Rule2026-18019
Airworthiness Directives; Pratt & Whitney Division Engines
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
September 3, 2026
Effective
October 8, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA is adopting a new airworthiness directive (AD) for certain Pratt & Whitney Division (PW) Model PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3 engines. This AD was prompted by the discovery of a quality escape involving incorrect shot peening on certain high- pressure compressor (HPC) drum rotor disk assemblies. This AD requires visually inspecting the HPC drum rotor disk assembly for incorrect shot peen coverage and, depending on the results of the inspection, replacing the HPC drum rotor disk assembly with a part eligible for installation. This AD also requires removing and replacing certain HPC drum rotor disk assemblies before reaching certain life limits. The FAA is issuing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 91 Issue 170 (Thursday, September 3, 2026)</title>
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[Federal Register Volume 91, Number 170 (Thursday, September 3, 2026)]
[Rules and Regulations]
[Pages 56578-56581]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-18019]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-2724; Project Identifier AD-2025-01606-E;
Amendment 39-23451; AD 2026-17-08]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney Division Engines
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 Pratt & Whitney Division (PW) Model PW4074D, PW4077D, PW4084D,
PW4090, and PW4090-3 engines. This AD was prompted by the discovery of
a quality escape involving incorrect shot peening on certain high-
pressure compressor (HPC) drum rotor disk assemblies. This AD requires
visually inspecting the HPC drum rotor disk assembly for incorrect shot
peen coverage and, depending on the results of the inspection,
replacing the HPC drum rotor disk assembly with a part eligible for
installation. This AD also requires removing and replacing certain HPC
drum rotor disk assemblies before reaching certain life limits. The FAA
is issuing this AD to address the unsafe condition on these products.
DATES: This AD is effective October 8, 2026.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of October 8,
2026.
ADDRESSES:
AD Docket: You may examine the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2026-2724; 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.
[[Page 56579]]
Material Incorporated by Reference:
<bullet> For PW material identified in this AD, contact PW, 400
Main Street, East Hartford, CT 06118; phone: (800) 565-0140; email:
<a href="/cdn-cgi/l/email-protection#80e8e5ecf0b2b4c0f0f2e1f4f4f7e8e9f4eee5f9aee3efed"><span class="__cf_email__" data-cfemail="a1c9c4cdd19395e1d1d3c0d5d5d6c9c8d5cfc4d88fc2cecc">[email protected]</span></a>; website: <a href="http://connect.prattwhitney.com">connect.prattwhitney.com</a>.
<bullet> You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 1200 District Avenue,
Burlington, MA 01803. For information on the availability of this
material at the FAA, call (817) 222-5110. It is also available at
<a href="http://regulations.gov">regulations.gov</a> under Docket No. FAA-2026-2724.
FOR FURTHER INFORMATION CONTACT: Molly Sturgis, Aviation Safety
Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone:
(562) 627-5373; email: <a href="/cdn-cgi/l/email-protection#75181a19190c5b145b06010007121c06351314145b121a03"><span class="__cf_email__" data-cfemail="6d0002010114430c431e19181f0a041e2d0b0c0c430a021b">[email protected]</span></a>.
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 PW Model
PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3 engines. The NPRM was
published in the Federal Register on March 24, 2026 (91 FR 13984). The
NPRM was prompted by a notification from the manufacturer of a repair
shop quality escape, which revealed that certain HPC drum rotor disk
assemblies were shot peened in an area where peening was prohibited.
Further investigation by the manufacturer revealed that incorrect shot
peening of the HPC drum rotor disk assembly reduces the life of the
part, and PW identified a select number of fielded HPC drum rotor disk
assemblies that could have experienced the same quality escape and may
have been peened in a prohibited area. As a result, PW revised the
airworthiness limitations section of the existing aircraft maintenance
manual to reflect the reduced life limit for the affected part and
published updated service material with instructions for removal of
affected HPC drum rotor disk assemblies prior to reaching the updated
reduced life limits, and inspections of affected HPC drum rotor disk
assemblies for incorrect shot peening. In the NPRM, the FAA proposed to
require visually inspecting the HPC drum rotor disk assembly for
incorrect shot peen coverage before accumulating between 8,600 and
10,400 total life cycles since new, as applicable to HPC drum rotor
disk assembly, and, depending on the results of the inspection,
replacing the HPC drum rotor disk assembly with a part eligible for
installation. The FAA also proposed to require removing and replacing
certain HPC drum rotor disk assemblies before reaching certain life
limits. The FAA is issuing this AD to address the unsafe condition on
these products.
Discussion of Final Airworthiness Directive
Comments
The FAA received comments from three commenters. The commenters
were the Air Line Pilots Association, International (ALPA), All Nippon
Airways (ANA), and The Boeing Company (Boeing). ALPA and Boeing
supported the NPRM without change. The following presents the comments
received on the NPRM and the FAA's response to each comment.
Request To Clarify Acceptable Inspection Results and a Part Eligible
for Installation
ANA requested that the FAA revise the NPRM to clarify what action
should be taken if evidence of shot peening is not discovered during
the visual inspection of the HPC drum rotor disk assembly, and to
clarify that affected HPC drum rotor disk assemblies that have passed
the visual inspection required by the NPRM are still eligible for
installation. Specifically, ANA requested that the FAA add the
following language to paragraphs (g) and (h)(2) of the proposed AD:
``HPC drum rotor disk assemblies that have passed the inspection
specified in paragraph (h)(1) of this AD with ``SB A72-373'' marking
can be treated as a part eligible for installation.''
The FAA partially agrees. The FAA disagrees with the specific
language proposed by the commenter but agrees to update the definitions
in paragraph (g) of this AD to clarify that HPC drum rotor disk
assemblies that pass the visual inspection required by paragraph (h)(1)
of this AD are considered eligible for installation.
Request To Allow Future Revisions of Service Material
ANA requested that the FAA revise the material citations specified
in the NPRM to read ``or later'' following the revision date. ANA
stated that future revisions of the material are possible.
The FAA disagrees with the request. Referring to documents that do
not exist at the time the AD is published violates Office of the
Federal Register (OFR) regulations, 1 CFR part 51, regarding approval
of materials ``incorporated by reference'' in rules. These OFR
regulations require that either the service document be submitted to
the OFR for approval as ``referenced'' material, in which case it may
be simply called out in the text of an AD, or the service document
contents be published as part of the actual AD language. Per 1 CFR
51.1(f), an AD may reference only the specific service document that
was submitted to and approved by the OFR for ``incorporation by
reference.'' In order for operators to use later revisions of the
referenced document (issued after the publication of the AD), either
the FAA must revise the AD to reference the specific later revisions,
or operators must request the approval of their use as an alternative
method of compliance (under the provisions of paragraph (i) of this
AD). The FAA did not change this AD as a result of this comment.
Request To Refer to Service Material
ANA requested that the FAA revise paragraphs (h)(3) and (4) of the
proposed AD by incorporating the following language: ``. . . remove the
HPC drum rotor disk assembly from service in accordance with the
Accomplishment Instructions, paragraph 1.A., of PW Service Bulletin
PW4G-112-A72-370, Original Issue or later, and replace with a part
eligible for installation.'' ANA noted that as the NPRM is currently
written, it is unclear that these paragraphs are requirements of PW
Service Bulletin PW4G-112-A72-370.
The FAA infers that ANA is requesting for PW Service Bulletin PW4G-
112-A72-370 to be incorporated by reference. The FAA disagrees with the
request to incorporate PW Service Bulletin PW4G-112-A72-370 by
reference. Paragraphs (h)(3) and (4) of this AD identify the part
numbers and serial numbers for the affected HPC drum rotor disk
assemblies that need to be replaced, as well as the compliance times
for replacement. The FAA did not incorporate PW Service Bulletin PW4G-
112-A72-370 by reference because the AD allows any FAA-approved method
for replacing the HPC drum rotor disk assembly and incorporating this
service bulletin by reference would unnecessarily restrict operators.
The FAA did not change this AD as a result of this comment.
Request for Issue Date and Effective Date of NPRM
ANA requested that the FAA provide ANA with the issue date and
effective date of the NPRM.
The FAA agrees to clarify. The issue date for the NPRM was March
20, 2026, which is included at the bottom of the NPRM after the final
paragraph. NPRMs do not have an assigned effective date. The FAA did
not change this AD as a result of this comment.
[[Page 56580]]
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, and
any other changes described previously, 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 PW Alert Service Bulletin (ASB) PW4G-112-A72-373,
dated September 10, 2025. This material specifies procedures for a
visual inspection of the HPC drum rotor disk assembly for incorrect
shot peen coverage. This material also provides updated inspection
thresholds for visual inspection of affected HPC drum rotor disk
assemblies. 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.
Costs of Compliance
The FAA estimates that this AD affects four engines installed on
airplanes of U.S. registry. The FAA estimates that one of the four
engines installed on an airplane of U.S. registry has an HPC drum rotor
disk assembly installed that requires replacement of the HPC drum rotor
disk assembly at the reduced life limit.
The FAA estimates the following costs to comply with this AD:
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product Cost on U.S. operators
----------------------------------------------------------------------------------------------------------------
Visually inspect HPC drum rotor 10 work-hours x $85 $0 $850 $2,550.
disk assembly. per hour = $850.
Replace HPC drum rotor disk 10 work-hours x $85 1,622,040 1,622,890 Up to $6,491,560.
assembly. per hour = $850.
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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,
(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:
2026-17-08 Pratt & Whitney Division: Amendment 39-23451; Docket No.
FAA-2026-2724; Project Identifier AD-2025-01606-E.
(a) Effective Date
This airworthiness directive (AD) is effective October 8, 2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all Pratt & Whitney Division (PW) Model
PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3 engines.
(d) Subject
Joint Aircraft System Component (JASC) Code 7230, Turbine Engine
Compressor Section.
(e) Unsafe Condition
This AD was prompted by the discovery of a quality escape
involving incorrect shot peening on certain high-pressure compressor
(HPC) drum rotor disk assemblies. The FAA is issuing this AD to
prevent failure of the HPC drum rotor disk assembly. The unsafe
condition, if not addressed, could result in uncontained debris
release, damage to the engine, and damage to the airplane.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Definitions
For the purpose of this AD, a ``part eligible for installation''
is:
(1) Any HPC drum rotor disk assembly having a part number (P/N)
and serial number (S/N) that is not identified in paragraph (h) of
this AD.
(2) Any HPC drum rotor disk assembly having a P/N and S/N
identified in paragraph (h)(1) of this AD that has passed the
inspection required by paragraph (h)(1) of this AD.
(h) Required Actions
(1) For HPC drum rotor disk assemblies having P/N 50S634, and S/
N CENCD26931, CENCD29577, CENCD29597, CENCD41851, or CENCD43536, as
applicable, before accumulating the total life cycles since new in
Table 1 of the Accomplishment Instructions of PW Alert Service
Bulletin (ASB) PW4G-112-A72-373, dated September 10, 2025 (PW ASB
PW4G-112-A72-373), perform a visual inspection of the HPC drum rotor
disk assembly in accordance with the Accomplishment Instructions,
paragraph 1.B., of PW ASB PW4G-112-A72-373.
(2) If, during the inspection required by paragraph (h)(1) of
this AD, evidence of incorrect shot peening is discovered, before
further flight, replace the HPC drum rotor
[[Page 56581]]
disk assembly with a part eligible for installation.
(3) For the HPC drum rotor disk assembly having P/N 50S634 and
S/N CENCD30975, before accumulating 9,800 total life cycles since
new, remove the HPC drum rotor disk assembly from service and
replace with a part eligible for installation.
(4) For the HPC drum rotor disk assembly having P/N 50S634 and
S/N CENCD42978, before accumulating 11,000 total life cycles since
new, remove the HPC drum rotor disk assembly from service and
replace with a part eligible for installation.
(i) Alternative Methods of Compliance (AMOCs)
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 local Flight
Standards District Office, as appropriate. If sending information
directly to the manager of the AIR-520 Continued Operational Safety
Branch, send it to the attention of the person identified in
paragraph (j) of this AD and email to:
<a href="/cdn-cgi/l/email-protection#91d0dcded2d1f7f0f0bff6fee7"><span class="__cf_email__" data-cfemail="57161a18141731363679303821">[email protected]</span></a>. Before using any approved AMOC, notify your
appropriate principal inspector, or lacking a principal inspector,
the manager of the local flight standards district office/
certificate holding district office.
(j) Additional Information
For more information about this AD, contact Molly Sturgis,
Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines,
WA 98198; phone: (562) 627-5373; email: <a href="/cdn-cgi/l/email-protection#a9c4c6c5c5d087c887dadddcdbcec0dae9cfc8c887cec6df"><span class="__cf_email__" data-cfemail="e28f8d8e8e9bcc83cc91969790858b91a2848383cc858d94">[email protected]</span></a>.
(k) Material Incorporated by Reference
(1) The Director of the Federal Register approved the
incorporation by reference (IBR) 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) Pratt & Whitney Division (PW) Alert Service Bulletin PW4G-
112-A72-373, dated September 10, 2025.
(ii) [Reserved]
(3) For PW material identified in this AD, contact PW, 400 Main
Street, East Hartford, CT 06118; phone: (800) 565-0140; email:
<a href="/cdn-cgi/l/email-protection#177f727b672523576765766363607f7e6379726e3974787a"><span class="__cf_email__" data-cfemail="f8909d9488caccb8888a998c8c8f90918c969d81d69b9795">[email protected]</span></a>; website: <a href="http://connect.prattwhitney.com">connect.prattwhitney.com</a>.
(4) You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 1200 District Avenue,
Burlington, MA 01803. For information on the availability of this
material at the FAA, call (817) 222-5110.
(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 <a href="http://www.archives.gov/federal-register/cfr/">www.archives.gov/federal-register/cfr/</a>ibr-locations or email <a href="/cdn-cgi/l/email-protection#0462762a6d6a77746167706d6b6a446a6576652a636b72"><span class="__cf_email__" data-cfemail="7315015d1a1d00031610071a1c1d331d1201125d141c05">[email protected]</span></a>.
Issued on August 20, 2026.
Brian Knaup,
Acting Deputy Director, Integrated Certificate Management Division,
Aircraft Certification Service.
[FR Doc. 2026-18019 Filed 9-2-26; 8:45 am]
BILLING CODE 4910-13-P
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