back to article Mystery GPS glitch grounds flights, leaves passengers in the bar

Hundred of flights were cancelled and aircraft grounded stateside over the weekend due to a mystery GPS glitch. Reported in Hackaday and also discussed on PPrune (a site for pilots both professional and armchair-based to talk about aviation issues), the problem appears to lurk within the Automatic Dependent Surveillance- …


  1. big_D Silver badge


    for the pilots to get their maps and sextants back out...

    1. Ochib

      Re: Time

      The problems with sextants that make them impractical for modern air travel are:


      Sextants don't tell you where you are, they tell you where you were when you made the observation. There are averaging mechanisms that allow aircraft sextant to partially account for the fact that the aircraft was moving (both vertically and horizontally), but at modern speeds you cover a minute of arc pretty quickly. Radio navigation systems and GPS provide much faster position updates than you could get with a sextant.

      2.Complexity of the instrument

      Aircraft sextants are precision instruments. They need to be maintained and calibrated or they won't be accurate when you need them, and there are a lot more moving parts to an aircraft bubble sextant than a basic ship's sextant.

      3.Complexity of the process

      Using a sextant also require an operator (navigator) who knows what they're doing in order to take the sighting and compute the position, compared to radio navigation (VORs, VOR/DME, or GPS). Most pilots don't have any training in using a sextant, so having one would be useless to them.


      While the sextant is a reliable instrument the stars are not reliable: They're always there, but sometimes they're not visible. You can't see most of the stars & constellations you would take a sighting of during the day (usually only one star is visible), and clouds can obscure them when you want to take a sighting, delaying or preventing your position fix.

      1. Cynic_999

        Re: Time

        And (most important)

        5) Airliners are not fitted with an astrodome (bubble window on the top of the fuselage) so getting sights of any body above 40 degrees or so of elevation and an azimuth not within 40 degrees or so of the aircraft's heading would be problematic

        1. david 12 Silver badge

          Re: Time

          Well, they're not fitted with an observation port because navigators aren't using celestial navigation any more. Airplanes (like the 747) /were/ fitted with observation ports when navigators were using celestial navigation.

          But evidentially it was relatively complex: I was intrigued to see that Kee Bird (in 1947), was carrying both a navigator and an "astro navigator".

    2. Chris G

      Re: Time

      Yep! VFR with an OS map. Though I never was able to find a big PH written on the ground and there were lots of them on the map.

      I blame the GPS problems on (in no particular order) Huawei, the Russians and Brexit , with Brussels interference as a runner up.

      1. cantankerous swineherd

        Re: Time

        I've never been able to find one either, so I just give up and have a pint in the nearest pub.

      2. Anonymous Coward
        Anonymous Coward

        Re: Time

        Surely Hillary and 8-18 angry Democrats.

      3. hoola Silver badge

        Re: Time

        That is going to work well over a large expanse of water.

        Going round in circles anyone?

    3. Anonymous Coward
      Anonymous Coward

      Re: Time

      Inertial nav is good for an 11 hour flight. So no need for sextants unless really long-haul.

      Plus it's only the ADS-B transmission of the plane's GPS position that's up-the-creek. There's no suggestion that the GPS display in the cockpit is wrong so the pilot still knows where he is - it's just ATC that doesn't. ;-)

      1. big_D Silver badge

        Re: Time

        It was more a comment that we are making things needlessly complicated and often (not specifically air travel) dumbing things down so far that many people can't function without their technological crutches.

        I know people who won't leave the house without turning on their navigation system. I use the navigation system in my car maybe 3 or 4 times a year.

        1. VonDutch

          Re: Time

          I turn mine on even on well known routes so that I have something to argue with about directions when I don't have a passenger.

          1. big_D Silver badge

            Re: Time

            Yeah, I hate that my nav system can't seem to cope with the multiple ways, it usually sends me on a 90KM detour when going north/south around Würzburg, it will try and send me over Frankfurt, even though it is in the wrong direction, adds additional kilometers to the journey, is full of road works and traffic jams...

            1. Robert Carnegie Silver badge

              Re: Time

              Does your navigation system have up-to-date mapping? An old box won't know about new roads, but you may be able to get an update to load into it.

              I think that the most fancy systems get current information about road repairs and even accidents that obstruct your journey. That may be worth being told about.

              1. big_D Silver badge

                Re: Time

                It isn't up to date, but the roads have been there for several decades. It just won't use the direct route or the fast route, it always diverts to Frankfurt. This is / was also true of Google Maps and Nokia Here. They all seem to throw a wobbly at this route.

              2. Stuart Castle Silver badge

                Re: Time

                Even when GPS has up to date maps, there can still be errors..

                A few years ago, I used to use CoPilot on my iPhone. I don't drive, so used it for walking directions. One day, I noticed that if I ever got directions home, it would never direct me to enter my road from the end farthest from my house, even though entering it from the other end results in a longer journey for me.

                I could understand if I was actually asking for driving directions, as the end of the road it would not direct me to go to is blocked off to cars, but pedestrians are allowed to walk through it.

                So, I did a little investigating (nothing more than looking up every route I could), and I found that Co Pilot would never direct me to drive or walk through the bit of main road that end of my road feeds into, even though the routes it suggested added (in some cases considerable) distance to the journey. It's as if that bit of main road isn't in their maps, even though the App shows it.. I have reported it, but I've stopped using CoPilot, so no idea if they've fixed it.

                1. ICPurvis47

                  Re: Time

                  Some years ago I had a very early Garmin SatNav (I don't remember the model). I took a friend and her daughter to Disneyland Paris on the 4th July holiday (2006, I think), and used the SatNav to get me there. Coming out of Calais Tunnel terminal, it directed me up the coast into Belgium and then down an Autoroute back into France, eventually arriving at the hotel. On the way back I decided to drive into Paris first to visit the Eiffel Tower, and on the way out, followed the roadsigns to Calais, via the Autoroute. At every junction, the Garmin was screaming at me to leave the (direct) Autoroute and cross over to the other one, which ran parallel but several miles off to the North East. I ignored it and continued to follow the signs for Calais, and as we passed the last exit before Calais, the Garmin suddenly gave up and told me to continue straight on to the Tunnel terminal. I can only assume that the mapping did not include that last junction, and was therefor trying to send me by what it thought was the fastest route.

                  Closer to home, and more recently, I was using Google Maps on my Android phone as a satnav to go across country because I didn't want to take the direct route through Shrewsbury. I was driving along a B road and was instructed to turn right down a small lane. The lane got smaller and narrower, and eventually ended at the gates of a level crossing, which had obviously not been opened for several years as there was a grassy hump engulfing the bottom rail of the gate and a huge rusty padlock and chain. I could see the main road traffic going past on the other side of the crossing, but there was no way I could reach it. I had to make a 3 point turn, with a trailer on, and retrace my route back to the B road, turn right, and continue on until I reached its junction with the A road, whereupon I turned right and went back past the other set of crossing gates, also similarly padlocked shut, and continued on my way. As soon as I got back home, I went on Google Maps, found the road in question, and marked it as "Permanently Closed". I have similarly renamed other wrongly named roads in my area.

          2. vtcodger Silver badge

            Re: Time

            "I turn mine on even on well known routes so that I have something to argue with about directions when I don't have a passenger."

            And you use a portable unit located -- as tradition demands -- in the back seat?

        2. RFC822

          Re: Time

          I always use my sat nav on my daily drive to and from work.

          Sure I know the way already, but Mr Google has a much better knowledge of traffic conditions on any given day, and has routed me around some major hold-ups. (I know that whenever I have ignored it, and carried on with my usual route, I have always regretted it...)

          1. Muscleguy

            Re: Time

            I know what you mean. Back when the Forth Road Bridge was out of action for repairs, the QC was barely started and it was Clacks or Stirling I drove a friend from Edinburgh to Anstruther in Fife so her pooch could see a specialist Vet for treatment and back again.

            Google took us two different routes around the M90 motorway going from coming back but it following it was flawless. No satnav but the friend's phone. I knew roughly where we were at all times but as you say knowing traffic flow issues was what mattered.

            That it worked during a major traffic snafu like that and updated in a relatively short time shows it is worth paying attention to.

        3. Jason Bloomberg Silver badge

          Re: Time

          It was more a comment that we are making things needlessly complicated and often (not specifically air travel) dumbing things down so far that many people can't function without their technological crutches.

          I don't think either is the case here. ADS-B is simply a tool which allows ATC to do a better job. They can do without, and have, it's just that without ADS-B one cannot handle as many planes nor be so certain as to where they are.

          The situation which arose is just the same as it would have been had ADS-B not existed; fewer flights taking off, fewer planes in the air. It's not 'dumbing down' so much as providing additional useful information. It's not a 'crutch' but a facilitator for doing more.

          And it's not 'needlessly complicated'. ADS-B merely blindly transmits a plane's ID and where it is. That's as simple as it gets.

          1. agurney

            Re: Time

            "ADS-B merely blindly transmits a plane's ID and where it is. That's as simple as it gets."

            also transmits altitude, speed and heading .. easy to receive and plot with a raspberry Pi and cheap SDR dongle.

        4. Tom Paine

          Re: Time

          In othe rwords,

        5. tip pc Silver badge

          Re: Time

          My car nav will tell me if there is traffic and I should go the alternate route. I have no clue about traffic along the journey unless I turn the nav on.

      2. not.known@this.address

        Re: Time

        "Inertial nav is good for an 11 hour flight. So no need for sextants unless really long-haul."

        Depending on your inertial nav hardware, you might well be right. But don't forget that a 4000-hour mean time between failures* doesn't seem so much when you have several thousand aircraft flying 4+ hours each; fortunately the equipment is normally far more reliable than the requirements state, but there is a reason aircraft (especially those carrying fare-paying self-loading cargo) prefer to fly with backup systems.

        * I was involved in acceptance testing for IN gear in the mid 80s and that was the target at the time. I hope it has become more reliable since then, but then someone rolls out an update and...

        1. tip pc Silver badge

          Re: Time

          The nav on my car works in underground car parks. I assume it has IN in addition to gps. It shows me driving along, turning to group and down ramps etc with an overlay of the building on top.

          1. ~chrisw

            Re: Time

            What you driving, Airbus or Boeing?

    4. STOP_FORTH Silver badge

      Re: Time

      Back in the day (50s and 60s), flight crew consisted of Pilot, Co-Pilot, Flight Engineer and Navigator. The last had the sextant and maps.

  2. Anonymous South African Coward Bronze badge

    Imagine this sort of thing happening with a virtual pilot in the cockpit.

    1. Michael Hoffmann Silver badge

      1. msknight

        I picked a hell of a day to give up posting.

        1. The Oncoming Scorn Silver badge

          Don't Call Me Shirley

  3. amanfromMars 1 Silver badge

    A Most Plausible XPlaNation ... for Boffins Work.

    Worlds Captured in Almighty Webs Opening Heavenly Doors to New Beginnings. The Future Presented to Nations for Broad Band Casting

    While the cause of the problem is not yet clear, one poster has suggested that the Wide Area Augmentation System (WAAS) system on GPS satellites received a software upgrade that has left the system borked as far as the receivers on Rockwell Collins' gear is concerned.

    Bravo, Sir and/or Madam. That Genie is never going back into the Bottle/Cage/Den, of that can one be sure and assured.

    Now, regarding ... Future Boffins Work with/in New XPlaNations? What's Selling Outside ... Who's Buying Inside are always Prime Timely Questions for Uncovering and Assessing Competition or Opposition.

    1. Tom Paine

      Re: A Most Plausible XPlaNation ... for Boffins Work.

      * nodding thoughfully

      1. amanfromMars 1 Silver badge

        Re: A Most Plausible XPlaNation ... for Boffins Work.

        * nodding thoughfully ... Tom Paine

        Here's something else thoughful to be thoughtful on, TP ......

        amanfromMars [1906111426] ..... letting fly on

        So, is Hu one of the few extremely well-sourced quasi-independent journalists operating in a media ecosystem where he's forced to push try and get away with as much as he can get away with in order to bring his (mostly western) audience the truth? Or is his his twitter feed effectively an economic weapon wielded by the Communist Party against American equity markets as just another instrument of pressure in what has become a sprawling trade spat?

        Whenever it is both, and why couldn't it be, is it something else again quite different and unusual and even more powerful with SMARTR Application in SMARTR Applications.  It's a Big Step to Do Justice to the Fruits of Long Marches whenever and wherever Leaps Forward are the Great Attraction.  And a Key Future AI Requirement for Pleasing Retirements.

        Only Huawei Knows what Huawei Does .... and apparently it is exceedingly good at doing what it does, and knowing what needs to be done for a more uniformly informed society model where secrets are taboo and forbidden upon pain of exposure, is something they can be real good at too, methinks. Just how far they have got into that sort of application is surely, and quite rightly so, an highly sensitive and extremely disruptive proprietary intellectual property field in a Virtual AIMaster Endeavour .

        Is that as a Universal Statement, Questioned? ....... Doubted? ........ Feared? ..... Welcome and Fully to be Supported ..... with AIded Developments?

        And what whenever all four at the same time? That's sure to generate a novel alternate direction, with myriad available tangents to explore and exploit for Virtual Server Operations with Global Quantum Communications Head Quarters.

        Whenever Unique is IT Original Equipment Source for Global Operating Device Users ... and again very likely to be abused and/or misused, questioned, doubted and feared rather than welcomed and engaged and fully to be supported via Future AIded Development.

        Such would appear to be a Serious Serial Human Failing and Algorithmic Anomaly ........which Leads to False Results.

        1. amanfromMars 1 Silver badge

          Re: nodding thoughfully

          Hi, Tom Paine,

          I simply presumed and assumed thoughful was intentional given the Greater Fields of Play IT Presents for AI Populations with Thoughts that TerraPhorm.

  4. Khaptain Silver badge


    The Captain could simply stick his mobile phone against the cockpit window, start up Waze and then instruct Waze to forward his position to a friendly control tower.

    Everytime I start up WAZE it's always harcelling me to share my location so why not put this wonderful function to good use ......

  5. Down in the weeds

    Horse & Cart? Cart or Horse??

    In which direction does causality's arrow fly?

    "However, and alarmingly, it appears that the GPS system is having a bit of a wobble as far as certain types of ADS-B hardware is concerned"


    "GPS satellites received a software upgrade that has left the system borked as far as the receivers on Rockwell Collins' gear is concerned"

    Nope & nope

    The 'GPS system' is not borked. The GPS signal as upgraded is no longer available to / correctly processed by unmodified receiver equipment; rendering the onward system - ADS-B - borked

    Aircraft type is irrelevant

    "The aircraft types affected include some Airbus A320s, the Boeing 737-900 and Bombardier CRJ 700 and 900."

    Who cares?

    The position of the aircraft reported into ADS-B is mostly the position of the GPS receiver system fitted (actually the electrical centre of the antenna)

    Although, strictly speaking: "The source of the state vector and other transmitted information as well as user applications are not considered to be part of the ADS-B system" (URL:; it is FAA mandate that GPS is used in source data to compute the state vector (URL:

    1. tip pc Silver badge

      Re: Horse & Cart? Cart or Horse??

      “Aircraft type is irrelevant”

      Some aircraft are only certified with specific systems and it may be just those specific systems that are impacted. A 741 through 744 May not be impacted or an a380 might be ok where a 737 or a320 is due to the vendor or generation of certified kit onboard.

  6. Ugotta B. Kiddingme

    back in MY day...

    long before GPS was anything more than a military wet-dream we were taught to navigate using, among other things, an E6B flight computer. Pretty sure I still have one in a closet somewhere. Many modern commercial pilots probably have no clue how to use one.

    1. John Brown (no body) Silver badge

      Re: back in MY day...

      I remember being taught how to use an abacus when I first started school. I bet most people don't have a clue how to use one. Am I missing your point?

      1. Ugotta B. Kiddingme

        Re: back in MY day...

        Yes, I think you are. When technology fails, a manual alternative is very useful to know.

        1. Mike 16

          Re: back in MY day...

          Yep. I was in a private 4-seater when VOR failed on one way-point. The pilot just reached back and grabbed his charts and proceeded using a couple other way-points. This was daylight, VFR, so not all _that_ concerning.

          Maybe modern systems could fall back to LORAN...

          1. Dyspeptic Curmudgeon

            Re: back in MY day...

            Loran C was turned off in North America in 2010. Apparently, still running elsewhere in the world.

            1. ElectricPics

              Re: back in MY day...

              Not operational anywhere apart from possibly China now. eLoran is running in the UK for shipping and bound to be adopted worldwide.

          2. ElectricPics

            Re: back in MY day...

            eLoran is operational in the UK with seven land stations but it only has a maritime application. Other countries including the USA are conducting trials.

          3. VeganVegan

            Re: back in MY day...

            Used to navigate using LORAN, it’s simples triangulation, and surprisingly accurate, will get you to within 10’s of yards of a spot in the middle of the ocean (well not quite, but anywhere off the coast within reach of the LORAN signals). Sadly, all the newfangled tech resulted in the LORAN stations being turned off for cost savings.

    2. SkippyBing

      Re: back in MY day...

      An interesting point considering at no point were the pilots having any problem with navigation. The problem was with ATC not being told where the aircraft was.

      The E6B was certainly still part of the CPL syllabus when I did it back in 2012 so I doubt your last sentence holds.

      1. the Jim bloke
        Thumb Up

        Re: back in MY day...

        The problem isnt with any individual pilot not knowing where they are.

        The problem is with SOME pilots not knowing where they are in relation to everyone else

        Add in liability issues - when ATC are providing instructions to pilots that are now based on poor quality information, and it all descends into a legal septic tank.

        For the people who will be held responsible, the responsible thing to do is say "no".

    3. Cynic_999

      Re: back in MY day...

      All pilots are still being taught to use the E6B in initial training. Unlike a sat-nav it can be used to plan the flight - finding ground speed, heading and EET in advance using the forecast winds. Although electronic navigation calculators or computer applications are more likely to be used these days which can give far more planning information (required fuel, weight & balance etc.) Some people find the E6B easier to understand as it shows the vectors graphically rather than as numbers, especially when looking to see how much cross-wind there will be on landing.

  7. Alister

    No mention of TCAS

    Unless I missed it, neither the article nor any commentard has mentioned that the primary reason for the grounding of aircraft is that the Traffic Collision Avoidance System (which is mandatory on all turbine powered commercial aircraft with more than 30 passengers seats) takes data from the ADS-B.

    On affected aircraft using Rockwell-Collins hardware, ADS-B is no longer functional, and therefore TCAS isn't either. This is therefore a safety issue, rather than just a navigational issue, and that is why affected aircraft have been grounded.


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