Airlines urged to comply with 5G network. The Federal Aviation Administration (FAA) is giving civil aviation operators an additional year to correct issues related to 5G network interference on certain aircraft instruments.
Compliance as of February 1, 2024
Of the 7,993 aircraft registered in the American register, around 1,000 aircraft are still affected by a problem of interference with the radio altimeter, reveals the FAA in a document relayed by Ars-Technica. To correct these interferences, 180 aircraft will have to be changed and 820 will be able to make do with anti-interference filters. Airlines are ordered to make the changes before February 1, 2024. Operators will thus be able to continue the deployment of 5G in C-band, which is more interesting for data transport.
As a reminder, the radio altimeter of an airplane is used to measure the distance of the device from the ground. To calculate the altitude of the aircraft, the tool uses microwave radar on a spectrum from 4.2 GHz to 4.4 GHz. Frequencies very close to the C band of the 5G network in the United States. Some radio altimeters can thus receive waves emitted in the 3.7-3.98 GHz band, used by 5G antennas on the ground. The calculation of the height of the airplane is therefore distorted and can generate false alerts, which are then sometimes ignored by the pilots.
“False system warnings due to radio altimeter malfunction lead to flight crew desensitization to system warnings. Such desensitization negates the safety benefits of the warning itself and may lead to a catastrophic event”warns the FAA.
Strict measures in France
The risks of interference with frequencies close to those of the radar were not anticipated when the radio altimeters were designed. Indeed, at the time, only satellites, on neighboring frequencies, could have disturbed the reception of waves by the device. A situation that has never occurred due to the low power used by space equipment to communicate. “This led the early designers of altimeters to decide that they could really ignore the limits of the spectrum assigned to them and as a result they let transmitted energy into the receiver well beyond their band”explained Dennis Roberson during a hearing before the US Congress in February 2022.
In France, the C band of the 5G network is further from the frequencies used by radio altimeters. Interference would thus, for the time being, not be demonstrated in France. Studies are, however, still underway to make sure.
Pending fixed conclusions, strict regulations govern the deployment of 5G around airports. Antennas can only be activated at low power within a one kilometer area around the track. Moreover, “the time to remove the doubt on the reality of the problem highlighted by the manufacturers, the 5G mobile operators are also prohibited from directing their antennas towards approaching aircraft”assured Gilles Bregant, director general of the National Frequency Agency (ANFR) in the columns of the Parisian in January 2022.