Agency Issues SAFO 21007

The FAA has updated its guidance pertaining to 5G C-Band interference and the potential adverse effects thereof on aircraft Radio Altimeters (RA). The agency recommends operators equip affected aircraft with 5G-tolerant radio altimeters as soon as possible.

Subject guidance, published in Safety Alert for Operators (SAFO) 21007, titled Risk of Potential Adverse Effects on Radio Altimeters when Operating in the Presence of 5G C-Band Interference, is the latest official update set forth by the FAA since the 01 July 2023 deadline the agency set for airlines to equip their aircraft with filters capable of shielding aircraft components and systems from the adverse effects of 5G C-Band interference.

SAFO 21007 is prefaced: “A SAFO contains important safety information and may include recommended action. Besides the specific action recommended in a SAFO, an alternative action may be as effective in addressing the safety issue named in the SAFO. The contents of this document do not have the force and effect of law and are not meant to bind the public in any way. This document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies”

By dint of SAFO 21007, the FAA explains the risk of 5G C-Band interference is highest for aircraft that have not been retrofitted and interference could cause systems to operate in an unexpected way during any phase of flight but most critically during takeoff, approach and landing phases. The FAA cautions operators to be cognizant of the radar altimeter’s salience to the following aircraft systems, and recommends adherence to all Standard Operating Procedures related thereto, and to safety of flight in general:

• Terrain Awareness Warning Systems (TAWS-A and HTAWS)
• Ground Proximity Warning Systems (EGPWS and GPWS)
• Traffic Alert and Collision Avoidance Systems (TCAS)
• Take-off guidance systems
• Flight Control (control surface)
• Tail strike prevention systems
• Windshear detection systems
• Envelope Protection Systems
• Altitude safety call outs/alerts/Aural warnings
• Autothrottle
• Thrust reversers
• Flight Director/Flight Displays
• Primary Flight Display of height above ground
• Alert/warning or alert/warning inhibit
• Stick pusher / stick shaker
• Engine and wing anti-ice systems
• Auto-Flight Systems

The FAA conceded the preceding list falls short of comprising the entirety of radar-altimeter-dependent aircraft systems.

Presently, an additional 19 wireless companies are about the business of deploying 5G C-Band emitters throughout the contiguous U.S. The rate of emitter proliferation renders the NOTAM process and Alternative Method of Compliance runway lists “untenable;” so contends the FAA.

NBAA senior director of air traffic services and infrastructure Heidi Williams remarked: “NBAA encourages aircraft owners and operators to consult with their OEMs regarding the need and availability of upgrades or filters. Pilots and operators should continue to watch for relevant NOTAMs related to 5G interference risks.”

Finally, the FAA requested questions or comments germane to SAFO 21007 be forwarded to the Flight Technologies and Procedures Division, Flight Operations Group at (202) 267-8790 or e-mail: 9-AWA-AVS-AFS410@faa.gov.

FMI: www.faa.gov