Several international airlines paused Boeing 777 routes to the U.S. over questions of whether the FAA would allow them to land in the U.S. under normal conditions or whether flights would be required to divert over technical concerns. U.S. airlines filed diversion plans for some flights in case their planes weren’t allowed to land at major U.S. airports where 5G was going to get rolled out. And the 5G service rollout was partially delayed again.
And it’s all either a trumped up non-issue, or an aviation apocalypse, depending on whom you ask. The worry is that C-band 5G at the power and frequency that will be used in the U.S. could send confusing signals to radio altimeters in aircraft, leading to confusion over the altitude at which the plane is flying, and problems for other systems in some aircraft like Boeing 777s as well. What’s going on here?
- 5G should be fine. 5G rollout has been figured out in Europe without a conflict with aircraft altimeters, and there’s even a bigger frequency buffer in the U.S. So the band gap is enough that altimeters shouldn’t have a problem, but there may be some limited circumstances where they do anyway because of the specific different frequencies being used here. The altimeters needed to be updated, and weren’t. We don’t actually know this will be an issue, there’s some very limited data suggesting it could be. And aviation doesn’t take even small risks.
- There’s a potential problem with the altimeters which don’t seem to be masking out of band signals, since there wasn’t anything which would have been a conflict with the signal range they used 40 years ago when their standards were put in place. So there was no reason to add cost and complexity. But this should all have been dealt with years ago and wasn’t.
- Everyone closed their eyes and played chicken. 5G rollout has been known for years, with published specifications, and at the last minute there’s a game of chicken. There’s plenty of data suggesting this would be fine, and the government agency in charge (FCC) signed off, which telecomm agencies relied on in spending $80.9 billion in the government auction which gives them the right to roll out 5G using specs determined by the feds.
- Turf war between regulatory agencies, with the FAA raising its concerns at the last minute. They’ll say that there were issues noted earlier but that’s barely true in the most technical of senses. But the FAA has a hammer, which is the ability to regulate airlines in an extreme manner. And no one wants to see major disruption to aviation, and no one wants to do anything that will lead them to be blamed for an accident (even if it turns out to have nothing to do with 5G). And the disruption of FAA restrictions is massive. As American Airlines Chairman Doug Parker told employees earlier this month,
There were two days in the last couple of weeks of December..if we could only fly Cat 1 Dallas and DFW wouldn’t have opened until 10 a.m.
If DFW doesn’t open until 10 a.m. that’s 400 cancellations. And that’s if we knew about it the night before. That’s if we don’t start launching airplanes and then divert.. we didn’t cancel 400 flights on the mainline through all of this mess. Those are two days that were perfectly fine operations.
…The altimeter is used for other parts of the airplane…It’s tied to the heads up display. Boeing has it tied to..help with tail strikes on the 777-300s, all sorts of things that if you’re concerned about the use of the altimater we’re not going to be flying 777-300s into any affected airport.
Meanwhile the FCC knows there’s been plenty of notice, their studies suggest this should all be fine, and lacks sympathy for engineers who didn’t address concerns they may have had with mission-critical systems for years.
So what happens next? Everyone finds a temporary fix to a limited set of planes and airports and defers major costs.
There needs to be a retrofit of existing altimeters, perhaps in some case replacement. We don’t really know whether there’s risk of displaying wrong altitude or other issues with existing altimeters since the FAA hasn’t done much to study the issue over the past several years. Now they want time.
5G is actually very valuable to the public, and the retrofit costs are much smaller than the benefit to the service. This is indisputable. But there’s also jockeying not just for time but over ‘who pays’. And a crisis facilitates potentially getting the government to pay, out of a portion of that $80 billion from the spectrum auction perhaps.
This conclusion from reader Steve seems right to me, who notes that we probably should agree to pay for altimeter upgrades out of auction proceeds to ratchet down the rhetoric.
Nobody is going to want to be the one to decide the risks with the current altimeters are small and end up with a crash, even if it turns out later to have nothing to do with this issue and since shutting down 5G is a shifted cost (ie it doesn’t fall on the airlines) they are going to scream for as much as they can get arguing the inconvienence of not having faster cellphones is outweighted by not killing people (really the remote chance of killing people).
The right answer is a fast track program for outfitting those altimeters that can with an inline filter and replacing those that can’t. That would be a boon to any companies that have a certified solution since they’d just have to scale up production but even that will take months so it will come down to how much of the 5G coverage the airlines/Boeing vs the cell companies can agree is enough.
Given the political power of each side that could turn out to be a very interesting fight. What I’m sure will be lost is any sort of rational decision making and it sidesteps the real problem which is why given it’s been known for years that these frequencies were set to be utilized these tests were only ran just over a year ago and the issue is only coming to a head now.