Is A 5G Showdown Looming?


Although we often complain that aviation doesn’t get the attention it deserves in Washington, I have a feeling that’s about to change. From what I can read into the somewhat alarming news first broken by The Wall Street Journal, the FAA is about to engage in a test of wills with the equally powerful and influential Federal Communications Commission over the rollout of 5G cell service scheduled for Dec. 5.

As we are reporting, according to the Journal and follow-up reporting by Reuters, the FAA is sufficiently concerned about the potential disruption of radar altimeter function by the 5G signals that it’s going to issue a Special Airworthiness Information Bulletin (SAIB) and an Airworthiness Directive to address that concern. Both are potent actions with potentially far-reaching impacts, with the SAIB alerting crews to the issue without regulating a response. The AD is the regulatory action that tells everyone what must be done if the circumstances in the SAIB come true.

And that’s where it could get interesting. Since the radar altimeter is a major component in modern instrument landing systems, the wording of both the SAIB and AD will determine just how significant this action will be.

The stakes are pretty high. Trillions of dollars of investment and revenue are wrapped up in two things Americans can’t get enough of: internet bandwidth and safe, convenient and reliable air travel. The public doesn’t want either of them messed with and the politicians are keenly aware of that.

I’m not betting on this being a shot across the bow by the FAA, though. It seems like a cry for help to address what might be a big problem. Failure of the radar altimeter is not something to be taken lightly. It not only determines decision height for an instrument approach, it’s the primary source of altitude information for Cat 2 and Cat 3 approaches. If that function can’t be guaranteed, the FAA must regulate that it can’t be used. If there’s even a chance that the cell signals will cause the radar altimeter to fail at a critical moment, which is just about all the time the altimeter is in use, there’s a significant threat to flight safety.

That raises the specter of a ban on Cat 2 and Cat 3 approaches at airports within range of 5G transmitters. On Dec. 5, that will be 46 of the country’s largest metropolitan areas. The mind boggles at the potential consequences given the weather much of the country has been having lately. And within a few years, 5G will be everywhere if the telecoms have their way.

For its part, the FCC says the threat is minimal and it should be up to the aviation industry to deal with the potential interference. Apparently there are ways to harden radar altimeters to shrug off stray cellphone energy and the FCC is of the view that the cost of retrofitting the fleet should be borne by the aircraft operators. That attitude has naturally galvanized aviation into a rare block of unanimity against the rollout.

The telecoms say 5G hasn’t caused any major issues in other countries and keeps reminding us they spent almost $80 billion to buy the radio spectrum they were assured could be used for 5G. Their customers are panting for the blazing speeds and tremendous features that will come with the new service.

Of course, neither extreme is going to fly with the public. We want it all and the FAA and FCC will have to figure out how to deliver that sizzling wireless experience without interfering with our business or vacation travel plans.

The two agencies are reportedly in talks to mitigate any potential impacts and that raises another perplexing aspect. It seems no one really knows if this is a real problem. Maybe that’s a good place to start and for a potential strategy the two agencies might look north.

Canada has taken what seems to be a common-sense approach by limiting and restricting 5G transmitters around big airports. Radar altimeters are highly directional by nature so it would seem that keeping the high-powered cellular signals away from approach paths and runway thresholds is a good first step. 

It doesn’t have to end there, though. By establishing no-5G zones around airports, the Canadian regs naturally create the ideal environment to test just how serious the threat to ILS systems is under real-world conditions. In the meantime cell customers near the airports can make do with their existing service while the issues are sorted out.

It seems unlikely that there will have to be a hard choice between safe air travel and the latest in wireless technology but the nature of the FAA actions and the response from the FCC will set the tone for finding a solution that will allow us to have it all. 

Accurately and completely identifying the problem in a cooperative and respectful way seems like a place to start.

Russ Niles
Russ Niles is Editor-in-Chief of AVweb. He has been a pilot for 30 years and joined AVweb 22 years ago. He and his wife Marni live in southern British Columbia where they also operate a small winery.

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  1. “Accurately and completely identifying the problem in a cooperative and respectful way seems like a place to start.”

    It would seem, but I’m struggling to remember the last time government was able to identify a problem in a cooperative and respectful way.

    It will be interesting to see who wins this battle: the telecoms and their lobbying efforts, or the airlines and their lobbying efforts. Neither are lightweights.

  2. “That raises the specter of a ban on Cat 2 and Cat 3 approaches at airports within range of 5G transmitters. On Dec. 5, that will be 46 of the country’s largest metropolitan areas. The mind boggles at the potential consequences given the weather much of the country has been having lately.”

    Are there any data on the actual number of Cat 2 and 3 approaches flown per year?

    • “Are there any data on the actual number of Cat 2 and 3 approaches flown per year?”

      My guess is that the FAA has such statistics.

      More important, though, is many carriers mandate auto-land for CAT I ILS when RVR is less than 4,000, or such.

  3. We all know that the FAA, given the pace of change in tech, couldn’t get a change to the altimeter systems in time. It would take them 6 months to agree on a group to decide if a test was warranted followed by another 6 months to agree on what test and who would be involved. Never mind the real challenges in changing the equipment. Any such undertaking under the FAA would be done just in time for rollout f 9G.

    The FCC likely is similar yet didn’t see that as a problem they might have with the FAA until now. After the inevitable and tragic crash, the books will likely reveal great stories about how stupid each agency found the other.

    • What change could be made? A completely new system, operating outside of the 5G spectrum? From what I’ve seen, you are likely talking tens of thousands of dollars of now-useless equipment in a given plane, that must be replaced with ten of thousands of dollars worth (or more) of equipment that hasn’t been designed, tested, and certified yet.
      Seems to me someone screwed the pooch on this one. Though I do remember the telecom companies stating (testifying?) that their equipment wouldn’t affect navaids or other aircraft systems. Will someone hold their feet to the fire?

      • Who was using the spectrum first?… then someone comes in and causes harm to others with their use of the spectrum… who do you think will pay when the lawsuits begin to fly? They will… and these phone companies with deep pockets now will find out how expensive flying costs…
        Oddly, they know of the problem… this means some jurisdictions may file criminal charges against the executives making the orders for wrongful death.
        YIKES… I wouldn’t want to be in their shoes no matter how much money they are making…

  4. Ahm, last time I checked we are in 2021.
    A year where scientists and engineers are quite capable of measuring nano-hertz radio signals, and making and using equipment based on nano-hertz technology.
    So I see the panic over possible interference between a 3.7 GHz – 3.98 GHz band and a 4.2 GHz-4.4GHz band as being laughable.
    Unless of course the makers of either radio altimeters or 5G equipment just ignored the instructions and what they put on the box and shoved some very cheap, poorly designed electronics in their products.
    But that never happens in a highly certified environment, does it?

    • I agree John, but some Radar Altimeters from the early ’70s are/could be still in use today. I would suspect those to be the most vulnerable to interference. Should we still be using technology from 50 years ago for measuring the last 200′ or so above the ground? Probably not; I’m surprised we haven’t seen a laser based solution offered by Bendix or RCA (I doubt the market is large enough for Garmin to be interested).

    • I’m sorry John but your assessment is incorrect. There was and still is no certification required for interference from adjacent bands, Radar altimeters are inherently wideband systems, and currently have no
      requirements for front-end rejection. You can argue whether that was a smart idea, but it’s the reality of the way they operate today. So adjacent signals can and will bleed into the operating band. This is not a ‘laughable’ theoretical risk, but a very real concern, hence the action by the FCC.

      This RTCA presentation gives a really good overview of the problem, especially page 15 for a summary of the issue.

    • I was a radar, communications (HF, VHF, UHF, and microwave), Navigation systems tech for the FAA and DOD. People go off assigned frequencies all the time. Transmitters have bad final amps that splatter the entire spectrum. These things happen.
      I’m not sure why anyone would want any spectrum near any aviation band. They are open for a law suit now for any accident that can be remotely tied to an accident. It is going to cost them so much they will move quickly to another band, as quickly as plane manufacturers go out of business when they face piles of lawsuits.

  5. Aviation is under attack from bandwidth hungry internet companies. RA’s are one issues but a larger and more widespread showdown between the FCC and FAA over interference from Ligado’s 5G network to GPS users everywhere needs more attention. The FCC approved an operating band for Ligado’s 5G network that abuts GPS/GNSS L1 bands.

    And Ligado are saying bad luck, if you receive interference then that’s down to the RF front end of your GPS device. Us, as legitimate users of GPS will be the ones that have to bear the cost of fixing the issue, if that is even possible. This is not just an aviation issue, but a transportation, critical infrastructure, power grid and civil and military users.

    I’m not being overly dramatic when I say this is going to be a huge issue, and GPS performance degradations, RAIM warnings and missed approaches as your nav system looses GPS are going to be common. Oh, and over 80 companies/organizations are pushing for a revocation of the operating license for Ligado.

    This Congressional Research Service report is a good read

    • Buying band width next to an aviation band that can cause an accident is begging to be sued out of business… if the government gives you a bandwidth… that doesn’t waive liability if you cause harm to anyone Ben close to your bandwidth…
      YIKES… that was a super stupid move to even buy the bandwidth.
      They are about to find out what happens to an aircraft tire manufacturer when someone stalls on approach to final… they will be sued.

  6. As an electronics type as well as a self-financed aviator I sort of see both sides of these spectrum clashes.

    From an electronics point of view, yes, the basic problem is not with the 5G folks, it is that the legacy equipment (GPS, radio altimeters, etc.) was designed under the assumption it would not have to deal with strong signals close to their operating frequencies. At the time, there was plenty of room to go around. The 5G side says “well, that’s your problem, having inferior equipment doesn’t mean you inherit some inalienable right to control spectrum outside your own licensed domain.”

    Conversely, those who use the legacy equipment feel FAA’s initial approval of its design should come with a guarantee the government will protect it from obsolescence by maintaining the spectrum environment that dictated its design criteria. It’s a conundrum, but I think ultimately the huge demand for RF spectrum will win out over the hassle & cost of having to upgrade the avionics.

    • Who was there first?… that is what the lawyers will ask at trial. The person that came in second and caused harm will have to pay… and it will likely cost far more then what was paid for the bandwidth.
      The government sells bandwidth, it does sell protection from liability when you use said bandwidth. Any crash that can remotely be blamed on interference… they will go after these deep pocket companies like bees to honey.
      I just wish I had an law license now… this is going to be a gold rush.

      • Who was there first? Since when has who was there first ever mattered? Just ask the Lakota, Sioux, Apache, Cheyenne, Hopi, Navajo, Kaw, Wichita, Osage, … … …

        • And we already know that aviation generally loses with the “we were here first” factual statement. In this society, the “first” is usually the one who loses the most. Except in this case, I worry it will also mean a loss of life.

      • I think there is a misunderstanding over the concept of “interference” and the legal aspects related thereto. Richard G. properly ties liability to a case where a spectrum user whose transmissions are defective in some way (unfiltered harmonics, etc.). If, however, the user’s transmissions are fully within the FCC’s standards for his license to use the spectrum, well, a lawsuit would not be likely to go forward, or at worst not survive appeal. I, for example, am a “Ham” radio operator and can (and do) utilize frequencies that lie quite near various aviation bands. If a neighbor complained that my within-standards transmissions interfered with his reception of aviation frequencies because his receiver couldn’t cope with them, tough.

  7. I wish I was an aviation lawyer… this is the case of idiots doing stupid costly things. The first crash that can remotely be tied to a radar approach and they will pay dearly. They will get a expensive welcome to what people in aviation get to deal with…. HUGE LAW SUITS
    Just because the government opens up a spectrum for you to use, doesn’t mean you can use the spectrum to cause harm to others…


    In the end this may cost these companies more than the spectrum they paid to use. It would be an extremely wise move to pay for new radar systems on all effected aircraft, before it costs them many hundreds of millions more.