FAA Wants US Airlines To Retrofit, Replace Radio Altimeters (reuters.com) 71
The Federal Aviation Administration (FAA) will meet Wednesday with telecom and airline industry officials on a push to retrofit and ultimately replace some airplane radio altimeters that could face interference from C-Band 5G wireless service. Reuters reports: The altimeters give data on a plane's height above the ground and are crucial for bad-weather landings, but airline concerns about wireless interference from a planned 5G rollout led to disruptions at some U.S. airports earlier this year. The FAA wants to use the meeting to establish "an achievable timeframe to retrofit/replace radar altimeters in the U.S. fleet," according to a previously unreported letter from the FAA's top aviation safety official Chris Rocheleau reviewed by Reuters. It also asked aviation representatives "to offer options and commit to actions necessary to meet these objectives."
The planned three-and-a-half hour roundtable meeting will also include a discussion on prioritizing retrofits with antenna filters, which mitigate potential interference from 5G. Antenna filters are currently in production, officials said. A key question is how to determine which planes are most at risk of interference and should therefore get retrofitted first. The meeting will also look at what is set to happen after July 5 and outline "changes to U.S. national airspace operating environment as a result of future 5G C-band deployment in the coming months."
The planned three-and-a-half hour roundtable meeting will also include a discussion on prioritizing retrofits with antenna filters, which mitigate potential interference from 5G. Antenna filters are currently in production, officials said. A key question is how to determine which planes are most at risk of interference and should therefore get retrofitted first. The meeting will also look at what is set to happen after July 5 and outline "changes to U.S. national airspace operating environment as a result of future 5G C-band deployment in the coming months."
Re:International planes? (Score:4, Interesting)
In some countries 5G uses different bands, so does not affect aircraft. In others they have the same problem so will be mandating retrofits too. Any aircraft planning to land in the US must comply with US rules. Not sure about overflights.
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Any aircraft planning to land in the US must comply with US rules.
That's not necessarily true. You need to conform to operating rules specific to the country (security, etc) but generally speaking if you have a valid airworthiness certificate for your non-N-registered aircraft, you're free to operate it in the US if you've got the appropriate ticket in the aircraft's home jurisdiction.
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If the US requires radar altimeters that actually work within their allocated band as required equipment for Cat II/III landings then anybody who wants to perform that kind of landing will have to have one.
International aviation is pretty well coordinated though. Probably everyone will introduce the requirement at around the same time. The FAA is just figuring out what kind of timeline to advocate for.
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In some countries 5G uses different bands, so does not affect aircraft. In others they have the same problem so will be mandating retrofits too. Any aircraft planning to land in the US must comply with US rules. Not sure about overflights.
Overflights happen at a high altitude, where no radio altimeter is used.
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I think this problem already has a solution. [faa.gov]
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How is this going to solve the problem of international planes not having retrofitted their altimeter radars while landing in the US?
I think they are (for the most part) way ahead of the curve on this.
Damn right they do (Score:5, Insightful)
Frequency allocations aren't a game. They're absolutely serious.
The managers who decided that they should be cheaper and therefore receive signals outside their allocation are the ones to blame for this debacle.
Re:Damn right they do (Score:5, Informative)
Frequency allocations aren't a game. They're absolutely serious.
Oh hell yes. Some might use the term deadly serious.
The managers who decided that they should be cheaper and therefore receive signals outside their allocation are the ones to blame for this debacle.
Welcome to my world (I'm not working this issue however) If it were only that simple. What is needed is a combination of filtering, and digital signal processing. When these devices on these planes were designed, there wasn't a need for DSP. There wasn't a need for filters either. They didn't have time machines back then like we do now. 8^) And fixing - while filters sound like a panacea, they aren't. They'll work for out of band, not for 5G signals in band though. And they will have insertion loss, reducing the strength of in band signals.
Intermodulation. This is of two sorts, often caused by something going non-linear, such as a connection going bad, often a grounding problem on a tower.
But mostly for us, a lot of the intermod is two signals beating against each other, producing more signals nearby.
Best way to imagine this is a guitar string vibrating, and another string close to the first string's frequency. You'll hear a warbling sound, not produced by either string. That's not an exact analogy, being audio rather than electromagnetic, but showing how new frequencies are created from nearby frequencies.
5G was quite simply going to cause a problem. The number of planes likely to experience problems has grown. Welcome to a shitshow.
So no one is at "fault" other than regulators who were chosen for political reliability, and have proven they know very little about RF. They learning now. https://www.aviationtoday.com/... [aviationtoday.com]
So filters - sure. Deploy filters, maybe tweak the plane systems for a bit more power.
DSP - well, now we're talking about something a lot more complex. Given that there will be noise and signals from 5G showing up on the same frequencies the altimeter radar is operating, but exactly where is never known, let us hope that the DSP works well. In real life this is going to take a lot of testing, because the interference will be all over the place.
But this is a problem that shouldn't have happened. the 5G C band should not have been the place to park 5G. We have a real frequency allocation issue though, one that isn't controllable by ideology or politics. I used to have this printed out full size in my office. https://www.ntia.doc.gov/files... [doc.gov]
But a hellava problem. A lot of money to be made by paying customers who want their facebook and their pR0n on their phones, and 5G appears to be spreading out to people's main internet connectivity now.
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But this is a problem that shouldn't have happened. the 5G C band should not have been the place to park 5G. We have a real frequency allocation issue though, one that isn't controllable by ideology or politics. I used to have this printed out full size in my office. https://www.ntia.doc.gov/files... [doc.gov]
But a hellava problem. A lot of money to be made by paying customers who want their facebook and their pR0n on their phones, and 5G appears to be spreading out to people's main internet connectivity now.
They should have just given the unallocated 0Khz spectrum to 5G - a simple solution to a complex problem.
But yea, interference is a complex issue and spectrum allocation unfortunately is as much a political as technical issue; and the politicians will blame the technical folks when something goes wrong; because, well, they can't be blamed, they just hold hearings.
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"They should have just given the unallocated 0Khz spectrum to 5G"
I don't think there's much bandwidth at 0 Khz.
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"They should have just given the unallocated 0Khz spectrum to 5G"
I don't think there's much bandwidth at 0 Khz.
To a politician Bandwidth is always infinite. Anyhow, that 0KHz BW was part of a joke.
As an aside, I've been convinced for a long time that we need to go to fiber when at all possible, and just use low powered RF in a wireless config.
Fiber always has as much bandwidth as you need - need more? Run another and separate fiber.
What is worse is that much of the RF spectrum is useless for computing purposes. HF and lower frequencies are an unruly beast, with different frequencies acting differently at di
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> When these devices on these planes were designed,
> there wasn't a need for DSP
Perhaps not, but the altimeters' designers and manufacturers, and their airline customers, did know that RF spectrum is a limited resource, that the FCC assigned them a specific portion of it, and that other portions of spectrum could and would be assigned to other users by the FCC. They were obligated from the outset to operate within their assigned spectrum, regardless of if or how or by whom the rest of the RF spectrum
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> When these devices on these planes were designed, > there wasn't a need for DSP
Perhaps not, but the altimeters' designers and manufacturers, and their airline customers, did know that RF spectrum is a limited resource, that the FCC assigned them a specific portion of it, and that other portions of spectrum could and would be assigned to other users by the FCC.
Your statement reminds of the Dilbert comic where the pointy haired boss demanded that they design a system that needs to take into account all of the unforseen problems.
That' really not how this stuff works. 5G showing up in the Spectrum that radar altimeters operate in is the 5G signal showing up outside of it's allocation. So about the only fix is Digital Signal Processing. But here's the issue. You have to have the interference in order to design the DSP. If ther is no interfereing signal, you don't
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Look. No one expects engineers* to be precognisant. But we do expect them to read and correctly implement the spec.
*Or, more likely, the managers or whoever.
Nice sentiment, but someone in here does expect them to be able to predict the future.
As may father told me long ago, the hardest work is always easy for thos who don't do the work.
Anyhow - it's the field I'm working in now, and I'm considered an expert by my peers. I'm not trying to argue from authority - just giving everyday experience. If you know better - want a job?
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" the altimeter radar people had to know all of the possibilities that might ever cause them problems,"
I have a tale you might find interesting about altimeters.
I don't think I have posted this here, it was on the power satellite economics google group back in early 2019 when they were discussing spillover effects from the power beams on aircraft operations.
In the course of some professional activities, I met another EE. Over a long lunch, he told me a spellbinding story about when he worked for a governme
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And perhaps account for the first civilian airliner damaged by an EMP.
Very plausible. We occasionally have less gargantuan interference generating devices that someone sets up for fun, like people building Wimshurst machines, or even just retro'ing spark gap generators. Those just cause wideband interference, not that monstrosity you describe. But I can very much imagine that being built by folks who weren't paying attention. They really needed a RF guru to tell them to stand down with that insanity.
I had a sorta similar situation a few years back when some one was transmi
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5G showing up in the Spectrum that radar altimeters operate in is the 5G signal showing up outside of it's allocation.
Well, you're the expert, but it seems to me that only if there's noise there directly from the 5G equipment is it the 5G equipment's fault. But if there's always some bleed onto neighboring frequencies then that always has to be taken into account somehow. Maybe it was, maybe these altimeters were so cheap because they didn't have more filtering that they saved enough money to justify replacing them now, but I somehow doubt that. To my mind, as expensive as testing and certification makes avionics, skimping
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5G showing up in the Spectrum that radar altimeters operate in is the 5G signal showing up outside of it's allocation.
Well, you're the expert, but it seems to me that only if there's noise there directly from the 5G equipment is it the 5G equipment's fault. But if there's always some bleed onto neighboring frequencies then that always has to be taken into account somehow. Maybe it was, maybe these altimeters were so cheap because they didn't have more filtering that they saved enough money to justify replacing them now, but I somehow doubt that. To my mind, as expensive as testing and certification makes avionics, skimping on a filter that is going to make relatively little difference in the cost of the final product seems insensible. Even if DSP is required to solve the problem (and reports on that vary, and I don't know who to believe) it would seem to me to be worth it in the general case simply to have equipment that is resistant to interference in general.
It's a matter of time. When the frequencies for radar altimetry were originally allocated, DSP either didn't exist or was at an early stage. And it was definitely in hardware. My software today has some very impressive DSP, even so, it is not a perfect solution, and is tailored to the specific interference. It can minimize interference, but some times cannot fix an issue without knocking out the signal I want.
It's obvious that filters can help if noise is encroaching. But when a signal pops up right in t
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Lol, no, we're talking shitty filter that can't tell 3.9ghz and 4.2ghz apart, plus magnetron emitters that blast all over the place.
But even if it were harmonics and radar a lil bit modern (say, 90s tech vs 60s tech), that would happen down the line anyway. Simply by virtue how side bands get crowded (and most of the spectrum is a side in the end, as you bump harmonics order). We're talking aggregate EM pollution here, not an actual in-spectrum interference like 802.11a 5Ghz radios vs
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Lol, no, we're talking shitty filter that can't tell 3.9ghz and 4.2ghz apart, plus magnetron emitters that blast all over the place
Now you're challenged to show me where I ever typed harmonics. That you chose to quote me as saying.
Sorry you liar - One thing worse than a AC - it's a person who makes shit up for the other person to say, lying while a simple search shows I never typed such a thing.
Given the other parts of your response are pretty irrelevant, let the adults chat now - perhaps you can find liars on Youtube to scream at and be among those of your own kind. They like to type LOL too.
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You're ranting about sidebands, don't pretend you don't. I wonder why do you feel the need to resort to ad-hominems, instead of going a lil bit more technical?
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You're ranting about sidebands, don't pretend you don't. I wonder why do you feel the need to resort to ad-hominems, instead of going a lil bit more technical?
You truly have absolutely zero idea of what you are talking about . First you claim I'm talking about harmonics - now sidebands? No. Not even. Never would. This has nothing to do with sidebands. or harmonics. There's a whole world of interference that has nothing to do with either.
If I'm to have a technical conversation with you, you first have to have some understanding of what I'm talking about. Which you have adequately proven that you don't.
You would be much better off posting as an AC. Thats th
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The managers who decided that they should be cheaper and therefore receive signals outside their allocation are the ones to blame for this debacle.
Ahhh yes, the old "someone bought something cheap" blamegame. No regard for how the neighbouring guard band was allocated. No regard for the fact these old Altimeters met all the requirements of the international standards. No regard for the simply physics that provide for an increased accuracy over a wider band.
It's all because someone bought something cheap. Riiiight.
Drinkpoo I think little of you, but even I think you can do better than this. Not ever fucking thing is a cost saving conspiracy. Leave that
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It kind of literally is a cost saving issue.
A band pass filter consists of capacitors and coils, which are tuned to allow a specific frequency range through. All radios require one, so what they must have done is not used the right values for the caps and coils, or else they wouldn't be getting crosstalk.
https://en.wikipedia.org/wiki/... [wikipedia.org]
These aren't complicated electronic devices, the calculations are trivial to figure to make a filter for a specific frequency band.
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Its not as simple as capacitors and inductors. That works at low frequency, but even there "parasitics" are an issue - every capacitor has some inductance and resistance, every inductor some capacitance and resistance. The the component values themselves have manufacturing tolerances as do the parasitics. All these v
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Coils and caps CAN NOT create a perfect cutoff. Even a so called 'brick wall' filter will not cut off in a binary manner such that you receive 24350 Hz perfectly and 24351 not at all. You're asking for a special dispensation from physical law but none are on offer.
And, btw brick wall filters introduce a lot of new problems including distortion of the signals inside the pass band.
The real issue here is that aviation was granted a band for use in radio altimeters with a suitable guard band around it. Now regu
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Suppose you are allocated a 200 Mhz band in the 4.2 Ghz range. A 200 Mhz guard band has been preserved immediately below that no one else can use. Do you think it is legitimate to squat on a frequency band from say 3.5 Ghz to 5.5 Ghz just because your equipment is defective?
Filters what are those? Let's just listen to the entire spectrum while we are at it, and complain if anyone transmits any signal anywhere on the off chance our defective equipment might have a problem with it.
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You mean the fully certified and approved equipment?
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Sure. A great deal of the blame belongs to the FAA for certifying defective equipment here. Not the FCC, it is not against FCC rules to design your equipment to receive garbage (unless you are trying to spy on someone perhaps). The integrity of a receiver for FAA purposes, on the other hand, matters quite a bit.
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Coils and caps CAN NOT create a perfect cutoff.
That is true, but there are technologies such as Surface Acoustic Wave devices (SAWs) that get pretty close. I had to design one in to a radio fire alarm, in order to meet specs for resistance to RF interference.
In the UK, the attitude of the regulatory bodies appears to be that users of old kit that does not meet current RF immunity standards have no cause for complaint when their kit goes wrong due to legitimate RF transmissions. For example, an ancient TV might be subject to malfunction due to somebody u
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It's all well and good for consumer devices like an old TV, quite another thing for an aircraft altimeter. People generally don't die if the TV reception is less than perfect. In the U.S., TVs fall under part 15, they must not generate interference from licensed users and must deal with interference from licensed users. All the same, most hams have traditionally helped out neighbors if there were problems.
A TV also has a much shorter design life.
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I take the point about the difference between a domestic TV and an aircraft altimeter. I think the basic point is that kit needs to be upgraded to meet current requirements, and those requirements reflect the RF environmental threats that currently exist. Before mobile phones, it was not necessary to consider malfunctions caused by RF interference in the UHF band, but you certainly have to consider it now.
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There is "no regard" for anything that's not relevant. RF spectrum is limited, the FCC licenses users for specific portions of it, and other portions can and will be assigned to other users. Period. Full stop. And everybody knows this. Just because an adjacent band is not in use when you apply for and are assigned yours is no guarantee the other will never be assigned to other users. Everybody also knows this. You design and build your kit to operate within your assigned spectrum, regardless of what
Senority doesn't matter? (Score:2)
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Not in this game. What does matter is a fair and equitable...equal outcome for all.
.
Ok, fancy newspeak aside.
RF communications, whether it be broadcast over the air or over a cable, only works well for all involved when all transmitters and receivers stay within the artificially defined boundaries for a given usage.
Think about it this way. You want to watch some sports channel on your cable or satellite TV and that broadcast keeps getting drown out by an unwanted TV news programme.
That's a case of a transmi
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Not in this game. What does matter is a fair and equitable...equal outcome for all.
That's a strange way of saying "someone with money wants us to ignore ITU standards and shit on a radio band purposefully kept low to not interfere with someone else".
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The altimeters stay in their band transmission wise. The problem is that they are sensitive to signals far outside their band reception wise, and so when some noisy neighbors showed up in a neighboring band it caused potential problems with the over-sensitive altimeter reception of signals in those bands.
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The world evolves, laws changes, etc.
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Are they waiting for a government subsidy? (Score:2)
Well, why wouldn't they, given the power of lobbyists.
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Cell companies need to be compelled to pay for this. They are the ones who bought the politicians, lobbied the government to sell off spectrum they had no business selling, and bought it for lots of money. They caused the problem and they clearly have the money to fix it.
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They are the ones who bought the politicians, lobbied the government to sell off spectrum they had no business selling, and bought it for lots of money.
If government has no bushiness selling off spectrum, I would like to know who does have authority. Bandwidth allocations are subject to complex international negotiations. Sometimes, old usages are made obsolete, to make way for more useful services. RF spectrum is a scarce resource. I do think, though, that selling spectrum for millions of dollars has limited economic justification.
There are cases where misuse of RF spectrum gets clobbered by regulatory authorities. One I recall is mains communication, whi
Buffering pron (Score:2)
The FAA is the reason altimeters haven't changed (Score:2, Interesting)
The FAA's onerous requirements to recertify the entire plane when changing one part like this is a major reason why some altimeters have not already been replaced. I don't know if 737s have a problem or not, but there are 25,000 737s in use and a new 737 made today has to use the same altimeter that the original 737 rolled off the line with. We know from the 737 Max debacle the lengths to which plane manufactures will go to in order to avoid the multi-year delays associated with a full recertification. T
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Here ya go: https://www.rtca.org/wp-conten... [rtca.org]
It's not the FAA, but it's the report that started the whole thing. The objection seems to be that under some circumstances it might be possible for 5G signals to produce more interference than allowed by ICAO safety margins. The FAA has certified all (most?) of the radar altimeters to operate now, so their own testing must have indicated that some simple precautions around airports are sufficient.
This action seems to be more about fixing something that really sh
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The contention is over the spurious emissions IN the radio altimeter band from 5G equipment. (Same figure).
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No, it's about interference. Some of that will come from harmonics and things from adjacent bands, that's unavoidable. Some of it will come from using shit front end filtering, that is avoidable.
But yes, safety critical radio altimeters should be required to modulate their signal and process the return so they're resistant to in-band interference too. It's not 1950.
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Can't Stop the Doppler Weather Radar Interference (Score:2)
5 Oh Gee (Score:2)
Plenty of blame to go around (Score:4, Interesting)
This caught my eye mostly when the problem was described as 'C-band interference'. For a very brief period I worked with equipment that used S-Band and C-Band, and if you're clever you've figured out the nature of that work. Suffice that I learned some interesting things.
For one, how trivial it is to interfere with current commercial aircraft radar altimeters. You could shut down an airport with a relatively trivial effort, just wipe your fingerprints off everything and don't buy the things you need in your own name.
It's fairly obvious that the altimeter manufacturers relied on lack of interest in the lower C-band to construct simple and cheaper devices. Bad practice in hindsight, but understandable. C-band is used for many different purposes, from the current bogyman, terrestrial comm, to space sensing. It was a favorite of military systems, SAM systems for instance. It does seem, again in hindsight, that the choices these altimeter manufacturers made were short-sighted, but that is common in what can generally be described as radio. If it works and doesn't infringe on another use, it's a go.
I'm disappointed this was not resolved so much earlier, equally disappointed that other users in that band were not given many good options to relocate at significant expense. But in this case, the 5G rollout was too profitable to resist. The FCC/FAA agencies could not just say 'no', even 'not yet'.
But seeing the FAA NG rollout and the recent FCC licensing site fiasco, I'm much less critical of my employer's penchant for updating and renewing critical systems so often. Stuff goes 'obsolete' so quickly, old systems become marginally supportable due to lost talent and higher expenses, and sure our government doesn't plan ahead often enough. But this was an avoidable problem. Now there is pain and expense, always inevitable, but could have been less disruptive and more manageable.
We'll see.
Re: Plenty of blame to go around (Score:2)
If they were to design it today they should use a shielding cone with a phased array at the bottom. Expiring patents put old military tech in reach of commercial aviation (minituarization helps, but the phase shifters still have to be able to deal with the jamming power so they can't be too small).
Only looking at a received signal directly below the plane combined with crosscorrelation of a pseudo random sequence should make it work at ridiculously low SNR.
system design (Score:2)
There has been no real world interference (Score:2)
This is just the FCC going "you say there's going to be real world interference, we say the opposite, you fix it however expensively you think is necessary".
Suddenly the "real world" aviation was using will change, needing to spend their dollars force their "real world" to become more realistic.
your airline ticket (Score:2)
Your airline ticket is going to cost more in order to make telecom companies richer.
Uncertified Radio Apparatus (Score:2)
The FAA wants to replace a bunch of FCC uncertified radio equipment with properly FCC certified standard compliant equipment.
I wonder how the FAA managed to install non-certified equipment in the first place?
If the radio equipment were FCC certified/compliant then it would be able to handle cross-chatter and interference without a problem (it is a certification requirement).
I can only conclude that the root of the problem is the use of uncertified and uncertifiable equipment.
Whoever it was that authorized t
Who's going to pay for it? (Score:2)
The FAA may want this, but the airlines aren't going to pay for it, and we're talking seriously expensive pieces of kit, probably in the mid 5 to 6 figure range.
The FAA demanded the adoption of ADS-B. GA and the military complied by the deadline (the military were the first to fully equip, for obvious reasons, but GA's compliance was over 90% by the deadline). Commercial airlines are cheap and do the bare minimum, they basically didn't comply until they were forced to after having the deadline extended.
They
The 5G licensees should be paying for it, no? (Score:2)
Surely, there should be a fee they need to pay the FAA or FCC for this that can get allocated to the airlines for the retrofit.
Or does that just make too much sense for it to actually ever happen?
Re:The 5G licensees should be paying for it, no? (Score:4, Interesting)
The 5G users paid a fortune to gain rights to the spectrum allocation in question. Tens of billions of dollars. It does not overlap the radio altimeter band and there is in fact a sizable guard band in between.
For better or worse, if the plane owners have equipment that is overly sensitive to signals far outside the assigned radio altimeter band, it is defective, potentially unsafe, and they are going to have to fix it. The 5G people didn't make the Boeings of the world adopt defective designs for their radio altimeters after all - as long as they are within the legal limits of their spectrum allocation, they are in the clear. It is not an easy problem, but basically the radio altimeter designers cheated by assuming there wouldn't be any substantial transmissions within a very large frequency range of their assigned band. Defective, by design, from the beginning.
No testing found any interference.... (Score:2)
What's odd to me about this is that the "interference" is purely hypothetical. If all the devices operate to spec there should be no interference, and quite a bit of the relevant equipment has done the testing and certified that there's no interference. So the whole issue is that the airlines haven't tested and certified the rest of the equipment and they're trying to force the cell phone networks not to roll out to give them more time. But to put the icing on the cake, I've not found any reports at all of
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What's odd to me about this is that the "interference" is purely hypothetical.
It won't be hypothetical when the tests are done, which is obviously what should happen next. There could be a problem with interference due to 5G transmissions, which existing EMC standards do not cover. If that is the case, then the standards need to be amended. if the standards are amended, then I presume that existing kit needs to be brought into compliance with the latest standards.
FCC? (Score:1)
Why do we even have a FCC if they can't even manage trivial matters like this? The FCC should have to pay to fix every plane with a radio altimeter. Maybe next time they'll be more careful.