Aircraft Operations and Radar Altimeter Interference from 5G


June 21, 2022

As this is a developing situation, ALPA will update this page with additional operational resources and information for pilots as they become available. Learn more about this issue.

Background

In early 2021, the Federal Communications Commission (FCC) awarded the mobile wireless industry radio spectrum to operate 5G transmissions in the “C-Band,” or 3.7-3.98 GHz, adjacent to the spectrum used by radar altimeters. This approval was made despite the aviation industry informing the FCC since 2018 of the need to ensure that radar altimeters are protected from 5G interference. The 5G signals in the United States are at higher power levels than any other deployment currently in use elsewhere in the world and also with closer proximity to airports. 

In the United States, wireless broadband deployment was originally scheduled to begin on December 5, 2021. After high-level talks, mobile wireless has agreed with the Federal Aviation Administration  (FAA) to delay broadcast of C-Band 5G until January 19, 2022, and placed voluntary limitations to C-Band 5G deployment until July 5, 2022, to permit continued access to airport by a substantial portion of the airline fleet.

On Friday June 17, 2022, FAA convened a meeting of key aviation stakeholders including ALPA to inform them of FAA’s strategy for future co-existence with C-Band 5G transmissions.  Mobile wireless industry has committed to continue current voluntary limits until January 2023, and relaxed limits until July 2023.  This will prevent significant disruption after July 5, 2022, when the original agreement was due to expire.

In conjunction with mobile wireless’s extension, FAA has received commitments from operators of the lowest performing radar altimeters (Embraer regional jets and certain legacy aircraft equipped with particular models of radar altimeters) to upgrade them with Radio Frequency (RF) filters by January 2023.  FAA continues to work with both industries on resolving the significant outstanding issues for the remaining airline fleet for July 2023. 
 
The goal of these upgrades is to eliminate the current Alternate Methods of Compliance (AMOCs) and their associated airport/runway lists that are cumbersome and difficult for airlines and pilots to manage, but it is too soon to tell whether this goal can be met for all aircraft by July 2023.

Canada has also approved 5G in the C-Band, but with restrictions against using C-Band in the vicinity of 26 airports and other measures to ensure aviation safety. Canada has convened a 5G Radar Altimeter Working Group within the Radio Advisory Board of Canada to work through what operational limitations would apply on both mobile wireless and aviation to ensure safety as Canada plans their 5G deployment.

Keep reading for guidance for both U.S. and Canadian airline operations.

Flight Safety Concerns

Radar altimeter interference from 5G signals can take the form of loss of radar altitude information or, worse, incorrect radar altitude information unknowingly being generated. There have been fatal accidents associated with incorrect radar altitude, most recently Turkish Airlines Flight 1951 in Amsterdam in 2009.

Altitude information derived from radar altimeters has been deeply integrated into aircraft systems and automation, with the latest aircraft using it to change aircraft handling qualities and prepare systems such as ground spoilers and thrust reversers for deployment prior to touchdown. This is in addition to radio altimeter use for autoland and in Category (CAT) II/III and Required Navigation Performance (RNP) AR approaches.

FAA Actions and Operational Updates

  • On November 2, 2021, the FAA issued a special airworthiness information bulletin (SAIB) alerting operators to the potential for severe restrictions in flight operations to ensure safety. An updated version, SAIB AIR-21-18R1, was published on December 23, 2021.
  • On December 9, 2021, the FAA issued  an Airworthiness Directive (AD) covering all transport category aircraft. The AD requires the following Airplane Flight Manual (AFM) revision that prohibits the following operations in the presence of possible 5G interference:
Figure 1 to paragraph (g)—AFM Revision     (Required by AD 2021-23-12)

Radio Altimeter Flight Restrictions 

When operating in U.S. airspace, the following operations requiring radio altimeter are prohibited in the presence of 5G C-Band wireless broadband interference as identified by NOTAM (NOTAMs will be issued to state the specific airports where the radio altimeter is unreliable due to the presence of 5G C-Band wireless broadband interference): 

  • Instrument Landing System (ILS) Instrument Approach Procedures (IAP) SA CAT I, SA CAT II, CAT II, and CAT III 
  • Required Navigation Performance (RNP) Procedures with Authorization Required (AR), RNP AR IAP 
  • Automatic Landing operations 
  • Manual Flight Control Guidance System operations to landing/head-up display (HUD) to touchdown operation 
  • Use of Enhanced Flight Vision System (EFVS) to touchdown under 14 CFR 91.176(a)

 

  • On December 23, 2021, the FAA issued Safety Alert for Operators 21007 (12): Describes some of the other aircraft systems that may be affected by C-Band 5G interference on radar altimeters and also contains examples of 5G interference NOTAMs.
  • On January 4, 2022, the FAA published a list of 50 airports where mobile wireless will transmit at reduced power for a period of 6 months (until July 6, 2022). This list has since been expanded to over 100 airports.
  • On January 13, 2022, the FAA issued NOTAMS for all airports and approaches that are restricted by the AD. ALPA has downloaded the full list (view Excel file), which was valid at the time it was downloaded, but pilots should check the latest NOTAMs before flight. 
  • FAA has stood up a C-Band 5G/radar altimeter interference page at www.faa.gov/5g.
  • Since mid-January 2022, FAA has issued Alternate Methods of Compliance (AMOCs) for aircraft/radar altimeter combinations, which allow for the 5G NOTAMs to be disregarded when interference has been determined to not present a safety hazard when operating to or from particular airports and runways. These AMOCs have been updated on a monthly basis.
  • On June 17, 2022, the FAA announced an agreement with mobile wireless for continued voluntary limitations, ending in July 2023. The FAA is therefore requiring airlines to upgrade their radar altimeters to tolerate full urban C-band 5G operations by July 2023. FAA also announced that AMOCs developed under the current process will expire in July 2023, and intends to replace them with new, non-airport specific AMOCs.

Guidance and Limitations by Aircraft Manufacturers

It is further anticipated that, depending on the aircraft, aircraft manufactures may identify additional limitations on specific aircraft. If they do, the FAA may restrict the use of other aircraft systems with additional ADs. The limitations imposed by the ADs protect operations by preventing the most critical hazards from occurring in the case of radar altimeter interference. It is not yet clear how these ADs will change as July 2023 approaches.

  • Airbus has issued Flight Operations Transmission 999.0002/22 (01/10/2022) which describes the currently understood effects of radar altimeter anomalies.  Guidance is provided for A320 family, A330, and A340 aircraft for handing these anomalies. No effects are currently expected for A300/A310, A350, and A380 aircraft.
  • FAA has issued Airworthiness Directive 2022-04-05 for Boeing B757 and B767 aircraft, which modifies the approach, landing, and missed approach procedures at any airport where a 5G NOTAM is in effect. In particular, the AD requires the Flight Directors, Autopilots, and Autothrottles to be turned off or disconnected prior to glideslope intercept for all remaining ILS approaches at 5G NOTAM airports. In addition, landing procedures for aircraft equipped with the Yaw Damper Stabilizer Trim Module (YSM), and go-around procedures are modified. Note that if an AMOC is issued that covers the aircraft for the original AD (2021-23-12), that AMOC will also provide relief for this AD.
  • FAA will be issuing Airworthiness Directive 2022-03-05 for all models of B777 and B747-8, which prohibits dispatch to any airport where a 5G NOTAM is in effect, regardless of weather conditions. Boeing has determined that radar altimeter interference can affect pitch control, and prevent entering the landing and tail strike protection laws. This AD will be published on Thursday 1/27/2022 and will be effective upon publication. B777 and B747-8 crews will be receiving an AFM supplement with this language. Note that if an AMOC is issued that covers the aircraft for the original AD (2021-12-23), that AMOC will also provide relief for this AD (see bottom p.11).
  • FAA will be issuing Airworthiness Directive 2022-02-16 specific to the Boeing B787 which affects the MEL and operational procedures associated with Landing Systems and Landing Distance Calculations.  This AD will be published on Wednesday 1/19/2022 and will be effective upon publication. B787 crews should be receiving a bulletin which covers these Airplane Flight Manual changes.
  • The FAA has issued Airworthiness Directive 2022-05-04 for non-MAX Boeing B737 aircraft, including all models from B737-100 to B737-900ER. The AD cites 5G interference on radar altimeters as possibly causing anomalies in the autopilot flight director system, autothrottles, automatic speedbrake deployment, flight instruments, TCAS, GPWS, and configuration warning systems. The  AD requires modification of procedures in Approach, Landing, and Go-Around/Missed Approach operations. Note that an AMOC approved for AD 2021-23-12 also functions as an AMOC for this AD.
  • FAA will be issuing Airworthiness Directive 2022-03-20 for Boeing B737 MAX aircraft. The AD cites numerous autoflight systems such autothrottle, thrust reversers, speedbrake/spoiler, and the Landing Attitude Modifier that may behave incorrectly or fail to deploy as normal. This modifies the MEL requirements for these systems and changes related operational procedures including operations on runways with poor/nil braking action, and takeoff and landing performance.
  • FAA has issued Airworthiness Directive 2022-06-16 for Boeing B747 aircraft from the B747-100 through the B747-400. The AD cites C-Band 5G interference on radar altimeters that may affect autopilot, flight director, and landing systems. As a result, it requires modification to the Airplane Flight Manual for takeoff, approach, landing, and go-around/missed approach procedures. As with other ADs, an AMOC to AD 2021-23-12 (the ‘blanket’ AD) will also function as an AMOC to this AD.
  • AA has issued Airworthiness Directive 2022-09-18 affecting legacy Boeing and Douglass products including B707, B727, DC-8/-9/-10, MD-80/90 series, B717, and MD-10/MD-11 aircraft. The AD cites C-Band 5G interference on radar altimeters that may affect autopilot, flight director, and landing systems.  As a result, it requires modification for approach, landing, and go-around/missed approach procedures.  As with other ADs, and AMOC to AD 2021-23-12 (the “blanket” AD) will also function as an AMOC to this AD.
  • Embraer Flight Operations Letter 170-001/22 and Operational Bulletin 170-001/22 (01/02/2022): Describe the possible effects of C-Band 5G interference on its E170, E175, E190, and E195 aircraft. Note: The FAA has not yet issued ADs based on these bulletins.
  • Additional restrictions or limitations will be listed here when they are published.

Alternate Methods of Compliance

The FAA has developed a process by which better performing radar altimeters that are able to reject 5G interference can be approved to operate without regard to the AD and NOTAMs. These AMOC approvals will be specific to a combination of aircraft model and radar altimeter model.

The method of approval will take into consideration the performance of the aircraft/radar altimeter combination, as well as the location and power of the 5G transmitter in the vicinity of the airport. Therefore, the AMOCs are being issued with a list of airports where they are effective.

  • As of 4/25/2022, FAA has approved AMOCs for most airports for radar altimeters installed on Boeing 717, 737, 747, 757, 767, 777, 787, and MD-10/-11; Airbus A220, A300, A310, A319, A320, A321, A330, A340, A350, and A380; Canadair CRJ aircraft; DeHavilland Canada DHC-8; Embraer 120; and ATR-42/-72 aircraft.
  • Embraer 145, 170, 175, 190, and 195 aircraft continue to see significant impacts from 5G AD/NOTAMs in operations.
  • AMOCs are revised each month by FAA and distributed by aircraft manufacturers to their airline customers.
  • Revised AMOCs for aircraft which have received radar altimeter retrofits will be issued. It should be noted that once an aircraft is updated, a different AMOC with improved airport access will apply to that aircraft. Operators, including pilots and dispatchers, will need to be aware of the upgrade status of the particular aircraft they are flying, to understand which AMOC applies

Additional ALPA Recommendations

It is critical for pilots to be aware of and comply with any restrictions imposed via AD, AFM, and NOTAMs by the FAA and airline. The flight manual restrictions from the airworthiness directive coupled with NOTAMs that inform of the presence of 5G (C-Band) or restrictions of specific instrument procedures are important triggers, that pilots must carefully evaluate their aircraft’s ability to be safely operated and determine what additional contingencies must be considered.

During flight planning and advanced preparation, consider whether the weather forecast allows for the use of the available instrument approach procedures, should an alternate airport be required. Alternate airports may need to be selected that are further away from the intended destination and may impact fuel loading plans significantly.

Follow company guidance for operating in the 5G interference areas and actively pursue information from your air carrier when you have questions.

Pilots are also advised to:

  • Always err on the side of caution.
  • Reinforce to passengers that all phones must be in airplane mode.
  • Know the equipage of the specific aircraft you will be flying, and any limitations.
    • Remember that air traffic control (ATC) doesn’t know the capabilities or limitations of the aircraft you are operating.
    • Inform ATC of your limitations as needed and be prepared to utilize “unable.”
  • Read the AD and NOTAMs very carefully for your airports and alternates.
    • The AD and NOTAMs will discuss very specific combinations of approaches and aircraft functions that are not authorized.
    • In addition, the NOTAMs may change rapidly on a daily or weekly basis as further data is analyzed. It is imperative a thorough review of the NOTAMs is conducted before each flight.
  • Have documentation of any AMOC that allows the AD/NOTAM to be disregarded.
  • Utilize dispatch to carefully screen what limits are in place for the airports and alternates, including
    • Weather and forecasts and
    • Fuel load and contingency plans for diversion and ATC flow control actions.
  • Be especially aware of any anomalies during operations below 5,000 feet AGL.
  • Follow any guidance provided by your airline and, in the case of conflicting guidance, follow the airline procedures.

Report Radar Altimeter Anomalies

If a radar altimeter anomaly is seen in operations:

  • Report issues immediately to ATC.
  • Report any issues or experiences via ASAP/SMS after the flight is complete.
  • Also, after flight completion, submit a radar altimeter anomaly report:
    • US pilots are requested to file an FAA anomaly report.
    • Canadian pilots are also requested to report any anomalies to Transport Canada. The form requires input from both the Pilot-In-Command and the airline operator. Fill out Parts 1 and 3 of this form, then submit to your airline using the process established by the airline. In the event that a company does not have a process set up to fill out Part 2 of this form, ALPA recommends that pilots send the partial report to Transport Canada to the e-mail address at the bottom of the form.

Canadian Operations

Canadian Aviation Regulation 605.84 already requires US-type-certificated aircraft registered in Canada to comply with US ADs when operating in the US.  Transport Canada has additionally issued Canadian Airworthiness Directive CF-2021-52 extending this requirement to all Canadian-registered aircraft that fly in the US, and Canadian members are therefore also prohibited from performing the operations listed above on this page when the appropriate NOTAMs are in effect.

Canada has also approved 5G in the C-Band but with restrictions against using C-Band in the vicinity of 26 airports and other measures to ensure aviation safety. Canada is not expected to start 5G service in the C-Band until June 2022 and will initially operate in a lower frequency band (3.45-3.65 GHz). Service in the same frequencies as the United States will start no earlier than 2023.

26 Protected Airports in Canada

Abbotsford

CYXX

Calgary

CYYC

Charlottetown

CYYG

Churchill

CYYQ

Edmonton

CYEG

Fort McMurray

CYMM

Fredericton

CYFC

Gander

CYQX

Moncton

CYQM

Halifax

CYHZ

Iqaluit

CYFB

Hamilton

CYHM

London

CYXU

Montreal Mirabel

CYMX

Montreal Trudeau

CYUL

Ottawa

CYOW

Prince George

CYXS

Quebec City

CYQB

Regina

CYQR

Saskatoon

CYXE

St John’s

CYYT

Thunder Bay

CYQT

Toronto

CYYZ

Vancouver

CYVR

Winnipeg

CYWG

Yellowknife

CYZF

View an interactive map showing the location and extent of protected and exclusion zones around these airports.

Any additional restrictions on operations by Transport Canada will be added here as they become available.

In December 2021, the Radio Advisory Board of Canada (RABC) stood up a working group chaired by one representative each from aviation and mobile wireless to work through the technical issues on how C-Band 5G and aviation radar altimeters can coexist. The working group is overseen jointly by Transport Canada and Innovation, Science, and Economic Development (ISED) Canada. ISED is the radio spectrum regulator of Canada. ALPA is a member of this working group.

ISED and Transport Canada have worked together to perform laboratory and flight testing of radar altimeter equipment in the presence of C-Band 5G transmissions. As of June 21, 2022, ISED Canada and Transport Canada are performing analyses based on the lab and flight test data and will brief the aviation and mobile wireless working group in the near future.  It is not yet clear whether or how Canada will use information about the FAA’s plan for radar altimeter retrofits in their findings and rules going forward.