COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 107 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Propellers - Variable Pitch - McCauley AD/PMC/21 Three Blade Propeller Hub - Modification or Replacement 7/71 Applicability: Models D3A32C77, C79, C88 and C90 models with no model number change letter or letter "A" to "J" fitted to Cessna 206 series aircraft with normally aspirated Continental IO-520 engine not modified in accordance with McCauley SB No. 88 (AD/PMC/20 refers). Document: 1. Cessna SL SE71-15; or 2. McCauley SB No. 89. Compliance: 1. For propellers which have completed 600 hours or more total time in service - within 25 hours time in service after 30 July 1971. 2. For propellers which have completed 500 hours total time in service - before achieving 600 hours total time in service.