By Jeff Wagner

This was originally published on Jan. 18, 2022.

MINNEAPOLIS (WCCO) — Warnings of a “catastrophic disruption” to the air travel industry have subsided, for now.

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AT&T and Verizon will roll out their 5G coverage countrywide Wednesday, but it won’t happen near some airports.

We wanted to know: Why is 5G a concern around airplanes? And what solutions are in the works? WCCO’s Jeff Wagner got a lesson in aviation.

You do it, as least you’re supposed to do it, moments before the plane you’re sitting in takes off. Airplane Mode is meant to keep your cellphone from interfering with the plane’s navigation system. Regardless, planes still fly and land successfully.

But take that issue and amplify it to the point of airlines, like Emirates, announcing it will suspend flights to several major United States airports starting Wednesday. That is the level of concern AT&T and Verizon’s 5G service rollout has caused nationwide because of its potential impact on a plane’s radar altimeter.

The critical device sends out a signal measuring a plane’s height above ground, specifically at 2,500 feet or less.

Terry McVenus is president and CEO of RTCA, a nonprofit that helps set performance standards for the aviation industry.

“The airplane utilizes that information on a number of the systems on the airplane, including autoland, autothrottles that are used, a number of collision avoidance systems,” McVenus said.

(credit: CBS)

How would 5G interfere with radar altimeter? It has to do with the frequency band in which both operate. 5G cell towers operate between 3.7-3.9 GHz. Radar altimeters operate at a frequency of 4.2-4.4 GHz.

That closeness on the frequency band could lead them to interfere with each other, especially if the tower is near an airport, right when a plane is trying to land. Altimeters play an especially crucial role when there’s low visibility.

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“If [the altimeter] got a bad signal, if the airplane thought it was higher than it really was or lower than it really was, the airplane could do something that the flight crew may now want it to do,” McVenus said.

That safety concern is why the airline industry sent a letter to the FAA, FCC, and U.S. Department of Transportation Monday, pleading for the agencies to make sure 5G is not rolled out near airports. Tuesday, Verizon and AT&T appeased that request, a move applauded by President Joe Biden.

Can airplanes be modified so altimeters are not impacted by the 5G rollout?

“Short answer is yes. The rest of the story is it doesn’t happen overnight,” McVenus said.

He said a new altimeter would first need to be designed, then approved by the FAA. After that, manufacturers would then have to build the new altimeters to the new FAA standard, followed by replacing them in airplanes. McVenus estimates the entirety of that process to take 8-10 years.

The FAA released this statement about the matter Wednesday:

The FAA issued new approvals Wednesday that allow an estimated 62 percent of the U.S. commercial fleet to perform low-visibility landings at airports where wireless companies deployed 5G C-band.

The new safety buffer announced Tuesday around airports in the 5G deployment further expanded the number of airports available to planes with previously cleared altimeters to perform low-visibility landings. The FAA early Wednesday cleared another three altimeters.

Even with these approvals, flights at some airports may still be affected. The FAA also continues to work with manufacturers to understand how radar altimeter data is used in other flight control systems. Passengers should check with their airlines for latest flight schedules.

Airplane models with one of the five cleared altimeters include some Boeing 717, 737, 747, 757, 767, 777, MD-10/-11 and Airbus A300, A310, A319, A320, A330, A340, A350 and A380 models.

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Click here for more information about the decision to delay the 5G rollout. And click here to learn what steps the FAA is taking to work around the issue.

Jeff Wagner