{"id":"F2009L02260","name":"AD/DHC-8/148 - Elevator Power Control Unit","slug":"ad-dhc-8-148-elevator-power-control-unit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":162110,"registerId":"commonwealth-F2009L02260-current","compilationNumber":null,"startDate":"2026-04-04","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-8/148 | Elevator Power Control Unit | 7/2009 |\n| ------------ | --------------------------- | ------ |\n\n| Applicability: | Bombardier Inc. DHC-8 Models 400, 401 and 402, Serial Numbers (S/N) 4135 through 4149. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement: | 1. Inspect the serial number of each of the six installed elevator Power Control Units (PCU)s, Part Number (P/N) 390600-1007.a. Compliance with this AD is complete, and no further action is required, if all six of the installed PCUs have suffix “A” after the serial number and/or have a serial number that is not in the following range:PCU S/Ns 238, 698, 783 through 788, 790, 793, 795, 802, 806, 807, 810, 820 through 823, 826 through 828, 831, 835, 838, 840, 886 through 889 or 898 through 955.b. If one or more of the installed PCUs has a serial number in the above range without a suffix “A”, proceed to Requirement 2 of this AD.Note 1: Suffix “A” after the S/N indicates that the PCU has already passed a magnetic particle inspection and is cleared for continued use.2. Perform a daily check for the correct operation of all installed elevator PCUs.Note 2: Requirement 2 of this AD is only applicable if required by Requirement 1.b.) of this AD.Note 3: Requirement 2 of this AD is no longer required following accomplishment of Requirement 3 of this AD.Note 4: Requirement 2 of this AD can be achieved by accomplishment of the procedures detailed in Appendix A, B or C of Bombardier Q400 All Operator Message No. 217B, dated 26 April 2007.3. a. Remove all elevator PCUs that have S/Ns listed in Requirement 1.a.) of this AD and do not have suffix “A” after the S/N.b. Replace each removed PCU with a PCU, P/N 390600-1007, which has a S/N outside the range listed in Requirement 1a) of this AD or has suffix “A” after the S/N. |\n\n| | Note 5: Bombardier Service Bulletin (SB) 84-27-32, Revision A, dated 18 January 2008, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provides approved instructions for the removal and replacement of the PCUs and for subsequent rigging of the elevators.Note 6: Previous accomplishment of Bombardier SB 84-27-32, original issue, dated 1 May 2007, meets Requirement 3 of this AD.Note 7: Transport Canada AD CF-2009-16 dated 20 April 2009 refers. |\n| ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | For Requirement 1 - Within 30 days after the effective date of this AD.For Requirement 2 - Commencing no later than 30 days after the effective date of this AD.For Requirement 3 - Within 2000 flight hours or within 12 months after the effective date of this AD, whichever comes first, unless already accomplished. |\n| | This Airworthiness Directive becomes effective on 2 July 2009. |\n| Background: | There has been one case reported of failure of a shaft (tailstock) on an elevator PCU, P/N 390600-1007. Continued actuation of the affected PCU caused damage to the surrounding structure. Subsequent investigation determined that the failure was the result of a material defect and that the shafts installed on a total of 88 suspect PCUs.Each elevator surface has three PCUs, powered by separate independent hydraulic systems, and a single elevator PCU shaft failure may remain dormant. Such a dormant loss of redundancy, coupled with the potential for a failed shaft to produce collateral damage, including damage to hydraulic lines, could possibly affect the controllability of the aircraft.This AD mandates an identification check for elevator PCU serial numbers, a daily check for correct operation of all suspect PCUs and, finally, replacement of all suspect PCUs. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n22 May 2009","sortOrder":0},{"sectionNumber":"AD/DHC-8/148","sectionType":"part","heading":"AD/DHC-8/148","content":"## AD/DHC-8/148","sortOrder":1},{"sectionNumber":"Elevator Power Control Unit","sectionType":"part","heading":"Elevator Power Control Unit","content":"## Elevator Power Control Unit","sortOrder":2},{"sectionNumber":"7/2009","sectionType":"part","heading":"7/2009","content":"## 7/2009","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The AD targets a clearly defined subset of aircraft and PCU serial numbers to address a specific material defect; it prescribes identification, temporary monitoring, and replacement actions consistent with that safety objective and does not expand beyond correcting the identified hardware fault."},"complexity_factors":["Narrow applicability tied to specific aeroplane models and a defined range of PCU serial numbers (identification complexity).","Multiple compliance actions (inspection, recurring daily checks, and eventual replacement) with different deadlines.","Technical requirement to recognize suffix “A” indicating prior magnetic particle inspection and its effect on compliance.","Maintenance complexity: removal/replacement of PCUs requires follow-up rigging per Bombardier service bulletin.","Dependence on availability of replacement PCUs with acceptable serial numbers or modified (suffix “A”) units.","Cross-references to manufacturer service bulletins and a related Transport Canada AD, introducing procedural dependencies.","Operational burden from mandated daily checks until replacement is complete (increased crew/maintenance tasks)."],"plain_english_summary":"This Airworthiness Directive requires operators of Bombardier DHC-8 Models 400/401/402 (S/Ns 4135–4149) to check the serial numbers of the six elevator Power Control Units (PCUs), carry out daily operation checks if any PCU is suspect, and replace suspect PCUs within a set flight‑hour/time limit. Transport Canada says the measures respond to a material defect that caused a PCU shaft failure. Operators must perform inspections, maintenance staff decide removals/replacements, and operators bear the cost, parts and rigging work under service bulletin instructions."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific mechanical defect in a limited fleet of aircraft. The scope remains precisely focused on the original safety issue — defective elevator PCU shafts in specific Bombardier DHC-8-400 series aircraft. There is no evidence of scope creep; the directive follows the standard AD structure of identification, interim measures, and permanent corrective action."},"complexity_factors":["Multiple conditional pathways: Requirement 1 branches into 1a (compliance complete) or 1b (proceed to Requirement 2), creating a decision tree structure","Cross-references to external documents: References Bombardier Service Bulletin 84-27-32 (Revision A), Bombardier Q400 All Operator Message No. 217B, and Transport Canada AD CF-2009-16","Serial number range exceptions: Requirement 1a contains a complex list of specific serial numbers and ranges (238, 698, 783-788, 790, etc.) that must be precisely matched","Interdependent requirements: Requirement 2 is only triggered by 1b, and Requirement 3 terminates Requirement 2, creating temporal dependencies","Multiple compliance deadlines: Three separate timelines (30 days for Requirement 1, 30 days to commence Requirement 2, and 12 months/2,000 hours for Requirement 3)","Suffix notation system: Understanding of \"A\" suffix as indicating prior magnetic particle inspection requires external technical knowledge"],"plain_english_summary":"This AD requires operators of Bombardier DHC‑8‑400 series aircraft (S/N 4135–4149) to inspect elevator Power Control Units for suspect serials and, where necessary, perform interim checks and replace affected units with approved parts within the mandated compliance period. It addresses a reported PCU shaft failure that could damage hydraulic lines and lead to loss of control, and aligns with a Transport Canada directive."},"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-8-148-elevator-power-control-unit","history":"/api/acts/ad-dhc-8-148-elevator-power-control-unit/history","analysis":"/api/acts/ad-dhc-8-148-elevator-power-control-unit/analysis","conflicts":"/api/acts/ad-dhc-8-148-elevator-power-control-unit/conflicts","importantCases":"/api/acts/ad-dhc-8-148-elevator-power-control-unit/important-cases","documents":"/api/acts/ad-dhc-8-148-elevator-power-control-unit/documents"}}