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 170/28 Wing Strut Attachment Strap 9/73 Applicability: All model 172 with S/No. 17261664 to 17261808. Requirement: Action in accordance with Cessna SL SE 73-20. Compliance: Within 100 hours time in service after 24 September 1973.