The Federal Aviation Administration (FAA) is ratcheting up its concern about airline safety when 5G deployments begin on C-band, a fear it’s been sounding an alarm about for a year, Inside Towers reported. Now that network carriers are expected to begin using the spectrum starting December 5, starting in 46 markets, the FAA plans to issue a Special Airworthiness Information Bulletin and an airworthiness directive about the issue, two officials told Reuters, confirming a Wall Street Journal report.
FAA Deputy Administrator Bradley Mims wrote in a previously unreported October 6 letter, the agency shares, “the deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C-band.” An FAA spokeswoman told Reuters on Friday it “continues to engage with other agencies so that aviation and the newest generation of 5G cellular technology can safely coexist.”
The FCC said it remains “committed to ensuring air safety as the agency’s successful track record demonstrates, while moving forward with the deployment of new technologies that support American business and consumer needs.”
FAA and FCC officials have held numerous discussions about the topic. The FAA held an October 14 meeting with 19 companies and associations within the aviation industry on the issue, including Airbus, the Air Line Pilots Association, Boeing, Honeywell International and Lockheed Martin Corporation, according to an FCC filing. The aviation and aerospace industries wanted the agency to reconsider its March 2020 Report and Order authorizing the lower portion of the C-band for wireless use. They pressed the Commission to take measures to ensure aviation and public safety by protecting radio altimeters on 4.0 GHz – 4.2 GHz from harmful interference from 3.7 GHz licensed operations.
In March 2020, the Commission concluded in its order that its rules “would protect radio altimeters used by aircraft. And we continue to have no reason to believe that 5G operations in the C-band will cause harmful interference to radio altimeters.” The agency added that the “altimeters operate with more than 200 MHz of separation from the C-band spectrum to be auctioned, more protection than is afforded in some other countries.”
During a meeting this August, the groups said, “until long-term solutions can be implemented by the aviation and aerospace industry,” the industry has determined that “closing the mitigation gap is not possible without the flexible use licensees being required to take their part. Without appropriate mitigation measures taken by 3.7 GHz flexible use licensees to reduce sufficiently the potential for harmful interference to radio altimeters, the result is likely to be substantial disruption to the use of the National Airspace System,” the groups told the FCC. They said this will adversely impact the flying public, the economy, and critical aviation services, according to an agency filing.
During the C-band auction last December, the FCC made available 280 MHz of mid-band flexible use licenses in the 3.7-3.98 GHz band. Inside Towers reported that Airlines for America, representing major airlines including American Airlines, Delta Air Lines and United Airlines, the Aerospace Industry Association, General Aviation Manufacturers Association, major aviation unions and others, raised fears about the auction, because the C-band changes could impact the adjacent aviation frequency band.
They said a six-month review of 5G network emissions with radio altimeter performance by the Radio Technical Commission for Aeronautics found risks of harmful interference on all types of aircraft. The review suggested the risk “is widespread and has the potential for broad impacts” to U.S. aviation operations, “including the possibility of catastrophic failures leading to multiple fatalities, in the absence of appropriate mitigations.” That led House Committee on Transportation and Infrastructure Chair Peter DeFazio (D-OR) to urge the auction be delayed, Inside Towers reported. He called on the FCC to work with the FAA and aviation industry experts to ensure “the safety of the hundreds of millions of Americans who fly each year is not endangered by the FCC’s rushed plan.”
But the FCC didn’t delay the auction, which garnered over $80 billion in bids — a monetary record for Commission auctions. Twenty-one bidders won all the available 5,684 licenses.
Wireless trade group CTIA said Friday that 5G networks can safely use C-band spectrum “without causing harmful interference to aviation equipment.” The association cited numerous active 5G networks using C-band in 40 countries. “Any delay in activating this spectrum risks America’s competitiveness,” according to CTIA.
One longer-term solution is retrofitting some altimeters with “out-of-band filters,” but industry officials note it would likely take years and “many thousands of civil aircraft are likely to be impacted,” the aviation industry said, according to Reuters.
By Leslie Stimson, Inside Towers Washington Bureau Chief