FAA: Airlines must retrofit defective altimeters “immediately.”

FAA has a proposal to replace or retrofit airplane altimeters that can’t filter out outside broadcasts. AT&T and Verizon have been unable to completely implement 5G on C-Band spectrum licenses they bought for $69 billion.

In recent months, the FAA urged airlines to retrofit or replace altimeters. FAA: “Airlines and other operators of concerned aircraft must install filters or other upgrades soon.”

AT&T and Verizon plan to increase 5G deployments near airports in the next months, although they will continue “voluntary mitigations” until July 2023.

Altimeters measure altitude on planes. New FAA “Regional aircraft operators must retrofit radio altimeters with radio frequency filters by 2022. This work has begun and will go quickly.”

The radio-altimeter manufacturers have worked at an unprecedented pace with Embraer, Boeing, Airbus and Mitsubishi Heavy Industries to develop and test filters and installation kits for these aircraft. Customers are receiving the first kits now. In most cases, the kits can be installed in a few hours at airline maintenance facilities.

Throughout this process, the FAA will work with both industries to track the pace of the radio altimeter retrofits while also working with the wireless companies to relax mitigations around key airports in carefully considered phases.

Additionally, “filters and replacement units for the mainline commercial fleet should be available on a schedule that would permit the work to be largely completed by July 2023,” the FAA sd

The FCC permitted mobile use in the C-Band in February 2020. As aviation altimeters use 4.2-4.4 GHz, a 220 MHz guard band protects them from 5G transmissions.

Given the extent of the guard band and power constraints for C-Band broadcasts, the FCC judged detrimental interference to altimeters unlikely “under reasonable scenarios.” The FCC also recommended the aviation industry to perform more research “on why there may be a potential for some interference given that well-designed equipment should not normally receive significant (let alone severe) interference under these circumstances.”

FAA and aviation industry were unprepared for C-Band deployments in 2021. AT&T and Verizon agreed to a six-week countrywide pause and airport rollout constraints until mid-2022. Last week, airlines decided to extend airport restrictions for another year.

“During early conversations in January, the wireless carriers volunteered to maintain mitigations in place until July 5, 2022,” the FAA said Friday. Wireless operators volunteered Friday to prolong voluntary mitigations for another year based on stakeholder roundtable results.


Scroll to Top