perfect.

The military created the GPS system to put warheads on foreheads and in the last 2 weeks I have personally seen my gps tell me I am 500 yds away from my correct position (verified by visual fix).

And it was telling me I had a FOM 1 (as good as it gets) the whole time.
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Please take your comments to a different thread
 
John Collins said:
I have been asked to collect any information on GPS outages and how it affected the flight. GPS outages can be due to Interference, Jamming, GPS/WAAS System failures, Military Tests, or GPS RAIM/Integrity issues.

If you have had a GPS in flight failure, please post a response. When and where did it happen? What was going on at the time, were you enroute or on an approach? Did you determine the cause, if so what was it? How did you deal with the loss at the time, were you able to use other navigation capability or radar?

Thanks in advance.
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How about also calculating the number of hours they work flawlessly?
 
John Collins said:
Please take your comments to a different thread.
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As my dad would say if you can't take a joke the hell with ya.

Anyway, I have had a loss of gps signal, once through the cascade pass, once in NV, didn't effect anything, still had chart and eyeballs, flight following and VORs.
 
John Collins said:
Please take your comments to a different thread
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I would John, but you asked for info on GPS failures.

While I was replying to a trolling post, the info I added directly relates to your original question.

While it may not even be noticeable in enroute flight, a 500 yard position error would be pretty significant if it happened in an aproach phase. The techs still haven't figured out what is wrong, but I suspect an antenna issue or possible issue with the cable.

My biggest concern was that when I was getting the error, there was no absolutely no indication of error, other than my military GPS was telling me that I was somewhere that my eyes and a commercial gps were not.
 
I've gotten a RAIM failure on the approach in actual once. Went missed and had them vector me for the VOR-A. It was a King KLN-89B, IIRC. Not really a "failure" because it correctly reported the loss of signal, but the end result was the same; no GPS approach possible.
 
N801BH said:
This begs the question , who asked you to collect the information?:dunno:

Inquiring minds and all..:D
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Please take your comments to a different thread.;)
 
I haven't had any experience with this as of yet. Never really got to fly GPS even once during my training but of course this was back in 2005 before all the real fancy I-pad apps and software.

RAIM WARNINGS AND MESSAGES
a. For most phases of flight, the GPS receiver will provide an immediate annunciation of a loss
of RAIM capability. The exception to this is the five minutes following passage over the final
approach waypoint of a non-precision approach during which time, a loss of RAIM
annunciation will be inhibited. GPS navigation may still be possible during this RAIM
outage.
b. The GPS receiver automatically performs an approach RAIM prediction just prior to passing
the final approach waypoint and will only enter approach mode if RAIM at the 0.3nm horizontal integrity limit is predicted to be available from the final approach waypoint to the
missed approach waypoint.
c. RAIM Loss - A RAIM loss will be indicated when the system is unable to provide integrity
at the required horizontal integrity limit. This is usually due to insufficient satellites in view
or poor satellite geometry. Navigation may still be possible.

If a loss of RAIM occurs it's recommended that you do not continue to use the system and to use an alternate means of navigation immediately following the loss. You immediately go around, sort it out and try again, but do not try and fix it on the way down to the ground.

I believe when it comes to aviation a contingency plan is extremely vital to the safety of life, especially when operating in IMC. Purchase an I-pad or a Nexus 7 and there are apps you can download and pay an annual subscription for that will not only load your approach plates for you but also show your current location on the approach. If this can be used in lieu of RAIM loss on an approach in IMC, it may just save your life.
 
Kevin H. said:
I believe when it comes to aviation a contingency plan is extremely vital to the safety of life, especially when operating in IMC. Purchase an I-pad or a Nexus 7 and there are apps you can download and pay an annual subscription for that will not only load your approach plates for you but also show your current location on the approach. If this can be used in lieu of RAIM loss on an approach in IMC, it may just save your life.
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Kevin, one of the reasons handheld devices can't be approved for IFR use is that they have no ability to warn you of invalid data. If your certified GPS is unable to get a reliable fix, it is not recommended to go to an uncertified system that won't tell you that its position is erroneous. Instead of saving your life, it could send you right into terrain. Instead, break off the approach and use non-GPS sources of navigation (while they still exist!)
 
I have had outages on a handheld device outside of Greensborough NC, Central Florida approaching Ft. Lauderdale, and Northern Michigan over Beaver Island.
 
gprellwitz said:
Kevin, one of the reasons handheld devices can't be approved for IFR use is that they have no ability to warn you of invalid data. If your certified GPS is unable to get a reliable fix, it is not recommended to go to an uncertified system that won't tell you that its position is erroneous. Instead of saving your life, it could send you right into terrain. Instead, break off the approach and use non-GPS sources of navigation (while they still exist!)
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Much better idea Grant. You are absolutely correct. Thanks for the correction :)
It would be pretty stupid to use a non-certified device if a certified device fails. Total morning blonde moment on my part.
 
I experienced a loss of satellites at about 2300Z this evening on the FAS of the RNAV 18 @ KFNT. That's the first time I've had a loss of satellites anywhere but near KVLL. At first it behaved the way it usually does when I lose satellites, showing all of them in yellow, and also coming back repeatedly and then going out again over a period of about 3 minutes. I went missed immediately and asked for vectors, then after the satellites seemed stable again I got cleared to fly to the published missed approach fix (POLAR). But then suddenly I lost ALL the satellites. As in the satellite page was completely blank. At this time we were a mile or so south of KFNT, climbing through 2000 MSL. That has NEVER happened to me before. ATC told us that another aircraft had also reported a loss of satellites in the same area a couple of hours before us.

I asked for vectors to the ILS 9, then spent a while fighting a very stiff SW wind trying to negotiate the hold at KATTY for the published miss. All this time there were no further satellite outages, so we then returned to the RNAV and completed the approach without incident, and then flew back to KVLL and flew the RNAV 9 without any further difficulties. But this is getting very concerning as I have no idea whether there is a problem with my 480, my antenna, or whether there was something jamming GPS signals in the area. I am fairly certain there is some kind of interference affecting GPS reception near KVLL, since I was definitely not the only pilot to report having that problem at the same time in the same general area. (Maybe I should say "was", since it hasn't happened to me near KVLL in a couple of months now.)
 
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