COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 106 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Teledyne Continental Motors Piston Engines AD/CON/78 Roller Rockers 5/98 Applicability: TCM O-470, IO-470, IO-520, TSIO-520 and IO-550 series engines incorporating "Performance Engineering" exhaust valve roller rockers fitted in accordance with FAA Supplemental Type Certificate (STC) SE8594SW. Note 1: Only engines which have had exhaust valve roller rockers fitted by an STC are affected by this directive. Such engines should have details of the STC certified in the engine log book. Engines fitted with the standard TCM valve rockers are not affected. Requirement: To prevent an exhaust valve roller rocker failure resulting in a loss of engine oil, engine power loss and possible engine failure, remove "Performance Engineering" exhaust valve roller rockers fitted in accordance with STC SE8594SW from service. Note 2: FAA Airworthiness Directive 98-01-08 refers. Compliance: Within 25 hours time in service effective from 23 April 1998. This airworthiness directive becomes effective on 23 April 1998. Background: This directive has been issued to require certain valve rockers to be removed from service. The requirement is in response to reports of failures of "Performance Engineering" roller rocker arms installed under STC SE8594SW. An investigation of the failed roller rocker arms disclosed evidence of manufacturing errors. Valve rocker arm failure will result in a loss of engine power and possible loss of engine oil. Continued operation could then result in engine failure.