DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-2539; Project Identifier MCAI-2023-00971-E;
Amendment 39-22985; AD 2025-05-13]
RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney Canada Corp. 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 Canada Corp. (P&WC) Model PW535E and PW535E1
engines. This AD was prompted by a manufacturer design review that
indicated certain flange bolts securing the gas generator case and
turbine support case are susceptible to cracking at their current low-
cycle fatigue (LCF) life. This AD requires repetitive borescope
inspections (BSI) of the gas generator case to turbine support case
retaining bolts for evidence of bolt cracks, bolt fracture, missing
bolts, or loose bolts and replacement, if necessary, as specified in a
Transport Canada AD, which is incorporated by reference. The FAA is
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective April 23, 2025.

The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of April 23, 2025.

ADDRESSES:

AD Docket: You may examine the AD docket at regulations.gov under
Docket No.FAA-2024-2539; 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, the mandatory continuing airworthiness
information (MCAI), 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 Transport Canada material identified in this AD,
contact Transport Canada, Transport Canada National Aircraft
Certification, 159 Cleopatra Drive, Nepean, Ontario, K1A 0N5, Canada;
phone: (888) 663-3639; email: TC.AirworthinessDirectives-Consignesdenavigabilite.
TC@tc.gc.ca; website: tc.canada.ca/en/aviation.

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-2024-2539.

FOR FURTHER INFORMATION CONTACT: Barbara Caufield, Aviation Safety
Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198; phone:
(781) 238-7146; email: barbara.caufield@faa.gov.

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 P&WC Model
PW535E and PW535E1 engines. The NPRM published in the Federal Register
on November 26, 2024 (89 FR 93225). The NPRM was prompted by Transport
Canada AD CF-2023-60, dated August 14, 2023 (Transport Canada AD CF-
2023-60) (also referred to as the MCAI), issued by Transport Canada,
which is the aviation authority for Canada. The MCAI states that data
from a design review by the manufacturer identified insufficient LCF
life for flange bolts, having part number (P/N) MS9696-08 and P/N
MS9489-06, that secure the engine gas generator and turbine support
cases. At certain high-stress circumferential locations, LCF cracks
could develop on the flange bolt and lead to fracture of the bolt.
Multiple fractured bolts could lead to flange separation or case
rupture, which may damage the engine and the airplane. To address this
unsafe condition, the manufacturer published material that provides
instructions for repetitive BSIs and replacement of the affected parts.

In the NPRM, the FAA proposed to require repetitive BSI of the gas
generator case to turbine support case retaining bolts for evidence of
bolt cracks, bolt fracture, missing bolts, or loose bolts, and
replacement, if necessary. The FAA is issuing this AD to address the
unsafe condition on these products.

You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2024-2539.

Discussion of Final Airworthiness Directive

Comments

The FAA received no comments on the NPRM or on the determination of
the costs.

Conclusion

These products have been approved by the aviation authority of
another country and are approved for operation in the United States.
Pursuant to the FAA's bilateral agreement with this State of Design
Authority, it has notified the FAA of the unsafe condition described in
the MCAI referenced above. The FAA reviewed the relevant data 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.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Transport Canada AD CF-2023-60, which identifies
the affected gas generator case to turbine support case retaining bolts
and specifies procedures for repetitive BSIs and replacement.

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.

Differences Between This AD and the MCAI

Where the service information referenced in Transport Canada AD CF-
2023-60 requires reporting certain information to the manufacturer,
this AD does not require such a submission.

Costs of Compliance

The FAA estimates that this AD affects 521 engines installed on
airplanes of U.S. registry.

The FAA estimates the following costs to comply with this AD:

Estimated Costs

The FAA estimates the following costs to do any necessary
replacements that are required based on the results of the inspection.
The agency has no way of determining the number of engines that might
need these replacements:

On-Condition Costs

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

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

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

Sec. 39.13 [Amended]

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