How 5G Clashed With an Aviation Device Invented in the 1920s

A technological innovation that helped pilots fly fighter jets during World War II is at the center of the dispute between airlines and AT&T and Verizon over 5G, an innovative service meant to speed up mobile devices.

The clash came to a head in the last few weeks. The airlines warned that interference from 5G could cause a crucial device on planes to malfunction and force them to cancel flights. International airlines canceled flights to the United States on Tuesday despite the airport restriction.

A radio altimeter is the instrument in question. It was developed in the 1920s and still helps pilots determine a jet's altitude and distance from other objects. In some planes, altimeter readings are fed directly into automated systems that can act without input from pilots. The 5G system used by AT&T and Verizon works in the same way as the ones used by altimeters, according to aviation experts.

Diana Furchtgott-Roth was a former deputy secretary at the Department of Transportation and was in charge of researching new technologies. Aviation regulators were correct in raising concerns about 5G and taking appropriate steps to ensure safety.

The aviation business has had years to prepare for what little risk there is, and telecommunications experts say there is little or no risk to altimeters from 5G. Tom Wheeler, a former chairman of the Federal Communications Commission, wrote in a piece for the Brookings Institution in November that it was hard to repeal the laws of physics.

Lloyd Espenschied worked for more than 40 years for Bell Labs, the celebrated research arm of AT&T, and patented the altimeter.

Peter Lemme, a former Boeing engineer who spent 16 years at the company designing safety, said that if an altimeter's waves don't bounce back because of 5G interference, or can't be distinguished from other nearby waves, it could give the wrong reading or not function at

A malfunctioning altimeter could prompt a plane's computers to warn pilots about phantom obstacles or prevent systems from warning pilots of real threats.

The Helicopter Association International held a seminar for its members. One of thePanelists was a radar system engineer at the company, which makes altimeters for many aircraft, including its own military helicopters. Mr. Frick said that the company had found a number of errors in the testing of 5G interference.

Mr. Frick said he didn't know if there were any cases where there was no interference.

When visibility is limited by fog, pilots rely on altimeters. Some wireless experts have dismissed the aviation industry's concerns as hyperbolic because they are not used in most landings. Most modern altimeters should be able to filter out interference, according to experts.

Tim Farrar, a wireless industry consultant who has looked at the issue, said he sees why it is a greater concern. I don't think you will see interference.

It is a image.

After more than 300 people died in two crashes, the Boeing Max was grounded for nearly two years.

The reverse thrusters that slow the plane once it has landed are a key part of the landing system. Mr. Lemme said that a Boeing patent suggested that the function was completely automated, meaning that a pilot wouldn't be able to reverse the plane's thrusters if the altimeter malfunctioned. The landing gear brakes, which are triggered by weight, would still function. Mr. Lemme said it would be difficult for pilots to stop planes before they reach the end of the runway.

He said that there could be planes running through runways.

Boeing didn't reply to the request for comment.

On Friday, the F.A.A. issued a notification that it had detected anomalies that could cause 5G interference to affect a number of the 787's automated systems. The agency said that the presence of 5G C-band interference can cause degraded deceleration performance, increased landing distance and runway excursion. There are more than 1,100 notifications worldwide, and 137 in the United States.

Many of these safety concerns should be addressed by AT&T and Verizon limiting their new 5G network to two miles from airports. Questions have been raised about why airlines, the F.A.A., the wireless companies and the F.C.C. did not resolve them earlier.

Ms. Furchtgott-Roth said previous warnings had been ignored. She said that in December 2020, the Transportation Department sent a letter to the National Telecommunications and Information Administration warning that allowing 5G to operate in its proposed frequency band would cause problems for flight safety systems. She said that the letter was never sent to the F.C.C.

The F.C.C. went ahead with the planned auction despite the concerns of 5G safety. In February, carriers bid more than $80 billion to use that portion of the wireless spectrum for 5G.

Ms. Furchtgott-Roth said that wireless carriers have a right to expect a return on their investment. You should be happy that the F.A.A. is taking a strong stance.

Brendan Carr, a Republican member of the F.C.C., dismissed the warnings from the F.A.A. and airlines, arguing that 5G interference does not pose a safety risk.

Each plane model had to be tested to fully resolve the issue, said Ms. Furchtgott-Roth, who teaches transportation economics at George Washington University. She said that the newer ones are not going to work. It is the opposite in some cases. The F.A.A says it has cleared more than half of the commercial fleet in the United States.

The airline industry is working on new standards for radio altimeters that will address 5G interference and other issues. The standards are not due to be released until October. The F.A.A. has approved five models of altimeters as 5G compliant in the past week, but the approvals are based on the combination of altimeter and plane model, and no altimeters have been approved for use in 787s.

The most likely solution is to swap out the altimeters, said Mr. Lemme, the former Boeing engineer.

It could cost billions of dollars to upgrade. The airlines and the wireless companies don't want to bear that burden.

The government could spend some of the $82 billion it received from selling 5G frequencies to the wireless companies, and the wireless industry could be forced to pay additional fees.

The temporary limits that AT&T and Verizon have placed on their 5G networks near airports should be made permanent. The companies could either reduce the strength of the 5G signals near airports or change the way they are used to limit or eliminate the impact on planes. These options would make 5G networks less useful in those areas, and possibly not available for those who live within the buffer zones of certain airports.

The solution will have to be negotiated between the airlines and the F.A.A. Harold Feld is a senior vice president at Public Knowledge, a research and advocacy group that has received funding from AT&T and Verizon.

He said that the assumptions for how 5G towers and altimeters interact in the real world from each side are vastly different.