5G communications equipment could interfere with aircraft safety systems, according to the Federal Aviation Administration (FAA), which has warned operators to prepare for the potential failure of safety systems as wireless operators begin using more spectrum for 5G services in December.
The FAA released an advisory warning about potential adverse effects on aircraft radio altimeters from mobile broadband devices, with the Special Airworthiness Bulletin highlighing potential problems from the 3.7 to 3.98GHz band.
The band in question is where most commercial 5G activity will take place, according to the GSMA, which has called for regulators to assign as much contiguous spectrum as possible in that range to 5G operations. The 5G community knows this as the C-band spectrum.
The Federal Communications Commission (FCC) has allowed wireless broadband deployment in the lower 100MHz of this spectrum band starting next month.
Radio altimeters operate at 4.2 to 4.4GHz, according to the advisory, which warns the FAA's technical standards don't consider potential interference from adjacent bands.
"Operators should ensure their pilots are aware of the potential degradation of the radio altimeter capabilities and any means to compensate for in-flight radio altimeter anomalies," the advisory read. "Consider both erroneous altimeter readings and loss of altimeter function."
It also warned that operators should be ready to deal with pilots who lose trust in aircraft safety systems.
The document warns pilots to ask passengers to turn off mobile devices or set them to non-transmitting mode. It also recommends altimeter manufacturers test each model to see how susceptible it is to interference from equipment operating in the 3.7 to 3.98GHz spectrum. Aircraft manufacturers should tell the FAA which radio altimeters are installed on their aircraft, it adds.
The advisory follows a letter from the FAA revealed by Reuters last week. The communication voiced "deep concern about the potential impact to aviation safety resulting from interference to radar altimeter performance from 5G network operations in the C band."
The FAA is conducting a risk analysis to see whether it should take further action.
