The FAA believes it will cost about $26 million to fix or replace radio or radar altimeters that it says could be susceptible to 5G interference on C-band. That figure is part of a Notice of Proposed Rulemaking the FAA issued this week that would apply to transport and commuter planes equipped with such gear. Inside Towers reported the FAA is suggesting that airlines be given another year (to February 2024) to make repairs — delaying when AT&T and Verizon can transmit 5G on C-band frequencies near certain airports.
Out of nearly 8,000 airplanes in the U.S. registry, the FAA believes “about 180 airplanes would require radio altimeter replacement and 820 airplanes would require the addition of radio altimeter filters to comply with the proposed modification requirement.” It estimates the filters cost at $5,020 per unit and radio altimeter replacement at “up to $80,000 per airplane.” The exact total estimate given in the NPRM is $26,049,810.
The FAA came to this conclusion after studying the effects of 5G transmissions on C-band on certain planes for a year, gradually reducing the protected space around the ends of runways during takeoffs and landings. The FAA says it’s now able to assess the 5G C-band transmissions’ impact to aviation operations in a specific area, taking into account the particularities of the signal and the airport environment.
“AT&T and Verizon coordinated their deployment around 5G C-band mitigated airports (5G CMAs), including in some cases reducing emission power around airports and committing to antenna pointing angles in the vertical plane to limit the potential for interference within the tailored runway safety zones,” says the FAA. It notes this collaborative effort has allowed safe transport and commuter airplane operations to continue in the short term.
While only AT&T and Verizon are impacted by the restrictions they agreed to now, the FAA says that eventually 19 other telecoms will have the authority to deploy 5G base stations near airports. It expects these base stations to transmit in the entire 5G C-band (from 3.7 to 3.98 GHz). Whereas 5G transmissions were initially limited to 3.7 to 3.8 GHz, these transmissions have also begun to expand to 3.8 to 3.98 GHz, and the FAA expects deployment at the higher end of the frequency range to expand after June 2023 after satellite incumbents vacate the frequencies.
These higher frequencies are nearer to the spectrum allocation where radio altimeters operate (4.2 to 4.4 GHz), which means that the potential for interference to radio altimeters from in-band and spurious emissions may be more likely, according to the FAA. As the 21 telecommunication companies authorized to transmit 5G C-band continue to expand transmissions throughout the country, using Notice to Air Missions (NOTAMS) to identify affected areas “will become untenable,” it says.
The FAA has received over 420 reports of radio altimeter anomalies occurring within a known location of a 5G C-band deployment. Some 315 were not related to C-band interference. But roughly 100 were within NOTAM areas, and it says 5G C-band interference could not be ruled out.
These approximately 100 incidents included a variety of erroneous warnings concerning collisions, terrain awareness, landing gear and “the erroneous display of radio altimeter data,” says the FAA. The FAA is worried these erroneous warnings could distract flight crews who could eventually become desensitized to warnings.
The FAA is taking public comments on its NPRM (Docket No. FAA2022-1647 using regulations.gov). Comments close on February 9 following Federal Register publication on January 11.
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