{"id":"F2006B09225","name":"AD/DHC-8/68 - Beta Backup Test Switches","slug":"ad-dhc-8-68-beta-backup-test-switches","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53093,"registerId":"commonwealth-F2006B09225-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-8/68 - Beta Backup Test Switches","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes\n\nAD/DHC-8/68 Beta Backup Test Switches 1/2000\n\nTX\n\nApplicability: DHC-8 aeroplanes Models 102, 103, 106, 201, 202, 301, 311, 314 and 315 Serial Numbers 003 up to and including 538.\n\nRequirement: 1. Inspect the two beta back-up test switches in accordance with Bombardier Alert Service Bulletin A8-61-30 Revision B dated 6 December 1999 to ensure switches are Part Number (P/N) MS27407-6.\n\n2. If, during the Requirement 1 inspection, a switch with other than P/N MS27407-6 is found to be fitted, replace the switch with a P/N MS27407-6 switch.\n\nNote: Transport Canada Emergency AD CF-99-30 refers.\n\nCompliance: 1. Within 50 hours time in service from the effective date of this Directive.\n\n2. Before further flight.\n\nThis Airworthiness Directive becomes effective on 17 December 1999.\n\nBackground: An incorrect switch (P/N MS24524-27) is wrongly identified in the wiring diagram manuals as an allowable replacement for the Beta back-up test switch. This switch is used elsewhere on the aircraft and is physically interchangeable with the correct switch (P/N MS27407-6). However, the internal contacts are different, preventing the Beta back-up system from functioning correctly. Mechanical failure of the propeller control system with incorrect switches installed may result in the loss of automatic overspeed protection, allowing the propeller to go into an overspeed condition, resulting in possible engine and propeller damage.\n\nThis Directive requires that all Beta back-up switches be inspected to ensure that correct switches are fitted.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope — a targeted safety fix for a specific wiring diagram error affecting particular DHC-8 aircraft. There is no evidence of scope creep; the directive addresses exactly the problem described in the background (incorrect switch part number in manuals) with precise applicability limits."},"complexity_factors":["Single, specific technical requirement with clear sequential steps","Only 2 defined part numbers referenced","No nested exceptions or conditional logic beyond the basic 'if found, then replace' structure","Limited applicability (9 specific aircraft models, defined serial number range)","Short document (approximately 250 words) with straightforward compliance timeline","Single cross-reference to Canadian Transport Canada directive for background context only"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain Bombardier DHC-8 (Dash 8) aircraft to inspect the beta back-up test switches because the wiring manual incorrectly accepted an interchangeable part that disables propeller overspeed protection.  \n\nInspections must be done within 50 flight hours and any incorrect switches (P/N MS24524-27) must be replaced with the correct part (P/N MS27407-6) before further flight to prevent propeller/engine damage."},"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":2,"scope_assessment":{"changed":false,"description":"The Directive's scope matches the safety issue described in the Background: it targets the listed DHC‑8 models/serials and requires inspection and replacement of incorrectly identified switches. It does not broaden obligations beyond those aircraft, parts, and corrective actions specified in the AD and referenced service bulletin."},"complexity_factors":["Narrow applicability: specific DHC‑8 models and serial number range (Applicability).","Clear, binary requirements: inspect and, if needed, replace with specified P/N (Requirement 1–2).","Short compliance timing and mandatory pre‑flight action for replacements (Compliance: 50 hours; replace before further flight).","Reliance on a manufacturer Alert Service Bulletin for inspection procedure (Requirement references Bombardier ASB A8‑61‑30 Rev B).","Single technical identification issue (confusing interchangeable part P/N MS24524‑27 vs correct P/N MS27407‑6) with straightforward corrective action (Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of specified Bombardier DHC‑8 models (serials 003–538) to inspect the two beta back‑up test switches and replace any switch that is not P/N MS27407‑6, following Bombardier Alert Service Bulletin A8‑61‑30 Rev B. Owners/operators bear the inspection and replacement costs, must inspect within 50 flight hours and replace any incorrect switch before further flight. The rule aims to prevent loss of automatic overspeed protection caused by an interchangeable but incorrect switch (P/N MS24524‑27)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-68-beta-backup-test-switches","history":"/api/acts/ad-dhc-8-68-beta-backup-test-switches/history","analysis":"/api/acts/ad-dhc-8-68-beta-backup-test-switches/analysis","conflicts":"/api/acts/ad-dhc-8-68-beta-backup-test-switches/conflicts","importantCases":"/api/acts/ad-dhc-8-68-beta-backup-test-switches/important-cases","documents":"/api/acts/ad-dhc-8-68-beta-backup-test-switches/documents"}}