The FAA has published a Special Airworthiness Information Bulletin—AIR-21-18—that highlights potential radio altimeter interference issues by new 5G cellular networks. The 5G network deployment in the U.S. starting on December 5 is in the 3700 to 3800-MHz bands then later in the 3700 to 3980-MHz bands. Radio altimeters use the 4200 to 4400-MHz band.
In other countries, bands from 3300 to 4200 MHz are already deployed, according to the FAA, and some “have implemented temporary technical, regulatory, and operational mitigations, including temporary proximity and power restrictions.” The FAA added, “There have not yet been proven reports of harmful interference due to wireless broadband operations internationally, although this issue is continuing to be studied.”
The SAIB contains many recommendations for aircraft and avionics manufacturers and aircraft operators, ranging from reporting any problems to the FAA to documenting and reporting on the types of radio altimeters installed in aircraft.
by Matt Thurber