[Federal Register Volume 90, Number 234 (Tuesday, December 9, 2025)]
[Rules and Regulations]
[Pages 56986-56988]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-22344]
[[Page 56986]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-0474; Project Identifier AD-2024-00777-T;
Amendment 39-23186; AD 2025-23-03]
RIN 2120-AA64
Airworthiness Directives; The Boeing Company Airplanes
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain The Boeing Company Model 757 airplanes. This AD was prompted by
reports of precoolers that failed due to a wear-out condition, combined
with latently failed overheat detection thermal switches. This AD
requires an inspection for heat damage on the engine strut structure,
repetitive tests of the thermal switch temperature and ground wires,
replacement of the precooler on Model 757-300 airplanes, and applicable
on-condition actions. The FAA is issuing this AD to address the unsafe
condition on these products.
DATES: This AD is effective January 13, 2026.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of January 13,
2026.
ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2025-0474; 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 address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
For Boeing material identified in this AD, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110 SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; website myboeingfleet.com.
You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St., Des
Moines, WA. For information on the availability of this material at the
FAA, call 206-231-3195. It is also available at regulations.gov under
Docket No. FAA-2025-0474.
FOR FURTHER INFORMATION CONTACT: Kathryn Hill, Aviation Safety
Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-
231-3626; email: [email protected].
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain The Boeing
Company Model 757 airplanes. The NPRM was published in the Federal
Register on April 1, 2025 (90 FR 14346). The NPRM was prompted by
reports of precoolers that failed due to a wear-out condition, combined
with latently failed overheat detection thermal switches. In the NPRM,
the FAA proposed to require an inspection for heat damage on the engine
strut structure, repetitive tests of the thermal switch temperature and
ground wires, replacement of the precooler on Model 757-300 airplanes,
and applicable on-condition actions. The FAA is issuing this AD to
address the combination of a failed precooler and latently failed
overheat detection thermal switches. The unsafe condition, if not
addressed, may result in prolonged high temperature heat exposure on
the strut, which could lead to separation of the engine strut-to-wing
box connection.
Discussion of Final Airworthiness Directive
Comments
The FAA received comments from the Air Line Pilots Association,
International (ALPA), ProTech Aero Services Limited, a named
individual, and two anonymous commenters, who all supported the NPRM
without change.
The FAA received additional comments from Aviation Partners Boeing
(APB), European Air Transport Leipzig GmbH, and United Parcel Service
Co. (UPS Airlines). The following presents those comments and the FAA's
response.
Effect of Winglets on Accomplishment of the Proposed Actions
APB stated that the installation of winglets per Supplemental Type
Certificate (STC) ST01518SE does not affect compliance with the
required actions of the proposed rule.
The FAA agrees. The installation of STC ST01518SE does not affect
compliance with the required actions of this AD, specifically, the
accomplishment of the manufacturer's service instructions. The FAA has
not changed this AD in this regard.
Request To Revise Compliance Time for General Visual Inspection (GVI)
UPS Airlines requested the FAA revise the proposed AD to only
require a GVI of the strut if the thermal switch fails the test that is
required to be accomplished within 9,000 flight hours or 27 months from
the effective date of the AD, whichever occurs first. The commenter
stated there are multiple maintenance program inspections of the strut
that are accomplished at various intervals as specified in the Boeing
757 Maintenance Planning Data (MPD). The commenter also stated that MPD
inspections look for corrosion, heat damage, and any obvious signs of
damage. The commenter asserted the inspection of the strut in the
proposed AD is redundant to the MPD inspections and will not provide an
enhanced level of safety.
The FAA does not agree with the request. The maintenance tasks
provided in the Boeing 757 MPD are in general the manufacturer's
recommended tasks so that each operator can develop a customized
maintenance program. Also, the intervals of certain inspections can be
escalated depending on the operator's existing maintenance practices.
The FAA cannot be sure that all strut areas addressed by this AD will
be inspected in a timely manner by all affected operators based on each
operator's customized maintenance program. The FAA has determined that
a latent failure mode identified on the thermal switches may leave hot
air leakage due to precooler failure undetected for a prolonged period,
and this condition could eventually result in critical thermal damage
to the strut structure. The risk of having critical thermal damage
becomes significantly high for those airplanes that continue to operate
with latently failed thermal switches. Since the failure of thermal
switches cannot be detected until the switches are tested, the FAA
concluded that the strut should be inspected as soon as reasonably
practical to mitigate the risk by detecting thermal damage to the strut
structure. The FAA has not changed this AD in this regard.
Request To Correct Aircraft Maintenance Manual (AMM) Reference
European Air Transport Leipzig GmbH requested that the FAA correct
the reference to Boeing ``757 AMM 26-12-01'' for the thermal switch set
temperature test in Boeing Alert Requirements Bulletin 757-26A0062 RB,
dated January 17, 2025. The
[[Page 56987]]
commenter stated that ``757 AMM 26-12-00'' is the correct reference for
the accepted procedure.
The FAA agrees that the AMM reference to the accepted procedure for
the thermal switch set temperature test is incorrect, since 757 AMM 26-
12-01 relates to the removal and installation of the strut overheat
switch, and 757 AMM 26-12-00 relates to the thermal switch set
temperature test. However, no change to the AD is necessary in this
regard. The FAA notes that the incorrect AMM reference is in Boeing
Alert Service Bulletin 757-26A0062, dated January 17, 2025, not Boeing
Alert Requirements Bulletin 757-26A0062 RB, dated January 17, 2025. In
addition to containing the same information that is required for
compliance with the requirements bulletin, the service bulletin
provides additional guidance, including references to accepted
procedures for accomplishing the required actions. Since the reference
to the incorrect AMM section in the service bulletin is ``referred to''
as additional guidance, operators are not required to use it to
accomplish the thermal switch set temperature test. Operators may use
the appropriate AMM sections to accomplish the required actions. The
FAA has not changed this AD in this regard.
Conclusion
The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for minor editorial changes, this
AD is adopted as proposed in the NPRM. None of the changes will
increase the economic burden on any operator.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 757-26A0062 RB,
dated January 17, 2025. This material specifies procedures for a GVI
for heat damage on the left and right engine strut structure,
repetitive thermal switch temperature tests and continuity tests of the
ground wires, and, for Model 757-300 airplanes, replacement of the
precooler at intervals not to exceed 45,000 total precooler flight
hours. This material also specifies procedures for applicable on-
condition actions including repair of structures with heat damage,
replacement of the thermal switch, repair or replacement of failed
circuit wires, and a system test of the strut overheat detection
system, which includes doing applicable corrective actions until the
test is passed.
This material is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section.
Interim Action
The FAA considers this AD to be an interim action. If final action
is later identified, the FAA might consider further rulemaking then.
Costs of Compliance
The FAA estimates that this AD affects 235 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:
Estimated Costs
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Cost on U.S.
Action Labor cost Parts cost Cost per product operators
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Inspection.................... 12 work-hours x $0................... $1,020............... $239,700.
$85 per hour =
$1,020.
Temperature and continuity 20 work-hours x 0.................... 1,700................ $399,500 per
test. $85 per hour = test cycle.
$1,700.
Precooler replacement (21 34 work-hours x Up to $96,675........ Up to $99,565........ Up to $2,090,865
Model 757-300 airplanes). $85 per hour = per replacement
$2,890. cycle.
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The FAA estimates the following costs to do any on-condition
actions that would be required based on the results of the inspection
and test. The agency has no way of determining the number of airplanes
that might need these on-condition actions:
On-Condition Costs *
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Cost per
Action Labor cost Parts cost product
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Strut overheat detection system test.......... 2 work-hours x $85 per hour = $0 $170
$170.
Thermal switch replacement, part number (P/N) 2 work-hours x 85 per hour = 939 1,109
975-0304[dash]003. $170.
Thermal switch replacement, P/N 2 work-hours x 85 per hour = 1,704 1,874
975[dash]0304[dash]004. $170.
Thermal switch replacement, P/N 2 work-hours x 85 per hour = 3,810 3,980
975[dash]0304[dash]008. $170.
Wire repair or replacement.................... 2 work-hours x 85 per hour = 0 170
$170.
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* The FAA has received no definitive data on which to base the cost estimates for some of the on-condition
repairs specified in this AD.
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
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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,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.
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:
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:
2025-23-03 The Boeing Company: Amendment 39-23186; Docket No. FAA-
2025-0474; Project Identifier AD-2024-00777-T.
(a) Effective Date
This airworthiness directive (AD) is effective January 13, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to The Boeing Company Model 757-200, -200PF, -
200CB, and -300 series airplanes, certificated in any category, as
identified in Boeing Alert Requirements Bulletin 757-26A0062 RB,
dated January 17, 2025.
(d) Subject
Air Transport Association (ATA) of America Code 26, Fire
protection.
(e) Unsafe Condition
This AD was prompted by reports of precoolers that failed due to
a wear-out condition. The FAA is issuing this AD to address the
combination of a failed precooler and latently failed overheat
detection thermal switches. The unsafe condition, if not addressed,
may result in prolonged high temperature heat exposure on the strut,
which could lead to separation of the engine strut-to-wing box
connection.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
Except as specified in paragraph (h) of this AD: At the
applicable times specified in the ``Compliance'' paragraph of Boeing
Alert Requirements Bulletin 757-26A0062 RB, dated January 17, 2025,
do all applicable actions identified in, and in accordance with, the
Accomplishment Instructions of Boeing Alert Requirements Bulletin
757-26A0062 RB, dated January 17, 2025.
Note 1 to paragraph (g): Guidance for accomplishing the actions
required by this AD can be found in Boeing Alert Service Bulletin
757-26A0062, dated January 17, 2025, which is referred to in Boeing
Alert Requirements Bulletin 757-26A0062 RB, dated January 17, 2025.
(h) Exceptions to Requirements Bulletin Specifications
(1) Where the ``Boeing Recommended Compliance Time'' columns in
the tables under the ``Compliance'' paragraph of Boeing Alert
Requirements Bulletin 757-26A0062 RB, dated January 17, 2025, refer
to the Original Issue date of Requirements Bulletin 757-26A0062 RB,
this AD requires using the effective date of this AD.
(2) Where Boeing Alert Requirements Bulletin 757-26A0062 RB,
dated January 17, 2025, specifies contacting Boeing for repair
instructions, this AD requires doing the repair using a method
approved in accordance with the procedures in paragraph (i) of this
AD.
(i) Alternative Methods of Compliance (AMOCs)
(1) The Manager, AIR-520, Continued Operational Safety Branch,
FAA, has the 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 the Continued Operational
Safety Branch, send it to the attention of the person identified in
paragraph (j)(1) of this AD. Information may be emailed to
[email protected]. Before using any approved AMOC, notify your
appropriate principal inspector, or lacking a principal inspector,
the manager of the responsible Flight Standards Office.
(2) An AMOC that provides an acceptable level of safety may be
used for any repair, modification, or alteration required by this AD
if it is approved by The Boeing Company Organization Designation
Authorization (ODA) that has been authorized by the Manager, AIR-
520, Continued Operational Safety Branch, FAA, to make those
findings. To be approved, the repair method, modification deviation,
or alteration deviation must meet the certification basis of the
airplane, and the approval must specifically refer to this AD.
(j) Additional Information
(1) For more information about this AD, contact Kathryn Hill,
Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA
98198; phone: 206-231-3626; email: [email protected].
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (k)(3)
this AD.
(k) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference of the material listed in this paragraph
under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions
required by this AD, unless the AD specifies otherwise.
(i) Boeing Alert Requirements Bulletin 757-26A0062 RB, dated
January 17, 2025.
(ii) [Reserved]
(3) For Boeing material identified in this AD, contact Boeing
Commercial Airplanes, Attention: Contractual & Data Services (C&DS),
2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600;
telephone 562-797-1717; website myboeingfleet.com.
(4) You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St.,
Des Moines, WA. For information on the availability of this material
at the FAA, call 206-231-3195.
(5) You may view this material at the National Archives and
Records Administration (NARA). For information on the availability
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations, or email [email protected].
Issued on November 5, 2025.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2025-22344 Filed 12-8-25; 8:45 am]
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