9 ms·

FAA Shows ‘Sample NOTAMs’ for Possible 5G Restrictions

61 points by Stevvo 5y ago

sandworm101 5y ago
>> There are concerns that 5G signals, which use 3700-3998 MHz, can overpower radar altimeter signals, which operate in the 4200-4400 MHz band. RADALTs are tricky things. They are finicky. Sometimes they get good reflections and sometimes they are confused by irregular terrain, particularly over urban areas. Imho 5G would, at most, cause radalt blackout/failure (ie no displayed altitude) rather than the far more dangerous false readings. And any interference should be intermittent. Unless you are hovering over a cell tower the strength of the 5g signal should rise and fall pretty quickly as the aircraft moves between cells.
- p_l 5y ago
  That's why the areas most considered problematic are use of radar altimeter in terminal approach stages and automatic landing combined with high C-band 5G transmitters close to airport.
yellow_postit 5y ago
Is there a path to disprove the potential for interference here? This seems like an nearly impossible “prove a negative” task that likely becomes so common people ignore it as noise which seems counterproductive. Side note: NOTAM is a notice to pilots [1] the article doesn’t expand on. [1]: https://en.m.wikipedia.org/wiki/NOTAM https://en.m.wikipedia.org/wiki/NOTAM
- bdonlan 5y ago
  Presumably once this is broadly deployed, flight checks can be performed to check for interference.
- btmiller 5y ago
  Really get annoyed when publications introduce an acronym yet never define it. That’s 101 of writing. Thanks for doing their work for them :)
trebligdivad 5y ago
What's different in the US from the rest of the world that's been running 5G for a while?
- thetinguy 5y ago
  5g has been running for a couple of years in the US. The FAA’s problem is new spectrum that carriers want to deploy.
  - huslage 5y ago
    They have deployed it, it's just not turned on yet.
- londons_explore 5y ago
  Different countries use different frequency bands for both 5G and radar alitmeters. The FAA's concern here is that the bands will be neighbouring in the USA, which means if either the 5G equipment accidentally transmits a bit of signal outside its allocated band, or the altimeters accidentally interpret out-of-band signals they ought to ignore, then problems could happen. Since radar altimeters are pretty old tech, and very analogue, their concern isn't totally unwarranted.
  - trebligdivad 5y ago
    Thanks; so then the question is hth did the US manage to do this 5G allocation without thinking about the consequence?
    - bdamm 5y ago
      FAA is actually quite good at ignoring theoretical non-problems. This is a sample notam for what the anti-interference alert will look like.
    - NavinF 5y ago
      The bands seem to be 200mhz apart, which is a massive gap. If it was my decision, I wouldn’t think of any consequences. I still think this will only affect the crappiest of hardware with the crappiest of filters.
tyingq 5y ago
A document from pilot unions that expands a bit on the issue: https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/FSMP-WG11-IP08_ICAO%20Flight%20Operations%20Panel%20and%20IATA%20%20IFALPA%205G%20problem%20statement.pdf https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/...
- NelsonMinar 5y ago
  That has helpful technical info on the technical problem. Radar altimeters work in 4.2-4.4GHz. Some 5G systems use 3.7-3.98GHz. The document describes mostly theoretical problems; the only actual example they site was part of a deliberate radar jamming military test.
  - RF_Savage 5y ago
    Yep. There has been a lot of talk about intererence. But no measurements or proof of any real world harm has not been presented. It has been going for years.
gormandizer 5y ago
In my opinion this is required reading: https://wetmachine.com/tales-of-the-sausage-factory/what-the-eff-faa-my-insanely-long-field-guide-to-the-faa-fcc-5g-c-band-fight/ https://wetmachine.com/tales-of-the-sausage-factory/what-the...
akkawwakka 5y ago
I recommend checking out Juan Browne’s video [1] that contrasts studies from the aviation world and one from the telecoms. Spoiler: the former brings more technical analysis than the latter. I’d love to know why the FAA is ‘rolling over’ to the telecoms / FCC on this matter. The spectrum was in use for RADALTs before 5G and safety systems like autoland, used when visibility starts coming down to minimums, rely on them. Seems to me that, like Canada, the US should just not allow 5G cell sites near critical areas around an airport. [1]: https://youtu.be/942KXXmMJdY https://youtu.be/942KXXmMJdY
- oliveshell 5y ago
  I’ll second that recommendation. For any who don’t know him, Juan Browne’s videos are the best resource I’ve found for sober, no-bullshit reporting and analysis on everything related to aviation. Juan (a.k.a. Blancolirio on YouTube) is an airline pilot and former military aviator who doesn’t sensationalize and really knows his stuff.
  - MertsA 5y ago
    Not to mention all his videos on the Oroville dam spillway failure and reconstruction process. Top notch reporting on the subject from an individual.
- tssva 5y ago
  The spectrum in question was never allocated for use by RADALTs. Prior to being allocated for 5G use it was used for C-band satellite transmission. If there is an issue of interference with RADALTs the real question should be why did the FAA allow deployment of RADALTs in aircraft which could not operate in their allocated frequency band without risk of dangerous interference from already assigned frequencies. The second question should be what is the FAA, aircraft and airline industry going to do to quickly correct the issue they created.
- mdasen 5y ago
  I think there's a lot of pressure to get the spectrum in the hands of wireless carriers. They spent nearly $100B on that spectrum and Verizon and AT&T are anxious to put it into play. T-Mobile already has mid-band spectrum for 5G at 2.5GHz and they're seeing customers on their mid-band spectrum get speeds of around 300Mbps. As their mid-band coverage expands, Verizon and AT&T won't want to be left behind. Likewise, the administration would like for the US to be seen as a 5G leader. We see articles with headlines like "US carriers advertise 5G, but their speeds lag other countries." A huge part of that is that Verizon and AT&T haven't been able to deploy new spectrum. I don't know enough about how far around airports they'd want to block C-Band from being used, but in a city like San Diego, it would probably block off a decent amount of the city given where its airport is. In a place like New York, how far would you want to block off? Clearly not all of bravo airspace, but how much is needed (maybe you know how much Canada had to block off)? I'm not sure that the FAA is rolling over. In some ways, saying "we're going to make air-travel suffer huge problems if they start activating C-Band spectrum" is saying "if you activate C-Band spectrum, Congress is going to start having hearings as to why the government is letting wireless carriers prevent people from traveling." I think the FAA is noting exactly how bad the situation might be if they go forward with C-Band plans. I think it's also a situation where people might be unsure who has authority. Can the FAA ban wireless signals that the FCC says are ok? Can one government agency take another to court despite being part of the same administration? At some point the administration controls both and might need to make a decision. But I think there's a lot of pressure to let C-Band go forward. Wireless carriers are looking to 10x their wireless networks and it seems likely that wireless home internet will become a big way that more rural areas get high-speed internet (even C-Band signals can get decent range with good antennas and using low-frequency spectrum for uploads).
aDfbrtVt 5y ago
How could the 200MHz spacing between the frequency allocations be insufficient? I can't imagine the oscillators in either system are specified for deviations as high as +-100MHz over their lifetime.
- xxpor 5y ago
  You're right: they're perfectly fine. This whole thing is FUD from someone... just not sure who yet. My understanding is this band has been used for Europe for a few years already.
  - p_l 5y ago
    With effectively 400 MHz guard band, though.
  - onphonenow 5y ago
    Yeah, and all this drama vs actually you know, testing things in the 10 years they've had is rediculous by the FAA. Seriously, just test it. You have thousands of flights a day. On a day with visual flight rules put a transmitter at 4.0ghz, max power, worst case radiation pattern and land a 737, 787, A320 and A321 etc as a test. There is something going on here that we don't know about.
- jdiez17 5y ago
  I was also curious about this, so I looked at the Airworthiness Directive[1] referenced in the example NOTAM. Basically, the argument is that the radio altimeter receivers "must detect faint signals reflected off the ground to measure altitude" and [C-band 5G signals] "could significantly degrade RA functions [...] if the altimeter is unable to sufficiently reject those signals". So it seems it is basically a question of how wide is the RF input filter bandwidth of RAs on commercial aircraft. [1] https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/625b2b44ac41e39a862587a600628feb/$FILE/2021-23-12.pdf https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf...
  - p_l 5y ago
AnthonyMouse 5y ago
Can somebody explain what 5G is actually good for? With 4G you get fast enough coverage at long distances for basically everything. Maps for sure, but even streaming video as long as not everyone on the tower is trying to do it at once. With 5G you get more bandwidth, but you're not going to get it in the middle of the woods because it also requires more towers closer together. So it's for high population density areas. But those areas are the places where it's extremely cost effective to install fiber, and cellular will never ever be as fast as fiber, and installing a million towers everywhere is just about as expensive. If 4G is about all you're going to get in the middle of the woods and fiber (with the last hundred meters over Wi-Fi for mobiles) is the thing you actually want in the city, why is anybody even wasting money installing 5G towers anywhere?
- mhh__ 5y ago
  5G covers what 4G does as well IIRC. The really high frequency stuff is only what makes the news. Also the advantage of 5G as far as I'm concerned is being able to connect things (possibly in a mesh?) At very high throughput without cables. If you have an oscilloscope and a signal generator, you should be able to synthesize a (say) network analyzer out of the two of them by linking them via 5G.
  - AnthonyMouse 5y ago
    > 5G covers what 4G does as well IIRC. The really high frequency stuff is only what makes the news. Right, right, the really high frequency stuff is what we're talking about. It's confusing that they stick so many things under the same label. The parts of "5G" that are just 4G with better radios and algorithms are useful but also not so contentious. But for that you wouldn't need more towers at closer intervals. > Also the advantage of 5G as far as I'm concerned is being able to connect things (possibly in a mesh?) And now we're talking about a third thing. It could actually be quite useful to open up more unlicensed spectrum for things like this -- if nothing else so we could get better Wi-Fi to hook up to the fiber. But that's a different thing than having Verizon install a cellular tower on the end of every street corner for high frequency cellular 5G and then not having them come the rest of the way with the fiber into your house, which still seems like some kind of a bad joke.
Rebelgecko 5y ago
Is this a legado (neé lightsquared) issue, or a whole nother problem?
- RF_Savage 5y ago
  This is different from the Lightsquared L-band LTE proposal. This is about the C-band 3.5GHz 5G spectrum.
- upofadown 5y ago
  It is similar in that both situations resulted from the reallocation of a satellite downlink band to terrestrial use. Suddenly the the band that only had transmitters in space barely detectable on the ground has actual transmitters on the ground. It's like having noisy people move in next door when the previous occupants were very quiet.
kylehotchkiss 5y ago
Will 5g also affect radar-based cruise control in cars?
varelse 5y ago
So 5G may end up protecting us from chemtrails? What's a conspiracy nut to do?
JCM9 5y ago
Layman’s explanation: When modern planes land in bad weather, especially fog, the height off the ground is determined by bouncing radio waves off the ground. Essentially radar pointing down off the bottom of the plane. This provides added safety over the normal altimeter measurement using air pressure. 5G frequencies are too close to the frequencies used for this radar and so the theory is that this will cause dangerous interference that could cause issues during a critical phase of landing. Without these systems aircraft would not be able to use certain instrument approaches and thus couldn’t land during certain weather conditions when they can today. If the FAA pulls the plug on these it would cause big headaches during times when today planes can land without issue. tldr 5G might stop you from getting to your destination on time or at all on a future flight.
- sokoloff 5y ago
  That explanation is correct but somewhat incomplete. Precision approaches with low minimums (the decision point where a missed approach must be initiated) also have an alternate source of vertical guidance (in the typical case of an ILS, it’s a radio beam bounced off the ground and up along the approach path and the pilot has a very tight indication of whether they’re below, on, or above that beam). The radio altimeter is a secondary or tertiary source of height above terrain information, not a primary. Without a functioning radio altimeter, some aircraft on approach to some runways would have to use higher minimums than would be available if they have a functioning unit. This will contribute to some missed approaches or diversions in low weather. (Where a missed approach almost never ends in a crash in airline operations but rather a second attempt or a diversion.)
darksaints 5y ago
Since there's a lot of FUD going on here, I'm hoping I can clarify. This has nothing to do with 5g specifically, but rather a handful of channels in a specific band (of many possible 5g bands) that was newly auctioned. And the problem isn't technical, but rather political. This problem has been solved using existing techniques and regulations and tools in various countries. The political problem was that the FCC auctioned off the spectrum under the assumption that only half the licenses (the lower frequencies in the band), would have restrictions, and they would be lifted after a 3-year clearing period for satellite base stations to move to different bands. Now the FCC has realized that Landing instrument interference is going to be a problem, so they have to draft new regulatory restrictions. But this regulatory change is going to affect the market value of these licenses, and so the FCC is basically both preparing the new regulations (they are being modeled after similar regulations in Canada), as well as preparing to be sued by Verizon, and potentially AT&T, to try to recover some of the money they spent in the auction. The regulations are coming, but due to the politics and legal challenges, they're taking longer than expected. So the FAA is publishing their drafts as a PR strategy to force the FCC to hurry up and finalize the regulations. And it's working... I work in spectrum interference regulatory compliance, and we've been preparing for months for this rollout. Our software is already basically ready to deploy our compliance mechanisms within a days notice. All we need to do is a little bit of geospatial data entry on exclusion zones where transmission is not allowed. So we know that this nightmare scenario isn't gonna actually happen, but the threats have to happen in order to get the FCC to hurry the fuck up and finalize the regulations.

61 points by Stevvo 5y ago

>> There are concerns that 5G signals, which use 3700-3998 MHz, can overpower radar altimeter signals, which operate in the 4200-4400 MHz band. RADALTs are tricky things. They are finicky. Sometimes they get good reflections and sometimes they are confused by irregular terrain, particularly over urban areas. Imho 5G would, at most, cause radalt blackout/failure (ie no displayed altitude) rather than the far more dangerous false readings. And any interference should be intermittent. Unless you are hovering over a cell tower the strength of the 5g signal should rise and fall pretty quickly as the aircraft moves between cells.

p_l 5y ago
That's why the areas most considered problematic are use of radar altimeter in terminal approach stages and automatic landing combined with high C-band 5G transmitters close to airport.

yellow_postit 5y ago

Is there a path to disprove the potential for interference here? This seems like an nearly impossible “prove a negative” task that likely becomes so common people ignore it as noise which seems counterproductive. Side note: NOTAM is a notice to pilots [1] the article doesn’t expand on. [1]: https://en.m.wikipedia.org/wiki/NOTAM https://en.m.wikipedia.org/wiki/NOTAM

bdonlan 5y ago
Presumably once this is broadly deployed, flight checks can be performed to check for interference.
btmiller 5y ago
Really get annoyed when publications introduce an acronym yet never define it. That’s 101 of writing. Thanks for doing their work for them :)

trebligdivad 5y ago

What's different in the US from the rest of the world that's been running 5G for a while?

thetinguy 5y ago
5g has been running for a couple of years in the US. The FAA’s problem is new spectrum that carriers want to deploy.
- huslage 5y ago
  They have deployed it, it's just not turned on yet.
londons_explore 5y ago
Different countries use different frequency bands for both 5G and radar alitmeters. The FAA's concern here is that the bands will be neighbouring in the USA, which means if either the 5G equipment accidentally transmits a bit of signal outside its allocated band, or the altimeters accidentally interpret out-of-band signals they ought to ignore, then problems could happen. Since radar altimeters are pretty old tech, and very analogue, their concern isn't totally unwarranted.
- trebligdivad 5y ago
  Thanks; so then the question is hth did the US manage to do this 5G allocation without thinking about the consequence?
  - bdamm 5y ago
    FAA is actually quite good at ignoring theoretical non-problems. This is a sample notam for what the anti-interference alert will look like.
  - NavinF 5y ago
    The bands seem to be 200mhz apart, which is a massive gap. If it was my decision, I wouldn’t think of any consequences. I still think this will only affect the crappiest of hardware with the crappiest of filters.

tyingq 5y ago

A document from pilot unions that expands a bit on the issue: https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/FSMP-WG11-IP08_ICAO%20Flight%20Operations%20Panel%20and%20IATA%20%20IFALPA%205G%20problem%20statement.pdf https://www.icao.int/safety/FSMP/MeetingDocs/FSMP%20WG11/IP/...

NelsonMinar 5y ago
That has helpful technical info on the technical problem. Radar altimeters work in 4.2-4.4GHz. Some 5G systems use 3.7-3.98GHz. The document describes mostly theoretical problems; the only actual example they site was part of a deliberate radar jamming military test.
- RF_Savage 5y ago
  Yep. There has been a lot of talk about intererence. But no measurements or proof of any real world harm has not been presented. It has been going for years.

gormandizer 5y ago

In my opinion this is required reading: https://wetmachine.com/tales-of-the-sausage-factory/what-the-eff-faa-my-insanely-long-field-guide-to-the-faa-fcc-5g-c-band-fight/ https://wetmachine.com/tales-of-the-sausage-factory/what-the...

akkawwakka 5y ago

I recommend checking out Juan Browne’s video [1] that contrasts studies from the aviation world and one from the telecoms. Spoiler: the former brings more technical analysis than the latter. I’d love to know why the FAA is ‘rolling over’ to the telecoms / FCC on this matter. The spectrum was in use for RADALTs before 5G and safety systems like autoland, used when visibility starts coming down to minimums, rely on them. Seems to me that, like Canada, the US should just not allow 5G cell sites near critical areas around an airport. [1]: https://youtu.be/942KXXmMJdY https://youtu.be/942KXXmMJdY

oliveshell 5y ago
I’ll second that recommendation. For any who don’t know him, Juan Browne’s videos are the best resource I’ve found for sober, no-bullshit reporting and analysis on everything related to aviation. Juan (a.k.a. Blancolirio on YouTube) is an airline pilot and former military aviator who doesn’t sensationalize and really knows his stuff.
- MertsA 5y ago
  Not to mention all his videos on the Oroville dam spillway failure and reconstruction process. Top notch reporting on the subject from an individual.
tssva 5y ago
The spectrum in question was never allocated for use by RADALTs. Prior to being allocated for 5G use it was used for C-band satellite transmission. If there is an issue of interference with RADALTs the real question should be why did the FAA allow deployment of RADALTs in aircraft which could not operate in their allocated frequency band without risk of dangerous interference from already assigned frequencies. The second question should be what is the FAA, aircraft and airline industry going to do to quickly correct the issue they created.
mdasen 5y ago
I think there's a lot of pressure to get the spectrum in the hands of wireless carriers. They spent nearly $100B on that spectrum and Verizon and AT&T are anxious to put it into play. T-Mobile already has mid-band spectrum for 5G at 2.5GHz and they're seeing customers on their mid-band spectrum get speeds of around 300Mbps. As their mid-band coverage expands, Verizon and AT&T won't want to be left behind. Likewise, the administration would like for the US to be seen as a 5G leader. We see articles with headlines like "US carriers advertise 5G, but their speeds lag other countries." A huge part of that is that Verizon and AT&T haven't been able to deploy new spectrum. I don't know enough about how far around airports they'd want to block C-Band from being used, but in a city like San Diego, it would probably block off a decent amount of the city given where its airport is. In a place like New York, how far would you want to block off? Clearly not all of bravo airspace, but how much is needed (maybe you know how much Canada had to block off)? I'm not sure that the FAA is rolling over. In some ways, saying "we're going to make air-travel suffer huge problems if they start activating C-Band spectrum" is saying "if you activate C-Band spectrum, Congress is going to start having hearings as to why the government is letting wireless carriers prevent people from traveling." I think the FAA is noting exactly how bad the situation might be if they go forward with C-Band plans. I think it's also a situation where people might be unsure who has authority. Can the FAA ban wireless signals that the FCC says are ok? Can one government agency take another to court despite being part of the same administration? At some point the administration controls both and might need to make a decision. But I think there's a lot of pressure to let C-Band go forward. Wireless carriers are looking to 10x their wireless networks and it seems likely that wireless home internet will become a big way that more rural areas get high-speed internet (even C-Band signals can get decent range with good antennas and using low-frequency spectrum for uploads).

aDfbrtVt 5y ago

How could the 200MHz spacing between the frequency allocations be insufficient? I can't imagine the oscillators in either system are specified for deviations as high as +-100MHz over their lifetime.

xxpor 5y ago
You're right: they're perfectly fine. This whole thing is FUD from someone... just not sure who yet. My understanding is this band has been used for Europe for a few years already.
- p_l 5y ago
  With effectively 400 MHz guard band, though.
- onphonenow 5y ago
  Yeah, and all this drama vs actually you know, testing things in the 10 years they've had is rediculous by the FAA. Seriously, just test it. You have thousands of flights a day. On a day with visual flight rules put a transmitter at 4.0ghz, max power, worst case radiation pattern and land a 737, 787, A320 and A321 etc as a test. There is something going on here that we don't know about.
jdiez17 5y ago
I was also curious about this, so I looked at the Airworthiness Directive[1] referenced in the example NOTAM. Basically, the argument is that the radio altimeter receivers "must detect faint signals reflected off the ground to measure altitude" and [C-band 5G signals] "could significantly degrade RA functions [...] if the altimeter is unable to sufficiently reject those signals". So it seems it is basically a question of how wide is the RF input filter bandwidth of RAs on commercial aircraft. [1] https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/625b2b44ac41e39a862587a600628feb/$FILE/2021-23-12.pdf https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf...
- p_l 5y ago

AnthonyMouse 5y ago

Can somebody explain what 5G is actually good for? With 4G you get fast enough coverage at long distances for basically everything. Maps for sure, but even streaming video as long as not everyone on the tower is trying to do it at once. With 5G you get more bandwidth, but you're not going to get it in the middle of the woods because it also requires more towers closer together. So it's for high population density areas. But those areas are the places where it's extremely cost effective to install fiber, and cellular will never ever be as fast as fiber, and installing a million towers everywhere is just about as expensive. If 4G is about all you're going to get in the middle of the woods and fiber (with the last hundred meters over Wi-Fi for mobiles) is the thing you actually want in the city, why is anybody even wasting money installing 5G towers anywhere?

mhh__ 5y ago
5G covers what 4G does as well IIRC. The really high frequency stuff is only what makes the news. Also the advantage of 5G as far as I'm concerned is being able to connect things (possibly in a mesh?) At very high throughput without cables. If you have an oscilloscope and a signal generator, you should be able to synthesize a (say) network analyzer out of the two of them by linking them via 5G.
- AnthonyMouse 5y ago
  > 5G covers what 4G does as well IIRC. The really high frequency stuff is only what makes the news. Right, right, the really high frequency stuff is what we're talking about. It's confusing that they stick so many things under the same label. The parts of "5G" that are just 4G with better radios and algorithms are useful but also not so contentious. But for that you wouldn't need more towers at closer intervals. > Also the advantage of 5G as far as I'm concerned is being able to connect things (possibly in a mesh?) And now we're talking about a third thing. It could actually be quite useful to open up more unlicensed spectrum for things like this -- if nothing else so we could get better Wi-Fi to hook up to the fiber. But that's a different thing than having Verizon install a cellular tower on the end of every street corner for high frequency cellular 5G and then not having them come the rest of the way with the fiber into your house, which still seems like some kind of a bad joke.

Rebelgecko 5y ago

Is this a legado (neé lightsquared) issue, or a whole nother problem?

RF_Savage 5y ago
This is different from the Lightsquared L-band LTE proposal. This is about the C-band 3.5GHz 5G spectrum.
upofadown 5y ago
It is similar in that both situations resulted from the reallocation of a satellite downlink band to terrestrial use. Suddenly the the band that only had transmitters in space barely detectable on the ground has actual transmitters on the ground. It's like having noisy people move in next door when the previous occupants were very quiet.

kylehotchkiss 5y ago

Will 5g also affect radar-based cruise control in cars?

varelse 5y ago

So 5G may end up protecting us from chemtrails? What's a conspiracy nut to do?

JCM9 5y ago

Layman’s explanation: When modern planes land in bad weather, especially fog, the height off the ground is determined by bouncing radio waves off the ground. Essentially radar pointing down off the bottom of the plane. This provides added safety over the normal altimeter measurement using air pressure. 5G frequencies are too close to the frequencies used for this radar and so the theory is that this will cause dangerous interference that could cause issues during a critical phase of landing. Without these systems aircraft would not be able to use certain instrument approaches and thus couldn’t land during certain weather conditions when they can today. If the FAA pulls the plug on these it would cause big headaches during times when today planes can land without issue. tldr 5G might stop you from getting to your destination on time or at all on a future flight.

sokoloff 5y ago
That explanation is correct but somewhat incomplete. Precision approaches with low minimums (the decision point where a missed approach must be initiated) also have an alternate source of vertical guidance (in the typical case of an ILS, it’s a radio beam bounced off the ground and up along the approach path and the pilot has a very tight indication of whether they’re below, on, or above that beam). The radio altimeter is a secondary or tertiary source of height above terrain information, not a primary. Without a functioning radio altimeter, some aircraft on approach to some runways would have to use higher minimums than would be available if they have a functioning unit. This will contribute to some missed approaches or diversions in low weather. (Where a missed approach almost never ends in a crash in airline operations but rather a second attempt or a diversion.)

darksaints 5y ago

Since there's a lot of FUD going on here, I'm hoping I can clarify. This has nothing to do with 5g specifically, but rather a handful of channels in a specific band (of many possible 5g bands) that was newly auctioned. And the problem isn't technical, but rather political. This problem has been solved using existing techniques and regulations and tools in various countries. The political problem was that the FCC auctioned off the spectrum under the assumption that only half the licenses (the lower frequencies in the band), would have restrictions, and they would be lifted after a 3-year clearing period for satellite base stations to move to different bands. Now the FCC has realized that Landing instrument interference is going to be a problem, so they have to draft new regulatory restrictions. But this regulatory change is going to affect the market value of these licenses, and so the FCC is basically both preparing the new regulations (they are being modeled after similar regulations in Canada), as well as preparing to be sued by Verizon, and potentially AT&T, to try to recover some of the money they spent in the auction. The regulations are coming, but due to the politics and legal challenges, they're taking longer than expected. So the FAA is publishing their drafts as a PR strategy to force the FCC to hurry up and finalize the regulations. And it's working... I work in spectrum interference regulatory compliance, and we've been preparing for months for this rollout. Our software is already basically ready to deploy our compliance mechanisms within a days notice. All we need to do is a little bit of geospatial data entry on exclusion zones where transmission is not allowed. So we know that this nightmare scenario isn't gonna actually happen, but the threats have to happen in order to get the FCC to hurry the fuck up and finalize the regulations.