{"id":"F2006B02205","name":"AD/AC-SNOW/14 Amdt 4 - Wing Spar and Wing Attachments","slug":"ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41435,"registerId":"commonwealth-F2006B02205-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC-SNOW/14 Amdt 4 - Wing Spar and Wing Attachments","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/14\n\nAmdt 4\n\n  \nWing Spar and Wing Attachments 10/95\n\nApplicability: All models S2D, S2R, S2R-R1820, S2R-T15 and S2R-T34.\n\nRequirement: 1. Visually inspect the lower wing spar centre section in accordance with Ayres Corporation Service Letter SL-AG-97.\n\n    2. For aircraft listed in Ayres Corporation Service Bulletin SB-AG-23; Inspect the wing main spar and wing attachment hardware in accordance with Ayres Corporation Service Bulletin SB-AG-23, Accomplishment Instructions. Externally inspect the lower surface of the wing from the root rib to the outboard end of the fuel tank for evidence of fuel leakage. If a fuel leak, originating from the wing main spar, is found inspect the forward face of the wing main spar web common to the fuel tank for cracks.\n\nNote: Inspection of the forward face of the wing main spar will require draining of the fuel tank and removal of the fuel tank sealant.\n\n    3. Retire the wing main spar lower cap assembly from service.\n\nCompliance: 1. Initially inspect in accordance with Requirement 1 before 2500 hours’ time in service or before 100 hours’ time in service after 14 September 1995, whichever occurs later. Re-inspect at intervals not to exceed 500 hours’ time in service.\n\n    2. Initially inspect in accordance with Requirement 2 before 250 hours’ time in service after 14 September 1995 or before 14 September 1996, whichever occurs first. Re-inspect at intervals not to exceed 500 hours’ time in service.\n\n    3. Retire, in accordance with Requirement 3, before 25000 hours’ time in service.\n\nFor aircraft incorporating FAA STC SA 1463 NM (46.5 inch wing tip extensions) the threshold and interval values for all Requirements are to be halved.\n\nNote: The limitation on STC SA 1463 NM may be lifted by the Authority upon receipt of fatigue and fail safe substantiation data. This limitation does not apply to the Ayres factory designed wing tip extensions.\n\nThis amendment is effective 14 September 1995.\n\nBackground: The Requirements in this Directive are based on fatigue and fail safe analyses carried out by the manufacturer of the aircraft and service experience. The limitation on STC SA 1463 NM wing tip extensions is imposed as no fatigue analysis for the modified wing has been provided.\n\nThis amendment includes inspection of the wing spar and attachment hardware for aircraft built with aluminium spar webs and doublers. A crack in the wing main spar web was found on one aircraft when repairing a fuel leak. The aft face of the spar web is not visible due to the presence of a doubler.\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":6,"scope_assessment":{"changed":true,"description":"This amendment expands scope to explicitly include inspection of wing spars and attachment hardware for aircraft built with aluminium spar webs and doublers (Background). It also imposes a mandatory retirement life for the wing main spar lower cap (Requirement 3) and applies stricter (halved) thresholds and intervals to aircraft fitted with FAA STC SA 1463 NM (46.5\" wing tip extensions) until fatigue substantiation is provided (Compliance; Note)."},"complexity_factors":["Multiple referenced documents: inspections must follow Ayres Service Letter SL-AG-97 and Service Bulletin SB-AG-23, creating dependency on external technical instructions (Requirements 1–2).","Staggered and conditional compliance thresholds: different initial and repeat inspection triggers (e.g. before 2500 hrs or 100 hrs after 14 Sept 1995; before 250 hrs or before 14 Sept 1996) and 500‑hour re‑inspection intervals increase scheduling complexity (Compliance).","Modification-specific rules: for aircraft with FAA STC SA 1463 NM the thresholds and intervals are halved, imposing stricter burden until substantiation is provided (Compliance; Note).","Physical inspection difficulty: inspecting the forward face of the main spar may require draining the fuel tank and removal of tank sealant, increasing labour, downtime and skill requirements (Requirement 2 Note).","Mandatory life limit: retirement of the wing main spar lower cap at 25,000 hours imposes a non‑negotiable replacement cost and planning requirement (Requirement 3; Compliance 3).","Regulatory discretion tied to technical data: the STC limitation can be lifted only if fatigue and fail‑safe substantiation data are supplied to the Authority, creating an evidentiary gate for relief (Note; Background).","Design variation risk: the amendment explicitly adds aircraft with aluminium spar webs and doublers because some damage (a crack) was not visible without added inspection, increasing applicability and inspection scope (Background)."],"plain_english_summary":"This airworthiness directive requires owners/operators of Ayres Thrush Commander S2 series aeroplanes to carry out regular visual inspections of the lower wing spar, wing main spar and wing attachment hardware, and to retire the wing main spar lower cap by 25,000 hours. Inspections must follow Ayres Service Letter SL-AG-97 and Service Bulletin SB-AG-23.\n\nInspection intervals vary by condition and are halved for aircraft fitted with FAA STC SA 1463 NM (46.5\" wing tip extensions) until fatigue substantiation is supplied; some checks require draining the fuel tank and removing sealant."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This appears to be a focused amendment (Amendment 4) to an existing Airworthiness Directive. The scope remains tightly constrained to wing spar safety inspections for the specified aircraft models. The amendment adds inspection requirements for aluminium spar webs and doublers based on new service experience (discovered crack), which is consistent with the original safety purpose rather than an expansion beyond it."},"complexity_factors":["Multiple compliance pathways with 'whichever occurs first/later' conditional logic (3 separate timing triggers)","Cross-references to external manufacturer documents (Service Letter SL-AG-97, Service Bulletin SB-AG-23) without reproducing their content","Nested conditional modification for STC SA 1463 NM aircraft affecting all three requirements","Exception to the exception: STC limitation can be lifted by Authority upon data submission, and factory extensions are explicitly exempted","Technical aviation terminology requiring domain knowledge (spar, doubler, STC, time in service, fuel tank sealant)","Amendment structure implies this is a revision to an existing directive, requiring understanding of what changed from previous versions"],"plain_english_summary":"This CASA safety directive requires owners/operators of specified Ayres Thrush (Snow) Commander models to perform mandatory wing-spar inspections and, at 25,000 flight hours, permanently remove the wing main spar lower cap assembly to prevent catastrophic wing failure. It follows discovery of a spar crack and targets metal fatigue risks.\n\nAircraft with 46.5‑inch STC wing tip extensions must inspect at half the intervals unless fatigue-safety data is supplied; factory tip extensions are exempt."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments","history":"/api/acts/ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments/history","analysis":"/api/acts/ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments/analysis","conflicts":"/api/acts/ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments/conflicts","importantCases":"/api/acts/ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments/important-cases","documents":"/api/acts/ad-ac-snow-14-amdt-4-wing-spar-and-wing-attachments/documents"}}