COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes AD/CESSNA 170/29 Amdt 1 Aft Fuselage Bulkhead Assembly 2/74 Applicability: All models 172 with S/Nos. 17260759 to 17261495, F17200905 to F17201034, FR17200351 to FR17200440. Requirement: Action in accordance with Cessna SL SE73-37. Compliance: Within 100 hours time in service after 28 February 1974.