{"id":"F2006B02209","name":"AD/AC-SNOW/18 - Wing Front Spar Corrosion","slug":"ad-ac-snow-18-wing-front-spar-corrosion","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41439,"registerId":"commonwealth-F2006B02209-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC-SNOW/18 - Wing Front Spar Corrosion","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/18 Wing Front Spar Corrosion 6/93\n\nApplicability: Models Serial Numbers\n\nS2D all serial numbers\n\nS2R 5000 through 5099, 1380R,, and 1416R through 2583R S2R-R1340 R1340-001 through R1340-030 (with or without DC suffix) S2R-R3S R3S-001 through R3S-011 (with or without DC suffix) S2R-R1820 R1820-001 through R1820-035 (with or without DC suffix) S2R-T11 T11-001 through T11-005 (with or without DC suffix)\n\nS2R-T15 T15-001 through T15-029 with or without DC suffix) and T15- 031 (with or without DC suffix); and T27-001 through T27-029 (with or without DC suffix) and T27-031 (with or without DC suffix)\n\nS2R-T34 6000 through 6049,, T34-001 through T34-178 (with or without DC suffix); T41-001 through T41-178 (with or without DC suffix) and T34-180 (with or without DC suffix); and T41-180 (with or without DC suffix)\n\nS2R-T45 T45-001 through T45-003 (with or without DC suffix)\n\nS2R-T65 and S2RHG-T65\n\n  \nT65-001 through T65-010 (with or without DC suffix)\n\nS2R-G6 G6-101 through G6-107 (with or without DC suffix)\n\nRequirement: 1. Inspect the wing front spar for corrosion in accordance with the “Accomplishment Instructions: I. Inspection of Front Spar” section of Ayres Service Bulletin\n\nSB-AG-29.\n\n2. If corrosion is found; treat and repair the corrosion damage in accordance with the “Accomplishment Instructions: II. Repairs” section of Ayres Service Bulletin\n\nSB-AG-29.\n\nNote: FAA AD 93-01-03 Amdt 39-8456 refers.\n\nCompliance: 1. Prior to 27 August 1993, unless already accomplished, and thereafter at intervals not to exceed 12 calendar months.\n\n2. Prior to further flight, if corrosion is found.\n\nBackground: The investigation of an accident involving one of the affected aircraft revealed extensive corrosion on the upper and lower portions of the front spar.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive confines action to specified Ayres Thrush (Snow) Commander models/serials and requires inspection and repair of the front spar following corrosion found in an accident investigation. It does not add airworthiness obligations beyond inspection/repair mechanics and scheduling; therefore scope remains consistent with addressing the corrosion risk identified in the Background and the Requirements."},"complexity_factors":["Detailed applicability by model and multiple serial‑number ranges increases administrative burden for operators to determine applicability (Applicability).","Mandates adherence to an external technical document (Ayres Service Bulletin SB‑AG‑29) for inspection and repair methods, creating dependency on that SB's clarity and availability (Requirement).","Two distinct timelines: a one‑off initial deadline (27 August 1993) and a recurring 12‑month interval require recordkeeping and scheduling (Compliance).","Immediate 'prior to further flight' repair obligation if corrosion is found creates operational disruption and potential grounding costs for owners/operators (Requirement; Compliance).","Cross-reference to FAA AD 93‑01‑03 introduces potential alignment issues between jurisdictions and documents (Note).","Multiple suffixes and slightly inconsistent punctuation in serial listings (e.g. repeated commas, parenthetical 'with or without DC suffix') can cause ambiguity when determining affected airframes (Applicability)."],"plain_english_summary":"This airworthiness directive requires owners/operators of specified Ayres Thrush (Snow) Commander models and serial numbers to inspect the wing front spar for corrosion using Ayres Service Bulletin SB‑AG‑29 and to repair any corrosion before further flight. Initial inspections were to be completed by 27 August 1993 and must be repeated at intervals not exceeding 12 months. Aircraft owners/operators pay for inspections and repairs, and the Civil Aviation Safety Authority enforces compliance under Part 39."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on wing front spar corrosion in a defined aircraft type. It has not expanded beyond its original purpose of addressing the specific safety defect identified in the accident investigation."},"complexity_factors":["Extensive serial number applicability lists with multiple model variants and suffix combinations (DC suffix variations)","Cross-reference to external technical document (Ayres Service Bulletin SB-AG-29) for actual inspection and repair procedures — the AD itself does not contain the technical details","Reference to corresponding FAA Airworthiness Directive (93-01-03 Amdt 39-8456) for additional context","Dual compliance structure: one-time initial deadline plus recurring 12-month intervals, with an immediate 'prior to further flight' requirement if defects found","Minor formatting inconsistencies in the text (e.g., double commas, inconsistent bracketing of 'with or without DC suffix')"],"plain_english_summary":"Owners and operators of certain Ayres Thrush (Snow) Commander agricultural aeroplanes must inspect the wing front spar for corrosion and repair any damage per Ayres Service Bulletin SB‑AG‑29. This CASA Airworthiness Directive mandates an initial inspection before 27 August 1993 (if not already done) and repeat inspections every 12 months, with any corrosion repaired before further flight.\n\nIt was issued after an accident found extensive front‑spar corrosion that could lead to wing failure, so the AD preserves structural safety."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-snow-18-wing-front-spar-corrosion","history":"/api/acts/ad-ac-snow-18-wing-front-spar-corrosion/history","analysis":"/api/acts/ad-ac-snow-18-wing-front-spar-corrosion/analysis","conflicts":"/api/acts/ad-ac-snow-18-wing-front-spar-corrosion/conflicts","importantCases":"/api/acts/ad-ac-snow-18-wing-front-spar-corrosion/important-cases","documents":"/api/acts/ad-ac-snow-18-wing-front-spar-corrosion/documents"}}