7 ms·

FAA Files Reveal a Surprising Threat to Airline Safety: US Military's GPS Tests

43 points by blendo 6y ago

t0mas88 6y ago
And this is why it's mandatory to check GPS availability when planning an IFR flight to an airport that only has GPS approach procedures. And it's also required to plan an alternate airport that has a non-GPS approach available.
- lovecg 6y ago
  I’m not too worried about commercial airlines. I’m more worried about press-button-and-fly weekend IFR warriors.
  - toomuchtodo 6y ago
    I would also be worried about systems like Cirrus’ VisionJet Safe Return, that turn the aircraft into an autonomous vehicle if a passenger activates the system due to an incapacitated pilot, as GPS is required for its automated path planning to autonomously return to an airport and land. I haven’t investigated, but I would be curious how such a system responds when GPS is degraded or unavailable.
    - kevin_thibedeau 6y ago
      Surely they also use GLONASS and Galileo.
      - deleted 6y ago
        [deleted]
    - lovecg 6y ago
      That’s already a rare event though, so the probability of it coinciding with a GPS outage is smaller still. Time integral of risk exposure and all that.
      - danaliv 6y ago
        Rare as it is—and I’d argue it’s not as rare as some people think, having experience three avionics GPS loss-of-signal events in the past two years (in different aircraft)—they’d be nuts not to have considered that risk in the design. I can’t find the AFM supplement for Safe Return but to a first approximation, it wouldn’t be out of the question for it to go into a heading and altitude hold until it reaquires.
- mbrameld 6y ago
  It's not required to plan an alternate that has a non-GPS approach if you have a WAAS-enabled GPS receiver, which is almost all of them these days. You can file a primary and alternate with only RNAV approaches.
  - danaliv 6y ago
    WAAS won’t help you when the GPS signal is being jammed. It’s ground-based navaids, pilotage, or stay home.
    - mbrameld 6y ago
      That's a non-sequitur. The person I was replying to said you always have to plan at least one airport with a non-GPS approach.
      - danaliv 6y ago
        You’re right of course. I was addressing the larger question of the impact of GPS jamming tests on aviation in general. Less of a reply to you and more of a note to anyone else reading.
  - t0mas88 6y ago
    But you are still required to check GPS availability and these jamming tests are published way in advance.
    - mbrameld 6y ago
      I don't remember saying you didn't... Of course you still have to check RAIM availability, but you don't have to plan an alternate with a different approach type.
- AWildC182 6y ago
  That doesn't really have anything to do with the GPS jamming tests. That's because GPS isn't actually global, or at least wasn't a couple decades ago. What you're checking is the number of satellites available on your flight path at the time you'll be there such that you can create an accurate and redundant 3d fix.
  - danaliv 6y ago
    You’re talking about RAIM. But you’re also required to check NOTAMs, where these tests are documented, under the “all pertinent information” clause of the preflight regs.
  - t0mas88 6y ago
    You're required to check both, RAIM availability (unless you have a WAAS type GPS) and also the NOTAMs where these jamming tests are published.
United857 6y ago
Curious -- how feasible is it for an aircraft to simultaneously support multiple systems for redundancy (e.g. GPS/Galileo/Glonass/BeiDou)?
- nickff 6y ago
  I don't know how common/feasible it is for aircraft, but most new GPS receivers are capable of receiving two or three of the systems (usually GPS & Galileo or Glonass)
- angry_octet 6y ago
  Totally possible. It's also very easy to jam any or all of them with a $50 box.
  - sudosysgen 6y ago
    You'll need a bit more than 50$ to jam them for an aircraft, though
    - NickNameNick 6y ago
      Depends where the plane is. High altitude, away from any precision navigation areas, not a huge risk. Flying a GPS approach to an airport - definite risk. Bear in mind that a GPS satellite has a power budget of ~4kw, and it's >12,000 miles up. A jammer may only have a watt or two of transmit power, but it can put all of that into a single channel, and it's only going to be a few miles away from your receiver.
      - userbinator 6y ago
        You're off by around an order of magnitude: https://apps.fcc.gov/els/GetAtt.html?id=110032&x= https://apps.fcc.gov/els/GetAtt.html?id=110032&x=. Transmitter power is only 25W. EIRP is ~450W.
      - sudosysgen 6y ago
        Of course. But then you'd have to do it while right next to an airport, which is a quick ticket to jail. In practice, the aircraft will do a go around then proceed with ATC vectoring or inertial navigation.
dalrympm 6y ago
On the west coast it has pretty much become a standing Notice to Airmen (NOTAM) that some agency will potentially be interfering with GPS signals. Sadly they continue to decommission VOR stations across the country. https://bruceair.wordpress.com/tag/vor-decomissioning/ https://bruceair.wordpress.com/tag/vor-decomissioning/
angry_octet 6y ago
This article is really glossing over the fact that non-military jamming now occurs all the time, courtesy of truckers and criminals. Actual GPS jamming is only done rarely on special military ranges with significant separation from civilian traffic, or very rare wide-area trials (days when I would not have flown anywhere near the area in the NOTAM). One thing is true: GA and Amati pilots rely too heavily in GPS. If they can't fly with DR+VOR in VFR then maybe they shouldn't fly through an area with GPS interference...
- AWildC182 6y ago
  Try explaining that to the FAA. They've been shutting down more VORs and airways every year.
  - angry_octet 6y ago
    The FAA is guilty of cost focused magical thinking. They had some idea that anti-jam techniques would migrate to civilian platforms, but that is delusional, especially as the number of GPS enabled in flight devices has exploded. Maybe for special certified devices for ADS-B. But it is extremely sensitive tech, and anything smarter than a noise jammer can be difficult to deal with. I think they plan on having jamming surveillance nodes set up near airports. But of course, detecting isn't fixing. How long did that (imaginary?) drone take out Heathrow airport for?
    - AWildC182 6y ago
      It's not that awful of a problem. Simply making the antenna directional enough is a solution, such as using a phased array coupled with an IMU to tell if the signal is coming from a known satellite location.
      - angry_octet 6y ago
        It depends on how severe and consistent the jamming is. If the receiver has a good lock (and a good clock) and a basic IMU then jamming on the last few minutes of approach might not cause too much drift -- but it could certainly spook a pilot into diverting. As to mitigation, it is all expensive (in terms of antenna construction and processing) and GA is price sensitive. Airports with urban buildup get multi-path interference in the GPS signal and jamming signals, and it becomes complicated to computationally null the jamming signals. Chirp jammers are now as cheap as basic noise jammers. Anyway, it's not so easy, look at any current research paper on anti-jam. Imagine if 500 MAGA/Antifa types plugged in PPDs over a city wide area and kept them mobile? It would be chaos.
jcrawfordor 6y ago
The FAA has issued a recommendation that pilots who are experiencing a safety problem that they believe to be related to military electronic warfare exercises should use the term "Stop Buzzer." This term, borrowed from military range safety practices, is intended to make it clear among controllers that they should use a procedure specified with the NOTAM to request immediate termination of the exercise or testing. I am not especially clear on the criteria for use of this procedure, I'm not sure if a controller would comply without a declared emergency. I'm also not sure how quick the response will be in all cases - White Sands controllers are in close contact with Albuquerque Center but you'll probably see a slower response if you're talking to someone else or 121.5. This recommendation came out because there are multiple cases where pilots have declared emergencies related to GPS jamming but controllers have not requested termination of the jamming because of miscommunication or not realizing that the emergency was related. This is all pretty new and it has not really been communicated very well, I only know about it because of something I saw in _AOPA Pilot_. It has been reported that some aircraft, I forget which but I believe a light jet, react particularly badly to loss of GPS and it can get as bad as loss of attitude information, potentially as a result of a bug.
- nieve 6y ago
  This is probably the one you're thinking of: "The Embraer EMB-505 Phenom 300, for instance, entered service in 2009 and has since become the world’s best-selling light jet. In 2016, the FAA warned that if the Phenom 300 encountered an unreliable or unavailable GPS signal, it could enter a Dutch roll (named for a Dutch skating technique), a dangerous combination of wagging and rocking that could cause pilots to lose control. The FAA instructed Phenom 300 owners to avoid all areas of GPS interference."
berkut 6y ago
I've always wondered what GPS degradation (i.e. during tests) would do for things like Required Navigation Performance operations... Having flown into Queenstown in NZ several times when it's very cloudy, it's quite impressive how they're able to maintain operations apparently without seeing much, when there are mountains very close and depending on the approach, the aircraft is basically flying down a valley. I don't even think that airport has an ILS system for final approach... https://www.youtube.com/watch?v=Rhkbia1dMcI https://www.youtube.com/watch?v=Rhkbia1dMcI
- throw0101a 6y ago
  > I don't even think that airport has an ILS system for final approach... NZQN approach plate using VOR/DME: * http://www.aip.net.nz/pdf/NZQN_43.1_43.2.pdf http://www.aip.net.nz/pdf/NZQN_43.1_43.2.pdf * http://www.aip.net.nz/NavWalk.aspx?section=CHARTS&tree=Queenstown http://www.aip.net.nz/NavWalk.aspx?section=CHARTS&tree=Queen... It's a 4.9M PDF that loads at about 13 kB/s over ~4 minutes. Because the valley is curved, ILS cannot be used as a straight-in glide slope is not possible, so you have to 'swing around'.
sneak 6y ago
Maybe I'm missing something, but does El Paso not have localizers/ILS? GPS isn't used for the final, why did a GPS outage put this flight in danger? https://en.wikipedia.org/wiki/Instrument_landing_system_localizer https://en.wikipedia.org/wiki/Instrument_landing_system_loca...
- lpmusix 6y ago
  There is ILS, but only on RW 22 -- https://flightaware.com/resources/airport/ELP/IAP/ILS+OR+LOC+RWY+22/pdf https://flightaware.com/resources/airport/ELP/IAP/ILS+OR+LOC... Based on the article, I assume they tried that a few times but (cross)winds made it too risky.

43 points by blendo 6y ago

And this is why it's mandatory to check GPS availability when planning an IFR flight to an airport that only has GPS approach procedures. And it's also required to plan an alternate airport that has a non-GPS approach available.

lovecg 6y ago
I’m not too worried about commercial airlines. I’m more worried about press-button-and-fly weekend IFR warriors.
- toomuchtodo 6y ago
  I would also be worried about systems like Cirrus’ VisionJet Safe Return, that turn the aircraft into an autonomous vehicle if a passenger activates the system due to an incapacitated pilot, as GPS is required for its automated path planning to autonomously return to an airport and land. I haven’t investigated, but I would be curious how such a system responds when GPS is degraded or unavailable.
  - kevin_thibedeau 6y ago
    Surely they also use GLONASS and Galileo.
    - deleted 6y ago
      [deleted]
  - lovecg 6y ago
    That’s already a rare event though, so the probability of it coinciding with a GPS outage is smaller still. Time integral of risk exposure and all that.
    - danaliv 6y ago
      Rare as it is—and I’d argue it’s not as rare as some people think, having experience three avionics GPS loss-of-signal events in the past two years (in different aircraft)—they’d be nuts not to have considered that risk in the design. I can’t find the AFM supplement for Safe Return but to a first approximation, it wouldn’t be out of the question for it to go into a heading and altitude hold until it reaquires.
mbrameld 6y ago
It's not required to plan an alternate that has a non-GPS approach if you have a WAAS-enabled GPS receiver, which is almost all of them these days. You can file a primary and alternate with only RNAV approaches.
- danaliv 6y ago
  WAAS won’t help you when the GPS signal is being jammed. It’s ground-based navaids, pilotage, or stay home.
  - mbrameld 6y ago
    That's a non-sequitur. The person I was replying to said you always have to plan at least one airport with a non-GPS approach.
    - danaliv 6y ago
      You’re right of course. I was addressing the larger question of the impact of GPS jamming tests on aviation in general. Less of a reply to you and more of a note to anyone else reading.
- t0mas88 6y ago
  But you are still required to check GPS availability and these jamming tests are published way in advance.
  - mbrameld 6y ago
    I don't remember saying you didn't... Of course you still have to check RAIM availability, but you don't have to plan an alternate with a different approach type.
AWildC182 6y ago
That doesn't really have anything to do with the GPS jamming tests. That's because GPS isn't actually global, or at least wasn't a couple decades ago. What you're checking is the number of satellites available on your flight path at the time you'll be there such that you can create an accurate and redundant 3d fix.
- danaliv 6y ago
  You’re talking about RAIM. But you’re also required to check NOTAMs, where these tests are documented, under the “all pertinent information” clause of the preflight regs.
- t0mas88 6y ago
  You're required to check both, RAIM availability (unless you have a WAAS type GPS) and also the NOTAMs where these jamming tests are published.

United857 6y ago

Curious -- how feasible is it for an aircraft to simultaneously support multiple systems for redundancy (e.g. GPS/Galileo/Glonass/BeiDou)?

nickff 6y ago
I don't know how common/feasible it is for aircraft, but most new GPS receivers are capable of receiving two or three of the systems (usually GPS & Galileo or Glonass)
angry_octet 6y ago
Totally possible. It's also very easy to jam any or all of them with a $50 box.
- sudosysgen 6y ago
  You'll need a bit more than 50$ to jam them for an aircraft, though
  - NickNameNick 6y ago
    Depends where the plane is. High altitude, away from any precision navigation areas, not a huge risk. Flying a GPS approach to an airport - definite risk. Bear in mind that a GPS satellite has a power budget of ~4kw, and it's >12,000 miles up. A jammer may only have a watt or two of transmit power, but it can put all of that into a single channel, and it's only going to be a few miles away from your receiver.
    - userbinator 6y ago
      You're off by around an order of magnitude: https://apps.fcc.gov/els/GetAtt.html?id=110032&x= https://apps.fcc.gov/els/GetAtt.html?id=110032&x=. Transmitter power is only 25W. EIRP is ~450W.
    - sudosysgen 6y ago
      Of course. But then you'd have to do it while right next to an airport, which is a quick ticket to jail. In practice, the aircraft will do a go around then proceed with ATC vectoring or inertial navigation.

dalrympm 6y ago

On the west coast it has pretty much become a standing Notice to Airmen (NOTAM) that some agency will potentially be interfering with GPS signals. Sadly they continue to decommission VOR stations across the country. https://bruceair.wordpress.com/tag/vor-decomissioning/ https://bruceair.wordpress.com/tag/vor-decomissioning/

angry_octet 6y ago

This article is really glossing over the fact that non-military jamming now occurs all the time, courtesy of truckers and criminals. Actual GPS jamming is only done rarely on special military ranges with significant separation from civilian traffic, or very rare wide-area trials (days when I would not have flown anywhere near the area in the NOTAM). One thing is true: GA and Amati pilots rely too heavily in GPS. If they can't fly with DR+VOR in VFR then maybe they shouldn't fly through an area with GPS interference...

AWildC182 6y ago
Try explaining that to the FAA. They've been shutting down more VORs and airways every year.
- angry_octet 6y ago
  The FAA is guilty of cost focused magical thinking. They had some idea that anti-jam techniques would migrate to civilian platforms, but that is delusional, especially as the number of GPS enabled in flight devices has exploded. Maybe for special certified devices for ADS-B. But it is extremely sensitive tech, and anything smarter than a noise jammer can be difficult to deal with. I think they plan on having jamming surveillance nodes set up near airports. But of course, detecting isn't fixing. How long did that (imaginary?) drone take out Heathrow airport for?
  - AWildC182 6y ago
    It's not that awful of a problem. Simply making the antenna directional enough is a solution, such as using a phased array coupled with an IMU to tell if the signal is coming from a known satellite location.
    - angry_octet 6y ago
      It depends on how severe and consistent the jamming is. If the receiver has a good lock (and a good clock) and a basic IMU then jamming on the last few minutes of approach might not cause too much drift -- but it could certainly spook a pilot into diverting. As to mitigation, it is all expensive (in terms of antenna construction and processing) and GA is price sensitive. Airports with urban buildup get multi-path interference in the GPS signal and jamming signals, and it becomes complicated to computationally null the jamming signals. Chirp jammers are now as cheap as basic noise jammers. Anyway, it's not so easy, look at any current research paper on anti-jam. Imagine if 500 MAGA/Antifa types plugged in PPDs over a city wide area and kept them mobile? It would be chaos.

jcrawfordor 6y ago

The FAA has issued a recommendation that pilots who are experiencing a safety problem that they believe to be related to military electronic warfare exercises should use the term "Stop Buzzer." This term, borrowed from military range safety practices, is intended to make it clear among controllers that they should use a procedure specified with the NOTAM to request immediate termination of the exercise or testing. I am not especially clear on the criteria for use of this procedure, I'm not sure if a controller would comply without a declared emergency. I'm also not sure how quick the response will be in all cases - White Sands controllers are in close contact with Albuquerque Center but you'll probably see a slower response if you're talking to someone else or 121.5. This recommendation came out because there are multiple cases where pilots have declared emergencies related to GPS jamming but controllers have not requested termination of the jamming because of miscommunication or not realizing that the emergency was related. This is all pretty new and it has not really been communicated very well, I only know about it because of something I saw in _AOPA Pilot_. It has been reported that some aircraft, I forget which but I believe a light jet, react particularly badly to loss of GPS and it can get as bad as loss of attitude information, potentially as a result of a bug.

nieve 6y ago
This is probably the one you're thinking of: "The Embraer EMB-505 Phenom 300, for instance, entered service in 2009 and has since become the world’s best-selling light jet. In 2016, the FAA warned that if the Phenom 300 encountered an unreliable or unavailable GPS signal, it could enter a Dutch roll (named for a Dutch skating technique), a dangerous combination of wagging and rocking that could cause pilots to lose control. The FAA instructed Phenom 300 owners to avoid all areas of GPS interference."

berkut 6y ago

I've always wondered what GPS degradation (i.e. during tests) would do for things like Required Navigation Performance operations... Having flown into Queenstown in NZ several times when it's very cloudy, it's quite impressive how they're able to maintain operations apparently without seeing much, when there are mountains very close and depending on the approach, the aircraft is basically flying down a valley. I don't even think that airport has an ILS system for final approach... https://www.youtube.com/watch?v=Rhkbia1dMcI https://www.youtube.com/watch?v=Rhkbia1dMcI

throw0101a 6y ago
> I don't even think that airport has an ILS system for final approach... NZQN approach plate using VOR/DME: * http://www.aip.net.nz/pdf/NZQN_43.1_43.2.pdf http://www.aip.net.nz/pdf/NZQN_43.1_43.2.pdf * http://www.aip.net.nz/NavWalk.aspx?section=CHARTS&tree=Queenstown http://www.aip.net.nz/NavWalk.aspx?section=CHARTS&tree=Queen... It's a 4.9M PDF that loads at about 13 kB/s over ~4 minutes. Because the valley is curved, ILS cannot be used as a straight-in glide slope is not possible, so you have to 'swing around'.

sneak 6y ago

Maybe I'm missing something, but does El Paso not have localizers/ILS? GPS isn't used for the final, why did a GPS outage put this flight in danger? https://en.wikipedia.org/wiki/Instrument_landing_system_localizer https://en.wikipedia.org/wiki/Instrument_landing_system_loca...

lpmusix 6y ago
There is ILS, but only on RW 22 -- https://flightaware.com/resources/airport/ELP/IAP/ILS+OR+LOC+RWY+22/pdf https://flightaware.com/resources/airport/ELP/IAP/ILS+OR+LOC... Based on the article, I assume they tried that a few times but (cross)winds made it too risky.