An RTCA Special Committee has issued a report that raises concerns about the frequency spectrum assigned to 5G applications interfering with aircraft radar altimeters. According to the report, the frequency spectrum from 3.7– to 3.98-GHz, which the Federal Communications Commission has assigned to upcoming flexible 5G telecommunications applications, may “introduce harmful radio frequency (RF) interference to radar altimeters currently operating in the globally-allocated 4.2– to 4.4-GHz aeronautical band."
The task force was formed in April to address this issue. In December, the FCC plans to auction licenses in the 3.7– to 4.2-GHz frequency band.
By evaluating radar altimeter performance in light of the “expected 5G emissions in the 3.7– to 3.98-GHz band,” the task force was able to test radar altimeters to determine their tolerance to the expected 5G interference signals, according to the report. Other research included a risk assessment of how much this interference might happen and its impact on aviation safety.
According to the task force, “The results presented in this report reveal a major risk that 5G telecommunications systems in the 3.7– to 3.98-GHz band will cause harmful interference to radar altimeters on all types of civil aircraft—including commercial transport airplanes; business, regional, and general aviation airplanes; and both transport and general aviation helicopters.” The problem isn’t limited to the 5G band allocation of 3.7– to 3.98-GHz, however, but also “the spurious emissions from such systems within the protected 4.2– to 4.4-GHz radar altimeter band directly.”
The report further warned of “the possibility of catastrophic failures leading to multiple fatalities, in the absence of appropriate mitigations.”