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FAA ADs re 5G interference

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FAA ADs re 5G interference

Old 18th Jan 2022, 19:30
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Whose Fault?

One could argue, that the government should never have sold this critical band in the first place.

As for the Air / Ground switching, I imagine that the good old WOW switch was thought old fashioned by the software boys.
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Old 18th Jan 2022, 19:45
  #102 (permalink)  
 
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Originally Posted by WillowRun 6-3
U.S. FAA has issed CAN-2022-01-2, "Continued Airworthiness Notification to the International Community" dated Jan. 14, 2022.
Subject is 5G interference as it affects certain functions or operations of 787 aircraft, worldwide.

(Apologies, not accessing FAA link to post here - but it's quite e-z to locate)
Continued Airworthiness Notification to the International Community - Boeing 787 Altimeter and 5G
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Old 18th Jan 2022, 20:26
  #103 (permalink)  
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The Canadian news perspective:

https://www.cbc.ca/news/world/5g-rol...ions-1.6319172
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Old 18th Jan 2022, 20:38
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Rumours Emirates not going to some US ports due this issue?
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Old 18th Jan 2022, 20:45
  #105 (permalink)  
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Latest news:

AT&T and Verizon to limit 5G network rollout near airports after airlines warn of major disruptionsThe wireless companies said Tuesday they would limit the rollout after U.S. carriers complained of the potential for interference with airplane safety technology. The telecom firms have twice delayed the rollout to give aviation safety regulators more time to analyze potential interference with devices on planes that are critical for landing in poor visibility
By Ian Duncan
and
Lori Aratani

Today at 3:16 p.m. ESTWireless companies AT&T and Verizon said Tuesday they would limit the rollout of 5G networks near airports after airlines warned of major disruptions because of the potential for interference with airplane safety technology.Wireless towers in other locations are set to come online Wednesday as scheduled. The telecom firms have twice delayed activating the towers in recent months — which will deliver higher-speed Internet — to give aviation safety regulators more time to analyze potential interference with devices on planes known as radio altimeters. The devices measure how high planes are flying and are critical for landing in poor visibility.
The two wireless carriers issued statements expressing disappointment that the Federal Aviation Administration had not been able to resolve the safety issues.

“At our sole discretion we have voluntarily agreed to temporarily defer turning on a limited number of towers around certain airport runways as we continue to work with the aviation industry and the FAA to provide further information about our 5G deployment, since they have not utilized the two years they’ve had to responsibly plan for this deployment,” AT&T said.

It was not immediately clear whether the steps taken by the two wireless carriers would alleviate the concerns airlines have expressed.
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Old 18th Jan 2022, 21:17
  #106 (permalink)  
 
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Originally Posted by Few Cloudy
One could argue, that the government should never have sold this critical band in the first place.

As for the Air / Ground switching, I imagine that the good old WOW switch was thought old fashioned by the software boys.
You could argue that, but realistically the "government" is big and not monolithic, at least in America. The FCC and FAA belong to different cabinet level departments and are strongly influenced by very different political forces. At the working level they, perhaps, work better together than at the executive level, but cooperation is not great and they have very disparate perspectives of the public interest they presumably serve.

With clear and widespread notification of the public safety risk, the 5G industry has perilous liability waters to swim through. They just cannot say they didn't know. This may have more influence on the outcome than actions taken by the government.
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Old 19th Jan 2022, 00:34
  #107 (permalink)  
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Something one could argue . . . . 'bout the government

GlobalNav's answer strikes me as quite very accurate. The respective "complex" or sometimes, "interagency complex" or just "interagency" surrounding each of these two disparate federal agencies are different in deeply rooted ways. Congressional staffs (primarily Committees) at senior levels, lobbying groups and lobbyists including but not only through the so-called revolving door, law firms and p.r. firms - like, different sub-sub-cultures of the Big Show that is Washington.

Probably everyone has read material from the wireless carriers attacking the supposed delay the aviation sector has caused by not innovating, upgrading, and otherwise facilitating the commercial interests of the wireless industry. Some of those attacks are polished and some just bitter snark, but their points are the same. If only running a national civil aviation sector were that easy, simple or matter-of-fact. .....

Wonder what the aviation professionals here would say to this: ask the wireless commercial interests to make a list of all the principal and second-tier entities and authorities which would have had to sign onto, and implement, a detailed technical plan to upgrade all avionics (and airport configs, to the extent it matters) so that no 5G interference is expected or possible within generally and widely accepted risk tolerances. And it's not too late to make their list, and get on with checkin' it twice . . . The diverse financial resources, Congressional backing or clout, technical fidelity or virtuosity, overall organizational readiness, and no doubt other descriptive factors of these would-be actors in a Big National Upgrade Plan.... they'd be all over the map, no? So to attack the aviation sector by saying 'HEY you shoulda been ready for this!!' is, as this SLF/atty sees it, highly dishonest -- and bad policy, as it significantly, perhaps even fundamentally, misunderstands the NAS and the aviation sector.

If a combination of Scoop Jackson, Wm. Winpisinger, and Melvin Belli suddenly appeared, isn't it obvious this hybrid figure would demand to know, 'are you gonna let the phone company push you around?' I mean, no offense to AT&T and/or Verizon . . . . . well, maybe a little.

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Old 19th Jan 2022, 03:02
  #108 (permalink)  
 
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Could this cause crashes? What mechanisms and procedures are there to prevent crashes if the radar altimeter malfunctions? What's the worst-case scenario?
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Old 19th Jan 2022, 07:27
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Originally Posted by SomeDanceToRemember
Could this cause crashes? What mechanisms and procedures are there to prevent crashes if the radar altimeter malfunctions? What's the worst-case scenario?
Worth a read: TK1951 Accident Report
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Old 19th Jan 2022, 08:12
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A question to the radio engineers among you: If you would need to design a radio altimeter today taking account of the increasing scarcity of radio frequency spectrum - what would be the minimum needed bandwidth including guard bands? I know it is always a trade off between cost, performance and need for spectrum, but looking at the whopping ~600 MHz now used by the radio altimeter service (including guard bands) one would think there would exist more spectrum-efficient solutions?
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Old 19th Jan 2022, 09:40
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Originally Posted by snowfalcon2
A question to the radio engineers among you: If you would need to design a radio altimeter today taking account of the increasing scarcity of radio frequency spectrum - what would be the minimum needed bandwidth including guard bands? I know it is always a trade off between cost, performance and need for spectrum, but looking at the whopping ~600 MHz now used by the radio altimeter service (including guard bands) one would think there would exist more spectrum-efficient solutions?
Briefly,
The band allocated internationally for this purpose is 4.2-4.4 GHz, so 200MHz wide. The adjacent spectrum either side is not officially guard band but allocated by national administractions, again within international regulations, in the knowledge of the radar and other systems.

The actual spectrum requirement of a radar transmission can be calculated from the pulse repetition frequency and pulse risetimes. I suspect that different manufacturers may use their own proprietary parameters. But prima facie the 200 MHz bandwidth seems quite adequate. The problem seems to be that the radar receivers respond to a much wider bandwidth than the 200 MHz, so they are susceptible to strong signals in adjacent frequency bands.

This has not been a problem until now, with 5G cellular being introduced into spectrum below the radar band. How much the receiver bandwidths can be reduced without limiting their performance is a matter for the manufacturers, but a simple modification to existing fitted equipment seems impractical.

There is also the issue of 5G transmissions radiating outside their own band and into the radar band. These are quite tightly controlled and are likely to be less of a problem.

The interference potential from 5G in C band is greater in the US because the allocated band goes up th 3.98 GHz, whereas in some other places including Europe it stops at 3.8 GHz. Also higher transmit powers are proposed

edited to add:
WillowRun 6-3's description of the relationships between the FAA and FCC may well explain the disgraceful lack of prior testing to evaluate potential problems, during the ample time available to carry out the work.
Was this a standoff, with each leaving the other to do something about it? If anyone is now suffering financial loss, they should be looking to see who was responsible.

Last edited by Sallyann1234; 19th Jan 2022 at 10:16.
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Old 19th Jan 2022, 10:49
  #112 (permalink)  
 
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Repurposing of Spectrum is an issue for aviation

Not a pilot but a PNT Technologist now (and ex FAA aircraft dispatcher)

The FCC in the US have made three big decisions recently in terms of opening up spectrum
  • Opening up C-Band frequencies for 5G
  • Ligado Networks allowed to repurpose L-band spectrum
  • Repurposing the 5.9 GHz “safety band”
In a nutshell, decision 1) has caused the RA problems, decision 2) will cause risk to GPS services and decision 3) may put transport (automotive) safety at risk
The spectrum is congested, there is increasing demand for fast broadband access practically everywhere, so perhaps its no surprise that we are losing the safety margins that we had around some of these critical services.

But in making these decisions the FCC are putting the burden of proof firmly onto the parties that oppose the introduction of a new technology, rather than the incumbent (I provided a reference to the presentation on the legalities which was made at the recent PNT Advisory Board meeting by Jeff Shane, IATA Representative & PNTAB Member. It's a comprehensive summary of the decision making process and the flaws in it.

Decision 2) the repurposing of the L-band spectrum is the issue I'm most involved with right now - this also has the potential to cause issues to aviation

Last edited by ex-Dispatcher; 19th Jan 2022 at 10:50. Reason: changed "FC" to "FCC"
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Old 19th Jan 2022, 16:13
  #113 (permalink)  
 
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Originally Posted by Few Cloudy
As for the Air / Ground switching, I imagine that the good old WOW switch was thought old fashioned by the software boys.
Rather ironically given the current issue, WOW (prox sensors) was not considered sufficiently robust with regard to ElectroMagnetic Interference and is typically single thread. LRRA designed and certified as a Critical "DAL A" system and nearly always has redundancy.

When we did the 747-8, we used a combination of WOW and LRRA for critical engine control functions - basically five sources (two WOW, three LRRA) - to indicate "On Ground" for critical functions we required three on-ground indications, with at least one each from WOW and LRRA.
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Old 19th Jan 2022, 17:39
  #114 (permalink)  
 
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Originally Posted by snowfalcon2
A question to the radio engineers among you: If you would need to design a radio altimeter today taking account of the increasing scarcity of radio frequency spectrum - what would be the minimum needed bandwidth including guard bands? I know it is always a trade off between cost, performance and need for spectrum, but looking at the whopping ~600 MHz now used by the radio altimeter service (including guard bands) one would think there would exist more spectrum-efficient solutions?
Itís a long long time since I was in practice in another life, but with just what I remember, I would posit hardly any. The aggressive way modern comms cram as many bits as possible into each Hz of bandwidth, means that it looks effectively like a broad swathe of noise; completely different to a radio altimeter which is just trying to determine time of flight of a reflected pulse, and there are multiple ways to make this more robust. They are affected by doppler effects but not that much, given aircraft vertical speeds compared with c. Iím sure there are technical edge cases where one could interfere with the other but from a (now) lay point-of-view, it just doesnít feel that likely.

Filter technology, both analog and digital, is pretty advanced these days, and out-of-band rejection a foregone conclusion. I can only think that old designs of RAs are really, really bad if they are susceptible to something hundreds of MHz away; certainly the 5G transmitters wonít be leaking onto the RA band. I havenít heard of anyone actually being able to generate false RA readings with 5G signals, so it seems to be conjecture at the moment...
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Old 19th Jan 2022, 18:12
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Imagine the litigation nightmare if Radar Altimeter interference due to 5G is even suspected in an aviation incident or accident.
FAA, FCC, 5G providers, airlines, manufacturers, airport authorities and anyone else down to the janitor will be sued. The list will be endless. Lawyers , high end car dealers, yacht brokers and real estate agents in Florida and the Caribbean will be most pleased.
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Old 19th Jan 2022, 21:22
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But with 5G access, they could report any accidents very quickly!

(Apologies in advance for tasteless joke.)
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Old 20th Jan 2022, 00:29
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Hm.... yes, the 747-8 has many of everything. It even has a system that protects against tailstrikes and looks a bit like the 737-Max system that didnīt work right at first. I wonder how the 3 LRRA cope with the 5G stuff...?

Originally Posted by tdracer
Rather ironically given the current issue, WOW (prox sensors) was not considered sufficiently robust with regard to ElectroMagnetic Interference and is typically single thread. LRRA designed and certified as a Critical "DAL A" system and nearly always has redundancy.

When we did the 747-8, we used a combination of WOW and LRRA for critical engine control functions - basically five sources (two WOW, three LRRA) - to indicate "On Ground" for critical functions we required three on-ground indications, with at least one each from WOW and LRRA.
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Old 20th Jan 2022, 01:23
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There are two types of aircraft “Radio Altimeters. I will not go into the technical details for each type.
The most common uses FMCW to determine altitude simplistically by measuring the frequency shift of the received signal from that of the transmitted signal.
less common are pulsed , should be called “Radar Altimeters” as they use pulse techniques, i.e. the altitude is determined by the time taken for the transmitted pulse to be received, different technique from FMCW but less liable to interference, but tend to cost more.
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Old 20th Jan 2022, 04:13
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Originally Posted by DaveReidUK
As a dutch pilot, I have read it more then once. If the RA had not malfunctioned, the crash would not have happened. If boeing had explained in their manual better what a RA failure could do to the ATHR, the crash might not have happened. If the pilots had realized that the numerous gear warning were related to an RA failure, the crash might not have happened. If the pilots had looked at the airspeed in the 30 seconds before the crash, it should not have happened. If they had responded correctly to the stall warning the crash would not have happened.

But I think that is different from the current discussion. Apparently, on the 787 the RA is even further integrated into the system, to the point that spoilers, reversers and autobrakes are affected, because the RA is part of the WOW, would not be surprised if the same applies to the MAX. Nothing from Airbus yet, but they aren't necessarily better about keeping the crew in the loop. I am really happy I don't fly raw data NDB approaches without EGPWS anymore, but the amount of automation autonomy the current aircraft have sometimes scares me.

Edit: just got a memo that on our A320 we can’t use the MEL for LGCIU2 “out of abundance of caution” for unknown risk related to 5G.

Last edited by hans brinker; 21st Jan 2022 at 00:52. Reason: Added
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Old 20th Jan 2022, 14:28
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Nothing from Airbus yet, but they aren't necessarily better about keeping the crew in the loop.
The Airbus RA1+2 ECAM is a beast. Definitely "keeps you in the loop" and things get even more exciting when the gear goes down. This fault is practiced in the sim quite often. The implications of this failure are well known to anyone flying the Airbus. And because an Airbus's thrust levers do not move by themselves and because power reduction has to be accomplished manually (except in an Autoland situation) you are not going to be susceptible to the kinds of issues a Boeing is. Airbus automation is superior in functionality and safety compared to a Boeing (I've flown both).
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