Is this a failure of the FCC to properly hand out frequencies?
These radar altimeters have very wide front-ends, as as a result are highly susceptible to out-of-band emissions. The radars are allocated from 4.2 to 4.4 GHz, so the bottom edge of the radar altimeter band is 200 MHz above the top end of the 5G band in question (3.98 GHz).
The fact that these radar altimeters are susceptible to out-of-band interference that is literally further away in the spectrum than the width of their entire allocation is IMO an engineering failure. Yes, spectrum management (rightfully) tends to err on the side of not forcing the incumbents to make modifications to existing systems. However, better filtering would resolve this issue and it is shocking that the engineers who designed them didn't foresee that other services would eventually be allocated in adjacent bands. Avionics is often NRE dominated, they couldn't have sprung for a cavity filter? Or if that was too expensive, designed more headroom in the LNA before saturation and filtered the out of band signal with a crystal or SAW filter at IF? Rejecting out of band that far away is not rocket science.
I don't think it's unreasonable in this case to temporarily suspend the rollout and give the aviation industry a deadline to fix its radars, but it should only be temporary. Any other radio service would be told to take a hike if it keeled over due to out of band interference that far away.
I completely agree that Boeing needs to issue a recall order on all affected hardware and provide a fix. This should be painful, it is basically punishment for trying to cut corners on safety equipment.
An modern commercial plane has tens of thousands of suppliers supplying millions of parts. No airline [1] could even imagine to have the staff to manage OEM relationships with that many indirect suppliers. That is what you pay Boeing for.
If that was the case no airline could afford to buy more than 1 type of plane or certainly not more than one manufacturer, you would need to handle all the suppliers in the industry?! it would be incredibly inefficient to do this for them individually .
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[1] Maybe United , American or Delta could have that kind of staff, but given the airlines operating margins in the last 2-3 decades even that seems unlikely
And you're grossly overstating how many suppliers are on a commercial aircraft. There are in total an average of 30 tier-1s on a modern airframe, and yes, airlines are expected to work with all of them. Radio Altimeters are typically made by avionics suppliers i.e. Collins, Thales, or Honeywell for Part-25 commercial airliners.
There's a reason why the only time two airplanes are identical is when they roll from assembly line as part of the very same order with same spec, and never again.
Boeing can argue with and sue their suppliers, but that's not a problem for anyone but them and their supplier.
If I made routers that flood the EM spectrum with random crap, even if their wifi 'worked' they wouldn't be fit for use, either.
Second, the FCC was already involved in their development and certification.
Third, these radars have been in operation for decades.
You are talking about thousands of planes that have to be modified to accommodate telcos. If anyone should pick up the tab for this it is Verizon and AT&T.
That makes their domination of spectrum far outside their range worse.
If anything, threaten to retroactively charge them for all that bandwidth.
Perhaps Boeing should have bid of the spectrum that their products depend on being unused.
This is essentially the government leasing out previously unused federal land for mineral extraction and a nearby rancher saying "it ruins my view," only with safety concerns added in.
This spectrum can’t simultaneously be “unused” and a problem for radar altimeters.
Who cares? The comment you are responding to says "they did shoddy work on the altimeters." That doesn't mean that Boeing built the altimeters.
They specced them, procured, inspected, installed and sold it with the whole airplane. If the pilots' chair collapses, that's shoddy work on part of Boeing, and nobody would talk about how they are just buying the chairs from someone. Same with the radio altimeters.
> Third, these radars have been in operation for decades.
Ok? Sometimes corners cut bite you in the backside only after decades.
There is one question which matters: Are the 5G towers transmitting on frequencies assigned to the use of radio altimeters or not? If they are they must stop. If the radio altimeters degrade or might degrade because of transmission outside of their assigned range and guard then they are faulty.
I believe no agency should consider downstream effects of applying the law, to ensure fairness. Why should Boeing get a pass but say an out of compliance robotic lawnmower gets enforced?
(I do agree this is Boeing's issue to fix, 200MHz guard band is huge, Boeing needs filters)
The allocation of the spectrum is only for transmission, and the radar altimeters in question passed that spec. It says nothing about receive, and due to how radar altimeter works, it's much, much harder to filter out interfering signals from systems like 5G (5G in case of interference will just drop maximum data rate as it filters mismatched codes or incorrect checksums, radar altimeter might return incorrect altitude)
I think one of the big things in the US is that anything that makes C-Band harder to work with makes it hard for 2 of the 3 wireless carriers to compete. T-Mobile has a lot of 2.5GHz spectrum that it has been using to launch high-speed 5G services. Verizon and AT&T had been waiting for their C-Band spectrum to be usable to launch their high-speed 5G services. In Europe, if all carriers are facing the same restrictions, it's a level playing field. In the US, if Verizon and AT&T face restrictions that T-Mobile doesn't face (for most of its spectrum since it's 2.5GHz and not C-Band), that doesn't offer a level playing field.
I think it's also more contentious in the US because we have a much more suburban and rural population. Transmission distance is really important in the US because people expect to get modern services even in low-density areas. Verizon built its business on the idea that you should expect excellent wireless coverage even in places that have virtually no people.
I think another part of it is that the FAA is often very cautious and it seems like they didn't coordinate well with the FCC in voicing their concerns early on enough.
The FAA does have a web page on C-Band (https://www.faa.gov/5g) which is their official stance on the subject. They cite "Lower power levels, antennas adjusted to reduce potential interference to flights, different placement of antennas relative to airfields , and frequencies with a different proximity to frequencies used by aviation equipment" as reasons why the C-Band situation in the US is different from that in other countries. Is the FAA being too cautious? Maybe.
Ultimately, no one wants their business plans disrupted. Airlines don't want to see issues that delay landings. Verizon and AT&T don't want to see things that delay their ability to provide fast 5G service.
Blancolirio covers this in several videos, although his take is more nuanced than mine.
(I mean that i do not know the answer)