{"id":"F2011L01125","name":"AD/DHC-1/39 Amdt 1 - Flap Operating System Latch Plate","slug":"ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":86930,"registerId":"commonwealth-F2011L01125-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-1/39 Amdt 1 | Flap Operating System Latch Plate | 13/2011 |\n| ------------------ | --------------------------------- | ------- |\n\n| Applicability: | English production (C1) all models and Portuguese (T Mk 20) production models, fitted with flap operating system latch plate Part Number C1-CF-1489; or where the part number of the installed Latch Plate is unknown.                                                                                                                                                                                                                                                                                                                                                                    |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with Chipmunk TNS CT (C1) No. 208.Note: UK CAA AD G-2009-0001 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |\n| Compliance:    | At the next scheduled maintenance inspection after the effective date of this AD, unless already accomplished.                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |\n|                | This Amendment becomes effective on 23 June 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n| Background:    | A report was received of the in-service failure of a flap operating system Latch Plate, Part Number C1-CF-1489. Investigation revealed that the part in question had not been manufactured in accordance with the applicable De Havilland drawing, and failed due to rapid wear. Unless bogus latch plate(s) are detected and removed, failure could occur and result in uncommanded flap retraction.This amendment is issued to include the Portuguese manufactured T Mk 20 model in the applicability of this Directive.The original issue of this AD became effective on 9 April 2009. |\n\n![](image.001.png)  \nGlen Steemson  \nDelegate of the Civil Aviation Safety Authority\n\n17 June 2011","sortOrder":0},{"sectionNumber":"AD/DHC-1/39 Amdt 1","sectionType":"part","heading":"AD/DHC-1/39 Amdt 1","content":"## AD/DHC-1/39 Amdt 1","sortOrder":1},{"sectionNumber":"Flap Operating System Latch Plate","sectionType":"part","heading":"Flap Operating System Latch Plate","content":"## Flap Operating System Latch Plate","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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original 2009 directive only applied to English production models. This 2011 amendment expands the scope to include Portuguese-manufactured T Mk 20 models, broadening the safety requirement to cover additional aircraft that may have the same defective part."},"complexity_factors":["Single, specific mechanical part identified by part number","Clear applicability criteria (two production sources, one part number)","Single compliance action referencing external technical document","No nested conditions or exceptions — straightforward 'inspect and replace if needed' requirement","Short document with minimal cross-referencing (only references UK CAA AD and manufacturer service bulletin)","Simple effective date and compliance timeline"],"plain_english_summary":"This AD mandates inspection and possible replacement of the flap operating system latch plate (P/N C1-CF-1489) on English-built De Havilland DHC-1 Chipmunks (C1 series) and Portuguese-built T Mk 20s because counterfeit/worn parts can cause unexpected flap retraction. Owners/operators must follow Chipmunk TNS CT (C1) No. 208 at the next scheduled maintenance after 23 June 2011. This amendment adds Portuguese T Mk 20s to the original 2009 notice."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The amendment extends the original AD's applicability to explicitly include Portuguese manufactured T Mk 20 production models (in addition to English production C1 models). The original AD took effect 9 April 2009; this amendment takes effect 23 June 2011 to add the T Mk 20 models."},"complexity_factors":["Targeted applicability to specific production origins and a single part number (C1‑CF‑1489)","Compliance tied to the operator's next scheduled maintenance inspection (timing/coordination burden)","Dependence on an external technical instruction (Chipmunk TNS CT (C1) No. 208) for the required corrective action","Need to identify counterfeit or non‑conforming parts where part numbers are unknown (inspection and traceability burden)","Safety‑critical consequence (uncommanded flap retraction) but straightforward corrective pathway","Amendment expands applicability to include Portuguese manufactured T Mk 20 models (scope change)"],"plain_english_summary":"Requires operators of De Havilland DHC‑1 (Chipmunk) aeroplanes — English production (C1) models and Portuguese (T Mk 20) models fitted with, or of unknown, latch plate Part Number C1‑CF‑1489 — to carry out the actions in Chipmunk TNS CT (C1) No. 208 at the next scheduled maintenance. The amendment responds to a reported failure of a non‑conforming latch plate that wore rapidly and could cause uncommanded flap retraction. Effective 23 June 2011."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate","history":"/api/acts/ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate/history","analysis":"/api/acts/ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate/analysis","conflicts":"/api/acts/ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate/conflicts","importantCases":"/api/acts/ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate/important-cases","documents":"/api/acts/ad-dhc-1-39-amdt-1-flap-operating-system-latch-plate/documents"}}