8 ms·

Is this a failure of the FCC to properly hand out frequencies?

mulmen 5y ago
Yes. They knew the dangers but the telcos wanted frequency. So the FCC attempted to undermine the aviation industry group that actually knows how radar altimeters work. Blancolirio covers this in several videos, although his take is more nuanced than mine. https://www.youtube.com/watch?v=942KXXmMJdY https://www.youtube.com/watch?v=942KXXmMJdY
- atkailash 5y ago
- tempnow987 5y ago
  Absolutely garbage reporting. The FAA / Boeing have no right to the frequencies in question. Even worse, they were given guard bands the size of their entire allocation which is ridiculous, and it still wasn't enough.
  - mulmen 5y ago
    Juan Browne is an ex-military and current commercial pilot. I trust him to explain how radar altimeters work and what they are used for.
Sanzig 5y ago
While this should have been better studied before the spectrum was allocated, it's not really the fault of the FCC. These radar altimeters have very wide front-ends, as as a result are highly susceptible to out-of-band emissions. The radars are allocated from 4.2 to 4.4 GHz, so the bottom edge of the radar altimeter band is 200 MHz above the top end of the 5G band in question (3.98 GHz). The fact that these radar altimeters are susceptible to out-of-band interference that is literally further away in the spectrum than the width of their entire allocation is IMO an engineering failure. Yes, spectrum management (rightfully) tends to err on the side of not forcing the incumbents to make modifications to existing systems. However, better filtering would resolve this issue and it is shocking that the engineers who designed them didn't foresee that other services would eventually be allocated in adjacent bands. Avionics is often NRE dominated, they couldn't have sprung for a cavity filter? Or if that was too expensive, designed more headroom in the LNA before saturation and filtered the out of band signal with a crystal or SAW filter at IF? Rejecting out of band that far away is not rocket science. I don't think it's unreasonable in this case to temporarily suspend the rollout and give the aviation industry a deadline to fix its radars, but it should only be temporary. Any other radio service would be told to take a hike if it keeled over due to out of band interference that far away.
- jandrese 5y ago
  This seems like Boeing trying to get the government to cover their butt because they did shoddy work on the altimeters. They were allocated spectrum for the equipment and then built a system that monopolized frequencies well outside of the allocated spectrum. I completely agree that Boeing needs to issue a recall order on all affected hardware and provide a fix. This should be painful, it is basically punishment for trying to cut corners on safety equipment.
  - kube-system 5y ago
    Does Boeing even make the radio altimeters?
    - jandrese 5y ago
      They certainly certified them on the aircraft. If it means putting pressure on the subcontractor that actually built them or finding a suitable replacement then so be it.
    - gbear605 5y ago
      Unless the airlines are installing the altimeters themselves, it seems like Boeing is still the relevant company. If your car’s airbag has a malfunction, the car manufacturer does the recall even if the fault lies with the airbag manufacturer. Presumably Boeing would then go on to sue the altimeter manufacturer though.
      - kube-system 5y ago
        Yes, I am simply suggesting the accusations in the first two sentences are misplaced.
      - theYipster 5y ago
        Aviation doesn't work that way. Airlines have direct aftermarket relationships with all of the OEMs making the components on their airplanes. From a certification and warranty standpoint, Boeing is the design authority, and if there is an FAA mandated fix for 737 RAs, Boeing will have a role to play. Whether Boeing is responsible financially or logistically for the fix depends on the nature of the failure (is it limited to the component or is it a systems engineering issue) as well as the contracts Boeing has with their supply chain and their airline customers.
mdasen 5y ago
Yes and no. Many other countries are using C-Band, but often under slightly different conditions. Some countries licensed frequencies that stop significantly farther away from the spectrum used by radio altimeters. Some countries have mandated lower power levels for C-Band. Some countries have created larger exclusion areas around all airports (rather than the smaller, temporary exclusion areas around some airports in the US). Some countries have mandated a downward tilt for C-Band antenna panels (nationwide or in areas around airports) so that the transmissions aren't going go up as much (but a downward tilt also limits the transmission range which is bad for wireless carriers). I think one of the big things in the US is that anything that makes C-Band harder to work with makes it hard for 2 of the 3 wireless carriers to compete. T-Mobile has a lot of 2.5GHz spectrum that it has been using to launch high-speed 5G services. Verizon and AT&T had been waiting for their C-Band spectrum to be usable to launch their high-speed 5G services. In Europe, if all carriers are facing the same restrictions, it's a level playing field. In the US, if Verizon and AT&T face restrictions that T-Mobile doesn't face (for most of its spectrum since it's 2.5GHz and not C-Band), that doesn't offer a level playing field. I think it's also more contentious in the US because we have a much more suburban and rural population. Transmission distance is really important in the US because people expect to get modern services even in low-density areas. Verizon built its business on the idea that you should expect excellent wireless coverage even in places that have virtually no people. I think another part of it is that the FAA is often very cautious and it seems like they didn't coordinate well with the FCC in voicing their concerns early on enough. The FAA does have a web page on C-Band (https://www.faa.gov/5g https://www.faa.gov/5g) which is their official stance on the subject. They cite "Lower power levels, antennas adjusted to reduce potential interference to flights, different placement of antennas relative to airfields , and frequencies with a different proximity to frequencies used by aviation equipment" as reasons why the C-Band situation in the US is different from that in other countries. Is the FAA being too cautious? Maybe. Ultimately, no one wants their business plans disrupted. Airlines don't want to see issues that delay landings. Verizon and AT&T don't want to see things that delay their ability to provide fast 5G service.
jjtheblunt 5y ago
is this a failure of the lobbying system, with Qualcomm funding something in their interest which is contrary to aviation interests? (I mean that i do not know the answer)

Yes. They knew the dangers but the telcos wanted frequency. So the FCC attempted to undermine the aviation industry group that actually knows how radar altimeters work. Blancolirio covers this in several videos, although his take is more nuanced than mine. https://www.youtube.com/watch?v=942KXXmMJdY https://www.youtube.com/watch?v=942KXXmMJdY

atkailash 5y ago
tempnow987 5y ago
Absolutely garbage reporting. The FAA / Boeing have no right to the frequencies in question. Even worse, they were given guard bands the size of their entire allocation which is ridiculous, and it still wasn't enough.
- mulmen 5y ago
  Juan Browne is an ex-military and current commercial pilot. I trust him to explain how radar altimeters work and what they are used for.

Sanzig 5y ago

While this should have been better studied before the spectrum was allocated, it's not really the fault of the FCC. These radar altimeters have very wide front-ends, as as a result are highly susceptible to out-of-band emissions. The radars are allocated from 4.2 to 4.4 GHz, so the bottom edge of the radar altimeter band is 200 MHz above the top end of the 5G band in question (3.98 GHz). The fact that these radar altimeters are susceptible to out-of-band interference that is literally further away in the spectrum than the width of their entire allocation is IMO an engineering failure. Yes, spectrum management (rightfully) tends to err on the side of not forcing the incumbents to make modifications to existing systems. However, better filtering would resolve this issue and it is shocking that the engineers who designed them didn't foresee that other services would eventually be allocated in adjacent bands. Avionics is often NRE dominated, they couldn't have sprung for a cavity filter? Or if that was too expensive, designed more headroom in the LNA before saturation and filtered the out of band signal with a crystal or SAW filter at IF? Rejecting out of band that far away is not rocket science. I don't think it's unreasonable in this case to temporarily suspend the rollout and give the aviation industry a deadline to fix its radars, but it should only be temporary. Any other radio service would be told to take a hike if it keeled over due to out of band interference that far away.

jandrese 5y ago
This seems like Boeing trying to get the government to cover their butt because they did shoddy work on the altimeters. They were allocated spectrum for the equipment and then built a system that monopolized frequencies well outside of the allocated spectrum. I completely agree that Boeing needs to issue a recall order on all affected hardware and provide a fix. This should be painful, it is basically punishment for trying to cut corners on safety equipment.
- kube-system 5y ago
  Does Boeing even make the radio altimeters?
  - jandrese 5y ago
    They certainly certified them on the aircraft. If it means putting pressure on the subcontractor that actually built them or finding a suitable replacement then so be it.
  - gbear605 5y ago
    Unless the airlines are installing the altimeters themselves, it seems like Boeing is still the relevant company. If your car’s airbag has a malfunction, the car manufacturer does the recall even if the fault lies with the airbag manufacturer. Presumably Boeing would then go on to sue the altimeter manufacturer though.
    - kube-system 5y ago
      Yes, I am simply suggesting the accusations in the first two sentences are misplaced.
    - theYipster 5y ago
      Aviation doesn't work that way. Airlines have direct aftermarket relationships with all of the OEMs making the components on their airplanes. From a certification and warranty standpoint, Boeing is the design authority, and if there is an FAA mandated fix for 737 RAs, Boeing will have a role to play. Whether Boeing is responsible financially or logistically for the fix depends on the nature of the failure (is it limited to the component or is it a systems engineering issue) as well as the contracts Boeing has with their supply chain and their airline customers.

mdasen 5y ago

Yes and no. Many other countries are using C-Band, but often under slightly different conditions. Some countries licensed frequencies that stop significantly farther away from the spectrum used by radio altimeters. Some countries have mandated lower power levels for C-Band. Some countries have created larger exclusion areas around all airports (rather than the smaller, temporary exclusion areas around some airports in the US). Some countries have mandated a downward tilt for C-Band antenna panels (nationwide or in areas around airports) so that the transmissions aren't going go up as much (but a downward tilt also limits the transmission range which is bad for wireless carriers). I think one of the big things in the US is that anything that makes C-Band harder to work with makes it hard for 2 of the 3 wireless carriers to compete. T-Mobile has a lot of 2.5GHz spectrum that it has been using to launch high-speed 5G services. Verizon and AT&T had been waiting for their C-Band spectrum to be usable to launch their high-speed 5G services. In Europe, if all carriers are facing the same restrictions, it's a level playing field. In the US, if Verizon and AT&T face restrictions that T-Mobile doesn't face (for most of its spectrum since it's 2.5GHz and not C-Band), that doesn't offer a level playing field. I think it's also more contentious in the US because we have a much more suburban and rural population. Transmission distance is really important in the US because people expect to get modern services even in low-density areas. Verizon built its business on the idea that you should expect excellent wireless coverage even in places that have virtually no people. I think another part of it is that the FAA is often very cautious and it seems like they didn't coordinate well with the FCC in voicing their concerns early on enough. The FAA does have a web page on C-Band (https://www.faa.gov/5g https://www.faa.gov/5g) which is their official stance on the subject. They cite "Lower power levels, antennas adjusted to reduce potential interference to flights, different placement of antennas relative to airfields , and frequencies with a different proximity to frequencies used by aviation equipment" as reasons why the C-Band situation in the US is different from that in other countries. Is the FAA being too cautious? Maybe. Ultimately, no one wants their business plans disrupted. Airlines don't want to see issues that delay landings. Verizon and AT&T don't want to see things that delay their ability to provide fast 5G service.

jjtheblunt 5y ago

is this a failure of the lobbying system, with Qualcomm funding something in their interest which is contrary to aviation interests? (I mean that i do not know the answer)