FAA proposal imposes USD 4.5 billion radio altimeter cost on US aircraft operators
Dhaka: The Federal Aviation Administration has published a new proposal that would require US aircraft operators to replace or retrofit roughly 58,600 radio altimeters, at an approximate cost of USD 4.5 billion. The measure aims to address the potential interference existing radio altimeters may experience as the federal government further expands the 5G spectrum for wireless services.
A radio altimeter, also known as a radar altimeter, is a crucial instrument of modern aviation. It measures an aircraft's height above terrain and obstacles using low-power signals between the 4.2 and 4.4 GHz bands.
Pilots and multiple safety-critical systems onboard rely on this altitude information to ensure the overall safety of a flight, especially at low altitudes. The use cases include, but are not limited to, low-visibility approach, autoland, enhanced-vision operations, and safety mechanisms like terrain awareness and warning, wind shear alert, and traffic collision avoidance systems.
The FAA is concerned that higher-powered terrestrial wireless signals might interfere with a radio altimeter's ability to detect faint reflections from the ground and produce erroneous altitude information. This inaccurate data might lead to hazardous situations, with very little to no time for the pilot to react.
Therefore, the FAA would require aircraft operating under Part 121, along with large Part 129 aircraft with 30 or more passenger seats or a payload capacity above 7,500 pounds, to meet the new minimum performance standards by the date the FCC authorizes wireless services in the Upper C-band. For all other aircraft the agency would allow two more years.
Currently, wireless services operate in the 3.7-3.98 GHz range, which sits below the upper C-band. But it still caused several disruptions across the United States in the last couple of years. The FAA stated, as of August 2025, it had received 659 reports of potential C-band interference, including 493 associated with radio altimeters and related systems.
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