FAA issues warning on potential safety risks from 5G C-band

The Federal Aviation Administration on Tuesday upped the ante in what has been an ongoing scuffle between communications regulators and the wireless industry with aviation stakeholders – as the agency issued a warning over potential interference to airplane safety systems from upcoming 5G deployments in C-band frequencies.    

The FAA today released a Special Airworthiness Information Bulletin (SAIB), which provides information and recommendations for the aviation community  – including aircraft and equipment makers, operators and pilots – about the risk of potential negative effects on certain aircraft safety equipment from the planned rollouts of 5G using C-band spectrum and advises that action might be needed.

Wireless carriers paid big, in particular Verizon and AT&T at more than $45 and $23 billion respectively, to acquire new spectrum licenses in the 3.7-3.98 GHz range at auction earlier this year that are seen as key for 5G services. The start of initial deployments in major U.S. markets is expected just around the corner on December 5.

RELATED: Verizon ‘absolutely’ on track to build 7-8K C-band sites this year: CFO

The FAA responded to Fierce with a statement saying: “While the FAA continues to engage with other agencies to identify measures that would enable aviation and the newest generation of 5G cellular technology to safely coexist, the agency is simultaneously taking steps to provide aviation users with relevant safety information.”

Specifically at question of the ongoing debate is interference with radio altimeters, which operate in the nearby 4.2-4.4 GHz band and help with key systems such as landing in bad weather, avoiding collisions and preventing crashes.

“The bulletin urges stakeholders to be aware of the potential degradation to the capabilities of safety systems and other equipment that depend on radio altimeters, particularly during low-altitude operations. Operators should be prepared for the possibility that interference from 5G transmitters and other technology could cause certain safety equipment to malfunction, requiring them to take mitigating action that could affect flight operations,” the FAA statement continued.

CTIA President and CEO, Meredith Attwell Baker in response to the bulletin maintained that 5G using C-band won't cause interference and that timely deployments are key for 5G leadership. 

“5G networks using C-band spectrum operate safely and without causing harmful interference to aviation equipment. The evidence includes numerous active 5G networks using this spectrum band in 40 countries all over the world, as well as years of study and technical analysis by the FCC and international agencies, including material submitted by the aviation industry," Attwell said in a statement to Fierce. "C-band spectrum is critical to delivering 5G service in communities large and small across the country, ensuring all Americans benefit from these next generation networks. Any delay in activating this spectrum risks America’s competitiveness and jeopardizes our ability to ensure global 5G leadership.”

The SAIB said the FAA is collaborating with the FCC and the National Telecommunications and Information Administration to evaluate if there’s need for mitigation beyond the recommended action in today’s bulletin. The FAA requests parties voluntarily submit information to be considered by the three agencies before planned C-band wireless deployments begin.

RELATED: Aviation, wireless industries clash over C-band interference

Aviation groups already warned about the potential for an escalation of negative outcomes, such as delays, flight cancellations or shutting down runways on an indefinite basis.

Interestingly, one of the recommendations listed and called out in the FAA statement relates to 5G-equipped devices on board. A Friday report from the Wall Street Journal that cited government and aviation officials who said a warning was being drafted, indicated that FAA actions weren’t expected to be directed at consumers’ use of cellphones.

“Among the steps is a recommendation that pilots remind passengers that all portable electronic devices equipped with 5G be should be turned off or switched to airplane mode during flight. The bulletin also urges operators who experience interference to immediately report the situation to the FAA,” the agency said in its statement.

Recommended steps in the SAIB also focus on radio altimeter equipment manufacturers, who are told to continue testing about whether specific equipment could have interference from the 3.7-3.8 GHz frequencies and report concerns to civil aviation authorities and spectrum regulators.

“Longer term, these manufacturers should explore design changes that could mitigate the effects of interference,” the FAA stated.

RELATED: Lawmaker raises alarm bells over 5.9 GHz, C-band

For airline operators, the FAA said they should “ensure pilots are aware of the potential degradation to the capabilities of safety systems and other equipment dependent upon radio altimeters and any means to compensate for resulting anomalies” and to consider both the loss of the function of aircraft safety systems and the manners in which they malfunction.

It tells aircraft makers to continue testing, and to collaborate with radio altimeter manufacturers and issue guidance for operators on plans to retrofit equipment that’s susceptible to harmful interface from wireless service in the 3.7-3.8 GHz band.

The FCC completed its auction of C-band spectrum in the 3.7-3.98 GHz range in February. It had left a 220-megahertz guard band in place along with other rules after the aviation industry raised concerns.

However, those worries weren’t alleviated.

RELATED: Aviation community worries about possible effects of 5G in C-band

In meetings with FCC officials in August, a coalition of 19 aviation stakeholders said that would take several years to implement measures like new aviation standards and related certified equipment to then be installed on aircraft. The group argued that near-term steps needed to be taken by 3.7 GHz licensees to address the mitigation gap from when the first tranche of C-band spectrum is ready for use in 46 top U.S. markets this December.

Wireless industry groups like CTIA and 5G Americas had pushed back against studies from the aviation community that showed risk of interference from C-band, citing technical issues and saying real-world conditions supported different conclusions. (The FCC in its 2020 C-band order previously sided with the wireless industry and put in place rules it felt would prevent harmful interference with aviation, which the community could address by upgrading or retrofitting altimeters).

RELATED: Amid heated debate, FCC votes 3-2 to free up 280 MHz of C-band for 5G

5G Americas in a July white paper pointed to 5G deployments in Japan, South Korea and Europe in similar bands without reports of interference.

“Several countries have been deploying 5G in spectrum near the radio altimeter band with no reports of interference. In the United States, the federal government has operated radar and communications systems in spectrum near the radio altimeter band for decades,” the 5G Americas report stated.

Indeed, the FAA bulletin today noted that many countries worldwide are deploying wireless networks in spectrum bands from 3.3-4.2 GHz and some have implemented temporary mitigations including power restrictions and proximity on broadband networks in the 3.7-4.2 GHz range.

“There have not yet been proven reports of harmful interference due to wireless broadband operations internationally, although this issue is continuing to be studied,” the SAIB stated.  

In an October 31 note to investors, New Street Research analyst Blair Levin wrote about the threat to delaying the use of C-band because of aviation industry concerns – something the firm didn’t think was likley but said warranted keeping an eye on.

“These inter-agency battles over spectrum, of which there were many during the Trump Administration, have no clear process for resolution. They are something of deep state game of chicken,” wrote Levin. “In this case, the C-Band auction winners may have the right under FCC rules to operate networks, but if the FAA raises its voice in predicting safety problems and the airlines start canceling flights, the political backlash could force some delays and compromises.”

Still, New Street felt the real-world experience in other parts of the globe “has moved the critical mass of forces to the FCC’s side.”

Updated with statement from CTIA.