COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Schweizer (Hughes) 269 Series Helicopters AD/HU 269/29 Tail Rotor Blade Assembly - Inspection 12/68 Applicability: All models with tail rotor blade assemblies S/Nos up to and including 126-3312. Document: Hughes SIN N-58. Compliance: Within 25 hours time in service after 9 December 1968 and thereafter at intervals not exceeding 25 hours time in service.