On March 12, 2026, Lycoming Engines released Revision A of Mandatory Service Bulletin 667A, concerning the replacement of certain piston pins.
What is this about?
Lycoming determined that certain thin-wall piston pins (P/N LW-13445) installed in engines, sold as spares, or supplied in specified cylinder kits with an 8130-3 date between January 7, 2021 and December 15, 2025 may contain undesirable manufacturing artifacts in the inside bore.
Manufacturer warning: piston-pin failure can cause an uncommanded and complete loss of power.
Affected engines and parts
This is a mandatory Lycoming service bulletin. It covers:
- Lycoming engines or cylinder kits using LW-13445 piston pins, including the cylinder kits identified in the bulletin: 05K21213-A, 05K21215-A, 05K21231, 05K21117, 05K23037, 05K23038, 05K23040 and 05K29652.
- Spare LW-13445 piston pins with an 8130-3 date in Block 13 between January 7, 2021 and December 15, 2025.
- Specific O-235, O-540 and IO-540 engine serial numbers listed in the technical tables of the bulletin.
What Aéro Atelier is doing
Our team is reviewing our records to identify engines we have worked on that may fall within the affected population.
- Case review: We are identifying potentially affected engines based on the information available in our records.
- Direct communication: Where appropriate, we will contact customers to discuss the applicable next steps and available options.
Compliance, warranty and logistics
- Compliance: The required action and timing depend on the affected engine or spare-part category described in MSB 667A. Owners and maintainers should review the complete current bulletin and the applicable engine records before determining the required action.
- Lycoming warranty consideration: MSB 667A states that affected engines within the factory warranty period may qualify for parts and labour coverage. It also states that affected engines outside the factory warranty period may qualify for reimbursement of replacement parts, standard non-expedited freight, and removal/reinstallation labour in accordance with the applicable Lycoming warranty policy and allowance guide. Eligibility must be confirmed through the Lycoming warranty process.
- Unused affected pins: Lycoming instructs operators not to install affected LW-13445 pins and to remove and quarantine unused pins within the affected date range, then arrange their return through the Lycoming distributor from which they were obtained.
Next steps
If you have a Lycoming engine that may be affected and have questions about work previously performed by Aéro Atelier, contact us with your engine serial number at support@aeroatelier.aero. The complete Lycoming bulletin should be reviewed to determine applicability and required action for the specific engine or part.