We’ve heard about 5G networks for mobile phones for years. First, they were going to be super fast and amazing, then they were said to cause COVID, and now they’re predicted to bring the airline industry to its knees. That’s quite the resume for a little ole’ cell phone network. But here we are and the issue has exploded. What exactly happened? I’m going to do my best to break this down.
How C-Band 5G Came to Be
The term “5G” is just the next generation faster network that goes above and beyond 4G LTE. The mobile phone companies are all racing to roll out their networks as quickly as they can so they can crow about having the fastest, the most, the best, etc. The problem is finding enough spectrum in the right frequency to be able to serve the needs of the customer base of all the providers.
For years, there was a debate on how exactly to free up more spectrum, and in the waning days of the Trump presidency, it was finally auctioned off. The so-called “C-Band” mid-range frequencies were used by satellite operators, but the Federal Communications Commission (FCC) decided to kick them out and reallocate to the highest bidders. (They haven’t all been kicked out yet, but they will move up the ladder by the end of 2023, I believe.) In the end, AT&T, Verizon, and T-Mobile paid a combined $81 billion to get their hands on this chunk of spectrum. T-Mobile only picked up a small piece of it to supplement the network, so this is really an AT&T and Verizon story.
What those two providers got was in the 3.7 to 3.98 GHz range, a mid-band frequency that is good for mobile phones, because it travels long distances and goes through walls. But it’s also pretty close to the 4.2 and 4.4 GHz range that is used by radio altimeters on airplanes. There’s been concern about whether this explosion of use in the 3.7 to 3.98 GHz range near airports might impact the functioning of those radio altimeters.
The Mighty Radio Altimeter
In simple terms, a radio altimeter uses radio waves to figure out how high your airplane is off the ground. There are other kinds of altimeters that use air pressure to determine altitude, but the radio altimeter is important, because it ties into various systems on the airplane. Most notably, it is used to determine altitude while on an autoland approach in bad weather. It’s also an integral part of the heads-up display system in some airplanes, and it is responsible for triggering reverse thrust and spoilers upon landing in some fleets.
How often does an airplane need to use those things? Well, if the visibility is low enough, you need that radio altimeter to get you down on the runway safely. Ever seen Die Hard 2? You know when they change sea level so that Windsor Air crashes on the runway, thinking it’s higher than it really is? Well, that’s all absurd, BUT the point is kind of the same. If the airplane thinks its at a different height than it is, bad things can happen.
Further, the heads-up display is a great safety tool, and if you can’t use that, then it does degrade safety over what’s possible. And a delayed deployment of thrust reversers and spoilers won’t be a big deal unless you’re on a short and/or wet runway. Then it could be bad news.
The bigger issue here is that the Federal Aviation Administration (FAA) stepped in and declared that certain aircraft couldn’t be used at certain airports if the C-Band was flipped on. Is there really an issue? We don’t actually know for sure, but the risk is enough that the FAA decided it was worth stepping in… all because of that little radio altimeter.
With this reality that about half the US fleet wouldn’t be able to fly as normal, things got ugly very fast. It wasn’t just US airlines that panicked. Emirates, ANA, JAL, and others said they would stop some flights. Other airlines furiously tried to swap airplanes out for US flights at the last minute, using ones that had radio altimeters that had been cleared. This rush at the last minute was mind-boggling. How did we get to this point where it all ran up against a deadline? Shouldn’t this have been resolved before?
Shouldn’t This Have Been Resolved Before?
The answer to that is yes, but when you get several competitors and political bodies working against each other, things don’t go very smoothly. On the one hand, you had AT&T and Verizon not wanting to share what the other was doing. Once the C-Band auction was done, as I understand it, the wireless carriers could do pretty much whatever they wanted with it around airports. Then you have the political fight between the FCC and FAA.
The FCC sold off the C-Band spectrum, and many have wondered… why didn’t the FAA stop the FCC? Well, it couldn’t straight-up stop the FCC, but it did voice its displeasure. It tried to get the auction delayed when it happened at the end of 2020, but the FCC brushed it off, saying everything would be fine. The military did the same since it happens to fly a whole lot of airplanes itself. The RTCA put a study out in 2020 saying in part that “the results presented in this report reveal a major risk that 5G telecommunications systems in the 3.7–3.98GHz band will cause harmful interference to radar altimeters on all types of civil aircraft….”
Apparently all this fell on deaf ears, but that doesn’t mean the FAA should get off unscathed here. Maybe if it hadn’t waited so long to ban certain airplanes from flying after 5G deployment, then people would have listened more. Then again, the FCC under Ajit Pai seemed hell-bent on making this happen regardless. And now, here we are.
But, But, France
I know what you’re wondering… why can they roll this out in Europe just fine, but here it’s a massive problem? The devil is in the details, and the reality is that these may both be called 5G rollouts, but they are not the same thing.
France is one country that seems to be used as the posterchild for why aircraft can fly just fine with 5G operating, but what happened in France is very different from what’s happening in the US. In fact, I’m going to just steal this image from the FAA’s 5G page that has recently gone live.
The French antennas have permanent safeguards in airport buffer zones that provide more protection than the US ones. Further, the French antennas near airports have to be tilted downward to reduce interference, and the French antennas have far less power. Not mentioned here but also notable is that in Europe, the C-Band spectrum is in the 3.4 to 3.8 GHz range, so it’s further away from the range that radio altimeters use.
In the US, it’s just pure madness. Either regulatory authorities completely failed here, or the structure of the regulators just isn’t set up to properly handle this situation. Either way, it’s bad, and now we’re up against this deadline where everybody is pissed off.
The Solution
What’s the solution? There are so many. The most obvious is what seems to be happening now. AT&T and Verizon have — not because of regulation, mind you, but from pressure being exerted on them — limited their rollout near airports. AT&T sounds particularly dickish with this statement it gave to NBC.
We are frustrated by the FAA’s inability to do what nearly 40 countries have done, which is to safely deploy 5G technology without disrupting aviation services, and we urge it do so in a timely manner,
In the long run, presumably there will be more testing to prove which radio altimeters can function properly and which can’t. And eventually those that can’t, if there are any, will be phased out and replaced with something that doesn’t cause issues.
For now, however, just look for a lot of finger-pointing and confusion. It’s the American way.