EASA SIB NE-08-32R1: Propeller Governor — Idler Gear Shaft Set Screw

What to do

Operators of Lycoming wide cylinder flange engines should apply Loctite 290 to the propeller governor idler gear shaft set screw each time it is installed, following Lycoming SI No. 1343C. They should also periodically check the set screw security using the method in Lycoming SI No. 1560, especially during engine internals inspections. For aerobatic engines, compliance with AD 2015-02-07 mandating thread-locking compound use is required.

Summary

The Special Airworthiness Information Bulletin SAIB NE-08-32R1 is an FAA information bulletin addressing the propeller governor idler gear shaft set screw issue in Lycoming Engines wide cylinder flange models, including O, IO, LIO, AIO, AEIO-320, 360, 540, IO-580, and IO-720 series. It highlights a potential problem with the set screw that secures the propeller governor idler gear shaft, which if loose, can cause engine damage or shutdown. The bulletin provides guidance on the use of Loctite 290 thread-locking compound and a method to check the set screw security without engine disassembly.

What changed

SAIB NE-08-32R1 is a complete revision that continues to recommend using Loctite 290 on the set screw for non-aerobatic engines and introduces a non-mandatory method to check the set screw security without disassembling the engine. It clarifies that aerobatic engines require mandatory use of thread-locking compound per AD 2015-02-07. The bulletin also references updated Lycoming Service Instructions 1343C and 1560 for applying Loctite and checking the set screw, respectively.

Why it matters

This bulletin is important for aviation professionals because a loose or missing propeller governor idler gear shaft set screw can lead to engine oil loss, engine shutdown, and potential in-flight emergencies. Operators and maintenance personnel must ensure proper installation and security of the set screw to prevent engine damage and maintain airworthiness. The guidance helps reduce risk by recommending thread-locking compound use and providing a practical inspection method without engine teardown.