{"id":"F2006B09011","name":"AD/DHC-1/30 Amdt 1 - Engine Mount Upper Attachment Points/Reinforcing Plates","slug":"ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52674,"registerId":"commonwealth-F2006B09011-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-1/30 Amdt 1 - Engine Mount Upper Attachment Points/Reinforcing Plates","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)  \nDe Havilland DHC-1 (Chipmunk) Series Aeroplanes\n\nAD/DHC-1/30\n\nAmdt 1\n\nApplicability: All models.\n\n  \n\nEngine Mount Upper Attachment Points/Reinforcing Plates\n\n  \n10/86 DM\n\nRequirement: Action in accordance with:\n\n    British Aerospace TNS Chipmunk (C1) No. 180 Issue 1, and\n\n    b. British Aerospace Modification Chipmunk H358. Compliance: Prior to 1 August 1986.\n\nAircraft which have been modified to a different engine installation are affected by this Directive. Some of these aircraft have external reinforcing doublers which may not be sufficient to meet the requirements of this Directive. If there are no doublers present or if they do not cover the vertical and horizontal extent of Mod. H358, or are not of the required thickness, the aircraft will need further evaluation and/or modification in accordance with a scheme approved by the Secretary. For these aircraft only, the compliance date is extended to 31 December 1986.\n\nBackground: External reinforcing plates are introduced on the forward fuselage skin adjacent to the two engine upper mounting attachment points, together with an access hole for periodic inspection of the upper deck plate and adjacent internal structure. This amendment clarifies the position with regard to re-engined aircraft such as the DHC- 1/A1 and DHC-1/A2.","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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive. The amendment specifically clarifies the treatment of re-engined aircraft (DHC-1/A1 and DHC-1/A2 variants), which was apparently ambiguous in the original AD. The scope has not expanded beyond the original safety purpose — ensuring structural integrity of engine mount attachment points. The amendment tightens rather than broadens applicability."},"complexity_factors":["Single, specific aircraft type (De Havilland DHC-1 Chipmunk) with limited applicability","Two-tier compliance structure with conditional deadline extension for re-engined aircraft","References to external technical documents (British Aerospace TNS Chipmunk C1 No. 180 and Modification H358) without reproducing their content","One nested condition: re-engined aircraft with insufficient doublers require Secretary-approved scheme","Minimal defined terms (only 'Applicability' and 'Requirement' as standard AD structure)","Short length (approximately 200 words of substantive text)"],"plain_english_summary":"This CASA Airworthiness Directive mandates installation of reinforcing plates around the engine‑mount upper attachment points and cutting an access hole for periodic inspection on all De Havilland DHC‑1 Chipmunk aircraft. Re‑engined variants with existing external doublers may need further engineering assessment and CASA approval and have an extended compliance deadline. It addresses risk of cracking or structural failure at heavily loaded engine attachments to prevent in‑flight catastrophe."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This amendment clarifies that re‑engined variants (e.g. DHC‑1/A1, A2) are within scope and provides an extended compliance date for aircraft requiring further evaluation; otherwise it retains the original requirement to install reinforcing plates and inspection access on all models. (Background; Requirement)"},"complexity_factors":["Multiple compliance deadlines and an explicit extension for certain re‑engined aircraft (1 Aug 1986; 31 Dec 1986) (Requirement)","Applies to all DHC‑1 models but treats re‑engined examples differently, increasing applicability nuance (Applicability; Background)","Mandates compliance with external technical documents (British Aerospace TNS No.180 Issue 1 and Modification H358), creating dependence on external technical specifications (Requirement)","Permits alternative evaluation/modification only with Secretary approval, introducing administrative discretion and potential delay (Requirement)","Physical modification plus periodic inspection access increases both one‑off modification costs and ongoing maintenance burden for operators (Requirement; Background)"],"plain_english_summary":"Requires adding external reinforcing plates and an inspection access hole around the two upper engine‑mount attachment points on De Havilland DHC‑1 (Chipmunk) aircraft; applies to all models. General compliance is before 1 August 1986, with re‑engined aircraft that need further evaluation allowed an extension to 31 December 1986. (Requirement, Applicability)\n\nOwners/operators pay for the work and inspections; the Secretary must approve any alternative evaluation or modification scheme, creating administrative discretion and an operator compliance cost. (Requirement, Background)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates","history":"/api/acts/ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates/history","analysis":"/api/acts/ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates/analysis","conflicts":"/api/acts/ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates/conflicts","importantCases":"/api/acts/ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates/important-cases","documents":"/api/acts/ad-dhc-1-30-amdt-1-engine-mount-upper-attachment-points-reinforcing-plates/documents"}}