Airplane Landings at Risk of Delays on FAA Move To Ease 5G Risk - Slashdot

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Airplane Landings at Risk of Delays on FAA Move To Ease 5G Risk (bloomberg.com) 42

Airliners, private planes and helicopters may have to limit landings in low-visibility conditions and follow other restrictions under a government directive to ensure safe operations once a new band of 5G mobile-phone service starts in January. From a report: The Federal Aviation Administration on Tuesday issued two orders laying out potential flight restrictions that could cause severe restrictions at major airports during bad weather.

"The FAA is working closely with the Federal Communications Commission and wireless companies, and has made progress toward safely implementing the 5G expansion," the FAA said in a statement. "We are confident with ongoing collaboration we will reach this shared goal." The agency said in a press release that it believes "the expansion of 5G and aviation will safely co-exist" and stopped short of specific restrictions. But the two airworthiness directives lay the groundwork for what could be severe limitations across the nation's aviation system if the regulator believes the signals -- from a part of the spectrum called the "C-Band" that the mobile carriers have procured to expand their service -- threaten safety.

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Airplane Landings at Risk of Delays on FAA Move To Ease 5G Risk

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  • Seems that FCC would have the authority to limit transmit power of ground stations in the vicinity/line of sight to ILS transmitters. I'm assuming a plane full of phones on full blast would still be dwarfed by the power of an actual cell tower and that's the dominant concern.

    On the other hand...government is generally a place that attracts mediocrity and sometimes outright incompetence so I wouldn't be surprised if there is an actual problem that kept getting powerpointed away in regulatory discussions over

    • The "ILS transmitters" in question are radar altimeters on planes, so they are pretty mobile -- the FCC would have to put strict limits on base stations within several miles of any airport with a published ILS approach.

      Because RF power drops with the square of distance, a cell phone on a plane could potentially have higher received power than a distant base station. Between the metal shell of the airplane and antenna directionality, it's hard to be sure.

      For those paying more attention than our editors, thi

    • Re:Quiet zone! (Score:5, Interesting)

      by PPH ( 736903 ) on Tuesday December 07, 2021 @03:48PM (#62056223)

      I don't think this is a 5-G/ILS interference problem. ILS [wikipedia.org] operates at or below 335 MHz. C-Band is 4 GHz.

      There is a system that operates close to 5G frequencies: The Radio Altimeter (RA). The RA [wikipedia.org] is an essential part of the Ground Proximity Warning System (GPWS) and is used outside of the final approach paths that ILS is necessary for. So 5G C-band would have to be restricted pretty much everywhere.

      Face it. Ajit Pai sold off spectrum that he probably had no business messing with. All to satisfy his corporate overlords. The sooner we realize this and reverse those decisions, the less harm will be done to everyone else.

      • Not a fan of government getting captured by business. But maybe this spectrum is better off in the hands of telecom. Cell phone bandwidth is a benefit for 99% of the population. While very important, commercial airlines are a luxury mostly limited to the top 25% of the population.
        • I fly in economy class, and my safety while flying is of more interest to me than your ability to take a phone call.
      • by jonfr ( 888673 )

        This problem that FAA claims in the United States doesn't seems to be a problem in Europe. Most of 5G frequencies in United States are also in use in Europe. Since most 5G transmissions are on the old C-band for satellite (the C-band for satellite was moved a little up to 4Ghz). The 5G band is that mobile phones transmit and receive data on the same frequency. Unlike many other mobile bands that are in use today.

      • Face it. Ajit Pai sold off spectrum that he probably had no business messing with.

        Not really no. Firstly this spectrum was sold off the world over, this is not a USA unique problem. Secondly the spectrum sold off was free to be sold and repurposed, it wasn't owned by the FAA or aeronautical services at all.

        The more fundamental issues is that designers of RAs (and the standards they follow) made certain assumptions about how "friendly" the neighbouring spectrum was. The use of this spectrum was historically for fixed service narrow directivity communication or Space to Earth communication

        • by PPH ( 736903 )

          Firstly this spectrum was sold off the world over, this is not a USA unique problem.

          Not really. Different countries reserved varying amounts of guard bands around critical radio systems.

          If you want to start a real fight, ask which 5G phones are 'world phones', i.e. capable of operating on any 5G system. Like the old GSM system. Which only supported the concept of a world phone by providing 4 bands and switching between the North American frequency plan and the rest of the world's. There will be finger pointing and screaming. And in the end, nobody can recommend a phone model that definite

          • Not really. Different countries reserved varying amounts of guard bands around critical radio systems.

            Indeed, and yet so far all those guard bands have the same problem, precisely none of them are sufficient. Including the European guardband which is 150MHz larger than the USA's https://www.ecologie.gouv.fr/s... [ecologie.gouv.fr] and the Australian one which is another 100MHz larger than the European's https://www.acma.gov.au/sites/... [acma.gov.au]

            Spurious emissions occur well outside of the 3GHz band, and the fundamental even several hundred MHz lower is still strong enough to cause problems.

            So let me repeat myself: this is not a USA un

            • by PPH ( 736903 )

              If it's that bad and even the increased European and Australian guard bands are ineffective, maybe 5G needs to be pushed out of the C Band altogether.

      • by ceoyoyo ( 59147 )

        Radio altimeters typically only work up to a couple thousand feet. Restricting systems that work on those frequencies around the instrument approach paths would be sufficient. Indeed, that's the solution that was proposed.

        That's if the interference is actually a problem.

        • by PPH ( 736903 )

          Radio altimeters typically only work up to a couple thousand feet.

          Above the local terrain. Where I really want my RA to work properly is if there's a mountain top sneaking up underneath me.

          • by ceoyoyo ( 59147 )

            Yeah, it's not great for that. Radio altimeters pretty much look straight down. There was a system implemented in the 70s that used a radio altimeter only, and it saved lives, but it wasn't great. Airliners today typically use GPS positioning and a database of terrain and obstacles.

            Even so, if you can't see the ground you're flying IFR, and you only fly IFR near the ground when you're near an airport. The only actual requirement I'm aware of for a radar altimeter is when flying a category II/III precision a

            • by PPH ( 736903 )

              and you only fly IFR near the ground when you're near an airport

              Not really. You fly IFR any time you fly in Instrument meteorological conditions(IMC) [wikipedia.org]. Or above 18,000 ft MSL (mean sea level). There are mountains around here where "flying near the ground" puts you over that limit.

              Radio altimeters pretty much look straight down.

              And that's just fine. With EGPWS [wikipedia.org], the current altitude measured (using a radio altimeter) is compared to the GPS terrain map. The map data provides the ability to look ahead as long as the system knows where it is right now. [youtube.com]

  • ...5 hours waiting on the ground.

    • If your landing is delayed 5 hours, you'll end up waiting indefinitely because you already crashed.

  • Anyone has a link to a technical explanation or is this more of a shoe taking off security theater?
    • This pretty much describes it: https://skybrary.aero/articles... [skybrary.aero]

      Basically, 5G us using a band between 3.7 and 3.98 GHz a bit below the 4.2 GHz to 4.4 GHz that aircraft radio altimeters use. They use those on approach to airports as they are more precise than using the barometric altimeters they use most of the time. Plane bounces signal off the ground, and based on return time knows the distance to the ground.

      Concern is the 5G signal could cause interference with that - aka - cause plane to have false alt

      • by EvilSS ( 557649 )
        It's also only a problem in the US apparently, as 40+ other countries are using the same C-Band frequencies for 5G with no issues for aircraft (that use the same band as the US for their radio altimeters).
        • My guess is it's twofold.

          (1) There are possibilities in some worse case scenarios where interference might occur.
          (2) This is government agencies (FAA and FCC) flexing their muscles at each-other.

        • It's also only a problem in the US apparently, as 40+ other countries are using the same C-Band frequencies for 5G with no issues for aircraft (that use the same band as the US for their radio altimeters).

          What makes you say that? Ignorance? Firstly not all countries are using the same frequencies. Europe standardised on 100MHz lower than the USA. And the end result? Well the DGAC (French version of the FAA) can sum it up nicely for you: https://www.ecologie.gouv.fr/s... [ecologie.gouv.fr] it's still a problem even with an additional 100MHz gap and the French has excluded 5G antennas from the vicinity of airports.

          The Australians concluded that even 200MHz lower with an upper limit of 3700MHz based on modelling from the worst ca

      • by thegarbz ( 1787294 ) on Tuesday December 07, 2021 @06:11PM (#62056655)

        Now, I'm not sure why the 0.22 GHz gap there is not enough to avoid issues, but I'm not enough of an RF expert. Maybe Doppler shift related or something like that if I had to guess.

        The problem is RAs aren't narrowband and as such don't have very aggressive out of band filtering. Check out slide 15 for a great pictographic summary: https://www.rtca.org/wp-conten... [rtca.org] They are affected by a signal with a fundamental significant far away if it is powerful enough, which the RTCA report says it is. Also all radio system produce spurious emissions, typically at quite low levels compared to their fundamentals. The issue with RAs is they aren't very tolerant of such emissions.

        They were designed based on an assumption on what was in the neighbouring band. That assumption is now no longer valid. For the record the French have determined that even a 0.4GHz gap isn't enough, and the Australians have determined via simulation that even a 0.5GHz gap wasn't enough to cover the worst case scenario in the standards governing RAs (though they note that no complaints have been filed yet despite a rollout of 5G in the 3.7GHz band already).

      • by Agripa ( 139780 )

        Now, I'm not sure why the 0.22 GHz gap there is not enough to avoid issues, but I'm not enough of an RF expert. Maybe Doppler shift related or something like that if I had to guess.

        The radar altimeters were never designed with enough selectivity to reject powerful hostile signals outside of their operating frequencies, because it was never needed. The adjacent services previously were low power.

    • Anyone has a link to a technical explanation or is this more of a shoe taking off security theater?

      If you want technical you can get a juicy details in this white paper on the issue: https://www.rtca.org/wp-conten... [rtca.org]

  • Why is it even a question that implementation should be postponed instead of curbing options available for landing? It's a no-brainer. You don't take options away from pilots and flights full of passengers.
    • Yes, this is absolutely insane. There's no way that passenger aircraft radio altimeters essential for IFR approaches should have been allowed to be potentially compromised by a discretionary new commercial communications service. The (brain) rot obviously started from the top and made its way down to the FCC during the last administration.
      • The (brain) rot obviously started from the top and made its way down to the FCC during the last administration.

        As much as we like to shit on the FCC it's worth noting that this issue isn't limited to the USA, and in Europe where the 5G frequencies are even lower they present similar problems, and in Australia where they are even lower again (3.7GHz vs USA's 3.98GHz) they have *simulated* that according to the standards as written now interference can be a problem.

    • Why is it even a question that implementation should be postponed instead of curbing options available for landing? It's a no-brainer. You don't take options away from pilots and flights full of passengers.

      Probably because so far 100% of issues have been based entirely on computer simulations. Simulations which have determined that in Europe it is also a problem despite having even larger frequency gap between RAs and 5G, and in Australia having larger gaps still. Though interesting in Australia they noted that while the simulations show failure of the radio altimeter, in practice, despite some significant 5G rollout at airports, zero cases of interference have been reported to date.

      The answer may lie in how

  • by backslashdot ( 95548 ) on Tuesday December 07, 2021 @04:57PM (#62056435)

    The last thing I wanna do is catch Covid when my plane is landing.

  • Since I got my Covid booster. Also this alleged interference hasn't been an issue in any of the other countries that already implemented 5G.
  • by BobC ( 101861 ) on Tuesday December 07, 2021 @09:20PM (#62057197)

    I was developing aircraft instruments back when switching parts of the C-band to terrestrial cellular use was first being seriously considered. My employer received surveys from the FAA and FCC about the matter, and we did extensive work to respond to those surveys with, essentially, "OK, go for it." We not only made aircraft instruments, but we also owned and operated test ("Experimental") aircraft filled with equipment from other manufacturers.

    We contracted an RF lab to do instrument-level external C-band exposure testing (just a high-power run over part of the normal certification testing spectrum). We also rented a 4G signal generator, a C-band transmitter, and a Yagi antenna to test each of our aircraft (with a certified test pilot) at low altitude, well away from all other interference sources (engineers love field trips). Everything passed easily, no problem. In particular, all of our aircraft had radar altimeters, one of which was over 30 years old. No problems at all.

    Now, being test aircraft, all our equipment was in top shape and perfectly installed. Other aircraft do not need to meet such stringent needs, and even good instruments with, say, an aging cable ***could*** experience interference to a level that ***could*** affect correct instrument operation. But such aircraft would not be in commercial service, where inspection and maintenance requirements are stricter than for General Aviation.

    Clearly, the FAA is tripping over its own toes, which is not an uncommon thing for any Federal agency. The FAA had FULLY concurred with the spectrum auctions!

    Fortunately, only two 5G cellular bands are affected: n78 and n79. All that's needed is to temporarily avoid these bands (or reduce their output power) on cell towers close to any low-altitude portion (landing/take-off) of standard aircraft routes. Other nearby bands will suffice until the FAA finally manages to quit embarrassing itself.

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