Airworthiness Directives; Lycoming Engines

[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 [www.gpo.gov]
[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 regulations.gov 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: lycoming.com/contact/knowledge-base/publications.
    <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-2025-1365.

FOR FURTHER INFORMATION CONTACT: David Bergeron, Aviation Safety 
Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone: 
(516) 228-7321; email: [email protected].

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
----------------------------------------------------------------------------------------------------------------
                                                                                       Cost per    Cost on U.S.
                  Action                            Labor cost           Parts cost    product       operators
----------------------------------------------------------------------------------------------------------------
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.
----------------------------------------------------------------------------------------------------------------

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
----------------------------------------------------------------------------------------------------------------
                      P/N                                    Affected part                   Ship date range
----------------------------------------------------------------------------------------------------------------
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
----------------------------------------------------------------------------------------------------------------

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