{"id":"F2011L01722","name":"AD/DHC-1/41 Amdt 1 - Fuselage Rear Bulkhead Inspection / Modification","slug":"ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":126212,"registerId":"commonwealth-F2011L01722-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"De Havilland DHC-1 (Chipmunk) Series Aer","sectionType":"division","heading":"De Havilland DHC-1 (Chipmunk) Series Aeroplanes","content":"### De Havilland DHC-1 (Chipmunk) Series Aeroplanes\n\n| AD/DHC-1/41 Amdt 1 | Fuselage Rear BulkheadInspection / Modification | 17/2011 |\n| ------------------ | ----------------------------------------------- | ------- |\n\n| Applicability: | All Canadian production DHC-1 aircraft as specified in the requirement document.                                                                                                                                                                                                                                                                                                                   |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Inspect and modify the fuselage rear bulkhead in accordance with the technical requirements of Transport Canada Airworthiness Directive CF-52-06.Note: De Havilland Aircraft of Canada Limited Technical News Sheet C-33 refers.                                                                                                                                                                   |\n| Compliance:    | As stated in the requirement document unless reinforcing modification is incorporated.                                                                                                                                                                                                                                                                                                             |\n|                | This Amendment becomes effective on 26 August 2011.                                                                                                                                                                                                                                                                                                                                                |\n| Background:    | Cracking of the stiffener part No. 084 has been reported. Repetitive inspections are prescribed through the port and starboard fairings at the base of the rudder post. Modification by installing reinforcing plates on the bulkhead stiffener terminates repetitive inspection requirements.Amendment 1 of this directive reduces the applicability of the directive to Canadian Chipmunks only. |\n\n![](image.001.png)  \nMike Higgins  \nDelegate of the Civil Aviation Safety Authority\n\n23 August 2011","sortOrder":0},{"sectionNumber":"AD/DHC-1/41 Amdt 1","sectionType":"part","heading":"AD/DHC-1/41 Amdt 1","content":"## AD/DHC-1/41 Amdt 1","sortOrder":1},{"sectionNumber":"Fuselage Rear Bulkhead Inspection / Modi","sectionType":"part","heading":"Fuselage Rear Bulkhead Inspection / Modification","content":"## Fuselage Rear Bulkhead  \nInspection / Modification","sortOrder":2},{"sectionNumber":"17/2011","sectionType":"part","heading":"17/2011","content":"## 17/2011","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 narrows the directive's scope: it reduces applicability to Canadian-production DHC‑1 (Chipmunk) aircraft only. The directive's background explicitly states this reduction in applicability from its earlier, broader reach."},"complexity_factors":["Requires technical inspection and a structural modification (installation of reinforcing plates) — technical/engineering work required.","Prescribes repetitive inspections through port and starboard fairings unless modification is incorporated (creates a choice: recurring inspections vs one-off modification).","References an external instrument for technical detail (Transport Canada Airworthiness Directive CF-52-06) rather than reproducing full procedures.","Applicability limited to Canadian-production DHC-1 aircraft after Amendment 1 — scope narrowing affects which owners/operators are subject to costs.","Compliance timing and exact procedures are set out in the 'requirement document' rather than within the directive text, creating dependency on another document.","Effective date and amendment history (Amendment 1 effective 26 August 2011) set compliance onset and retrospective applicability considerations."],"plain_english_summary":"This directive requires owners/operators of Canadian-produced De Havilland DHC‑1 (Chipmunk) aeroplanes to inspect the fuselage rear bulkhead for cracking and to modify it by installing reinforcing plates in accordance with Transport Canada Airworthiness Directive CF‑52‑06. Repetitive inspections through the port and starboard fairings are required unless the reinforcing modification is fitted. The stated aim is to address reported cracking of stiffener part No.084; owners/operators pay inspection and modification costs, and the modification removes the need for ongoing repetitive inspections."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"Amendment 1 explicitly reduces the scope from the original directive. The background section states it 'reduces the applicability of the directive to Canadian Chipmunks only,' indicating the original AD/DHC-1/41 likely applied more broadly to other DHC-1 production variants (such as British-built Chipmunks). This amendment narrows the safety requirement to a specific manufacturing origin."},"complexity_factors":["Very short document (approximately 200 words)","Only 1 defined applicability criterion (Canadian production DHC-1 aircraft)","Single technical requirement referencing an external document (Transport Canada AD CF-52-06)","Simple compliance structure: inspect and/or modify by a deadline, with termination condition (modification completed)","No nested exceptions or conditional logic beyond the basic applicability limit","Minimal cross-referencing (only to Transport Canada directive and one technical news sheet)"],"plain_english_summary":"Owners/operators of Canadian-built De Havilland DHC-1 \"Chipmunk\" aircraft registered in Australia must inspect the rear fuselage bulkhead for cracks in metal stiffener Part No. 084 and install reinforcing plates if needed. The measure is compulsory and, once modified, stops repetitive inspections.\n\nThis AD prevents structural failure or loss of control by catching or permanently fixing cracking risk; Amendment 1 limits the requirement to Canadian-built Chipmunks."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification","history":"/api/acts/ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification/history","analysis":"/api/acts/ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification/analysis","conflicts":"/api/acts/ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification/conflicts","importantCases":"/api/acts/ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification/important-cases","documents":"/api/acts/ad-dhc-1-41-amdt-1-fuselage-rear-bulkhead-inspection-modification/documents"}}