Airworthiness Directives; Pratt & Whitney Division Engines

[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 [www.gpo.gov]
[FR Doc No: 2026-18019]


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

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.

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

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 regulations.gov 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: 
[email protected]; website: connect.prattwhitney.com.
    <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 
regulations.gov 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: [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 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.
----------------------------------------------------------------------------------------------------------------

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:
    [email protected]. 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: [email protected].

(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: 
[email protected]; website: connect.prattwhitney.com.
    (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 www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].

    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

The complete text was extracted from the official GovInfo HTML edition for this publication. Acquired 2026-10-09T00:46:24.060601+00:00. Text extraction preserves the recorded source wording; it does not determine current requirements.

Open the captured official edition

Source SHA-256

4a035da195c9484b861620af4f94e351c2df83f770c9336705499fad60b15ee5

Text SHA-256

257072ef0d54707103bb040fc3c916d4b546c6af5d6e10057681b8d6b0ffc941