The latest and greatest in cell phone technology, 5G, has been rolling out across the country since 2019. 5G promises faster download speeds and more consistent connectivity, especially in the most congested and highly populated areas. But as nice as it is to be able to watch Netflix anywhere without having to wait for it to buffer, there may be unintended consequences in the aviation world.

Back to School

If you took physics in high school, you may remember about something called the electromagnetic spectrum. This spectrum comprises all different forms of radiation waves, from visible light to microwaves, X-rays to radio waves.

These waves all travel at the speed of light. What makes different types of waves unique from each other are two things which are inversely related: the frequency, how many waves pass per second, and the wavelength, the physical length of the wave of energy. The spectrum can be divided into frequency bands, so each band can be used for a different purpose.

There are thousands of applications for harnessing the power of these waves. In modern society, we use these waves every day — microwave ovens, car radios, wi-fi, airplane communications, and plenty of others. But the most prevalent use of electromagnetic waves today is the device which you’re probably reading this post on right now – your cell phone.

Getting the Bands Together

Cell phones use different bands of the electromagnetic spectrum to transmit data. 5G towers can operate in three separate bands. The newest 5G towers, which are known as “C-band” or “Mid-Band,” use a frequency band which is adjacent to the band used by aircraft radar altimeters.

A radar altimeter (RADALT) is a device used by larger airplanes which determines the distance the airplane is from the ground. Essentially, it’s a miniature radar device. It transmits an electromagnetic signal out and measures how long it takes for that signal to bounce off the ground and back up to the airplane. Based on this time difference and the speed of light, the altitude can be determined. This only works up to around 2,500 feet above ground level (pretty low), so RADALTs are really only used for landing. (Planes have other ways of knowing how high they are flying when above 2,500 feet.)

So here’s the issue: when signal frequencies are close enough to each other, they can interfere. The 5G C-band is right next to the RADALT band. So, there is concern that cell companies operating 5G C-band transmitters near airports will prevent RADALTs from working. This could prevent planes from being able to land safely, especially in inclement weather when RADALTs are used the most.

How Much of an Issue Is It?

Unfortunately, the short answer is “we don’t know.” That’s never comforting, especially when people’s lives are at stake. Since the towers were activated in mid-January 2022 (only two weeks ago at the time of writing), pilots have reported over 100 incidents of potential RADALT interference. None of these have been verified and many have been ruled out, but there is cause for attention.

But safety is woven into the fabric of the aviation industry. The FAA, aviation manufacturers, and airlines have all put safeguards in place to ensure the safety of the systems.

What’s Being Done About It?

Tha FAA has been working with manufacturers of RADALTs to determine their safety and compatibility with the 5G C-band. Thankfully, at the time of writing, roughly 90% of the US-based commercial air fleet has been cleared to land in the 5G C-band environment.

There are still a handful of planes, though, which haven’t been approved yet. Approval also depends on the specific airport where the plane is landing. In certain locations, the telecommunications companies have heard the concerns and have delayed the rollout of their 5G C-band services near airports. This has, thankfully, allowed commercial air service to continue uninterrupted.

Conclusion

I’ve only scratched the surface of the complex issue that is 5G and RADALTs. The interactions of the two very different systems are at best complicated and at worst unclear. But it is at least an important consideration in the aviation industry today.

If you want to learn more, The FAA has a dedicated website that tracks the rollout of the 5G C-band in areas near airports. You can find it here. Also, the folks at the Dots, Lines, and Destinations podcast have done a great job covering the topic as it has unfolded.

Hopefully, in the coming weeks, it will become clear what changes may be needed to allow every plane to fly and land near 5G C-band towers. (Add that to my 2022 aviation predictions, I guess!) It’ll be a great day when we can all start streaming our shows again just a few seconds after the landing gear hits the runway.