FAA AD 2026-17-10 Addresses Certain Lycoming Piston Pins

The directive, effective 14 September 2026, applies to specified Lycoming O-235, O-540 and IO-540 engines fitted with affected LW-13445 piston pins. Absolute Aircraft Parts has confirmed that a small number of South African aircraft were affected, with replacement parts and warranty claims already handled for affected items supplied through the company.

At a Glance

FAA Airworthiness Directive 2026-17-10 became effective on 14 September 2026 and requires action on certain Lycoming engines fitted with affected LW-13445 piston pins.

The directive follows reports to Lycoming of metal particles found in engine oil and two engine failures. Lycoming’s investigation found that some thin-wall piston pins had been manufactured with microcracks and inclusions in the base metal following changes to honing and tooling processes at the supplier.

Piston pin failure can allow metal debris to circulate through the engine, with possible damage to bearings and other cylinders or blockage of oil passages.

Lycoming had already issued Mandatory Service Bulletin 667A on 12 March 2026. The bulletin covers engines, cylinder kits and spare LW-13445 piston pins associated with FAA Form 8130-3 production dates between 7 January 2021 and 15 December 2025.

Is Every O-235, O-540 or IO-540 Affected?

No. The engine family alone does not determine whether the AD applies.

The FAA directive applies to specified engine models with a serial number listed in Table 2 or Table 3 of Lycoming MSB 667A and an affected LW-13445 piston pin installed.

For the purposes of the AD, an LW-13445 piston pin is affected where the original equipment manufacturer’s FAA Form 8130-3 carries a production date between 7 January 2021 and 15 December 2025. The AD also treats the pin as affected if the production date cannot be determined or the relevant Form 8130-3 is unavailable.

An aircraft should therefore not be assumed to be affected simply because it is fitted with an O-235, O-540 or IO-540.

What Does the AD Require?

FAA AD 2026-17-10 requires replacement of affected piston pins with parts eligible for installation. It also requires an oil change and visual inspection of the engine oil filter, oil pressure screen and oil suction screen for metal particles on affected engines.

The timing depends on the engine’s serial-number group, time in service since installation of the affected pins and the result of the inspection.

For Table 3 engines with more than 150 hours since the affected pins were installed, the oil change and inspection are required before further flight. For other affected engines, if an oil change has not been carried out within the previous 10 hours time in service, the work is required within five hours after the AD became effective.

If metal particles are found during the required inspection, the affected piston pins must be replaced before further flight.

Where no metal is found, the replacement interval depends on whether the engine appears in Table 2 or Table 3 of MSB 667A. Table 2 engines may generally continue until the qualifying maintenance event or overhaul specified by the directive, while certain Table 3 engines are subject to the shorter replacement period set by the AD.

The directive also prohibits installation of an affected piston pin from 14 September 2026.

Important: Lycoming MSB 667A and FAA AD 2026-17-10 should not be treated as interchangeable documents. The FAA specifically added an oil change and inspection requirement within five hours time in service for certain engines where that work had not been completed within the preceding 10 hours.

Owners and operators should work through their maintenance organisation when determining applicability and compliance rather than relying on an article summary.

What Happened in South Africa?

Absolute Aircraft Parts has confirmed to African Pilot that affected engines and piston pins reached the South African fleet.

According to Sharlene Earle, Managing Director – Parts at Absolute Aircraft Parts, the local cases included a small number of new engines as well as some engines that had undergone maintenance.

Following publication of the AD, Absolute Aircraft Parts quarantined affected stock and traced the relevant piston pins and engines it had supplied. This allowed the company to identify affected sales and assist with the required AD compliance.

Absolute Aircraft Parts then contacted the maintenance organisations and aircraft owners that had purchased the affected parts or engines from the company, supplied replacement piston pins and processed the associated warranty claims.

The company reported no difficulty obtaining the required replacement parts from Lycoming.

Using Traceability to Identify Affected Parts

The South African response provides a practical example of how component records can be used when an airworthiness directive affects parts that may already have entered service.

Absolute Aircraft Parts was able to use its sales records and FAA Form 8130-3 documentation to identify affected components among the parts and engines it had supplied.

This can be particularly relevant where an engine has undergone cylinder work or had piston pins replaced during previous maintenance. The current engine configuration and component history, rather than the engine family alone, determine whether the aircraft falls within the affected population.

For owners who have not been contacted and remain uncertain, Absolute Aircraft Parts recommends working through their maintenance organisation, checking the engine serial number against the affected lists and reviewing the relevant component documentation.

Where to Check

The two principal documents are FAA AD 2026-17-10 and Lycoming Mandatory Service Bulletin 667A.

MSB 667A contains Lycoming’s affected engine serial-number tables and piston pin replacement information. FAA AD 2026-17-10 sets out the FAA’s regulatory requirements, inspection requirements and compliance periods.

SACAA also maintains information relating to foreign airworthiness directives. For a South African-registered aircraft, the applicability and required compliance action should be established against the current regulatory and maintenance requirements with the aircraft’s maintenance organisation.