This article is published in Aviation Week & Space Technology and is free to read until Feb 08, 2026. If you want to read more articles from this publication, please click the link to subscribe.
All airlines operating in the contiguous U.S. must use aircraft equipped with next-generation radio altimeters by 2032 at the latest.
The FAA, seeking to avoid the safety risk and general chaos triggered by the last major wireless services rollout four years ago, is proposing new altimeter tolerance standards and a retrofit schedule that will keep aviation ahead of telecommunications’ next planned expansion.
A draft rule released Jan. 7 proposes new minimum performance requirements for all “next-generation” radio (radar) altimeters (RA) on aircraft that operate in most U.S. airspace.
- New wireless services set to launch later this decade
- Spectrum use will further crowd radio altimeters
- FAA proposes upgrade plan to eliminate anticipated risk
The affected fleet—41,000 crewed aircraft that operate within the contiguous U.S.—would be broken into two categories. The first, U.S. and foreign commercial aircraft certified for 30 or more seats, would be upgraded before proposed new services debut. The rest of the fleet would have two more years to fortify their RAs.
Timing of the upgrades will be driven by the Federal Communications Commission auction of up to 180 MHz of upper C-band spectrum between 3.98 and 4.2 GHz. The agency issued a proposed rule in December that calls for auctioning at least 100 MHz by July 2027. The RAs must be designed to operate safely around new fifth- and sixth-generation (5G/6G) wireless services planned for the spectrum.
“FAA expects this initial RA performance deadline to be sometime between 2029 and 2032,” the FAA writes in the proposed rule’s preamble.
The new requirements would be based on a standard being developed by a joint U.S.-European effort through RTCA and Eurocae that began in 2019, when 5G was introduced. The current plan is to publish a final version in March 2027, but the FAA is pushing for publication by June 2026 “to align with FAA’s anticipated timeline for publication of a final rule,” the agency writes.
Once the standard is finalized, the FAA must develop technical standard orders (TSO) needed to obtain design and production approval for aircraft model-specific upgrades. “FAA will ensure that the TSOs conform to the interference tolerance mask (ITM) requirements in the final rule,” the agency adds.
FAA data indicates that about 27,600 RAs on Part 121 and 129 aircraft are subject to the initial deadline—17,000 of them in the domestic fleet. The second set of aircraft have 31,000 RAs. Some aircraft have more than one RA for redundancy.
The cost to upgrade the RAs is estimated to run $4.5 billion, which assumes $40,000-80,000 per aircraft and is based on existing avionics.
The FAA’s plan includes replacement of RA transceiver units only. While the entire RA system must meet the new ITM requirements, retrofitting the transceiver “is expected to solve the spectrum interference issue,” the agency says. This will permit use of existing antennas that have not been tested for interference tolerance from adjacent bands, which simplifies both the certification and retrofit processes. Upgrading the RAs should not require any wiring modifications—another anticipated time- and cost-saver.
The next-generation RAs will replace a patchwork of risk-mitigation steps put in place when wireless companies introduced 5G C-band services in 2022. RAs, built to standards created more than 40 years ago when adjacent C-band spectrum was not used, were upgraded with filters, and the FAA issued airworthiness directives with aircraft-specific operational restrictions. In response, wireless companies voluntarily scaled back deployment plans around nearly 200 airports.
A lack of coordination between aviation and wireless stakeholders left both sides scrambling long after the wireless license holders’ planned rollout date. This prompted the patchwork response, as well as months of finger-pointing (AW&ST Jan. 24-Feb. 6, 2022, p. 30).
Voluntary steps taken by 21 wireless providers, such as to limit the power of their new 5G equipment, are set to expire in 2028. That expiration and the additional planned C-band usage mean more tolerant RAs are required.
RAs, which operate in the 4.2-4.4-GHz band, measure an aircraft’s distance above terrain and obstacles. They are critical in low-visibility operations and as data sources for key onboard safety systems.
Signals from adjacent bands can interfere with RAs, resulting in inaccurate data. The agency said it has classified 118 interference incident reports as “potentially” caused by C-band services, after eliminating other potential sources. Signs of the errors included inaccurate data displayed on the RA and nuisance alerts from safety systems being fed inaccurate RA data, the FAA adds.
“These reports demonstrate that wireless signals disrupt radar altimeters as predicted,” the agency says.
Related Content
