It is possible that 5G signals could interfere with the radar altimeters (also known as radio altimeters) used in planes and helicopters.
FOCA SAND 2021-004
The purpose of this SAND is to raise awareness in the civil aviation community of the possibility that 5G signals could interfere with radar altimeters in aircraft.
As a precautionary measure, operators of complex aeroplanes or helicopters are advised to define operational measures on how to proceed in the event of interference.
This SAND also encourages the reporting of incidents to the supervisory authority, and explicitly mentioning the issue of 5G signals when filling out occurrence reports.
With the introduction of 5G technology for mobile telecommunications, new frequency ranges have been released that are close to the frequency range used by radar altimeters in planes and helicopters. A report published by the RTCA's SC-239 Steering Committee states that a possible negative impact of 5G on radar altimeters cannot be ruled out. The report looked at the frequency range used in the USA, which is 3.75 GHz to 3.98 GHz. In Europe, the planned frequency range for 5G networks is 3.4 GHz to 3.8 GHz, which is slightly farther from the frequency range used by radar altimeters. The chart below was published by Airbus; it shows the current and planned frequency ranges for 5G telecommunication in different regions of the world. Internationally operating crews are advised to consult this chart.
A further report by the European Communication Committee (ECC PT 1) is currently in progress and will provide information from November 2024 on whether negative effects are also to be expected in Europe.
The filters currently used in radar altimeters are known not to be very selective. Interference could cause a radar altimeter to show a false altitude or to fail entirely.
As a precautionary measure, all operators of aircraft that rely on radar altimeters functioning accurately are advised to define operational measures on how to proceed in the event of a malfunction. Especially in complex aircraft, radar altimeters perform additional functions that may not be obvious to operators.
This SAND is also meant to encourage pilots, air traffic controllers and technical personnel to consider 5G interference as a possible cause when reporting altimeter-related incidents. If, in the case of such an incident, a connection with 5G can be ruled out with certainty, this should be noted in the occurrence report. However, if 5G interference is suspected, any information pointing to this – for instance the presence of 5G antennas in the area – should be included in the report.
EASA reporting portal: aviationreporting.eu
In cooperation with the French and U.S. aviation regulatory authorities DGAC / FAA, the FOCA warns ATS Providers and Operators of potential interference to radio altimeters from 5G emissions and recommends the following measures:
- Operators should remind passengers and flight crews that all electronic devices should be carried in the cabin, on their person or in luggage. If these were placed in checked baggage, they should be turned off and protected from accidental activation.
- If 5G-compatible portable electronic devices (telephones, tablets, modems, etc.) are carried in the cabin or cockpit, they should be set so that they do not transmit on cellular networks (e.g. airplane mode) or switched off.
- For essential communications, e.g. during emergency medical service operations (EMS), crews should only use 3G or 4G communication devices.
- Operators and pilots who experience radio altimeter anomalies should notify air traffic controllers as soon as practical. Reports should include as much detail as possible and include information to describe radio altimeter anomalies In addition to the notification provisions to the authority under Regulation (EU) 376/2014, it is imperative that the air traffic service provider in contact with the aircraft is informed of the disturbance to the radio altimeter. The latter will then trigger the appropriate operational actions.
- Air Traffic Service Providers are encouraged to inform their controllers or AFIS staff of the possibility of jamming reported by crews, and to promptly report to aviationreporting.eu any repetitive reports of potential jamming. In addition, they are invited to inform the aerodrome operator if the interference was related to the proximity of a 5G antenna.
- Operators should seek information from the manufacturers of the aircraft and the radio altimeter on possible effects of harmful interference due to wireless broadband deployment in the 3400-3800 MHz band and possible pilot interventions.
- 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. Consider both erroneous altimeter readings and loss of altimeter function.
- Operators should ensure their pilots are aware of the potential degradation to the capabilities of safety systems and other equipment dependent upon radio altimeters and any means to compensate for resulting anomalies. Consider both the loss of function of the safety systems and other dependent systems and the manners in which they may malfunction.
- Operators should consider the potential loss of pilot trust in dependent aircraft safety systems in the assessment of existing and the development of new crew procedures.
FAA AD 2023-10-02
The US Federal Aviation Administration (FAA) has published a new Airworthiness Directive (AD), which replaces previous ADs on the subject of 5G.
NOTAMs are no longer published for aerodromes with 5G transmitters; instead, the FAA assumes 5G C-Band (3.7 to 3.98GHz) interference throughout US airspace.
The new AD distinguishes between 'radio altimeter tolerant airplanes' which are tolerant of 5G transmitters and no longer have any restrictions, and 'non-radio altimeter tolerant airplanes' which must still have a restriction in the Airplane Flight Manual.
A 'radio altimeter tolerant aircraft' is an aircraft that demonstrates the tolerances of the following two graphs.
EASA SIB 2021-16
The European Union Aviation Safety Agency, EASA, has decided not to adopt FAA ADs.
However, it has published a SIB 2021-16 and updated it in June 2023: EASA Safety Publications Tool (europa.eu)
EASA recommends the following to aircraft operators:
- Pay particular attention to any information promulgated by U.S.A (e.g. through ADs, NOTAMs, AIPs, Domestic Notices) prohibiting certain instrument approach procedures depending on aircraft radio altimeter configuration. Such prohibitions might significantly affect the approach and landing capability and can be issued without prior notice.
Current situation in Switzerland
An analysis by OFCOM has shown that the areas requiring special protection immediately in front of the touchdown zones of runways 14 and 16 at Zurich-Kloten, as well as runway 22 at Geneva, do not have 5G signal strengths that could cause interference with radio altimeters.
Mobile operators notify OFCOM in advance of any changes to their 5G infrastructure within a 3km radius of the critical zones so that the analysis can be repeated.
The situation is therefore under control in Switzerland. A report by the ECC on the situation in Europe is expected in autumn 2024.
Last modification 11.10.2023