Service Bulletin No. 639 A

Inspection of Rocker Arm, Part Number LW-15014

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SUBJECT

Inspection of Rocker Arm, Part Number LW-15014

DATE

October 8, 2026

MODELS AFFECTED

O-320-H2AD, O, LO, TO, LTO-360-E1A6D new, rebuilt, or overhauled engines shipped from Lycoming since June 2017 with less than 500 hours of operation or engines with less than 500 hours of operation since rocker arm replacement

TIME OF COMPLIANCE

At next scheduled oil change, then every 50 hours until 500 hours of engine operation

REASON FOR REVISION

Changed the “Rocker Arm Inspection Procedure” to the “Disassembly, Rocker Arm Inspection, and Reassembly”. Added Notice and updated step 4D. Added Hydraulic Lifter Body disassembly and inspection procedure to the “Disassembly, Rocker Arm Inspection, and Reassembly”. Added new “Visual Rocker Arm Inspection Procedure”. Added ICA statement.

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