FAA Issues Radio Altimeter Upgrade Mandate

The FAA has released a final rule upgrading the radio altimeter minimum performance requirements on aircraft operating in the 48 contiguous U.S. states and the District of Columbia to ensure that they can withstand interference from wireless services in the 3.70- to 4.2-GHz frequency (C-band) that is adjacent to frequencies used by aircraft. 

Under the rule announced late last week, the mandated upgrade applies to aircraft equipped with radio altimeters, including the majority of those flown under Parts 121, 125, 129, 91K, and 135, and a “minority” under Part 91.

Two compliance dates were established for the mandatory retrofits to upgraded equipment based on the operation. Those operating under Part 121 and large aircraft (30 or more passenger seats or 7,500 pounds or more payload) operating under Part 129 must meet the new standards by Dec. 30, 2030. All others must meet the requirements by Oct. 31, 2034.

The rule is in response to a measure in the Trump Administration's One Big Beautiful Bill Act directing the Federal Communications Commission to auction off at least 100 MHz in the upper C-band. According to the FAA, this is necessary “to ensure safe, efficient, and reliable aviation operations in the presence of wireless signals in the C-band. These new radio altimeters must withstand interference from wireless signals in neighboring spectrum bands and continue to provide accurate altitude readings.”