{"id":"F2006B02555","name":"AD/AT/6 Amdt 1 - Fuselage Fittings - Vertical Fin Front Spar Attachments - Inspection and Modification","slug":"ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41811,"registerId":"commonwealth-F2006B02555-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AT/6 Amdt 1 - Fuselage Fittings - Vertical Fin Front Spar Attachments - Inspection and Modification","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)  \nAirtractor AT-300, 400 and 500 Series Aeroplanes\n\nAD/AT/6\n\nAmdt 1\n\n  \n\nFuselage Fittings - Vertical Fin Front Spar Attachments \\- Inspection and Modification\n\n  \n11/83\n\nApplicability: All models AT-300, AT-301, AT-302 with S/Nos. 0001 to 0240\\. Document: 1. Snow Engineering Co. Service Letter No. 26 and\n\n2. Snow Engineering Co. Service Letter No. 47.\n\nNote: FAA AD 83-18-01 refers.\n\nCompliance: 1. Within 100 hours time in service after 31st July 1983 and thereafter at intervals not exceeding 100 hours time in service.\n\n2. Modification \\- prior to 2000 hours time in service.\n\nBackground: The manufacturer reports that service history indicates cracking of attachment fittings. Amendment 1 of this AD details Snow Engineering Co. Service Letter No. 26 for the repetitive inspection and notes the issue of FAA AD 83-18-01.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with a narrow, specific scope (particular aircraft models, specific structural component). The amendment (Amdt 1) simply updates the reference documentation (adding Snow Engineering Service Letter No. 26 and noting the FAA AD) without expanding the scope beyond the original safety issue."},"complexity_factors":["Very short document (approximately 150 words)","Only 3 defined applicability criteria (aircraft models and serial number range)","Simple two-part compliance structure (inspection interval + modification deadline)","No cross-references to other legislation sections","Single background issue (cracking fittings) with straightforward remedy","No conditional logic or nested exceptions"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific models of Air Tractor agricultural aircraft (AT-300, AT-301, AT-302 with serial numbers 0001 to 0240).\n\n**What it requires:**\n- **Inspections**: Owners/operators must inspect the vertical fin front spar attachments (structural fittings that connect the tail fin to the fuselage) every 100 hours of flight time, starting from 31 July 1983.\n- **Modification**: The aircraft must be modified before reaching 2,000 total flight hours.\n\n**Why it matters:**\nThe manufacturer discovered that these attachment fittings can develop cracks during normal use. Cracked fittings could cause the vertical fin (the tail) to detach in flight, leading to loss of control and potentially a crash. This AD forces operators to find problems before they become catastrophic.\n\n**Key terms explained:**\n- **Airworthiness Directive (AD)**: A legally enforceable safety notice that requires aircraft owners to perform specific inspections, repairs, or modifications.\n- **Time in service**: Actual flight hours (not just calendar time).\n- **S/Nos**: Serial numbers — the unique identifier for each aircraft."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"This instrument is an amendment (Amdt 1) that adds detail to the existing Airworthiness Directive by specifying Snow Engineering Co. Service Letter No. 26 for the repetitive inspection and by noting the related FAA AD (FAA AD 83-18-01). The amendment therefore narrows or clarifies procedural detail and cross‑references additional technical guidance that operators must follow. (Background; Applicability; Note)"},"complexity_factors":["Narrow and clearly defined applicability (specific models and serial number range) reduces scope complexity. (Applicability)","Simple, time‑based compliance requirements: repetitive inspection interval (100 hours) and a fixed deadline for modification (2,000 hours). (Compliance: 1–2)","Reliance on external technical documents (Snow Engineering Service Letters No. 26 and No. 47) for procedural detail introduces modest implementation complexity because the AD delegates technical specifics to those documents. (Applicability)","Cross-reference to an FAA AD (FAA AD 83-18-01) means operators may need to reconcile multiple authorities, slightly increasing administrative complexity. (Note)","No exemptions, alternative compliance pathways, or enforcement details are specified in the text provided, which simplifies legal analysis but shifts technical discretion to maintenance documents and the regulator. (Compliance)"],"plain_english_summary":"Requires owners/operators of Airtractor AT‑300, AT‑301 and AT‑302 (S/N 0001–0240) to perform repetitive 100‑hour inspections of the fuselage fittings at the vertical fin front‑spar attachments and to complete a specified modification before 2,000 hours, following Snow Engineering Service Letters No. 26 and No. 47. Prompted by reported in‑service cracking, the measure imposes recurring inspection work and a one‑time modification cost on operators and maintenance organisations."}},"importantCases":[],"_links":{"self":"/api/acts/ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification","history":"/api/acts/ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification/history","analysis":"/api/acts/ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification/analysis","conflicts":"/api/acts/ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification/important-cases","documents":"/api/acts/ad-at-6-amdt-1-fuselage-fittings-vertical-fin-front-spar-attachments-inspection-and-modification/documents"}}