Proposed AD “Falls Short” of Preserving Safe Aircraft Operations

A coalition of aviation groups has criticized a proposed FAA Airworthiness Directive (AD) addressing methods by which the agency proposes to mitigate the extent to which 5G telecommunications networks interfere with aircraft systems—radar altimeters in particular. The group states the proposed AD “falls short of the goal of preserving safe operation of airplanes in the National Airspace System (NAS).”

The National Business Aviation Association (NBAA), Aerospace Industries Association (AIA), and 19 additional industry groups comprising primarily avionics manufacturers and aircraft OEMs commented collectively and unfavorably on the FAA’s Notice of Proposed Rule-Making (NPRM) pertaining to interference deriving of 5G networks, which operate within and adjacent to the 4200-4400 MHz frequency range—a spectrum known as the C-Band. Subject frequency range is also utilized by radar altimeters—cockpit instruments by which pilots determine the absolute, Above Ground Level (AGL) altitude of in-flight aircraft.

The coalition noted the AD heralded by the NPRM offers an “incomplete solution” vis-a-vis the contemporaneous maintenance of a safe National Airspace System (NAS) and preservation of extant aviation operations as increasing numbers of 5G systems commence operation and wireless communication and data services continue to evolve. The group asserted the AD appears to pass responsibility for the NAS’s safety from the FAA to individual aircraft operators, calling the lapses in authority and operational control “significant deficiencies … to adequately provide equivalent levels of safety for airplane operations in the NAS given the rapid growth of 5G C-band emissions in the United States.”

As currently written, the proposed AD connotes the imposition of significant regulatory and financial burdens on business aviation operators. NBAA senior director for air traffic services and infrastructure Heidi Williams remarked: “While we recognize and appreciate the FAA’s work with industry stakeholders on mitigations to 5G interference, the proposed AD does not account for the full impact from this situation to all users.”

Although not stated specifically in its comments, the coalition prevailed upon the FAA to “consult with the aviation industry on the realistic cost breakdown” of research and development expenditures associated with developing and testing radar altimeters hardened against C-band signals, and the future work of retrofitting existing aircraft with such components.

Ms. Williams added: “As additional telecommunications providers get ready to activate new 5G networks, and with current mitigations to Verizon and AT&T 5G networks expiring in July, more work is necessary to ensure mitigations are readily available to all affected operators.”

Radar altimeters provide real-time measurement of a flying aircraft’s absolute altitude over terrain and obstacles immediately beneath. Data deriving of radar altimeters is germane to the function of Terrain Avoidance and Warning Systems (TAWS) and auto-land architectures, as well as ground spoilers, anti-skid brakes, cabin pressurization, and numerous additional aircraft systems.

FMI: www.nbaa.org