FAA giving airlines another year to fix altimeters that can’t handle 5G signals

Jan. 11, 2023
About 1,000 planes have altimeters listening to signals in the wrong frequencies, Jon Brodkin reports for Ars Technica.

WASHINGTON - The Federal Aviation Administration will give airlines another year to fix or replace airplane altimeters that can't filter out cellular transmissions from outside their allotted frequencies. In a notice of proposed rulemaking (NPRM) released today, the FAA proposed a deadline of February 1, 2024, to replace or retrofit faulty altimeters, which are used by airplanes to measure altitude, Jon Brodkin reports for Ars TechnicaContinue reading original article.

The Military & Aerospace Electronics take:

11 January 2023 - Commercial altimeters operate on an RF spectrum from 4.2 GHz to 4.4 GHz while 5G cell signals operate at 3.7-3.9 GHz. Despite the different operating ranges, the avionics are unable to filter out the lower frequency signals.

"Some radio altimeters may already demonstrate tolerance to the 5G C-Band emissions without modification," the FAA said. "Some may need to install filters between the radio altimeter and antenna to increase a radio altimeter's tolerance. For others, the addition of a filter will not be sufficient to address interference susceptibility; therefore, the radio altimeter will need to be replaced with an upgraded radio altimeter."

The FAA said it "estimates that approximately 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."

In total, this affects approximately one in eight registered aircraft in the United States.

Related: Aviation groups lobby for 5G delay

Related: 5G may have caused dozens of troubling in-flight avionics failures

Related: FAA threatens more 5G disruptions

Jamie Whitney, Associate Editor
Military + Aerospace Electronics

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