AD 99-04-04 64 FR 6516

This amendment adopts a new airworthiness directive (AD) that is applicable to Textron Lycoming IO-540 and O-540 engines equipped with Slick Aircraft Products magnetos. This action requires removal of the Slick magneto from the engine and inspection of the impulse coupling pawl for wear. This amendment is prompted by several service difficulty reports, two incidents, and an accident involving severely worn and failed impulse couplings. The actions specified in this AD are intended to prevent failure of the magneto impulse coupling, resulting in seizure of the engine.