COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Hiller UH-12 Series Helicopters AD/HILLER 12/9 Amdt 1 Horizontal Stabiliser Spar - Inspection 3/78 Applicability: All models UH-12, UH-12A, UH-12B and UH-12C. Requirement: Remove the horizontal stabiliser, and with the aid of a lens of not less than 8X power, inspect the spar tube for cracking in the vicinity of the stabiliser attachment bolt holes. Compliance: At intervals not exceeding 300 hours' time in service.