COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Propellers - Variable Pitch - Hamilton Standard AD/PHS/9 Model 54H60 Pitch Lock Regulator Assembly - Inspection and Modification Applicability: Propeller models 54H60-81, 91, 117, 125. Document: Hamilton Standard SB 54H60, No.-59 Rev. 1. Note: FAA AD 75-03-05 refers. Compliance: In accordance with the requirement document. Background: To reduce the possibility of separation of the pitchlock extension sleeve, modifications are introduced to the retention thread and surge valve housing. 11/81