Proposed Rule2026-05686
Airworthiness Directives; Pratt & Whitney Division Engines
Primary source
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Published
March 24, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA proposes to adopt a new airworthiness directive (AD) for certain Pratt & Whitney Division (PW) Model PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3 engines. This proposed 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 proposed AD would require 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 proposed AD would also require removing and replacing certain HPC drum rotor disk assemblies before reaching certain life limits. The FAA is proposing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 91 Issue 56 (Tuesday, March 24, 2026)</title>
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[Federal Register Volume 91, Number 56 (Tuesday, March 24, 2026)]
[Proposed Rules]
[Pages 13984-13987]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-05686]
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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]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney Division Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Pratt & Whitney Division (PW) Model PW4074D, PW4077D,
PW4084D, PW4090, and PW4090-3 engines. This proposed 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
proposed AD would require visually inspecting the HPC drum rotor disk
assembly for incorrect shot peen coverage and,
[[Page 13985]]
depending on the results of the inspection, replacing the HPC drum
rotor disk assembly with a part eligible for installation. This
proposed AD would also require removing and replacing certain HPC drum
rotor disk assemblies before reaching certain life limits. The FAA is
proposing this AD to address the unsafe condition on these products.
DATES: The FAA must receive comments on this proposed AD by May 8,
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 <a href="http://regulations.gov">regulations.gov</a>. 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 <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 NPRM, any comments received, and other
information. The street address for Docket Operations is listed above.
Material Incorporated by Reference:
<bullet> PW material identified in this proposed AD, contact PW,
400 Main Street, East Hartford, CT 06118; phone: (800) 565-0140; email:
<a href="/cdn-cgi/l/email-protection#aac2cfc6da989eeadad8cbdededdc2c3dec4cfd384c9c5c7"><span class="__cf_email__" data-cfemail="137b767f632127536361726767647b7a677d766a3d707c7e">[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.
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#3b5654575742155a15484f4e495c52487b5d5a5a155c544d"><span class="__cf_email__" data-cfemail="b5d8dad9d9cc9bd49bc6c1c0c7d2dcc6f5d3d4d49bd2dac3">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments using a method listed
under the ADDRESSES section. Include ``Docket No. FAA-2026-2724;
Project Identifier AD-2025-01606-E'' at the beginning of your comments.
The most helpful comments reference a specific portion of the proposal,
explain the reason for any recommended change, and include supporting
data. The FAA will consider all comments received by the closing date
and may revise this proposal 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
<a href="http://regulations.gov">regulations.gov</a>, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.
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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to Molly
Sturgis, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des
Moines, WA 98198. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.
Background
The FAA was notified by the manufacturer of a problem with PW Model
PW4074D, PW4077D, PW4084D, PW4090, and PW4090-3 engines where a repair
shop quality escape 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 which 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. This condition, if not
addressed, could result in uncontained debris release, damage to the
engine, and damage to the airplane.
FAA's Determination
The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed PW Alert Service Bulletin (ASB) PW4G-112-A72-373,
Original Issue, 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.
Proposed AD Requirements in This NPRM
This proposed AD would 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. This proposed AD would also
require removing and replacing certain HPC drum rotor disk assemblies
before reaching certain life limits.
Costs of Compliance
The FAA estimates that this AD, if adopted as proposed, would
affect three engines installed on airplanes of U.S. registry. The FAA
estimates that there is one engine installed on airplanes of U.S.
registry with an HPC drum rotor disk assembly installed that require
replacement of the HPC drum rotor disk assembly at the reduced life
limit.
The FAA estimates the following costs to comply with this proposed
AD:
[[Page 13986]]
Estimated Costs
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Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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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
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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 Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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:
Pratt & Whitney Division: Docket No. FAA-2026-2724; Project
Identifier AD-2025-01606-E.
(a) Comments Due Date
The FAA must receive comments on this airworthiness directive
(AD) by May 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) Definition
For the purpose of this AD, a ``part eligible for installation''
is 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.
(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, Original Issue, dated September 10,
2025 (PW ASB PW4G-112-A72-373, Original Issue), 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, Original Issue.
(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 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#ce8f83818d8ea8afafe0a9a1b8"><span class="__cf_email__" data-cfemail="efaea2a0acaf898e8ec1888099">[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#6c0103000015420d421f18191e0b051f2c0a0d0d420b031a"><span class="__cf_email__" data-cfemail="55383a39392c7b347b26212027323c26153334347b323a23">[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.
[[Page 13987]]
(i) Pratt & Whitney Division (PW) Alert Service Bulletin PW4G-112-
A72-373, Original Issue, 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#ddb5b8b1adefe99dadafbca9a9aab5b4a9b3b8a4f3beb2b0"><span class="__cf_email__" data-cfemail="6f070a031f5d5b2f1f1d0e1b1b1807061b010a16410c0002">[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/ibr-locations">www.archives.gov/federal-register/cfr/ibr-locations</a> or email <a href="/cdn-cgi/l/email-protection#d6b0a4f8bfb8a5a6b3b5a2bfb9b896b8b7a4b7f8b1b9a0"><span class="__cf_email__" data-cfemail="4b2d39652225383b2e283f2224250b252a392a652c243d">[email protected]</span></a>.
Issued on March 20, 2026.
Peter A. White,
Deputy Director, Integrated Certificate Management Division, Aircraft
Certification Service.
[FR Doc. 2026-05686 Filed 3-23-26; 8:45 am]
BILLING CODE 4910-13-P
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