COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Ayres Thrush (Snow) Commander Series Aeroplanes AD/AC-SNOW/17 Outer Wing Huck Bolts 5/93 DM Applicability: Models and serial numbers as listed in the Requirement Document. Requirement: Action in accordance with Ayres Corporation Service Bulletin SB-AG-33, Accomplishment Instructions Parts I and II. Compliance: For Part I: Initially, within 10 hours' time in service after 18 March 1993 and thereafter at intervals not to exceed 100 hours' time in service; until Accomplishment Instruction Part II, is complied with. For Part II: Within 500 hours' time in service after 18 March 1993. Background: A recent report was received from a local operator of sheared Huck bolts on the outer section of both wing upper spar caps. Additionally, the LH spar web was found creased at WS 183 upper. The Manufacturer has determined that progressive fastener failure from the wing tip towards the root is a catastrophic mode of failure and must be prevented from starting. This Directive requires on-going repetitive inspections until the existing aluminium Huck bolts are replaced with steel Huck bolts or NAS bolts.