In anticipation of more telecoms operating 5G networks near airports, the FAA has proposed rules for all helicopters equipped with a radio or radar altimeter flying in areas where 5G C-band operations can potentially interfere with the device’s operation. Aviation Today reports that operators will have the option to upgrade to a radio altimeter-tolerant helicopter if they wish to avoid the prohibitions in this proposed directive by July 1, according to the FAA.
Some operators may need to install filters between the radio altimeter and antenna to increase a radio altimeter’s tolerance. For others, the addition of a filter will not be sufficient to address interference susceptibility; therefore, the radio altimeter will need to be replaced with an upgraded radio altimeter, according to the FAA.
At least 19 telecoms are expected to expand their 5G networks beginning in June, notes the FAA. These carriers have C-band licenses on 3.7 to 3.98 GHz. The FCC created a 220 MHz guard band to protect airplane equipment operating on 4.2 GHz to 4.4 GHz.
But the FAA contends older or poorly built altimeters may be unable to filter out transmissions from other spectrum bands. Inside Towers reported the concern is that when operating near a 5G tower, certain radio frequencies can cause inaccurate altitude readings for certain radio/radar altimeters, causing a risk to the aircraft and its crew while in flight. Because of the potential extent of 5G C-band signals, using Notice to Air Missions and assessing proposed alternative methods of compliance on a case-by-case basis will become untenable, according to Helicopter Association International.
By Leslie Stimson, Inside Towers Washington Bureau Chief