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Published 2026-06-30 · Federal Register document 2026-13207

Airworthiness Directives; The Boeing Company Airplanes

Publication summary

The FAA is adopting a new airworthiness directive (AD) for all The Boeing Company Model 747-100, -100B, -100B SUD, -200B, -200C, - 200F, -300, -400, -400D, and -400F series airplanes. This AD was prompted by the determination that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band (5G Lower C-Band) while operating in Canadian airspace, and a determination that during takeoff, approach, landings, and go-arounds, as a result of this interference, certain airplane systems may not properly function, resulting in increased flightcrew workload while on approach with the flight director, autothrottle, or autopilot engaged, which could result in reduced ability of the flightcrew to maintain safe flight and landing of the airplane. This AD requires revising the existing airplane flight manual (AFM) to incorporate limitations prohibiting certain operations requiring radio altimeter data when operating in Canadian airspace. The FAA is issuing this AD to address the unsafe condition on these products.

Why this record is shown

Source: Federal Register annual FAA metadata. Acquired 2026-10-11T15:01:38.908778+00:00. The title, summary and date are source facts.

Source revision
federal_register_ad_metadata_2026-346456b685abaa6b
Source row
results[172]
Raw source SHA-256
346456b685abaa6b551902467a6384e655145a0a63f9cc15222fde6cb778bdfc

Final-rule publication

Recorded publication clauses

AD identifier printed in this edition
2026-13-14
Effective date printed in this edition
2026-07-01
Read 12 complete recorded clauses
Effective Date
(a) Effective Date

    This airworthiness directive (AD) is effective July 1, 2026.

Exact source excerpt. Text positions 22878–22964, end exclusive, in the original decoded publication. SHA-256: 63b12af81d893d5686e92d69bea62daaa244f6d607bd23d001a4c9cb1c54f20b

Affected ADs
(b) Affected ADs

    None.

Exact source excerpt. Text positions 22964–22993, end exclusive, in the original decoded publication. SHA-256: 871a4afc60ceeae06e8010585055188633d616078500c45937092bfe892239c0

Applicability wording · Applicability
(c) Applicability

    This AD applies to all The Boeing Company Model 747-100, -100B, -
100B SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F series 
airplanes, certificated in any category.

Exact source excerpt. Text positions 22993–23192, end exclusive, in the original decoded publication. SHA-256: 2d0a953c0791cdf879eeead755d5ee93c3a8129fb9802f033ad2c0b889064aa9

Subject
(d) Subject

    Air Transport Association (ATA) of America Code 34, Navigation.

Exact source excerpt. Text positions 23192–23274, end exclusive, in the original decoded publication. SHA-256: 0542bcd80d4296f1663f9c1a9ee6733c7599b54c556ebcd2abd87a0d6015adff

Unsafe Condition
(e) Unsafe Condition

    This AD was prompted by the determination that radio altimeters 
cannot be relied upon to perform their intended function if they 
experience interference from wireless broadband operations in the 3.7-
3.98 GHz frequency band (5G Lower C-Band) when operating in Canadian 
airspace, and the determination that during takeoff, approach, 
landings, and go-arounds, as a result of this interference, certain 
airplane systems may not properly function, resulting in increased 
flightcrew workload while on approach with the flight director, 
autothrottle, or autopilot engaged. The FAA is issuing this AD to 
address 5G Lower C-Band interference that could result in increased 
flightcrew workload and could lead to reduced ability of the flightcrew 
to maintain safe flight and landing of the airplane.

Exact source excerpt. Text positions 23274–24101, end exclusive, in the original decoded publication. SHA-256: cdb25a8de79515d40f875beda997a5a733099c10ff9835f292289de025e94c9b

Compliance
(f) Compliance

    Comply with this AD within the compliance times specified, unless 
already done.

Exact source excerpt. Text positions 24101–24203, end exclusive, in the original decoded publication. SHA-256: abbabaaf05573998de1d97fbb30ea4c00462eeb0a61e63718978c9d279c57885

Definitions
(g) Definitions

    (1) For purposes of this AD, a ``radio altimeter tolerant 
airplane'' is one for which the radio altimeter, as installed, 
demonstrates the tolerances specified in paragraphs (g)(1)(i) and (ii) 
of this AD, using a method approved by the FAA. No actions are required 
by this AD for radio altimeter tolerant airplanes.
    (i) Tolerance to radio altimeter interference, for the fundamental 
emissions (3.7-3.98 GHz), at or above the power spectral density (PSD) 
curve threshold specified in figure 1 to paragraph (g)(1)(i) of this 
AD.
[GRAPHIC] [TIFF OMITTED] TR30JN26.003

    (ii) Tolerance to radio altimeter interference, for the spurious 
emissions (4.2-4.4 GHz), at or above the PSD curve threshold specified 
in figure 2 to paragraph (g)(1)(ii) of this AD.

[[Page 39457]]

[GRAPHIC] [TIFF OMITTED] TR30JN26.004

    (2) For purposes of this AD, a ``non-radio altimeter tolerant 
airplane'' is one for which the radio altimeter, as installed, does not 
demonstrate the tolerances specified in paragraphs (g)(1)(i) and (ii) 
of this AD.

Exact source excerpt. Text positions 24203–25270, end exclusive, in the original decoded publication. SHA-256: 5905ee3dc3f7b7d1c6282ff6873c583c343c0ab563d59394e67b6c1ac83fa7cb

Airplane Flight Manual (AFM) Revision
(h) Airplane Flight Manual (AFM) Revision

    For non-radio altimeter tolerant airplanes: Before further flight 
in Canadian airspace, do the actions specified in paragraphs (h)(1) and 
(2) of this AD.
    (1) Revise the Limitations Section of the existing AFM to include 
the information specified in figure 3 to paragraph (h)(1) of this AD. 
This may be done by inserting a copy of figure 3 to paragraph (h)(1) of 
this AD into the existing AFM.

[[Page 39458]]

[GRAPHIC] [TIFF OMITTED] TR30JN26.005

    (2) Revise the Operating Procedures Section of the existing AFM to 
include the information specified in figure 4 to paragraph (h)(2) of 
this AD. This may be done by inserting a copy of figure 4 to paragraph 
(h)(2) of this AD into the existing AFM. An AFM with an Operating 
Procedures Section that complies with paragraph (h)(2) of AD 2023-12-
14, Amendment 39-22472 (88 FR 40003, June 21, 2023) is acceptable for 
compliance with the requirements of this paragraph of this AD.
[GRAPHIC] [TIFF OMITTED] TR30JN26.006

Exact source excerpt. Text positions 25270–26299, end exclusive, in the original decoded publication. SHA-256: f7c716baac9687b4f2dd728c4c53f2bb1da23eb9fef33bdca52b8dfb821ab059

Terminating Action for AFM Revision
(i) Terminating Action for AFM Revision

    (1) Modifying the airplane from a non-radio altimeter tolerant 
airplane to a radio altimeter tolerant airplane terminates the 
limitations in paragraph (h)(1) of this AD and the operating procedures 
in paragraph (h)(2) of this AD for that airplane.
    (2) After modifying the airplane to a radio altimeter tolerant 
airplane, the limitations in paragraph (h)(1) of this AD and the 
operating procedures in paragraph (h)(2) of this AD may be removed from 
the AFM.

Exact source excerpt. Text positions 26299–26812, end exclusive, in the original decoded publication. SHA-256: db5dfed3c736a86aeb2646441440e941bd0fb132d8370f9aa4913eb8c4e6b6a8

Alternative Methods of Compliance (AMOCs)
(j) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, AIR-520, Continued Operational Safety Branch, FAA, 
has the

[[Page 39459]]

authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send 
your request to your principal inspector or responsible Flight 
Standards Office, as appropriate. If sending information directly to 
the manager of AIR-520, Continued Operational Safety Branch, send it to 
the attention of the person identified in paragraph (k) of this AD and 
email to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager of 
the responsible Flight Standards Office.
    (3) The following AMOCs approved previously for AD 2023-12-14, 
Amendment 39-22472 (88 FR 40003, June 21, 2023) are approved as AMOCs 
for paragraph (g)(1) of this AD: FAA AMOC letters 720-23-00133, 720-23-
00137, 720-23-00138, and 720-23-00169.

Exact source excerpt. Text positions 26812–27830, end exclusive, in the original decoded publication. SHA-256: 4466ca888ea5a12a9375334d62ee25c5268235f360de1da2377c50855f166ad4

Additional Information
(k) Additional Information

    For more information about this AD, contact Ken Fairhurst, 
Continued Operational Safety Technical Advisor, FAA, 2200 South 216th 
St., Des Moines, WA 98198; phone: 817-222-5390; email: 
[email protected].

Exact source excerpt. Text positions 27830–28069, end exclusive, in the original decoded publication. SHA-256: c0662d25eb35500a5d133490c5906345171a49d717639c10ba7172a11a496010

Material Incorporated by Reference
(l) Material Incorporated by Reference

    None.

Exact source excerpt. Text positions 28069–28120, end exclusive, in the original decoded publication. SHA-256: 33b5654a42b7710d6e34eeb5d6f69110405cc721191b2e466fa582ff6e507325

No replacement link has been established from this edition. The complete historical rule chain and current legal effect remain unknown.

Find all recorded historical references to AD 2026-13-14 · 0 printed reference observations in this pinned collection.

These are observations from one dated publication. Current legal status is unknown; aircraft applicability, installed configuration, compliance and burden require separate evidence. Missing or unparsed conditions remain unknown.

Why these observations are shown

They were extracted offline from the same immutable official HTML source as the complete recorded text. The dated source wording, original text coordinates and exact quote digests are retained. PDF/text agreement and current regulatory effect have not been qualified.

Observation revision: whole-ad-publication-clause-observations-1.0.1. Text SHA-256: 2ae1065583ef5951d1e9e722f3fff4d4702938948505cb7d12a691d8128f6d38. Source manifest: c54a5647cf7ebca5f28efe6d96d6628af93fc044adda66818109904a09acfc9f.

Official source · 2026-06-30

Publication text

This is the complete recorded text of this dated publication.

Current legal effect is unknown. Aircraft applicability, installed configuration and compliance require separate evidence. PDF/text agreement has not been evaluated.

Read the complete official publication text
[Federal Register Volume 91, Number 124 (Tuesday, June 30, 2026)]
[Rules and Regulations]
[Pages 39452-39459]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-13207]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2026-7205; Project Identifier AD-2026-00549-T; 
Amendment 39-23397; AD 2026-13-14]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

[[Page 39453]]


ACTION: Final rule; request for comments.

-----------------------------------------------------------------------

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
The Boeing Company Model 747-100, -100B, -100B SUD, -200B, -200C, -
200F, -300, -400, -400D, and -400F series airplanes. This AD was 
prompted by the determination that radio altimeters cannot be relied 
upon to perform their intended function if they experience interference 
from wireless broadband operations in the 3.7-3.98 GHz frequency band 
(5G Lower C-Band) while operating in Canadian airspace, and a 
determination that during takeoff, approach, landings, and go-arounds, 
as a result of this interference, certain airplane systems may not 
properly function, resulting in increased flightcrew workload while on 
approach with the flight director, autothrottle, or autopilot engaged, 
which could result in reduced ability of the flightcrew to maintain 
safe flight and landing of the airplane. This AD requires revising the 
existing airplane flight manual (AFM) to incorporate limitations 
prohibiting certain operations requiring radio altimeter data when 
operating in Canadian airspace. The FAA is issuing this AD to address 
the unsafe condition on these products.

DATES: This AD is effective July 1, 2026.
    The FAA must receive comments on this AD by August 14, 2026.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
    <bullet> Federal eRulemaking Portal: Go to regulations.gov. Follow 
the instructions for submitting comments.
    <bullet> Fax: 202-493-2251.
    <bullet> Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.
    <bullet> Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    AD Docket: You may examine the AD docket at regulations.gov by 
searching for and locating Docket No. FAA-2026-7205; or in person at 
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The AD docket contains this final rule, any 
comments received, and other information. The street address for Docket 
Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Ken Fairhurst, Continued Operational 
Safety Technical Advisor, FAA, 2200 South 216th St., Des Moines, WA 
98198; phone: 817-222-5390; email: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written data, views, or arguments 
about this final rule. Send your comments using a method listed under 
the ADDRESSES section. Include Docket No. FAA-2026-7205 and Project 
Identifier AD-2026-00549-T at the beginning of your comments. The most 
helpful comments reference a specific portion of the final rule, 
explain the reason for any recommended change, and include supporting 
data. The FAA will consider all comments received by the closing date 
and may amend this final rule because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
regulations.gov, including any personal information you provide. The 
agency will also post a report summarizing each substantive verbal 
contact received about this final rule.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this AD contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this AD, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this AD. Submissions containing CBI should be sent to Ken 
Fairhurst, Continued Operational Safety Technical Advisor, FAA, 2200 
South 216th St., Des Moines, WA 98198; phone: 817-222-5390; email: 
[email protected]. Any commentary that the FAA receives that is 
not specifically designated as CBI will be placed in the public docket 
for this rulemaking.

Background

    The FAA issued AD 2021-23-12, Amendment 39-21810 (86 FR 69984, 
December 9, 2021) (AD 2021-23-12), for all transport and commuter 
category airplanes equipped with a radio altimeter. AD 2021-23-12 was 
prompted by a determination that radio altimeters cannot be relied upon 
to perform their intended function if they experience interference from 
wireless broadband operations in the 5G Lower C-Band, which is close to 
the frequency bands used by radio altimeters (4.2-4.4 GHz). AD 2021-23-
12 required revising the limitations section of the existing AFM to 
incorporate limitations prohibiting certain operations requiring radio 
altimeter data when in the presence of 5G Lower C-Band interference as 
identified by Notices to Air Missions (NOTAMs). The agency issued AD 
2021-23-12 because radio altimeter anomalies that are undetected by the 
automation or pilot, particularly close to the ground (e.g., landing 
flare), could lead to loss of continued safe flight and landing.
    The FAA subsequently identified an additional hazard presented by 
5G Lower C-Band interference on Boeing Model 747-100, -100B, -100B SUD, 
-200B, -200C, -200F, -300, -400, -400D, and -400F series airplanes and 
issued AD 2022-06-16, Amendment 39-21982 (87 FR 14780, March 16, 2022) 
(AD 2022-06-16). AD 2022-06-16 was prompted by the unsafe condition in 
AD 2021-23-12, as well as a determination that, during takeoff, 
approach, landings, and go-arounds, as a result of interference from 
the 5G Lower C-Band, certain airplane systems may not properly 
function, resulting in increased flightcrew workload while on approach 
with the flight director, autothrottle, or autopilot engaged, which 
could result in reduced ability of the flightcrew to maintain safe 
flight and landing of the airplane. AD 2022-06-16 required revising the 
limitations and operating procedures sections of the existing AFM to 
incorporate specific operating procedures for takeoff, instrument 
landing system (ILS) approaches, non-precision approaches, and go-
around and missed approaches, when in the presence of 5G Lower C-Band 
interference as identified by NOTAMs.
    After the FAA issued AD 2021-23-12 and AD 2022-06-16, the agency 
determined that additional limitations were needed due to the continued 
deployment of new 5G Lower C-Band base stations whose signals were 
expected to cover most of the contiguous U.S., as well as the 
determination that radio altimeter anomalies could lead to increased 
flightcrew workload and flightcrew desensitization to warnings. 
Therefore, the FAA issued AD 2023-10-02, Amendment 39-22438 (88 FR 
34065, May 26, 2023) (AD 2023-10-02), to supersede AD 2021-23-12, and 
the FAA

[[Page 39454]]

issued AD 2023-12-14, Amendment 39-22472 (88 FR 40003, June 21, 2023) 
(AD 2023-12-14), to supersede AD 2022-06-16.
    Currently, AD 2023-12-14 requires revising the limitations section 
of the existing AFM to incorporate limitations for dispatch or release 
to airports, and takeoff, approach, landing, and go-around on runways 
at all airports in the entire contiguous U.S. airspace instead of only 
in areas identified by NOTAM; however, AD 2023-12-14 permits radio 
altimeter tolerant airplanes to perform these operations at 5G Lower C-
Band mitigated airports as identified in an FAA Domestic Notice.

Actions Since AD 2023-12-14 Was Issued

    Since the FAA issued AD 2023-12-14, Transport Canada, which is the 
aviation authority for Canada, issued AD CF-2024-14, dated May 15, 2024 
(Transport Canada AD CF-2024-14), to correct an unsafe condition for 
all transport and commuter category airplanes with a radio altimeter. 
Transport Canada AD CF-2024-14 states that in July 2023, Innovation, 
Science and Economic Development Canada (ISED), Canada's spectrum 
regulator, published Standard Radio System Plans (SRSP)-520 Issue 3 \1\ 
and Radio Standard Specifications (RSS)-192 Issue 5,\2\ which define 
the spectrum environment for the 3.45-3.90 GHz frequency band in 
Canada. Transport Canada AD CF-2024-14 further states that spectrum 
auctions for the 3.45-3.65 GHz and the 3.65-3.9 GHz band were completed 
in 2021 and 2023, respectively.
---------------------------------------------------------------------------

    \1\ https://ised-isde.canada.ca/site/spectrum-management-telecommunications/en/devices-and-equipment/standard-radio-system-plans/srsp-520-technical-requirements-fixed-andor-mobile-systems-including-flexible-use-broadband-systems.
    \2\ https://ised-isde.canada.ca/site/spectrum-management-telecommunications/en/devices-and-equipment/radio-equipment-standards/radio-standards-specifications-rss/rss-192-flexible-use-broadband-equipment-operating-band-3450-3900-mhz.
---------------------------------------------------------------------------

    In July 2023, ISED implemented measures to mitigate Lower C-Band 
interference to radio altimeters, which provide the Canadian airspace 
greater protection from 5G Lower C-Band interference to radio 
altimeters as compared to the Lower C-Band environment in the 
contiguous U.S. airspace. These measures include exclusion and 
protection zones and airport effective isotropic radiated power (EIRP) 
elevation mask (a restriction that requires nearby cell tower signals 
to be angled downward so they do not interfere with aircraft 
altimeters) at certain airport runways covering the majority of air 
traffic in Canada, as well as nationwide reduced fundamental power 
emissions based on the degree of antenna uptilt above the horizon to 
minimize emissions from 5G base stations toward aircraft.
    In late March 2026, Transport Canada notified the FAA that, 
beginning July 1, 2026, changes in the 5G Lower C-band protection 
mitigations established by ISED in 2023 would result in a more severe 
5G interference environment in the Canadian airspace. Exclusion and 
protection zones at airports will no longer exist and updates to the 
airport EIRP elevation mask, nationwide tilt restriction, emitter 
height limitation and reduced spurious emissions will only protect 
airplanes that are radio altimeter tolerant. The change in mitigations 
will result in an unsafe condition in the Canadian 5G interference 
environment.
    Transport Canada determined that radio altimeters cannot be relied 
upon to perform their intended function if they experience interference 
from wireless broadband operations in the 3.45-3.98 GHz frequency band. 
Transport Canada based its determination on the same unsafe condition 
found by the FAA in AD 2023-10-02. As a result, Transport Canada AD CF-
2024-14 requires revising the limitations section of the existing AFM 
to incorporate limitations prohibiting certain operations requiring 
radio altimeter data, due to the presence of 5G Lower C-Band 
interference, while operating in Canadian airspace. As terminating 
action for the operating limitations, Transport Canada AD CF-2024-14 
provides that operators may upgrade their radio altimeters to 
demonstrate the tolerances for emissions as specified in Transport 
Canada AD CF-2024-14.
    Boeing subsequently conducted an analysis of the expected changes 
in the 5G Lower C-Band environment in Canada and the effects of 
interference with radio altimeters with respect to the Boeing fleet. In 
May 2026, Boeing reported that certain airplane configurations will not 
demonstrate tolerance to radio altimeter interference in the new 5G 
environment in Canada. Therefore, based on this information, the FAA 
determined that the unsafe condition identified in AD 2023-12-14 exists 
for Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, -
400D, and -400F series airplanes when operating in the Canadian 
airspace. As a result, operating limitations similar to the limitations 
required by AD 2023-12-14 are necessary.
    The FAA is issuing this AD to address the unsafe condition on these 
products.

FAA's Determination

    The FAA is issuing this AD because the agency has determined the 
unsafe condition described previously is likely to exist or develop in 
other products of the same type design.

AD Requirements

    For non-radio altimeter tolerant airplanes, this AD requires, 
before further flight in Canadian airspace, revising the existing AFM 
to incorporate limitations for dispatch or release to airports, and 
takeoff, approach, landing, and go-around on runways when operating in 
Canadian airspace. This AD provides that modifying the airplane from a 
non-radio altimeter tolerant airplane to a radio altimeter tolerant 
airplane terminates the AFM operating limitations for that airplane.
    While AD 2023-12-14 also specifies limitations for dispatch or 
release to airports and takeoff, approach, landing, and go-around on 
runways for radio altimeter tolerant airplanes except at 5G Lower C-
Band mitigated airports, this AD has no limitations for radio altimeter 
tolerant airplanes. The interference environment at Canadian airports 
after July 1, 2026, will be mitigated enough such that those 
limitations are not necessary for radio altimeter tolerant airplanes. 
The FAA also notes that most Model 747-100, -100B, -100B SUD, -200B, -
200C, -200F, -300, -400, -400D, and -400F series radio altimeter 
tolerant airplanes are not subject to the limitations in AD 2023-12-14 
under the provisions of an FAA-approved AMOC.
    An airplane that is a radio altimeter tolerant airplane using a 
method approved by the FAA for AD 2023-12-14 is also a radio altimeter 
tolerant airplane for the purposes of paragraph (g)(1) of this AD. 
Alternative methods of compliance (AMOC) listed in paragraph (j)(3) of 
this AD are approved for this AD.

Differences From Transport Canada AD CF-2024-14

    Transport Canada AD CF-2024-14 specifies the fundamental emissions 
are in the 3.45-3.98 GHz frequency band, while this AD specifies the 
3.7-3.98 GHz frequency band. AD 2023-10-02 and AD 2023-12-14 identified 
an unsafe condition from wireless broadband transmissions in the 3.7-
3.98 GHz frequency band, and this AD is based on that same 
determination. In addition, an airplane determined to be a radio 
altimeter tolerant airplane for the purposes of AD 2023-12-14, which 
has demonstrated the performance tolerances for fundamental emissions 
within the 3.7-3.98 GHz frequency

[[Page 39455]]

band, would also be a radio altimeter tolerant airplane for purposes of 
this AD. Frequencies less than 3.7 GHz are further away from the 
frequency bands used by radio altimeters (4.2-4.4 GHz), so an airplane 
determined to be tolerant in the range of 3.7-3.98 GHz is also tolerant 
to emissions less than 3.7 GHz.

Interim Action

    The FAA considers this AD to be an interim action. The FAA may 
consider further rulemaking if the Canadian 5G C-Band interference 
environment changes or if Canada issues an operational rule to address 
5G C-Band interference with radio altimeters.

Justification for Immediate Adoption and Determination of the Effective 
Date

    Section 553(b) of the Administrative Procedure Act (APA) (5 U.S.C. 
551 et seq.) authorizes agencies to dispense with notice and comment 
procedures for rules when the agency, for ``good cause,'' finds that 
those procedures are ``impracticable, unnecessary, or contrary to the 
public interest.'' Under this section, an agency, upon finding good 
cause, may issue a final rule without providing notice and seeking 
comment prior to issuance. Further, section 553(d) of the APA 
authorizes agencies to make rules effective in less than thirty days, 
upon a finding of good cause.
    An unsafe condition exists that requires the immediate adoption of 
this AD without providing an opportunity for public comments prior to 
adoption. The FAA has found that the risk to the flying public 
justifies forgoing notice and comment prior to adoption of this rule 
because radio altimeters cannot be relied upon to perform their 
intended function if they experience interference from wireless 
broadband operations in the 5G Lower C-Band. This interference can 
cause other airplane systems to not properly function, resulting in 
increased flightcrew workload, which could lead to reduced ability of 
the flightcrew to maintain safe flight and landing of the airplane. The 
urgency is based on a change in the 5G Lower C-band environment in 
Canada, which is scheduled to occur on July 1, 2026. Accordingly, 
notice and opportunity for prior public comment are impracticable and 
contrary to the public interest pursuant to 5 U.S.C. 553(b).
    In addition, the FAA finds that good cause exists pursuant to 5 
U.S.C. 553(d) for making this amendment effective in less than 30 days, 
for the same reasons the FAA found good cause to forgo notice and 
comment.

Regulatory Flexibility Act

    The requirements of the Regulatory Flexibility Act (RFA) do not 
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt 
a rule without prior notice and comment. Because the FAA has determined 
that it has good cause to adopt this rule without notice and comment, 
RFA analysis is not required.

Costs of Compliance

    The FAA notes that since operators must comply with this AD before 
further flight in Canadian airspace, airplanes that do not operate in 
Canada will not have to comply and therefore will have no costs under 
this AD.
    The FAA estimates that this AD affects 114 airplanes of U.S. 
registry. The FAA expects that many of the affected airplanes have 
upgraded radio altimeters; therefore, the FAA estimates the total 
number of airplanes affected by this AD to be less than the total fleet 
size provided in this AD. The FAA estimates the following costs to 
comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                              Cost per          Cost on U.S.
              Action                      Labor cost         Parts cost        product           operators
----------------------------------------------------------------------------------------------------------------
AFM revision for non-RAT airplanes  1 work-hour x $85 per              $0             $85  Up to $9,690.
                                     hour = $85.
----------------------------------------------------------------------------------------------------------------


                                      Estimated Costs for Optional Actions
----------------------------------------------------------------------------------------------------------------
                Action                        Labor cost               Parts cost            Cost per product
----------------------------------------------------------------------------------------------------------------
Modification (radio altimeter          .......................  .......................  Up to $120,000
 replacement option).                                                                     (includes parts and
                                                                                          labor).
Modification (filter addition option)  24 work-hours x $85 per  $12,000 per filter.....  Up to $14,040 (includes
                                        hour = $2,040 per                                 parts and labor).
                                        filter.
----------------------------------------------------------------------------------------------------------------

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII: Aviation Programs 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

    This AD will not have federalism implications under Executive Order 
13132. This AD will not have a substantial direct effect on the States, 
on the relationship between the national government and the States, or 
on the distribution of power and responsibilities among the various 
levels of government.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866, and
    (2) Will not affect intrastate aviation in Alaska.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 14 CFR part 39 as follows:

[[Page 39456]]

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2026-13-14 The Boeing Company: Amendment 39-23397; Docket No. FAA-
2026-7205; Project Identifier AD-2026-00549-T.

(a) Effective Date

    This airworthiness directive (AD) is effective July 1, 2026.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all The Boeing Company Model 747-100, -100B, -
100B SUD, -200B, -200C, -200F, -300, -400, -400D, and -400F series 
airplanes, certificated in any category.

(d) Subject

    Air Transport Association (ATA) of America Code 34, Navigation.

(e) Unsafe Condition

    This AD was prompted by the determination that radio altimeters 
cannot be relied upon to perform their intended function if they 
experience interference from wireless broadband operations in the 3.7-
3.98 GHz frequency band (5G Lower C-Band) when operating in Canadian 
airspace, and the determination that during takeoff, approach, 
landings, and go-arounds, as a result of this interference, certain 
airplane systems may not properly function, resulting in increased 
flightcrew workload while on approach with the flight director, 
autothrottle, or autopilot engaged. The FAA is issuing this AD to 
address 5G Lower C-Band interference that could result in increased 
flightcrew workload and could lead to reduced ability of the flightcrew 
to maintain safe flight and landing of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, unless 
already done.

(g) Definitions

    (1) For purposes of this AD, a ``radio altimeter tolerant 
airplane'' is one for which the radio altimeter, as installed, 
demonstrates the tolerances specified in paragraphs (g)(1)(i) and (ii) 
of this AD, using a method approved by the FAA. No actions are required 
by this AD for radio altimeter tolerant airplanes.
    (i) Tolerance to radio altimeter interference, for the fundamental 
emissions (3.7-3.98 GHz), at or above the power spectral density (PSD) 
curve threshold specified in figure 1 to paragraph (g)(1)(i) of this 
AD.
[GRAPHIC] [TIFF OMITTED] TR30JN26.003

    (ii) Tolerance to radio altimeter interference, for the spurious 
emissions (4.2-4.4 GHz), at or above the PSD curve threshold specified 
in figure 2 to paragraph (g)(1)(ii) of this AD.

[[Page 39457]]

[GRAPHIC] [TIFF OMITTED] TR30JN26.004

    (2) For purposes of this AD, a ``non-radio altimeter tolerant 
airplane'' is one for which the radio altimeter, as installed, does not 
demonstrate the tolerances specified in paragraphs (g)(1)(i) and (ii) 
of this AD.

(h) Airplane Flight Manual (AFM) Revision

    For non-radio altimeter tolerant airplanes: Before further flight 
in Canadian airspace, do the actions specified in paragraphs (h)(1) and 
(2) of this AD.
    (1) Revise the Limitations Section of the existing AFM to include 
the information specified in figure 3 to paragraph (h)(1) of this AD. 
This may be done by inserting a copy of figure 3 to paragraph (h)(1) of 
this AD into the existing AFM.

[[Page 39458]]

[GRAPHIC] [TIFF OMITTED] TR30JN26.005

    (2) Revise the Operating Procedures Section of the existing AFM to 
include the information specified in figure 4 to paragraph (h)(2) of 
this AD. This may be done by inserting a copy of figure 4 to paragraph 
(h)(2) of this AD into the existing AFM. An AFM with an Operating 
Procedures Section that complies with paragraph (h)(2) of AD 2023-12-
14, Amendment 39-22472 (88 FR 40003, June 21, 2023) is acceptable for 
compliance with the requirements of this paragraph of this AD.
[GRAPHIC] [TIFF OMITTED] TR30JN26.006

(i) Terminating Action for AFM Revision

    (1) Modifying the airplane from a non-radio altimeter tolerant 
airplane to a radio altimeter tolerant airplane terminates the 
limitations in paragraph (h)(1) of this AD and the operating procedures 
in paragraph (h)(2) of this AD for that airplane.
    (2) After modifying the airplane to a radio altimeter tolerant 
airplane, the limitations in paragraph (h)(1) of this AD and the 
operating procedures in paragraph (h)(2) of this AD may be removed from 
the AFM.

(j) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, AIR-520, Continued Operational Safety Branch, FAA, 
has the

[[Page 39459]]

authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send 
your request to your principal inspector or responsible Flight 
Standards Office, as appropriate. If sending information directly to 
the manager of AIR-520, Continued Operational Safety Branch, send it to 
the attention of the person identified in paragraph (k) of this AD and 
email to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager of 
the responsible Flight Standards Office.
    (3) The following AMOCs approved previously for AD 2023-12-14, 
Amendment 39-22472 (88 FR 40003, June 21, 2023) are approved as AMOCs 
for paragraph (g)(1) of this AD: FAA AMOC letters 720-23-00133, 720-23-
00137, 720-23-00138, and 720-23-00169.

(k) Additional Information

    For more information about this AD, contact Ken Fairhurst, 
Continued Operational Safety Technical Advisor, FAA, 2200 South 216th 
St., Des Moines, WA 98198; phone: 817-222-5390; email: 
[email protected].

(l) Material Incorporated by Reference

    None.

    Issued on June 25, 2026.
Brian Knaup,
Acting Deputy Director, Integrated Certificate Management Division, 
Aircraft Certification Service.
[FR Doc. 2026-13207 Filed 6-26-26; 4:15 pm]
BILLING CODE 4910-13-P


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