[Federal Register Volume 91, Number 166 (Friday, August 28, 2026)]
[Rules and Regulations]
[Pages 55451-55454]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2026-17584]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2026-8789; Project Identifier AD-2026-00678-E;
Amendment 39-23454; AD 2026-17-10]
RIN 2120-AA64
Airworthiness Directives; Lycoming Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule; request for comments.
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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain Lycoming Engines (Lycoming) Model O-235, O-540, and IO-540
engines with a certain piston pin installed. This AD was prompted by
several reports of piston pin failure that resulted in metal
particulate contamination in the engine oil and engine failure. This AD
requires replacement of the affected piston pin with a part eligible
for installation and, for certain engines, oil change and visual
inspection of the engine oil filter, oil pressure screen, and oil
suction screen for metal particulates. This AD also prohibits the
installation of an affected piston pin on any engine. The FAA is
issuing this AD to address the unsafe condition on these products.
DATES: This AD is effective September 14, 2026.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of September 14,
2026.
The FAA must receive comments on this AD by October 13, 2026.
ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to regulations.gov. Follow
the instructions for submitting comments.
Fax: (202) 493-2251.
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.
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 regulations.gov under
Docket No. FAA-2026-8789; or in person at Docket Operations between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD
docket
[[Page 55452]]
contains this final rule, any comments received, and other information.
The street address for Docket Operations is listed above.
Material Incorporated by Reference:
For Lycoming material identified in this AD, contact
Lycoming Engines, 652 Oliver Street, Williamsport, PA 17701; phone:
(800) 258-3279; website: lycoming.com/contact/knowledge-base/publications.
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-2026-8789.
FOR FURTHER INFORMATION CONTACT: Ramanpreet Singh, Aviation Safety
Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone:
(516) 228-7300; email: [email protected].
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites you to send any written data, views, or arguments
about this final rule. Send your comments using a method listed under
the ADDRESSES section. Include ``Docket No. FAA-2026-8789; Project
Identifier AD-2026-00678-E'' at the beginning of your comments. The
most helpful comments reference a specific portion of the final rule,
explain the reason for any recommended change, and include supporting
data. The FAA will consider all comments received by the closing date
and may amend this final rule 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
regulations.gov, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this final rule.
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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to
Ramanpreet Singh, Aviation Safety Engineer, FAA, 1701 Columbia Avenue,
College Park, GA 30337. 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 received reports from Lycoming of metal particulates found
in the engine oil during oil change and two non-detectable engine
failures on Lycoming Model O-235, O-540, and IO-540 engines. A
manufacturer investigation revealed that certain thin-wall piston pins
were manufactured with microcracks and inclusions in the base metal due
to honing and tooling process changes from the piston pin supplier,
making the pins more susceptible to failure. Piston pin failure can
cause metal debris to circulate throughout the engine, which can damage
bearings and other cylinders and can block oil passages and lead to oil
starvation. As a result, Lycoming Engines published updated service
material with a list of affected engines and instructions for
replacement of the affected piston pins and inspection of the oil for
metal particulates. The FAA is issuing this AD to prevent failure of
the piston pins. This condition, if not addressed, could result in
engine failure, loss of thrust control, in-flight shutdown, damage to
the airplane, and loss of control of the airplane. The FAA is issuing
this AD to address the unsafe condition on these products.
FAA's Determination
The FAA is issuing this AD because the agency determined the unsafe
condition described previously is likely to exist or develop in other
products of the same type design.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed Lycoming Mandatory Service Bulletin No. (MSB)
667A, dated March 12, 2026 (Lycoming MSB 667A), which identifies
affected engine serial numbers and specifies procedures for the
replacement of affected piston pins with a part eligible for
installation. Lycoming MSB 667A also specifies procedures for oil
change and visual inspection of the engine oil filter, oil pressure
screen, and oil suction screen for metal particulates. The FAA also
reviewed Lycoming Service Instruction No. 1009BE, dated April 24, 2020,
which identifies the compliance times between overhauls for certain
Lycoming Model engines. 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.
AD Requirements
This AD requires replacement of the affected piston pin with a part
eligible for installation and, for certain engines, oil change and
visual inspection of the engine oil filter, oil pressure screen, and
oil suction screen for metal particulates. This AD also prohibits the
installation of an affected piston pin on any engine.
Differences Between This AD and the Referenced Material
This AD requires oil change and visual inspection of the engine oil
filter, oil pressure screen, and oil suction screen for metal
particulates within 5 hours time-in-service (TIS) unless done within
last 10 hours TIS, while Lycoming MSB 667A does not have this
requirement.
Justification for Immediate Adoption and Determination of the Effective
Date
Section 553(b) of the Administrative Procedure Act (APA) (5 U.S.C.
551 et seq.) authorizes agencies to dispense with notice and comment
procedures for rules when the agency, for ``good cause,'' finds that
those procedures are ``impracticable, unnecessary, or contrary to the
public interest.'' Under this section, an agency, upon finding good
cause, may issue a final rule without providing notice and seeking
comment prior to issuance. Further, section 553(d) of the APA
authorizes agencies to make rules effective in less than thirty days,
upon a finding of good cause.
An unsafe condition exists that requires the immediate adoption of
this AD without providing an opportunity for public comments prior to
adoption. The FAA has found that the risk to the flying public
justifies forgoing notice and comment prior to adoption of this rule
because piston pin microcracks and inclusions are difficult to detect
prior to failure, and can result in internal damage to the engine, in-
flight shutdown, and loss of control of the airplane. The FAA has
determined that affected engines will need to be inspected and have
affected piston pins replaced within 25 hours time-in-service or
earlier after the effective date of this AD depending on the engine
model. Additionally, the compliance
[[Page 55453]]
time in this AD is shorter than the time necessary for the public to
comment and for publication of the final rule. Accordingly, notice and
opportunity for prior public comment are impracticable and contrary to
the public interest pursuant to 5 U.S.C. 553(b).
In addition, the FAA finds that good cause exists pursuant to 5
U.S.C. 553(d) for making this amendment effective in less than 30 days,
for the same reasons the FAA found good cause to forgo notice and
comment.
Regulatory Flexibility Act
The requirements of the Regulatory Flexibility Act (RFA) do not
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt
a rule without prior notice and comment. Because FAA has determined
that it has good cause to adopt this rule without prior notice and
comment, RFA analysis is not required.
Costs of Compliance
The FAA estimates that this AD affects 957 engines installed on
airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:
Estimated Costs
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Cost per Cost on U.S.
Action Labor cost Parts cost product operators
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Replacement of piston pin, oil change, 2 work-hours x $85 per $2,200 $2,370 $2,268,090
and oil inspection. hour = $170.
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The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some of the costs of this AD
may be covered under warranty, thereby reducing the cost impact on
affected operators.
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, and
(2) Will not affect intrastate aviation in Alaska.
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:
2026-17-10 Lycoming Engines: Amendment 39-23454; Docket No. FAA-
2026-8789; Project Identifier AD-2026-00678-E.
(a) Effective Date
This airworthiness directive (AD) is effective September 14,
2026.
(b) Affected ADs
None.
(c) Applicability
This AD applies to Lycoming Engines Model O-235, -A, -AP, -B, -
BP, -C, -C1, -C1A, -C1B, -C1C, -C2A, -C2B, -C2C, -E1, -E1B, -E2A, -
E2B, -F1, -F1B, -F2A, -F2B, -G1, -G1B, O-235-G2A, O-235-G2B, O-235-
H2C, O-235-J2A, O-235-J2B, O-235-K2A, O-235-K2B, -K2C, -L2A, -L2C, -
M1, -M2C, -M3C, -N2A, -N2C, -P1, -P2A, -P2C, and -P3C; O-540-A1A, -
A1A5, -A1B5, -A1C5, -A1D, -A1D5, -A2B, -A3D5, -A4A5, -A4B5, -A4C5, -
A4D5, -A4E5, -B1A5, -B1B5, -B1D5, -B2A5, -B2B5, -B2C5, -B4A5, -B4B5,
-D1A5, -E4A5, -E4B5, -E4C5, -F1A5, -F1B5, -G1A5, -G2A5, -H1A5, -
H1A5D, -H1B5D, -H2A5, -H2A5D, -H2B5D, -J1A5D, -J1B5D, -J1C5D, -
J1D5D, -J2A5D, -J2B5D, -J2C5D, -J2D5D, -J3A5, -J3A5D, -J3C5D, and -
L3C5D; IO-540-A1A5, -AA1A5, -AA1B5, -AB1A5, -AE1A5, -AC1A5, -AF1A5,
-B1B5, -AG1A5, -B1A5, -B1C5, -C1B5, -C1C5, -C2C, -C4B5, -C4B5D, -
C4C5, -C4D5, -C4D5D, -D4A5, -D4B5, -D4C5, -E1A5, -E1B5, -E1C5, -
G1A5, -G1B5, -G1C5, -G1D5, -G1E5, -G1F5, -J4A5, -K1A5, -K1A5D, -
K1B5, -K1B5D, -K1C5, -K1D5, -K1E5, -K1E5D, -K1F5, -K1F5D, -K1G5, -
K1G5D, -K1H5, -K1J5, -K1J5D, -K1K5, -K2A5, -L1A5, -L1A5D, -L1B5D, -
L1C5, -M1A5, -M1A5D, -M1B5D, -M1C5, -M2A5D, -N1A5, -P1A5, -R1A5, -
S1A5, -T4A5D, -T4B5, -T4B5D, -T4C5D, -U1A5D, -U1B5D, -V4A5, -V4A5D,
-W1A5, -W1A5D, and -W3A5D engines with a serial number listed in
Table 2 or Table 3 of Lycoming Mandatory Service Bulletin No. (MSB)
667A, dated March 12, 2026 (Lycoming MSB 667A), and an installed
piston pin having part number (P/N) LW-13445 with an FAA Form 8130-3
from the original equipment manufacturer for production dated
between January 7, 2021 to December 15, 2025. If the production date
on the FAA Form 8130-3 cannot be determined, or if the FAA Form
8130-3 is not available, this AD is applicable.
(d) Subject
Joint Aircraft System Component (JASC) Code 8530, Reciprocating
Engine Cylinder Section.
(e) Unsafe Condition
This AD was prompted by reports from Lycoming of metal
particulates found in the engine oil during oil change and two non-
detectable engine failures. The FAA is issuing this AD to prevent
failure of the piston pin. The unsafe condition, if not addressed,
could result in engine failure, loss of thrust control, in-flight
shutdown, damage to the airplane, and loss of control of the
airplane.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Definitions
(1) For the purpose of this AD, a ``part eligible for
installation'' is one of the following:
[[Page 55454]]
(i) A piston pin that does not have P/N LW-13445.
(ii) A piston pin having P/N LW-13445 with an FAA Form 8130-3
from the original equipment manufacturer for production that is not
dated between January 7, 2021 to December 15, 2025.
(2) For the purpose of this AD, an ``affected piston pin'' is a
piston pin having P/N LW-13445 and one of the following:
(i) An FAA Form 8130-3 from the original equipment manufacturer
for production dated between January 7, 2021 to December 15, 2025.
(ii) An FAA Form 8130-3 from the original equipment manufacturer
for which the production date on the Form 8130-3 cannot be
determined.
(iii) An FAA Form 8130-3 that is not available.
(h) Required Actions
(1) For all affected engines, perform an oil change and visual
inspection of the engine oil filter, oil pressure screen, and oil
suction screen for metal particulates as follows:
Note 1 to paragraph (h)(1): Guidance for engine oil filter, oil
pressure screen, and oil suction screen inspection instructions and
identification of metallic solids may be found in Lycoming MSB No.
480F, dated May 25, 2017.
(i) For engines listed in Table 3 of Lycoming MSB 667A with
greater than 150 total hours time-in-service (TIS) since
installation of the affected piston pins: before further flight.
(ii) For all other affected engines: if an oil change has not
been performed within the last 10 hours TIS, then within 5 hours TIS
after the effective date of this AD.
(2) At the applicable compliance time required in paragraph
(h)(2)(i), (ii), or (iii) of this AD, replace any affected piston
pin with a part eligible for installation in accordance with the
Required Action of Lycoming MSB 667A, as applicable to engine model.
(i) For engines where metal particulates were found during the
oil change and inspection required by paragraph (h)(1)(i) or (ii) of
this AD: before further flight.
(ii) For engines where metal particulates were not found during
the oil change and inspection required by paragraph (h)(1)(i) or
(ii) of this AD and with a serial number listed in Table 2 of
Lycoming MSB 667A: at the next maintenance event requiring the
removal of a cylinder assembly with an affected piston pin, or at
the next engine overhaul not to exceed the time between overhaul
specified in Lycoming Service Instruction No. 1009BE, dated April
24, 2020, whichever occurs first after the effective date of this
AD.
(iii) For engines where metal particulates were not found during
the oil change and inspection required by paragraph (h)(1)(i) or
(ii) of this AD and with a serial number listed in Table 3 of
Lycoming MSB 667A that have 150 hours total TIS or less since
installation of the affected pins: within 25 hours TIS after the
effective date of this AD but before or upon reaching 150 total
hours TIS since installation of the affected piston pins.
(i) Installation Prohibition
After the effective date of this AD, do not install an affected
piston pin as defined in paragraph (g)(2) of this AD, on any engine.
(j) No Return of Parts
Although the service material specifies returning certain parts
to the manufacturer, this AD does not include those requirements.
(k) Special Flight Permits
(1) Special flight permits may be issued in accordance with 14
CFR 21.197 and 21.199199 for the replacement requirements of this AD
provided no metal particulates are found during the inspection
required by this AD.
(2) Special flight permits, as described in 14 CFR 21.197 and
21.199, are not allowed for the visual inspection of the engine oil
filter, oil pressure screen, and oil suction screen for metal
particulates requirement of this AD.
(l) Alternative Methods of Compliance (AMOCs)
The Manager, East Certification 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 East Certification Branch, send it to the
attention of the person identified in paragraph (m)(1) 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.
(m) Additional Information
(1) For more information about this AD, contact Ramanpreet
Singh, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College
Park, GA 30337; phone: (516) 228-7300; email: [email protected].
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (n)(3)
of this AD.
(n) 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) Lycoming Mandatory Service Bulletin No. 667A, dated March
12, 2026.
(ii) Lycoming Service Instruction No. 1009BE, dated April 24,
2020.
(3) For Lycoming material identified in this AD, contact
Lycoming Engines, 652 Oliver Street, Williamsport, PA 17701; phone:
(800) 258-3279; website: lycoming.com/contact/knowledge-base/publications.
(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 21, 2026.
Paul R. Bernado,
Acting Director, Compliance & Airworthiness Division, Aircraft
Certification Service.
[FR Doc. 2026-17584 Filed 8-26-26; 11:15 am]
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