{"id":"F2006B09175","name":"AD/DHC-8/20 - Microwave Landing System Wiring","slug":"ad-dhc-8-20-microwave-landing-system-wiring","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":52930,"registerId":"commonwealth-F2006B09175-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-8/20 - Microwave Landing System Wiring","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-8/20 Microwave Landing System Wiring 8/92\n\nApplicability: All DHC-8 series aircraft listed in Boeing Canada, de Havilland Division, Service Bulletin 8-34-60 Revision C dated 1 November 1991, having Microwave Landing System (MLS) or MLS provisions installed.\n\nRequirement: Inspect the vertical deviation wiring interconnecting the MLS and the Ground Proximity Warning System and if necessary, rectify the wiring in accordance with the Boeing Canada, de Havilland Div, Service Bulletin 8-34-60 Revision C dated 1 November 1991.\n\nNote: Transport Canada AD CF-89-18R1 dated 11 May 1992 refers.\n\nCompliance: Prior to further operation of the Microwave Landing System or by 30 June 1993, whichever occurs first.\n\nNote 1: Previous accomplishment of the inspection and rectification in accordance with the original issue of SB 8-34-60 (12 August 1988) does not satisfy the requirements of this Directive.\n\nNote 2: The applicability of paragraphs III.c and III.d of the accomplishment instructions of SB 8-34-60 Revision A (21 September 1990) and Revision B (30 November 1990) differ from the applicability of the same paragraphs in SB 8-34-60 Revision C (1 November 1991). Because the applicability of these paragraphs was revised in Revision C of the Service Bulletin, operators of aircraft that had SB 8-34- 60 Revision A or B incorporated must verify that all applicable inspections and rectifications as required in SB 8-34-60 Revision C have been accomplished.\n\nBackground: The issue of this Directive was prompted by advice from the manufacturer that some aircraft prior to serial number 179, with provisions for MLS, were incorrectly wired.","sortOrder":0}],"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":3,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific wiring defect in specific aircraft. It has not expanded beyond its original purpose of ensuring correct MLS/GPWS wiring configuration."},"complexity_factors":["Single specific technical requirement (wiring inspection) with clear reference to external technical document (Service Bulletin 8-34-60 Revision C)","Limited applicability scope (specific aircraft series with specific equipment)","Two compliance deadlines with simple 'whichever occurs first' logic","Two notes clarifying grandfathering issues with previous service bulletin revisions","No nested conditional logic or extensive cross-referencing to other legislation","Straightforward background explanation linking to manufacturer advice"],"plain_english_summary":"Owners/operators of certain Bombardier DHC‑8 (Dash 8) aircraft must inspect and, if necessary, repair the vertical‑deviation wiring between the Microwave Landing System (MLS) and the Ground Proximity Warning System because some pre‑serial‑number‑179 airframes may have incorrect wiring that can impair GPWS during MLS approaches.\n\nWork must follow the manufacturer’s Service Bulletin 8‑34‑60 Revision C and be done before using the MLS (or by 30 June 1993). Earlier 1988 fixes are not acceptable; A/B revisions may need additional checks."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. Revision C of Service Bulletin 8-34-60 altered the applicability of specific accomplishment paragraphs (III.c and III.d). The Directive therefore requires operators who complied under the original issue or earlier revisions to verify that the Revision C inspections and rectifications have been completed, and makes earlier accomplishment explicitly insufficient in some cases (Note 1; Note 2)."},"complexity_factors":["Applicability tied to specific aircraft listed in Service Bulletin 8-34-60 Revision C (Applicability)","Technical requirement to inspect and rectify the MLS-to-GPWS vertical-deviation wiring (Requirement)","Compliance deadline that prohibits further MLS operation until the work is done or by a fixed date (Compliance)","Previous compliance under the original or earlier SB revisions does not necessarily satisfy this Directive, creating verification and possible rework (Note 1)","Revision C changed applicability of particular accomplishment paragraphs, so operators who incorporated Revision A or B must re-verify relevant inspections/rectifications (Note 2)","Identification of affected frames limited by manufacturer advice (pre-serial number 179), requiring operators to confirm applicability against the SB list (Background)"],"plain_english_summary":"This directive requires operators of certain Bombardier/De Havilland DHC‑8 aeroplanes with a Microwave Landing System (MLS) or MLS provisions to inspect the vertical‑deviation wiring between the MLS and the Ground Proximity Warning System and, if needed, repair it to match *Service Bulletin 8‑34‑60 Revision C*. It applies to aircraft listed in that service bulletin (including those previously modified under earlier revisions), must be done before any further MLS operation or by 30 June 1993, and places inspection, rectification and any related operational limits on the aircraft operator."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-20-microwave-landing-system-wiring","history":"/api/acts/ad-dhc-8-20-microwave-landing-system-wiring/history","analysis":"/api/acts/ad-dhc-8-20-microwave-landing-system-wiring/analysis","conflicts":"/api/acts/ad-dhc-8-20-microwave-landing-system-wiring/conflicts","importantCases":"/api/acts/ad-dhc-8-20-microwave-landing-system-wiring/important-cases","documents":"/api/acts/ad-dhc-8-20-microwave-landing-system-wiring/documents"}}