Rule2026-04281
Airworthiness Directives; Lycoming Engines
Primary source
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Published
March 4, 2026
Effective
April 8, 2026
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA is superseding Airworthiness Directive (AD) 2024-21- 02, which applies to Lycoming Engines (Lycoming) model engines that have certain connecting rod assemblies installed. AD 2024-21-02 required repetitive oil inspections for bronze metal particulates and, if found, additional inspections of the connecting rod bushings for damage, proper fit, movement, and wear, and replacement if necessary. As terminating action to the connecting rod bushing inspections, AD 2024-21-02 also required replacement of the connecting rod bushings with parts eligible for installation. Since the FAA issued AD 2024-21- 02, the ship date range for potentially affected parts that may be subject to connecting rod failure has been expanded, and additional parts that are eligible for installation have been identified. This AD requires the actions in AD 2024-21-02 and expands the applicability. 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 42 (Wednesday, March 4, 2026)</title>
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[Federal Register Volume 91, Number 42 (Wednesday, March 4, 2026)]
[Rules and Regulations]
[Pages 10506-10508]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-04281]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2025-1365; Project Identifier AD-2024-00684-E;
Amendment 39-23271; AD 2026-04-11]
RIN 2120-AA64
Airworthiness Directives; Lycoming Engines
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2024-21-
02, which applies to Lycoming Engines (Lycoming) model engines that
have certain connecting rod assemblies installed. AD 2024-21-02
required repetitive oil inspections for bronze metal particulates and,
if found, additional inspections of the connecting rod bushings for
damage, proper fit, movement, and wear, and replacement if necessary.
As terminating action to the connecting rod bushing inspections, AD
2024-21-02 also required replacement of the connecting rod bushings
with parts eligible for installation. Since the FAA issued AD 2024-21-
02, the ship date range for potentially affected parts that may be
subject to connecting rod failure has been expanded, and additional
parts that are eligible for installation have been identified. This AD
requires the actions in AD 2024-21-02 and expands the applicability.
The FAA is issuing this AD to address the unsafe condition on these
products.
DATES: This AD is effective April 8, 2026.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of April 8,
2026.
ADDRESSES:
AD Docket: You may examine the AD docket at <a href="http://regulations.gov">regulations.gov</a> under
Docket No. FAA-2025-1365; 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.
Material Incorporated by Reference:
<bullet> For Lycoming material identified in this AD, contact
Lycoming Engines, 652 Oliver Street, Williamsport, PA 17701; phone:
(800) 258-3279; website: <a href="http://lycoming.com/contact/knowledge-base/publications">lycoming.com/contact/knowledge-base/publications</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-2025-1365.
FOR FURTHER INFORMATION CONTACT: David Bergeron, Aviation Safety
Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone:
(516) 228-7321; email: <a href="/cdn-cgi/l/email-protection#cfabaeb9a6abe1a5e1adaabda8aabda0a18fa9aeaee1a8a0b9"><span class="__cf_email__" data-cfemail="93f7f2e5faf7bdf9bdf1f6e1f4f6e1fcfdd3f5f2f2bdf4fce5">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 to supersede AD 2024-21-02, Amendment 39-22869 (89 FR
86721, October 31, 2024) (AD 2024-21-02). AD 2024-21-02 applied to
Lycoming model engines that have certain connecting rod assemblies
installed. AD 2024-21-02 was prompted by several reports of connecting
rod failures, which resulted in uncontained engine failure and in-
flight shutdowns. The NPRM was published in the Federal Register on
August 7, 2025 (90 FR 38081). Since the FAA issued AD 2024-21-02, the
ship date range for potentially affected parts that may be subject to
connecting rod failure has been expanded, and additional parts that are
eligible for installation have been identified. In addition, the
manufacturer requested that credit be given to operators for the
actions required in AD 2024-21-02 provided that the operators already
accomplished AD 2017-16-11 and re-inspected any replacement connecting
rod bushings received from Lycoming in accordance with the required
actions of AD 2017-16-11. In the NPRM, the FAA proposed to require
repetitive oil inspections for bronze metal particulates and, if found,
additional inspections of the connecting rod bushings for damage (e.g.,
deterioration, missing metal), proper fit, movement, and wear, and
replacement if necessary. As terminating action to the connecting rod
bushing inspections, the NPRM also proposed to require replacement of
the connecting rod bushings with parts eligible for installation. The
NPRM also proposed to expand the applicability by extending the
shipping date range for affected parts. 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 one commenter, Lycoming. The
following presents the comment received on the NPRM and the FAA's
response to that comment.
Request To Modify List of Known Engine Models With Affected Parts
Installed
Lycoming requested that the FAA modify the list of engines known to
have an affected part installed in the proposed AD to include Lycoming
Model IO-580 series, IO-720 series, and O-290 series engines.
The FAA agrees with the commenter's request and has revised Note 1
to paragraph (c) of this AD to include Lycoming Model IO-580 series,
IO-720 series, and O-290 series engines.
Conclusion
The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting the 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 Lycoming Mandatory Service Bulletin No. 630B,
dated June 11, 2025, which specifies procedures for inspection of the
connecting rod bushings for damage, proper fit, movement, and wear.
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.
[[Page 10507]]
Costs of Compliance
The FAA estimates that this AD affects 45,152 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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Inspect oil.............................. 2 work-hours x $85 per hour $65 $235 $10,610,720
= $170.
Inspect connecting rod bushings.......... 1 work-hour x $85 per hour 0 85 3,837,920
= $85.
Replace connecting rod bushings (per 4.5 work-hours x $85 per 380 762 34,405,824
bushing). hour = $382.
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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:
0
a. Removing Airworthiness Directive 2024-21-02, Amendment 39-22869 (89
FR 86721, October 31, 2024); and
0
b. Adding the following new airworthiness directive:
2026-04-11 Lycoming Engines: Amendment 39-23271; Docket No. FAA-
2025-1365; Project Identifier AD-2024-00684-E.
(a) Effective Date
This airworthiness directive (AD) is effective April 8, 2026.
(b) Affected ADs
This AD replaces AD 2024-21-02, Amendment 39-22869 (89 FR 86721,
October 31, 2024); (AD 2024-21-02).
(c) Applicability
This AD applies to Lycoming Engines (Lycoming) model engines
that have an affected part and part number (P/N) installed and are
assembled within the ship date range, as specified in Table 1 to
paragraph (c) of this AD.
Table 1 to Paragraph (c)--Affected P/Ns
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P/N Affected part Ship date range
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LW-13923...................................... Connecting Rod Bushing................ 01/30/2009-09/09/2021
LW-11750...................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
78030......................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
LW-19332...................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
LW-13865...................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
77450......................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
LW-13422...................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
LW-13937...................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
LW-15288...................................... Connecting Rod Assembly............... 01/30/2009-09/09/2021
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Note 1 to paragraph (c): The affected parts are known to be
installed on Lycoming Model AEIO-320 series, AEIO-360 series, AEIO-
390 series, AEIO-540 series, AEIO-580-B1A, AIO-320 series, AIO-360
series, HIO-360 series, HIO-390-A1A, HIO-540-A1A, HO-360 series, IO-
320 series, IO-360 series, IO-390 series, IO-540 series, IO-580
series, IO-720 series, IVO-360-A1A, IVO-540-A1A, LHIO-360 series,
LIO-320 series, LIO-360 series, LO-360 series, LTIO-540 series, LTO-
360 series, O-233-A1, O-235 series, O-290 series, O-320 series, O-
340 series, O-360 series, O-435 series, O-540 series, SO-580 series,
TEO-540 series, TIGO-541 series, TIO-360 series, TIO-540 series,
TIO-541 series, TIVO-540-A2A, TO-360 series, TVO-435 series, TVO-
540-A1A, VO-360 series, VO-435 series, VO-540 series, and VSO-580-
A1A engines.
(d) Subject
Joint Aircraft System Component (JASC) Code 8500, Engine
(Reciprocating).
[[Page 10508]]
(e) Unsafe Condition
This AD was prompted by several reports of connecting rod
failures resulting in uncontained engine failure and in-flight
shutdowns (IFSDs). The FAA is issuing this AD to prevent connecting
rod failure. The unsafe condition, if not addressed, could result in
engine failure, an IFSD, and loss of control of the aircraft.
(f) Compliance
Comply with this AD within the compliance times specified,
unless already done.
(g) Required Actions
(1) At the next oil change or within 4 months after the
effective date of this AD, whichever occurs first, and thereafter at
every oil change until the bushing replacement required by either
paragraph (g)(3) or (4) of this AD is done, perform a visual
inspection of the engine oil filter, oil pressure screen, and oil
suction screen (depending on the engine configuration) for bronze
metal particulates. The actions required by this paragraph may be
performed by the owner/operator (pilot) holding at least a private
pilot certificate and must be entered into the aircraft records
showing compliance with this AD in accordance with 14 CFR 43.9(a)
and 91.417(a)(2)(v). The record must be maintained as required by 14
CFR 91.417, 121.380, or 135.439.
Note 2 to paragraph (g)(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 Mandatory
Service Bulletin No. (MSB) 480F, dated May 25, 2017 (Lycoming MSB
480F).
(2) If, during any inspection required by paragraph (g)(1) of
this AD, any bronze metal particulates are found and the source is
identified as the connecting rod bushings, before further flight,
inspect all affected connecting rod bushings for damage (e.g.
deterioration, missing metal), proper fit, movement, and wear in
accordance with ``Connecting Rod Bushing Inspection,'' of Lycoming
MSB 630B, dated June 11, 2025.
Note 3 to paragraph (g)(2): Guidance for identifying the source
of metallic contamination may be found in Table 3 of Lycoming MSB
480F.
(3) If the connecting rod bushings fail any inspection required
by paragraph (g)(2) of this AD, before further flight, replace the
connecting rod bushings with parts eligible for installation. This
terminates the repetitive inspection required by paragraph (g)(1) of
this AD.
(4) At the next engine overhaul, replace the connecting rod
bushings with parts eligible for installation. This terminates the
repetitive inspection required by paragraph (g)(1) of this AD.
(h) Definition
For the purpose of this AD, a ``part eligible for installation''
is any connecting rod bushing having P/N 01K28983 or AEL13923, and
any connecting rod assembly having P/N AEL11750, AEL78030, SL78030,
SL77450, SL13937, SL19332, SL11750, and SL13422.
(i) Credit for Previous Actions
(1) You may take credit for the actions required by paragraph
(g)(1) of this AD if you performed those actions before the
effective date of this AD using Lycoming MSB 480F.
(2) You may take credit for the actions required by paragraph
(g)(2) of this AD if you performed those actions before the
effective date of this AD using Lycoming MSB 630A, dated June 13,
2017.
(3) You may take credit for the actions required by paragraph
(g) of this AD if you accomplished AD 2017-16-11, Amendment 39-18988
(82 FR 37296, August 10, 2017) before the effective date of this AD.
Credit is not given if you received replacement bushings from
Lycoming as a result of accomplishing AD 2017-16-11 and you did not
perform the connecting rod bushing press-out verification procedure
on the replacement bushings in accordance with Lycoming Engines
Mandatory Service Bulletin No. 632B, dated August 4, 2017.
(4) You may take credit for the actions required by paragraph
(g) of this AD if you accomplished AD 2024-21-02, Amendment 39-22869
(89 FR 86721, October 31, 2024) before the effective date of this
AD.
(j) Alternative Methods of Compliance (AMOCs)
(1) 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 (k)(1) of this
AD and email to: <a href="/cdn-cgi/l/email-protection#4e0f03010d0e282f2f60292138"><span class="__cf_email__" data-cfemail="a1e0eceee2e1c7c0c08fc6ced7">[email protected]</span></a>.
(2) 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.
(k) Additional Information
(1) For more information about this AD, contact David Bergeron,
Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park,
GA 30337; phone: (516) 228-7321; email: <a href="/cdn-cgi/l/email-protection#d5b1b4a3bcb1fbbffbb7b0a7b2b0a7babb95b3b4b4fbb2baa3"><span class="__cf_email__" data-cfemail="cfabaeb9a6abe1a5e1adaabda8aabda0a18fa9aeaee1a8a0b9">[email protected]</span></a>.
(2) Material identified in this AD that is not incorporated by
reference is available at the address specified in paragraph (l)(3)
of this AD.
(l) 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. 630B, dated June 11,
2025.
(ii) [Reserved]
(3) For Lycoming material identified in this AD, contact
Lycoming Engines, 652 Oliver Street, Williamsport, PA 17701; phone:
(800) 258-3279; website: <a href="http://lycoming.com/contact/knowledge-base/publications">lycoming.com/contact/knowledge-base/publications</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#5137237f383f2221343225383e3f113f3023307f363e27"><span class="__cf_email__" data-cfemail="2442560a4d4a57544147504d4b4a644a4556450a434b52">[email protected]</span></a>.
Issued on February 18, 2026.
Paul R. Bernado,
Acting Director, Compliance & Airworthiness Division, Aircraft
Certification Service.
[FR Doc. 2026-04281 Filed 3-3-26; 8:45 am]
BILLING CODE 4910-13-P
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