{"id":"F2008L01929","name":"AD/DHC-8/141 Amdt 1 - Elevator Centering Torsion Springs","slug":"ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74156,"registerId":"commonwealth-F2008L01929-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bombardier (Boeing Canada/De Havilland) ","sectionType":"division","heading":"Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes","content":"### Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes\n\n| AD/DHC-8/141 Amdt 1 | Elevator Centering Torsion Springs | 7/2008 |\n| ------------------- | ---------------------------------- | ------ |\n\n| Applicability: | Bombardier Inc. DHC-8 Aircraft, Models 400, 401 and 402, Serial Numbers 4001, 4003, 4004 and 4006 through 4081 inclusive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Replace all elevator centering torsion springs with new springs by incorporating Modsum 4-113482 in accordance with Bombardier Service Bulletin (SB) 84-27-31, dated 27 April 2007 or later revisions approved by Transport Canada.Note: Transport Canada AD CF-2008-05R1 dated 27 February 2008 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n| Compliance:    | Within 5,000 flight hours after the effective date of this AD but not to exceed 22,000 flight hours since new.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n|                | This Amendment becomes effective on 3 July 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |\n| Background:    | There was one reported failure of the elevator centering torsion spring. Investigation revealed that the tangs on the torsion spring had been bent due to difficulty encountered during installation of the elevator centering torsion spring on the horizontal stabilizer torque tube. The bending of the tangs on the torsion spring would degrade its durability and could lead to premature failure of the elevator centering torsion spring. A control rod disconnect between the elevator aft quadrant and the elevator Power Control Unit input torque tube, in combination with the loss or reduction in elevator centering capability, could result in a significant reduction in aircraft pitch control.This amendment adds 1 additional serial number aircraft to the applicability section of this AD with no change to the requirement or compliance sections.The original issue of this AD became effective on 10 April 2008. |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n22 May 2008","sortOrder":0},{"sectionNumber":"AD/DHC-8/141 Amdt 1","sectionType":"part","heading":"AD/DHC-8/141 Amdt 1","content":"## AD/DHC-8/141 Amdt 1","sortOrder":1},{"sectionNumber":"Elevator Centering Torsion Springs","sectionType":"part","heading":"Elevator Centering Torsion Springs","content":"## Elevator Centering Torsion Springs","sortOrder":2},{"sectionNumber":"7/2008","sectionType":"part","heading":"7/2008","content":"## 7/2008","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment expands the AD's applicability by adding one additional aircraft serial number to the list of affected DHC‑8 Model 400-series aeroplanes. The required action (replacement per Modsum/SB) and the compliance timing (within 5,000 flight hours and not beyond 22,000 hours since new) remain unchanged (Background; Requirement; Compliance)."},"complexity_factors":["Narrow technical scope: applies only to DHC‑8 Models 400/401/402 and a specified set of serial numbers (Applicability).","Clear required action but dependent on external service data: replacement by incorporating Modsum 4‑113482 per SB 84‑27‑31, or later TC‑approved revisions (Requirement).","Dual flight‑hour compliance window: within 5,000 flight hours after the AD effective date but not to exceed 22,000 flight hours since new — creates a two‑limit scheduling constraint for operators (Compliance).","Safety rationale linked to installation damage and single reported failure; human factors in installation are material to the risk (Background).","Administrative amendment only: this version adds one serial number to applicability without changing the action or timing, increasing record‑keeping/tracking needs slightly (Background).","Inter‑jurisdictional reference: cites a Transport Canada AD (CF‑2008‑05R1), requiring coordination on approved revisions (Requirement/Background)."],"plain_english_summary":"**What it does:** This airworthiness directive requires replacement of the elevator centering torsion springs on specified Bombardier DHC‑8 Models 400/401/402 by incorporating Modsum 4‑113482 in accordance with Bombardier Service Bulletin 84‑27‑31 (or later Transport Canada–approved revisions).  \n**Who pays and why it matters:** Compliance must occur within 5,000 flight hours after the AD effective date and not exceed 22,000 hours since new. Aircraft owners/operators bear the replacement cost and maintenance effort; the rule depends on approved service data and regulator coordination."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope of the airworthiness directive. The only change is the addition of one aircraft serial number (4001) to the applicability list. The core safety requirement — replacing the elevator centering torsion springs — remains identical to the original April 2008 directive. This is a minor administrative expansion rather than a substantive broadening of scope."},"complexity_factors":["Single, specific mechanical requirement with clear reference to manufacturer service bulletin","Only 4 defined applicability criteria (model numbers and serial numbers)","Simple compliance timeframe with two clear boundaries (5,000 hours after effective date, 22,000 hours total)","No nested exceptions or conditional logic — requirement applies uniformly to all affected aircraft","Cross-reference to only one external document (Transport Canada AD) and one manufacturer bulletin","Short document length (approximately 250 words of substantive content)"],"plain_english_summary":"This CASA Airworthiness Directive mandates replacing the elevator centering torsion springs on certain Bombardier DHC‑8-400/401/402 aircraft (specific serials, with SN 4001 newly added) per the manufacturer's service bulletin. A failed or weakened spring can reduce or eliminate pitch control, so operators must comply within 5,000 flight hours after 3 July 2008 and before the aircraft reaches 22,000 total flight hours."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs","history":"/api/acts/ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs/history","analysis":"/api/acts/ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs/analysis","conflicts":"/api/acts/ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs/conflicts","importantCases":"/api/acts/ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs/important-cases","documents":"/api/acts/ad-dhc-8-141-amdt-1-elevator-centering-torsion-springs/documents"}}