FAA Proposes New Radar Altimeter Performance Standards

On Jan. 7, 2026, the Federal Aviation Administration published a proposed rule that would require all radio altimeters to meet specific minimum performance requirements.

These new radio altimeters must withstand interference from wireless signals in neighboring spectrum bands and continue to provide accurate altitude readings to both pilots and integrated aircraft safety systems. The minimum interference tolerance requirements proposed in this rule reflect the best achievable interference rejection using current technology without compromising radio altimeter system performance. 

These regulations would require all aircraft equipped with radio altimeters operating under Part 121 and those aircraft with radio altimeters operating under Part 129 with 30 or more passenger seats or a payload capacity of more than 7,500 pounds to comply with the minimum performance requirements by the date the Federal Communications Commission authorizes wireless services in the Upper C-band. 

All other aircraft equipped with radio altimeters would be required to comply with the same minimum performance requirements two years later. 

This proposed rule is a companion to the Federal Communications Commission’s NPRM to expand the ecosystem for next-generation wireless services in the 3.7-4.2 gigahertz band by making as much as 180, and at least 100, megahertz of the Upper C-band available for terrestrial wireless flexible use via a system of competitive bidding.

Why this matters
If approved, this proposal will require a retrofit of radar altimeters in nearly all legacy aircraft that are currently operating with radar altimeters.

Radar altimeters are safety-critical avionics that support autoland, TAWS, TCAS, wind shear detection, and rotorcraft automation. The FAA has determined that many existing radar altimeters are not sufficiently tolerant of current and future wireless interference, and that interim airworthiness directives are not a long-term solution. According to the FAA, “Compliance with new minimum performance standards will require widespread equipment upgrades or replacement.”

This proposal will introduce a new TSO for next-generation radar altimeter transceivers and a separate TSO for radar altimeter antennas. The existing TSO will likely be sunset.

Who is affected

• Installers and Part 145 repair stations
• Avionics manufacturers and OEMs
• Design approval holders (TC/STC) 
• Parts and distribution centers
• Aircraft owners and operators (Parts 91, 121, 129, 135)

Key dates

• Comments are due on or before March 9, 2026.
• Aircraft operating under 14 CFR Part 121, and aircraft operating under 14 CFR Part 129 with 30 or more seats or a payload capacity of more than 7,500 pounds, would be required to meet the minimum RA performance requirements by an initial RA performance date that would be specified in the final rule. 
• The initial RA performance deadline is proposed to coincide with the FCC’s date authorizing the initiation of new wireless services in the Upper C-band. The FAA expects this initial RA performance deadline to be sometime between 2029 and 2032.
• Proposed §91.220(a) would impose the same RA system performance requirement by the final RA performance deadline (two years after the initial compliance deadline) for all other aircraft equipped with RA operating under 14 CFR Part 91, including GA, rotorcraft, other commercial aircraft, and public aircraft.

To learn more, click here.

AC 20-199, Installation of an Airborne Low-Range Radio Altimeter System

The Federal Aviation Administration has published this draft advisory circular as a companion document to the notice of proposed rulemaking on radar altimeters.

Why this matters
This advisory circular provides guidance for the installation of a radio altimeter system to comply with the requirements of 14 CFR § 91.220(b), for operation in the airspace of the 48 contiguous United States and the District of Columbia. An RA system consists of an RA transceiver, RA antenna(s), and display or indicator. This AC provides guidance for all of the components of the RA system as well as for the use of existing RA antenna(s) and display or indicator as part of the RA system installation. This AC includes guidance for the system installation and testing to assure proper functioning of the installed RA system, including the radio frequency interference tolerance, as well as proper functioning of integrated avionics and flight control systems that utilize the RA.

Who is affected

• Radar altimeter system design organizations 
• Installers and Part 145 repair stations
• Avionics manufacturers and OEMs
• Design approval holders (TC/STC) 
• Aircraft owners and operators (Parts 91, 121, 129, 135)
• Foreign regulatory authorities 
• FAA engineers
• Administrator’s designees

Key dates
Comments are due no later than Feb. 9, 2026. To learn more, click here.

FOR MORE INFORMATION:
Contact Ric Peri, AEA vice president of government and industry affairs, by email at ricp@aea.net or by phone at 202-589-1144.