The FAA’s proposed airworthiness directive (AD) changes on 5G C-band interference mitigation on aircraft systems have caused an uproar among aviation groups. The ability to protect the safety of airplanes has been put into question as a result of the proposal. For more information on the potential rule modifications and more, continue reading.
A broad coalition of aviation groups is criticizing the FAA’s proposed airworthiness directive (AD) on 5G C-band interference mitigation on aircraft systems, saying it is technically flawed and ignores Part 91 and Part 135 operations. The coalition—including Helicopter Association International, NBAA, and 21 other aviation OEMs, companies, and associations—said the proposal “falls short of the goal of preserving the safe operation of airplanes in the National Airspace System (NAS),” calling it “incomplete” and charging that it would adversely impact aircraft operations.
The FAA issued an NPRM on the proposed AD on January 11 along with a 30-day comment period. The proposed AD supersedes all previously issued guidance and ADs (including 2021-23-12) dealing with the interference issue. The FAA said “additional limitations are needed” to deal with the 5G issue as wireless companies withdraw their voluntary signal mitigation around airports and more broadly roll out 5G C-band nationwide. The FAA said it expects 19 additional wireless companies to join AT&T and Verizon in rolling out 5G C-band. The agency said it has received reports of 420 possible instances of 5G C-band radio altimeter interference over the last year but eliminated 75 percent of those reports as unrelated.
Nevertheless, the FAA proposes to mandate modification of aircraft flight manuals (AFM) no later than July 1, 2023, to prohibit certain operations in the presence of 5G C-band (4.2-4.4 GHz) interference. Those operations include ILS approach procedures SA CAT I, SA CAT II, CAT II, and CAT III; automatic landing operations; manual flight control guidance systems operations to landing including head-up display (HUD) to touchdown; and use of enhanced flight vision system (EFVS) to touchdown under 14 CFR 91.176(a). Those operations would be allowed at airports the FAA identifies as 5G C-band mitigation airports (CMA), provided the aircraft are equipped with “a radio altimeter [interference] tolerant airplane.” The approved airports would be identified in an FAA Domestic Notice, as opposed to individual notams, which the FAA considers overly burdensome and unworkable.
The AD would also prohibit all Part 121 (airline) operations after Feb. 1, 2024, unless performed with a radio altimeter-tolerant airplane.
The FAA calls the proposed AD an “interim action” subject to change once a Technical Standard Order (TSO) for radio altimeters is established that meets international minimum operational performance standards (MOPS). Once equipped with these new radio altimeters, aircraft will be able to operate at 5G CMA and non-CMA airports, the FAA said.
The FAA estimates the new AD would impact 7,993 airplanes on the U.S. registry and also interpolates that 7,000 U.S. aircraft already are equipped or have been retrofitted to address radio altimeter interference with new radio altimeters or filters, or are not used for Part 121 operations, and therefore can be brought into compliance by simply modifying the AFM. The FAA estimates that of the remaining Part 121 fleet, 180 aircraft would need to be fitted with new radio altimeters while another 820 would need filtering. It estimates the cost of the AD at $26,049,810—$24,691,000 for new radio altimeters and filtering and the remainder for costs associated with AFM revisions.