Lycoming AD 2026-17-10 can apply to a listed engine when the release form for its piston pins is missing or its production date cannot be determined. Start with the exact engine model and serial number, then identify the installed pins and their paperwork; a missing form does not bring every Lycoming engine into scope.

An airworthiness directive (AD) is a mandatory rule addressing an unsafe condition. This final rule from the US Federal Aviation Administration (FAA) was published on August 28, 2026 and takes effect on September 14, 2026. As of this article's September 12 review, that effective date is still two days away. The comment period closes October 13; it does not postpone the effective date.

Establish which engine and pin you have

A piston pin connects the piston to the connecting rod. The FAA reports that certain thin-wall pins contained manufacturing flaws that could lead to pin failure, engine damage and loss of power. Its estimate of 957 affected engines on US-registered airplanes is a fleet cost estimate, not a count of engine failures.

Paragraph (c) of the AD combines these checks:

  1. Engine model. Compare the complete model designation with the list in paragraph (c). It includes specified O-235, O-540 and IO-540 variants, not every engine bearing those family names.
  2. Serial number. Match it to Table 2 or Table 3 of Lycoming Mandatory Service Bulletin (MSB) 667A, dated March 12, 2026. Record which table contains it, because the required actions differ.
  3. Installed pin. Check for part number LW-13445. A part number identifies a design of component; it is not the engine's serial number.
  4. Release form. Find the original equipment manufacturer's FAA Form 8130-3 for production of the pin. This is the manufacturer's authorized release document. The date window is January 7, 2021 through December 15, 2025. The bulletin points to the date in block 13; do not substitute the date of installation or a later sales invoice.

For that engine and pin population, paragraph (c) expressly makes the AD applicable if the production date on the form cannot be determined or the form is unavailable. Finding no form therefore does not leave this particular applicability check suspended while records are sought.

Paragraph (g) defines an affected LW-13445 pin using the same three conditions: a form dated within the window, an undeterminable production date, or an unavailable form. It also defines parts eligible for installation under this AD: a pin with another part number, or an LW-13445 pin with the manufacturer's production form dated outside the window. That definition does not authorize an otherwise incompatible pin for a particular engine.

Apply the inspection and replacement limits separately

The AD uses time-in-service (TIS). For maintenance records, 14 CFR 1.1 measures this from leaving the ground until touching down at the next landing. Do not silently substitute calendar time or a different engine-meter measure.

The following summarizes paragraph (h), subject to its instruction to comply unless already done. The maintenance professional must use the complete AD and the incorporated instructions for the actual work.

First, oil change and visual inspection:

  • Table 3 engines with more than 150 total hours TIS since the affected pins were installed: before further flight once the AD is effective.
  • All other affected engines: if an oil change has not been performed within the last 10 hours TIS, within 5 hours TIS after the effective date.

The inspection covers the oil filter, oil pressure screen and oil suction screen for metal particles. The AD points to Lycoming MSB 480F as inspection guidance. Its five-hour requirement for the other affected engines is an FAA addition to MSB 667A.

Then, replacement according to the findings:

  • If metal particles are found during the required inspection, replace affected pins before further flight.
  • If no metal is found and the engine is in Table 2, replace at the next maintenance event requiring removal of a cylinder containing an affected pin, or the next overhaul, whichever comes first after the effective date. The overhaul must not exceed the interval in Lycoming Service Instruction 1009BE, dated April 24, 2020.
  • If no metal is found and the engine is in Table 3 with 150 hours TIS or less since pin installation, replace within 25 hours TIS after the effective date, before or upon reaching 150 total hours TIS since installation. Both limits apply. The rule does not say strictly before 150.

The Table 3 case above 150 hours needs care

The AD expressly requires the before-further-flight oil inspection for this case. If metal is found, its replacement deadline is also explicit. However, paragraph (h)(2) does not state a separate replacement deadline for a Table 3 engine already above 150 hours with no metal found.

MSB 667A, page 2, separately specifies replacement within five hours of operation when its above-150-hour inspection produces no recommended corrective action under MSB 480. The AD incorporates the bulletin for required work but states its own compliance branches. Do not silently turn the bulletin's five-hour instruction into an express deadline in that missing AD branch, or read the gap as permission to continue indefinitely. Ask the FAA contact in paragraph (m) how the requirements apply before relying on a replacement schedule for that case.

Check replacement stock and keep the result

Paragraph (i) prohibits installing an affected pin on any engine after the AD's effective date. MSB 667A also instructs removal and quarantine of unused pins within its affected range. The AD's paragraph (j) does not require the bulletin's return of parts to the manufacturer.

A special flight permit, which authorizes a flight for a specified purpose under stated conditions, is not automatic. Paragraph (k) allows one for replacement only if no metal was found; it does not allow one to defer the required visual inspection. An alternative method of compliance also needs FAA approval under paragraph (l).

Keep the applicability check, relevant release form, hours and table used, inspection findings and maintenance entry together. 14 CFR 43.9 governs the maintenance entry. Section 91.417(a)(2)(v) requires the current status and method of compliance for applicable ADs. That status record transfers with the aircraft; ordinary maintenance entries have a different retention rule, and section 91.419 also governs their transfer.

These records show how the determination was made. They do not replace the required maintenance or an FAA clarification. For the wider handover, see our pre-purchase records guide.