{"id":"F2006B02208","name":"AD/AC-SNOW/17 - Outer Wing Huck Bolts","slug":"ad-ac-snow-17-outer-wing-huck-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41438,"registerId":"commonwealth-F2006B02208-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC-SNOW/17 - Outer Wing Huck Bolts","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nAyres Thrush (Snow) Commander Series Aeroplanes\n\nAD/AC-SNOW/17 Outer Wing Huck Bolts 5/93 DM\n\nApplicability: Models and serial numbers as listed in the Requirement Document. Requirement: Action in accordance with Ayres Corporation Service Bulletin SB-AG-33,\n\nAccomplishment Instructions Parts I and II.\n\nCompliance: 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.\n\nFor Part II: Within 500 hours’ time in service after 18 March 1993.\n\nBackground: 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.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: addressing a specific structural defect in a specific aircraft type. It has not expanded beyond the original safety issue of outer wing Huck bolt failures."},"complexity_factors":["Single, specific technical subject matter (Huck bolts on one aircraft series)","Clear two-part compliance structure (interim inspections + permanent replacement)","Only one defined term implicit ('time in service' — flight hours)","No nested exceptions or conditional logic beyond the two compliance paths","References external technical document (Service Bulletin SB-AG-33) but does not reproduce it","Short length (approximately 200 words of substantive content)"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of certain Ayres Thrush (Snow) Commander agricultural aircraft to inspect and replace failing Huck bolts in the outer wing sections. The bolts have sheared in service, risking progressive wing-spar failure and catastrophic wing loss.\n\nIt mandates interim, recurring inspections until a permanent repair — replacing aluminium Huck bolts with stronger steel or NAS bolts — is installed. It’s critical for crop‑duster operators because unchecked bolt failure threatens loss of the aircraft and lives."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive enforces the manufacturer’s response to reported fastener failures by mandating inspections and ultimate replacement per the Service Bulletin. The text implements that corrective scope (inspection until replacement and specific bolt substitution) without expanding beyond the stated safety purpose (Requirement; Compliance; Background)."},"complexity_factors":["References external documents: applicability depends on a separate Requirement Document and mandated work follows Ayres Service Bulletin SB-AG-33 (Applicability; Requirement).","Multiple staged compliance obligations: short‑term repetitive inspections (initial within 10 hours, then every 100 hours) until a one‑off replacement is completed, and a separate 500‑hour deadline for replacement (Compliance).","Technical maintenance action: fastener replacement between aluminium Huck bolts and listed alternatives (steel Huck or NAS) requires technical judgement and access to specific parts and procedures (Requirement; Background).","Safety‑critical consequence: directive responds to reported sheared bolts and creased spar web and treats progressive fastener failure as catastrophic, increasing enforcement and inspection importance (Background).","Operational impact: recurring inspection intervals impose scheduling and downtime considerations for operators, and create a direct compliance cost borne by operators (Compliance)."],"plain_english_summary":"This Airworthiness Directive requires operators of specified Ayres Thrush (Snow) Commander aeroplanes to carry out repetitive inspections of outer-wing Huck bolts under Ayres Service Bulletin SB-AG-33 and to replace existing aluminium Huck bolts with steel Huck bolts or NAS bolts within set flight‑hour limits (Applicability; Requirement; Background). Operators must pay for and schedule the work: inspections start within 10 hours and recur every 100 hours until replacement, and replacement must occur within 500 hours after 18 March 1993 (Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-snow-17-outer-wing-huck-bolts","history":"/api/acts/ad-ac-snow-17-outer-wing-huck-bolts/history","analysis":"/api/acts/ad-ac-snow-17-outer-wing-huck-bolts/analysis","conflicts":"/api/acts/ad-ac-snow-17-outer-wing-huck-bolts/conflicts","importantCases":"/api/acts/ad-ac-snow-17-outer-wing-huck-bolts/important-cases","documents":"/api/acts/ad-ac-snow-17-outer-wing-huck-bolts/documents"}}