COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Porsche Piston Engines AD/PORSCHE/3 Valve Springs 13/98 TX Applicability: Porsche PFM 3200 N01 and N03 engines. Requirement: To address a report of a broken valve spring resulting in a complete engine failure: A: By reviewing engine records, determine the operating hours of the cylinder heads, and B: in accordance with the instructions detailed in Porsche PFM 3200 Service Bulletin Number N/105-036, replace engine valve springs installed in cylinder heads which have a time in service greater than 500 hours . Note: German LBA Airworthiness Directive AD 1998-436 refers. Compliance: Unless previously accomplished; before further flight. This Airworthiness Directive becomes effective on 19 October 1998. Background: This directive has been issued to require the replacement of cylinder head valve springs which have been in service for greater than 500 hours. The requirement reflects a report of an engine failure in flight which resulted from a broken valve spring.