Regulatory Alert: AAAE Urges FAA to Extend Deadline for Retrofitting Altimeters to Ensure Safe Operations in 5G C-Band Environment

On February 10, AAAE submitted comments in response to the Federal Aviation Administration's (FAA) proposed rule that would create deadlines for airlines to retrofit their airplanes' radio altimeters to ensure safe operations in a 5G C-Band environment. Under the proposal, FAA would impose restrictions on low-visibility operations for any transport or commuter category airplane that is not equipped with an approved radio altimeter after June 30, 2023, and require that airplanes conducting air carrier operations under Part 121 be equipped with such an approved altimeter by February 1, 2024. 

In our comments, which were coordinated with our industry partners, AAAE emphasized the need for FAA to set reasonable deadlines for compliance that recognize the supply chain and logistical challenges with retrofitting a U.S. fleet that is comprised of nearly 8,000 airplanes. We also urged FAA to work closely with other federal agencies, along with industry, to develop a permanent solution that does not rely on voluntary mitigation measures from telecommunication providers like Verizon and AT&T. AAAE argued that such actions are needed to avoid potential disruptions to the air transportation system. 

Background. In December 2021, FAA found that radio altimeters could not work properly if they experience 5G C-Band signal interference and issued an airworthiness directive for all transport and commuter category airplanes. The directive prohibited airplanes equipped with these altimeters from conducting certain low-visibility operations at airports identified by FAA through Notice to Air Missions (NOTAMs). 

In January 2022, Verizon and AT&T voluntarily implemented mitigation measures around airports located in the 5G C-Band network, which made it easier for airplane manufacturers to demonstrate to FAA that their altimeters were not susceptible to potential interference. While this required FAA to issue case-by-case approvals, it allowed an overwhelming majority of the U.S. fleet to continue to conduct low-visibility operations at the affected airports.

Overview of FAA's Proposed Rule. In January 2023, FAA published a proposed airworthiness directive that, if adopted, would mark a significant shift in how the agency evaluates and approves low-visibility operations at airports where 5G C-Band signals are present. A summary of the key takeaways include: 

• Overall Approach: The proposed directive would prohibit any transport or commuter category airplane from conducting low-visibility operations after June 30, 2023, unless the airplane is (a) equipped with a radio altimeter that meets minimum performance standards and (b) operating at an airport identified by the agency through its FAA Domestic Notice system. 

• Airports Listed in FAA Domestic Notice System: An airport would be listed in the FAA Domestic Notice system if the telecommunications companies-including Verizon, AT&T, and any others that gain access to C-Band spectrum-have agreed to voluntarily limit their 5G deployment around that airport at the request of FAA. 'Domestic Notices' are special notices or notices containing graphics pertaining to almost every aspect of aviation. Last month, FAA published the first Domestic Notice that identifies 188 airports where Verizon and AT&T have implemented mitigation measures. You can view that here. 

• Mandatory Retrofits: FAA would require that airplanes conducting air carrier operations under Part 121 be equipped with a radio altimeter that meets certain minimum performance standards by February 1, 2024. 

Summary of AAAE's Comments and Recommendations. In our response, AAAE emphasized the need for reasonable deadlines for air carriers to retrofit their fleet, which would help avert operational impacts, and a permanent solution that does not rely upon voluntary mitigation measures from the telecommunications companies. A summary of the recommendations that we raised with FAA include the following: 

• FAA must set reasonable deadlines for upgrading radio altimeters that recognize ongoing logistical, supply chain, and certification challenges and prevent operational impacts. While airports are not in the best position to determine the appropriate timeline for retrofitting existing airplanes, comments from air carriers and manufacturers in response to the proposal and over the past several months have made it clear that the proposed deadlines are unachievable, and FAA needs to extend them to prevent disruptions to the air transportation system. 

• FAA must provide greater clarity on the process that FAA will use to identify airports where retrofitted airplanes are permitted to conduct low-visibility operations after the proposed deadlines. Many airports and operators are unfamiliar with the FAA's Domestic Notice system, including, for example, how often the list of airports will be updated and how much advance notice will be provided in the event that changes are made. This will be very important to avert major disruptions, especially if an airport is suddenly removed from the list. 

• FAA must provide guidance on how affected airplanes can safely conduct low-visibility operations at an airport where telecommunications providers have not implemented voluntary mitigation measures. FAA's proposed rule does not provide any information on these types of operations; it only explains how operators can continue to conduct low-visibility operations at airports where telecommunications companies maintain specific mitigation measures, i.e., airports listed in the Domestic Notice. A prohibition of low-visibility operations at airports not listed in the notice is an unacceptable outcome. 

• FAA must work with other federal agencies, along with the aviation and telecommunications industries, to develop a permanent solution that does not rely upon voluntary mitigation measures from telecommunications providers. One concerning part of FAA's proposal is that the minimum performance standards for altimeters were developed based on the assumption that these companies maintain at least some mitigation measures around airports for the foreseeable future. While FAA does not have the authority to require these providers to adjust antenna power levels or take other measures, a framework that relies upon and assumes voluntarily cooperation from 21 different telecommunications companies is unsustainable. 

What's Next? FAA will begin to review and adjudicate over 70 comments that the agency received in response to the proposed rule, although it is unclear how likely the agency is to adjust any of the proposed deadlines. AAAE will be working with our members and industry partners to ensure that operational disruptions are minimized, and the federal government develops and implements a permanent solution that allow aviation and the 5G C-Band network to safely co-exist.