{"id":"F2011L01061","name":"AD/DHC-1/33 Amdt 2 - Tailplane Support Struts","slug":"ad-dhc-1-33-amdt-2-tailplane-support-struts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":86867,"registerId":"commonwealth-F2011L01061-current","compilationNumber":null,"startDate":"2026-04-02","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-1/33 Amdt 2 | Tailplane Support Struts | 13/2011 |\n| ------------------ | ------------------------ | ------- |\n\n| Applicability: | English production (C1), all models, and Portuguese (T Mk 20) production models.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with British Aerospace Mandatory TNS CT(C1) 186 issue 2.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |\n| Compliance:    | 1. Unless already accomplished in accordance with the initial issue of this Directive and holding a BAe radiographic acceptable assessment from that inspection; within three months after the effective date of this AD or prior to CofA issue, whichever occurs first.2. Repeat inspections at periods not exceeding seven years after:a. the installation of new struts, orb. compliance with either the initial issue or this amendment of this Directive.Note: Compliance date for the initial issue of this Directive was 20 November 1992. This AD also applies to any struts held as spares.                                                                                                                                                                                                                                                                                                      |\n|                | This Amendment becomes effective on 22 June 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n| Background:    | A case of internal corrosion in a tailplane attachment strut was reported. The initial issue of the Directive required an external visual inspection, rework and NDI. Amendment 1 introduced a repeat inspection, and revised and clarified the technical requirements via the TNS.This amendment adds the Portuguese manufactured T Mk 20 to the applicability of this Airworthiness Directive. A review of documentation indicates that this inspection is applicable to any aircraft with P/N C1-T-5A tailplane support struts, which may be fitted to both the English and Portuguese produced models. However, the tailplane support strut part number should be checked to determine the applicability of this AD to your particular aircraft. Contact the manufacturer or TC holder for further information on applicability of this inspection to your particular aircraft if there is any doubt. |\n\n|     | There is no change to the requirements and the compliance wording has been clarified, but inspection interval is unchanged. |\n| --- | --------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nGlen Steemson  \nDelegate of the Civil Aviation Safety Authority\n\n16 June 2011","sortOrder":0},{"sectionNumber":"AD/DHC-1/33 Amdt 2","sectionType":"part","heading":"AD/DHC-1/33 Amdt 2","content":"## AD/DHC-1/33 Amdt 2","sortOrder":1},{"sectionNumber":"Tailplane Support Struts","sectionType":"part","heading":"Tailplane Support Struts","content":"## Tailplane Support Struts","sortOrder":2},{"sectionNumber":"13/2011","sectionType":"part","heading":"13/2011","content":"## 13/2011","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Scope was expanded to expressly include Portuguese‑manufactured T Mk 20 aircraft and any struts held as spares that use P/N C1‑T‑5A. The substantive inspection requirements and intervals remain unchanged."},"complexity_factors":["Narrow technical scope: applies to a specific part number (C1‑T‑5A) and tailplane support struts rather than multiple systems.","Clear compliance schedule: initial radiographic/NDI requirement within three months or before CofA, and fixed seven‑year repeat interval.","Applicability check required: operators must verify production origin and part number (administrative burden; potential need to consult manufacturer/TC holder).","Record/acceptance dependency: acceptance can rely on a prior BAe radiographic acceptable assessment (document‑based compliance path).","Affects spares as well as installed items, expanding inventory inspection obligations for owners/operators."],"plain_english_summary":"This AD extends an existing inspection requirement for De Havilland DHC‑1 tailplane support struts to explicitly include Portuguese‑built T Mk 20 aircraft and strut spares, clarifies compliance wording, and keeps the same inspection intervals. It requires operators to follow BAe Mandatory TNS CT(C1)186 issue 2 (radiographic assessment/NDI) within three months or before Certificate of Airworthiness issue, and repeat inspections every seven years. Owners/operators pay inspection and any rework costs, must verify strut part numbers, and contact the manufacturer if applicability is uncertain."},"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":4,"scope_assessment":{"changed":true,"description":"The original directive (1992) applied only to English production models. Amendment 1 added repeat inspections. Amendment 2 (this version) expands scope to include Portuguese-manufactured T Mk 20 aircraft, effectively doubling the geographic/manufacturing coverage of the directive while maintaining the same technical requirements."},"complexity_factors":["Multiple effective dates and compliance pathways (initial issue 1992, Amendment 2 effective 2011, spare parts applicability)","Conditional logic: 'Unless already accomplished...' creates an exception to the compliance deadline","Cross-reference to external technical document (British Aerospace Mandatory TNS CT(C1) 186 issue 2) — the actual inspection requirements are not contained in the directive itself","Dual applicability criteria: both aircraft manufacturing origin (English/Portuguese) AND specific part number (P/N C1-T-5A)","Nested timing calculations: 7-year repeat intervals measured from multiple possible starting points (new strut installation OR initial compliance OR Amendment 2 compliance)","Note regarding spare parts creates additional compliance obligation beyond installed aircraft components"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections of tailplane support struts on De Havilland DHC‑1 Chipmunk aircraft (English-built models, Portuguese T Mk 20s, and spare struts) after internal corrosion was found. Owners/operators must do an initial inspection within 3 months (or before a CofA) and repeat every 7 years, using the manufacturer’s procedure. Amendment 2 simply adds Portuguese T Mk 20s and clarifies wording; the inspection timing remains unchanged."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-1-33-amdt-2-tailplane-support-struts","history":"/api/acts/ad-dhc-1-33-amdt-2-tailplane-support-struts/history","analysis":"/api/acts/ad-dhc-1-33-amdt-2-tailplane-support-struts/analysis","conflicts":"/api/acts/ad-dhc-1-33-amdt-2-tailplane-support-struts/conflicts","importantCases":"/api/acts/ad-dhc-1-33-amdt-2-tailplane-support-struts/important-cases","documents":"/api/acts/ad-dhc-1-33-amdt-2-tailplane-support-struts/documents"}}