It is possible that 5G signals could interfere with the radar altimeters used in planes and helicopters.
FOCA SAND 2021-004
Context
Purpose
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.
Background
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 July 2023 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
Recommendation
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 2021-23-12
The U.S. Federal Aviation Administration (FAA) has additionally published two Airworthiness Directives (AD) that require Type Certification Holders of transport aircraft and helicopters equipped with a radio altimeter to add an amendment to the flight manual.
These supplements provide that certain operations will no longer be allowed if a NOTAM is published warning of known interference between 5G and radio altimeters at certain locations. The AD's are not yet in effect and may still be commented on. However, it is expected that after January 4, 2022, operations will only be allowed in U.S. airspace with amended flight manuals.
Examples:
For transport and commuter category airplanes equipped with a radio altimeter:
FRC_Document_AD-2021-01169-T-D.pdf (faa.gov)
For all helicopters equipped with a radio altimeter:
FRC_Document_AD-2021-01170-R-D.pdf (faa.gov)
EASA
EASA SIB 2021-16
The European Aviation Safety Agency, EASA, has decided not to adopt the FAA AD's.
However, it has published a SIB 2021-16: EASA Safety Publications Tool (europa.eu) eand issues the following additional recommendations for operators of complex aircraft:
It is recommended that operators:
- Whilst being reminded of the obligation prescribed in Air OPS ORO.GEN.110 to comply with the laws, regulations and procedures of those States in which operations are conducted, pay particular attention to any information promulgated by the State of the Aerodrome (e.g. through NOTAMs) prohibiting instrument approach procedures. Such NOTAMs might significantly affect the approach and landing capability and can be issued without prior notice.
- Consider in their safety risk assessment potential interference from 5G ground stations that might impair the reliable functioning of radio altimeters installed on the aircraft. Among the possible mitigations, operators should:
- - Consider exposing flight crews to unreliable radio altimeter scenarios in the approach and take-off phases of recurrent flight training sessions conducted in the Flight Simulation Training Devices. Such mitigation is particularly relevant in case flight crews undergo Low Visibility Operations training as per Air OPS SPA.LVO.120.
- - Whatever the type of approach conducted, ensure awareness of the crews of the potential degradation in the performance of installed radio altimeters and of other systems dependent on data from radio altimeters.
- Ensure that events of anomalous radio altimeter behaviour, including results of the defect investigation and rectification, are reported to the aircraft manufacturer without delay. Reports of consistent anomalous radio altimeter behaviour in approximately the same location could be an indication of potential interference. Individual cases may however be due to other causes than interference from 5G ground stations. Should such event be qualified as an occurrence, as prescribed by Regulation (EU) No 376/2014, operators are reminded of their mandatory reporting obligation.
- Finally, operators are reminded that anomalous radio altimeter behaviour can be caused by faulty radio altimeter equipment, or (e.g.) due to poor antenna bonding, water ingress or poor antenna cable connections. It is therefore essential that the appropriate maintenance actions continue to be performed in response to a report of anomalous radio altimeter behaviour.
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 summer 2023.
Links
Locations of 5G antennas in Switzerland
European Aviation Reporting Portal
DGAC Safety Information Leaflet
5G and Aviation Safety | Federal Aviation Administration (faa.gov)
Last modification 17.08.2022
