{"id":"F2011L01129","name":"AD/DHC-1/22 Amdt 4 - Tailplane Structure","slug":"ad-dhc-1-22-amdt-4-tailplane-structure","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":86938,"registerId":"commonwealth-F2011L01129-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-1/22 Amdt 4 | Tailplane Structure | 13/2011 |\n| ------------------ | ------------------- | ------- |\n\n| Applicability: | All English production (C1) all models and Portuguese production (T Mk 20) aircraft which have not been modified in accordance with a scheme approved by the authority (locally developed reinforcement kit).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Inspect the tailplane upper and lower spar flanges in accordance with British Aerospace TNS CT(C1) No. 157, Issue 3, dated 28 May 1986.Note: TNS No. 138 Issue 5 is the subject of UK CAA AD 2804 PRE 80 and CASA AD/DHC-1/12 Amendment 6.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |\n| Compliance:    | From the date of compliance with the initial inspection, repeat the inspections of paragraph 8 of the TNS at intervals not exceeding 6 years, unless the aircraft is operated on a Role Factor of 4 (see TNS CT(C1) No. 138 Issue 5), in which case the inspection interval shall not exceed 3 years.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |\n|                | This Amendment becomes effective on 22 June 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |\n| Background:    | This directive requires repetitive radiographic inspection of the tailplane upper and lower spar flanges at the fuselage attachment brackets. Some aircraft have been modified to incorporate a locally developed reinforcement kit, so as to be excluded from this AD.This amendment adds the Portuguese manufactured T Mk 20 to the applicability of this Airworthiness Directive. A review indicates that this inspection is also applicable to this model.Amendment history:Amendment 1, effective 30 November 1985, introduced a radiographic inspection of the tailplane front spar joints. It also required a repeat of the inspections carried out in accordance with the initial issue of this AD.Amendment 2, effective 13 July 2000, excluded modified aircraft from the requirement. |\n\n|     | Amendment 3, effective 23 October 2008, required repetitive radiographic inspections of the upper and lower spar flanges at the fuselage attachment brackets. Some aircraft have been modified to incorporate a locally developed reinforcement kit. The opportunity was also taken to update the TNS reference. No additional work was required as a result of this amendment. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nGlen Steemson  \nDelegate of the Civil Aviation Safety Authority\n\n16 June 2011","sortOrder":0},{"sectionNumber":"AD/DHC-1/22 Amdt 4","sectionType":"part","heading":"AD/DHC-1/22 Amdt 4","content":"## AD/DHC-1/22 Amdt 4","sortOrder":1},{"sectionNumber":"Tailplane Structure","sectionType":"part","heading":"Tailplane Structure","content":"## Tailplane Structure","sortOrder":2},{"sectionNumber":"13/2011","sectionType":"part","heading":"13/2011","content":"## 13/2011","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":6,"scope_assessment":{"changed":true,"description":"This amendment expands the applicability to include Portuguese-produced T Mk 20 aircraft that have not been modified with an approved local reinforcement kit. Earlier amendments introduced and refined the radiographic inspection requirement and excluded modified aircraft; this change brings an additional production batch (T Mk 20) within that inspection regime."},"complexity_factors":["Requires technical radiographic inspection methods (specialist equipment and skills).","Cross-reference to an external technical note: British Aerospace TNS CT(C1) No.157 Issue 3 (interpretation and dependency on outside document).","Variable repeat intervals tied to operational Role Factor (6 years generally; 3 years for Role Factor 4) increasing monitoring complexity.","Exclusion for aircraft modified with an approved local reinforcement kit requires record-checking and approval verification.","Applicability expanded to include Portuguese-produced T Mk 20 in this amendment, increasing affected fleet scope.","Amendment history and cross-references to other ADs/TNS documents require administrators and operators to track prior changes and related ADs."],"plain_english_summary":"This directive requires owners/operators of specified De Havilland DHC-1 (Chipmunk) aeroplanes to carry out radiographic inspections of the tailplane upper and lower spar flanges at the fuselage attachment brackets, using British Aerospace TNS CT(C1) No.157 Issue 3 (Requirement). Aircraft fitted with an approved local reinforcement kit are excluded.\n\nInspections repeat every 6 years (or every 3 years for aircraft operated on Role Factor 4) (Compliance). The stated purpose is defect detection; the direct costs and disruption fall on operators who must arrange radiography and follow the TNS procedure (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive (circa 1985) applied only to English production C1 models. Amendment 4 expands the scope to include Portuguese production T Mk 20 aircraft, representing a modest geographical/manufacturing expansion of the safety requirement. The core technical requirement (inspecting tailplane spar flanges) remains unchanged since Amendment 3 (2008)."},"complexity_factors":["Multiple amendment history references requiring cross-reading to understand full evolution","Technical aviation terminology requiring specialist knowledge (spar flanges, Role Factor, TNS references)","Conditional compliance periods (6 years vs 3 years based on operational intensity)","Exemption clause based on modification status (reinforcement kit)","Cross-reference to separate technical documents (British Aerospace TNS CT(C1) No. 157 and TNS No. 138)","Dual regulatory context (references UK CAA AD 2804 PRE 80 and CASA AD/DHC-1/12 Amendment 6)"],"plain_english_summary":"This AD mandates repetitive X‑ray inspections of the tailplane upper and lower spar flanges on specific De Havilland DHC‑1 Chipmunks (English C1 and now Portuguese T Mk 20), every 6 years (or every 3 years for high‑use Role Factor 4 aircraft). Aircraft fitted with the local reinforcement kit are exempt.\n\nIt matters because spar‑flange cracking can cause tailplane failure and loss of pitch control; this amendment adds Portuguese-built aircraft to the affected fleet."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-1-22-amdt-4-tailplane-structure","history":"/api/acts/ad-dhc-1-22-amdt-4-tailplane-structure/history","analysis":"/api/acts/ad-dhc-1-22-amdt-4-tailplane-structure/analysis","conflicts":"/api/acts/ad-dhc-1-22-amdt-4-tailplane-structure/conflicts","importantCases":"/api/acts/ad-dhc-1-22-amdt-4-tailplane-structure/important-cases","documents":"/api/acts/ad-dhc-1-22-amdt-4-tailplane-structure/documents"}}