FAA Finalizes Deadlines for Airlines to Retrofit Airplane Altimeters

The Federal Aviation Administration (FAA) released a final order that establishes deadlines for airlines to retrofit their airplanes' radio altimeters to ensure safe operations in a 5G C-Band environment. In the rule, FAA prohibits low-visibility operations for any transport or commuter category airplane that is not equipped with an approved radio altimeter after June 30, 2023, and requires that airplanes conducting air carrier operations under Part 121 be equipped with such an approved altimeter by February 1, 2024. 

There are two key points that are worth emphasizing regarding these deadlines.

First, in February, AAAE, along with several other groups, raised concerns over FAA's proposal that retrofitted airplanes only be permitted to operate at airports identified by the agency through its Domestic Notice system. FAA conducted further analysis and removed this condition in the final rule, due in part to mitigation measures that four telecommunication providers agreed to maintain until 2028. That means any retrofitted airplane can conduct low-visibility operations at any airport in the contiguous U.S. after June 30. This is a positive development and removes the uncertainty over which airports would be included in the Domestic Notice. 

Second, AAAE participated in a meeting with DOT and FAA leadership earlier this month on this issue. During the briefing, FAA indicated that about 58% of the domestic and international fleet, which is comprised of about 10,700 airplanes, has been retrofitted. The agency expects that number to increase to about 87% for the domestic fleet by July 1, although we believe that projection is optimistic. Nonetheless, DOT and FAA leadership have projected confidence to AAAE and other industry stakeholders that there will be minimal, if any, disruptions in July.

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 and allowed operations to continue with minimal disruption. 

Overview of FAA's Rulemaking. In January, FAA issued a proposed rule that would establish June 30, 2023, as the deadline for operators of transport or commuter category airplanes to ensure they have an altimeter that meets certain minimum performance standards in order to conduct low-visibility operations at airports identified by FAA through the Domestic Notice system. FAA also proposed February 1, 2024, as the deadline for transport or commuter category airplanes conducting air carrier operations under Part 121 to be equipped with a radio altimeter that meets certain minimum performance standards. 

In February, AAAE submitted comments in response to the proposal, emphasizing 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 about 7,000 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. You can read a summary of our comments in our February 13 Regulatory Alert and the comments here. 

FAA's Rule on Altimeter Retrofits and Key Takeaways. Based on AAAE's initial review of the final rule, there are several key takeaways: 

• Prohibition on Low-Visibility Operations: Unless the airplane is equipped with an altimeter meeting certain performance standards, FAA's airworthiness directive prohibits the following types of operations after June 30: (1) ILS Instrument Approach Procedures (IAP) SA CAT I, SA CAT II, and CAT III; (2) automatic landing operations; (3) manual flight control guidance system operations to landing/head-up display (HUD) to touchdown operation; and (4) the use of enhanced flight vision system (EFVS) to touchdown under Part 91. 

• Mandatory Retrofits: FAA requires 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. 

• Elimination of 5G NOTAMs and Case-by-Case Approvals: FAA is currently issuing 5G NOTAMs that identify the airports where certain low-visibility operations are prohibited (because of the presence of potential 5G C-Band signal interference) and determining which airplane models can operate at which airports on a case-by-case basis. After June 30, this process will be eliminated, and the existence of a retrofitted altimeter will instead determine if an airplane can conduct low-visibility operations. We would again emphasize that any retrofitted airplane can conduct low-visibility operations at any airport in the contiguous U.S. after June 30. 

• Mitigation Measures Become Binding: In March, Verizon, AT&T, T-Mobile, and UScellular agreed in writing to maintain certain mitigation measures until January 1, 2028. According to FAA, the agreement allows FAA to protect SA CAT I, SA CAT II, CAT II, and CAT III approach operations without limitations. You can review the March 31 agreement with the telecommunication providers, which further discusses the mitigation measures, here. 

• Cost of Retrofitting Altimeters: In January, FAA estimated that the cost of complying with the proposed rule for the industry would be about $26 million. This assumed about 180 airplanes would require replacement of the radio altimeter and 820 airplanes would require the addition of 'filters' to comply with the proposed modification requirement. In the final rule, FAA revised upward the cost of compliance to $35.2 million. Nonetheless, these cost projections did not affect FAA's approach to finalizing the order. 

What's Next? FAA plans to publish the final rule in the Federal Register tomorrow. AAAE will be working with our members, FAA, and industry partners to monitor for potential operational impacts due to the rule after June 30. In the event that the airlines can continue to retrofit their fleet in an expedited manner and impacts are minimized this summer, FAA and the aviation industry will have made significant progress towards implementing a permanent solution that allows aviation and the 5G C-Band network to safely co-exist.