{"id":"F2006B09157","name":"AD/DHC-6/7 Amdt 1 - Elevator Rear Spar - Inspection and Modification","slug":"ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52856,"registerId":"commonwealth-F2006B09157-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-6/7 Amdt 1 - Elevator Rear Spar - Inspection and Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  DHC-6 (Twin Otter) Series Aeroplanes\n\n \n\nAD/DHC-6/7\n\nAmdt 1\n\n\nElevator Rear Spar - Inspection and Modification\n\n\n1/68\n\n \n\nApplicability: All Models With S/Nos. 1 To 105.\n\n \n\nDocument: De Havilland Of Canada Mod. Bulletins 6/1134 And 6/1135.\n\n \n\nCompliance: Inspect In Accordance With Mod. Bulletin 6/1134 At Intervals Not Exceeding 50 Hours Time In Service Until Modified To Bulletin 6/1134 Or 6/1135. Modify In Accordance With Mod. Bulletin 6/1135 Before 1 April 1968.\n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive (AD/DHC-6/7). The scope remains tightly focused on the original safety issue: elevator rear spar integrity in early Twin Otter aircraft. The amendment appears to update compliance requirements or inspection intervals without expanding beyond the original affected aircraft population or safety concern."},"complexity_factors":["Very short document (under 200 words)","Only 4 defined elements: applicability (serial numbers 1-105), two referenced documents (Mod. Bulletins 6/1134 and 6/1135), and compliance deadlines","No nested conditional logic — simple 'inspect until modified' structure","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Single, clear compliance pathway with straightforward time-in-service calculation"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it as a \"recall notice\" for aircraft, but legally binding.\n\n**What it does:** It requires owners and operators of specific **De Havilland DHC-6 Twin Otter aircraft** (serial numbers 1 to 105) to:\n- **Inspect** the elevator rear spar (a structural beam in the tail that helps control the plane's pitch) every 50 flight hours, following a specific manufacturer's bulletin (6/1134)\n- **Modify** the aircraft by April 1, 1968, following another bulletin (6/1135) — this permanently fixes the problem the inspections are looking for\n\n**Who it affects:** Anyone operating these specific early-model Twin Otter aircraft in Australia.\n\n**Why it matters:** The elevator rear spar was apparently prone to cracking or failure. This AD prevents potential catastrophic loss of control by ensuring the problem is caught early (through inspections) and ultimately fixed permanently (through modification). Missing these deadlines could ground the aircraft or create serious safety risks."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This instrument is labelled as Amendment 1 (AD/DHC-6/7 Amdt 1), indicating it modifies a prior airworthiness directive. The observable, operative scope in the text is to require recurring inspections per Mod. Bulletin 6/1134 at intervals not exceeding 50 hours TIS until the aeroplane is modified to Mod. Bulletin 6/1134 or 6/1135, and to require completion of the modification per Mod. Bulletin 6/1135 before 1 April 1968. The amendment therefore establishes (or reiterates) a detailed interim inspection regime plus a fixed deadline for a one‑off modification as the enforceable obligations. (See Document and Compliance lines.)"},"complexity_factors":["Narrow technical scope limited to elevator rear spar on DHC-6 aeroplanes S/N 1–105 (low breadth).","Prescriptive, time‑bound compliance requirements (inspect every <=50 hours TIS; modify before 1 April 1968) reduce interpretive complexity.","Dependence on two external technical documents (Mod. Bulletins 6/1134 and 6/1135) requires consultation of specialist maintenance material.","Requires qualified technical execution (maintenance/engineering competence) even though the rule text is short.","Operational scheduling complexity from frequent interim inspections until the modification is completed."],"plain_english_summary":"Applies to De Havilland DHC‑6 (Twin Otter) aeroplanes S/N 1–105: operators must inspect the elevator rear spar per Mod. Bulletin 6/1134 at intervals not exceeding 50 hours TIS until they complete the one‑time modification required by Mod. Bulletin 6/1135.\n\nThis mandates owner/operator/maintenance action before 1 April 1968, imposing recurring inspection costs and scheduling burdens until the modification removes the short‑interval inspection requirement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification","history":"/api/acts/ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification/history","analysis":"/api/acts/ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification/analysis","conflicts":"/api/acts/ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification/important-cases","documents":"/api/acts/ad-dhc-6-7-amdt-1-elevator-rear-spar-inspection-and-modification/documents"}}