5G ADs

Hmm - speaking from a ham operator point of view - wondering if the radar altimeters could be retrofitted with a filter, to stop the lower frequency cell signals from the receiver. 220 MHz difference is significant. Presumably, the radar alt. systems were built as cheaply as possible, and did not bother with much selectivity on the receiver front-end - because it never used to matter. That was then! (Somewhat like the old issue with hams on 6 meters & channel 2 TV.)
 
40YearDream said:
Presumably, the radar alt. systems were built as cheaply as possible, and did not bother with much selectivity on the receiver front-end
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FYI: Most of the RAs that are affected by the ADs meet a TSO spec. and are required to be installed. But as to "blocking" the 5G its my understanding that is not possible given how the RA works by transmitting a signal then correcting/timing the signals return to the receiving antenna. I believe the whole issue is the 5G may block/delay/alter the RA signal at the receiving side.
 
I was on an easyJet flight from Nice to Paris and the FAs had us turn off our cell phones because of low weather. Not sure if wx was below CATI mins or not.
 
40YearDream said:
Hmm - speaking from a ham operator point of view - wondering if the radar altimeters could be retrofitted with a filter, to stop the lower frequency cell signals from the receiver. 220 MHz difference is significant.
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Bell206 said:
FYI: Most of the RAs that are affected by the ADs meet a TSO spec.
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220MHz is HUGE. As you infer, there's no excuse for a new design to suffer interference from a signal that far away in frequency space. But those signals were not there when these RAs were designed. Filtering probably won't address the entire issue - it would depend on the radar altimeter's vulnerability to leakage/interference/EMI after the antenna/filter stage. I haven't read the TSO, but my guess is it wasn't written with many strong, physically close transmitters in mind, but rather with distant sources (where filtering, which is probably already built in, addresses the problem). This'll be a mess for some folks.
 
TonyG said:
I haven't read the TSO, but my guess is it wasn't written with many strong, physically close transmitters in mind, but rather with distant sources (where filtering, which is probably already built in, addresses the problem).
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Here's a presentation from the RTCA that gives some background on the issue. Its mostly Greek to me but it may have some of your answers.
https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf
TonyG said:
This'll be a mess for some folks.
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Especially on the helicopter side which required there own AD on the matter. For some it will shut them down or require a rewrite of Part 135 regs.
 
Bell206 said:
Here's a presentation from the RTCA that gives some background on the issue. Its mostly Greek to me but it may have some of your answers.
https://www.rtca.org/wp-content/uploads/2020/12/Slides-5G-Interference-Risk-to-Radar-Altimeters.pdf
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Thanks, good info there. From just skimming it, the original specs laid out in the TSO didn't call for rejection of strong signals within 10% of the frequency band of the radar altimeters, which is right where folks want to put some 5G. Filters could help, but you'd be messing with already-TSO'd-equipment, which may be a non-starter. "Mess" may not be a strong enough word.
 
Why isn't the rest of the world, some of it farther along in its 5G rollout than the USA, having the problems the FAA is concerned about? I'm not hearing of planes slamming into the runway or dropping to the runway or flying into hills/mountains due to radio altimeter interference.
 
Domenick said:
Why isn't the rest of the world, some of it farther along in its 5G rollout than the USA, having the problems the FAA is concerned about?
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The EASA and others have been discussing this for some time. However, the EU does not have the flights destiny or fleet size of the US so the EU aviation component does not have the same stroke without the US taking action. And its not just the FAA but a number of other entities as well. With the issuance of these ADs there was a move in the EASA this week to bring this same topic to the EU admin level. And given how ICAO and the associated international agreements work this topic will become more visible globally. Regardless, there wasn't much that could be done until the 5G ready to go here which gives the rest of the aviation community more clout.
 
Domenick said:
Why isn't the rest of the world, some of it farther along in its 5G rollout than the USA, having the problems the FAA is concerned about? I'm not hearing of planes slamming into the runway or dropping to the runway or flying into hills/mountains due to radio altimeter interference.
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Many of those countries have been more proactive, and have restricted setting up 5G cell towers in the vicinity of large airports. The US FCC has not issued a similar limitation.

- Martin
 
This AD doesn't put a big load on pilots. (1) Post change to "Limitations section" of your RFM/AFM. Big deal. A routine Sunday afternoon task. Sure, you need to read it too. (2) Determine how it affects you or if it even does. (3) Change your procedures if or how it affects you. (4) Get a refill on your coffee.

Once upon a time, I began a check out in a type that had a cargo door aft of the cockpit. An AD sign off was required if that door was ever opened & then shut. I quick scanned the logs and found no compliance, ever, for that AD. Bitchin' that AD was like tilting at windmills.
 
Maxnr said:
This AD doesn't put a big load on pilots. (1) Post change to "Limitations section" of your RFM/AFM. Big deal. A routine Sunday afternoon task. Sure, you need to read it too. (2) Determine how it affects you or if it even does. (3) Change your procedures if or how it affects you. (4) Get a refill on your coffee.

Once upon a time, I began a check out in a type that had a cargo door aft of the cockpit. An AD sign off was required if that door was ever opened & then shut. I quick scanned the logs and found no compliance, ever, for that AD. Bitchin' that AD was like tilting at windmills.
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Yup…Just like bitchin’ about not being able to use GPS, not being able to use GPWS has no impact on safety.
 
Had an interesting chat with an Airbus pilot/check airman last evening. He's been working this issue for his carrier. There were some interesting tidbits like: 1) FCC won't even tell FAA/airlines where the 5G antennas are so they can assess risk, 2) If both RA's on the Airbus he flies (not sure which model) fail, it immediately goes into direct law which disables all envelope protection and makes all the related stuff (spoilers, thrust reversers, flare notification, etc.) manual. And given the nature of the 5G interference, this is most likely on takeoff or short final. His carrier had a dual RA failure in 2010 shortly before landing. Long story went with this but short version: it was fortunately a long runway and in included a tail strike before they got it down and tamed. This was largely due to a whole bunch of errors spewing and all the automation they were used to dropping out at a very inopportune time.
 
Maxnr said:
This AD doesn't put a big load on pilots. (1) Post change to "Limitations section" of your RFM/AFM. Big deal. A routine Sunday afternoon task. Sure, you need to read it too. (2) Determine how it affects you or if it even does. (3) Change your procedures if or how it affects you.
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I guess you missed item #3. To use your avatar as an example, given over 60K square miles of the GOM is getting 5G coverage, you wouldn't be able to use any of the deepwater IFR OSAPs and a majority of the shelf OSAPs when you flew your AW609 offshore. Unless you only plan fly VFR only. Just think all that time and money that went into the GOM ADSB grid to increase IFR flight densities will be moot because of this AD. While it might seem like an easy Sunday job to comply with that AD, it will end costing a lot more than $85 per airframe and a cup of coffee. The potential AD cost/loss numbers being discussed for the GOM alone are in seven figures.;)
 
MauleSkinner said:
Yup…Just like bitchin’ about not being able to use GPS, not being able to use GPWS has no impact on safety.
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Dear Sir: Your Airmanship:
The notice did say that limitations kick in when "5G interference is NOTAM'ed". Good airmen then take appropriate action. These are the ones that have more than a single card in their deck. Seriously, I need to see the change to the Limitations section before I lock my mind up.

I do recall another pilot safely completing a flight with his RADALT MEL'ed.
 
Bell206 said:
I guess you missed item #3. To use your avatar as an example, given over 60K square miles of the GOM is getting 5G coverage, you wouldn't be able to use any of the deepwater IFR OSAPs and a majority of the shelf OSAPs when you flew your AW609 offshore. Unless you only plan fly VFR only. Just think all that time and money that went into the GOM ADSB grid to increase IFR flight densities will be moot because of this AD. While it might seem like an easy Sunday job to comply with that AD, it will end costing a lot more than $85 per airframe and a cup of coffee. The potential AD cost/loss numbers being discussed for the GOM alone are in seven figures.;)
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Ah, my avatar. Note that it is in Bristow colors and Bristow did throw down a big deposit on two delivery positions. There were several times that GOM navaids were down, IFR not possible, and my buds and I just went VFR when possible or just cancelled. If enough flights are cancelled, the feds may take action.
 
Maxnr said:
Dear Sir: Your Airmanship:
The notice did say that limitations kick in when "5G interference is NOTAM'ed". Good airmen then take appropriate action. These are the ones that have more than a single card in their deck. Seriously, I need to see the change to the Limitations section before I lock my mind up.

I do recall another pilot safely completing a flight with his RADALT MEL'ed.
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Same with GPS.
 
Domenick said:
Why isn't the rest of the world, some of it farther along in its 5G rollout than the USA, having the problems the FAA is concerned about? I'm not hearing of planes slamming into the runway or dropping to the runway or flying into hills/mountains due to radio altimeter interference.
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The additional 5G spectrum that WILL cause RA interference (fundamental overload of RA receivers and spurious 5G emissions landing in the RA allocated frequencies) hasn't been implemented yet in the U.S. Not sure how far along other countries are.

This graph scares me.
Graph- Safe Interference Limit and Expected 5G Interference Levels.jpg
 
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^^^ The devil is in the details of any scientific study, from clinical trials to 5G interference. The results say nothing about the validity of the study design, use cases and equipment evaluated, and the statistics used to analyze the results.

I'm not saying the RTCA study is not valid. I am saying I need more than a simple recitation of the results to be convinced.
 
TonyG said:
220MHz is HUGE. As you infer, there's no excuse for a new design to suffer interference from a signal that far away in frequency space. But those signals were not there when these RAs were designed. Filtering probably won't address the entire issue - it would depend on the radar altimeter's vulnerability to leakage/interference/EMI after the antenna/filter stage. I haven't read the TSO, but my guess is it wasn't written with many strong, physically close transmitters in mind, but rather with distant sources (where filtering, which is probably already built in, addresses the problem). This'll be a mess for some folks.
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From the RTCA slides r/e this issue: (page 15)
"•Radar altimeters are inherently wideband systems, and currently have no requirements for front-end rejection—may be more susceptible to blocking than other types of receivers."
 
Let's see some real-life experiments. How about something simple like fly a radar-altimeter plane into a 5G area and see if there are effects?
 
Domenick said:
Let's see some real-life experiments. How about something simple like fly a radar-altimeter plane into a 5G area and see if there are effects?
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They have been live testing. However, they are also having to standardize the tests so there's usable data. But until there is such data (globally) there was no option with the current 5G rollout schedule. This has been a goat rope for some time now.
 
NBC news had a story on this last night talking about how 5G was going to wreak havoc on airline scheduling etc resulting in all kinds of flight scheduling problems. It's interesting that they mentioned it's being used in many parts of the world with no problem. You can't tell me that places like London, Paris, Rome, Tokyo, etc. don't have any 5G areas in the vicinity of airports considering their population densities. Just saying :dunno:
 
Archer Jack said:
NBC news had a story on this last night talking about how 5G was going to wreak havoc on airline scheduling etc resulting in all kinds of flight scheduling problems. It's interesting that they mentioned it's being used in many parts of the world with no problem. You can't tell me that places like London, Paris, Rome, Tokyo, etc. don't have any 5G areas in the vicinity of airports considering their population densities. Just saying :dunno:
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Foreign deployments use lower power levels, have exclusion zones around airports, and are farther away from the RA frequencies.
 
I believe this entire 5G fiasco is to allow social media, internet, etc. to cram more advertising down our throats (like we don't get enough already with 4G) :mad:
 
CEOs of the big name cattle cars testified in front of Congress yesterday and part of that was about 5G. Worth a watch for those who are interested in this subject.
 
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