Feb. 13, 2023
A proposed FAA airworthiness directive on methods to mitigate interference to aircraft systems from 5G telecommunications networks “falls short of the goal of preserving safe operation of airplanes in the National Airspace System (NAS),” stated a coalition of aviation groups.
NBAA joined with the Aerospace Industries Association (AIA) and 19 other industry groups, avionics manufacturers and aircraft OEMs in commenting on the FAA’s notice of proposed rulemaking (NPRM) addressing interference from 5G networks operating within and adjacent to the 4200-4400 MHz frequency range, also known as the C-Band, also used by radar altimeters.
The coalition noted the NPRM AD offers an “incomplete solution” for maintaining safety of the NAS while also preserving existing aviation operations, particularly as additional 5G networks come online and as both aviation operations and wireless services continue to evolve. The groups also expressed concern that the AD appears to pass responsibility for preserving the safety of the NAS from the FAA to individual operators.
These lapses represent “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,” the coalition stated.
As currently written, the proposed AD could also carry significant operational ramifications to business aviation operators. “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,” said Heidi Williams, NBAA senior director for air traffic services and infrastructure.
Although not specifically addressed in its comments, the coalition further requested that the FAA “consult with the aviation industry on the realistic cost breakdown” of the research and development costs associated with ongoing research and testing of radar altimeters hardened against C-band signals and future work to adapt such equipment to different aircraft models.
“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,” Williams added.
Radar altimeters provide a real-time measurement of an aircraft’s clearance over terrain or other obstacles, and may also be integrated with other aircraft systems including terrain avoidance and warning systems (TAWS) and autoland capabilities, as well as ground spoilers, anti-skid braking, pressurization and other seemingly unrelated aircraft systems.