The Federal Aviation Administration has issued a final rule establishing new interference-tolerance requirements for radio altimeter systems. The rule is intended to ensure that radio altimeters continue to provide reliable altitude information as additional commercial wireless services are introduced in portions of the C-band spectrum adjacent to frequencies used by aviation. To read the complete document, please click Here.

Radio altimeters may provide information not only to pilots, but also to aircraft systems such as terrain awareness, collision avoidance, automatic flight controls and certain low-visibility or helicopter operations. The FAA determined that some existing equipment may be susceptible to interference that could result in inaccurate or unavailable altitude information.

The rule generally applies to aircraft equipped with radio altimeters while operating in the contiguous United States and Washington, D.C. It does not require aircraft without a radio altimeter to install one.

The primary compliance dates are:

• December 30, 2030 for Part 121 aircraft and certain larger aircraft operating under Part 129.
• October 31, 2034 for most other radio-altimeter-equipped aircraft, including many aircraft operating under Parts 91 and 135.

The FAA established a performance-based standard rather than requiring one specific product or manufacturer. Depending on the aircraft and its existing installation, compliance could eventually involve an equipment upgrade, replacement or more extensive aircraft modification. Aircraft previously modified in response to earlier 5G-related requirements should not automatically be assumed to meet the new final rule.

Southeast Aerospace is reviewing the final rule and monitoring the development of compliant radio altimeter equipment, aircraft manufacturer guidance, certification pathways and the related FCC retrofit rebate program. SEA has created a condensed overview of the FAA Final Rule that you can view Here.

As more information and approved products become available, Southeast Aerospace will evaluate where its avionics, engineering, installation and aircraft modification experience may be applicable. This may be especially relevant for business aircraft, special-mission aircraft, helicopters and older platforms that could require aircraft-specific solutions.

At this early stage, equipment availability and approved installation options are still developing. Southeast Aerospace will continue working with industry partners and reviewing opportunities to assist affected aircraft owners and operators as practical solutions are introduced. Although the compliance dates are several years away, operators may benefit from identifying their current radio altimeter equipment, reviewing previous C-band modifications and monitoring future guidance for their aircraft type. Early awareness may become increasingly important as equipment demand and installation activity grow closer to the deadlines.