May 20, 2021
By Dan Namowitz
Source: AOPA (Aircraft Owners and Pilots Association)
The wireless communications industry has a “deficient level of understanding” of the threat to radar-altimeter system operation and flight safety posed by “flexible” uses of the 3.7 to 3.98 GHz band, a concern that should prompt the Federal Communications Commission to reconsider its policy of repurposing the C-band, a coalition of aviation organizations said in a regulatory filing.
The risk of harmful interference with radar altimeters that operate in the band just above that frequency range could have been avoided if the wireless-industry trade group CTIA participated in a technical assessment performed by a multi-stakeholder group of the aviation technical advisory organization RTCA, wrote AOPA and 19 other groups in a May 12 letter to the FCC.
“As a result, any use of the conclusions by CTIA performed without the support of rigorous technical analysis are dangerous for the Commission to consider,” the aviation groups said, defending RTCA’s findings on C-band mobile telecommunications interference with radar altimeter operations.
The letter was filed in response to a March 2020 FCC order in which the FCC noted that “by licensing only up to 3.98 GHz as flexible-use spectrum, we are providing a 220-megahertz guard band between new services in the lower C-band and radio altimeters and Wireless Avionics Intra-Communications services operating in the 4.2-4.4 GHz band.”
The letter added that CTIA’s position “actually underscores both the need for the Commission to grant the pending Petition to Ensure Aviation Safety and the urgency for the Commission to work with the Federal Aviation Administration… to develop appropriate mitigations before 3700-3980 MHz operations commence in December 2021.”