{"id":"F2006B09207","name":"AD/DHC-8/51 - Horizontal Stabiliser Skin Disbonding","slug":"ad-dhc-8-51-horizontal-stabiliser-skin-disbonding","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53039,"registerId":"commonwealth-F2006B09207-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DHC-8/51 - Horizontal Stabiliser Skin Disbonding","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-8/51 Horizontal Stabiliser Skin Disbonding 5/98\n\nDM\n\nApplicability: DHC-8 aircraft, models 102 and 103, with serial numbers 003 through 050.\n\nRequirement: Perform a one-time ultrasonic bond inspection of the upper and lower skin panels (part number 85510025 and 85510026) of the horizontal stabiliser for disbond as outlined in de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01.\n\nNote: Transport Canada AD CF-98-01 and Bombardier AOM 469 refer.\n\nCompliance: For aircraft serial numbers 010 through 040: within 20 flight cycles or 7 calendar days after 25 February 1998, whichever occurs first, unless already accomplished within the last 6 months.\n\nFor aircraft serial numbers 003 through 009, and 041 through 050: within 60 flight cycles or 7 calendar days after 25 February 1998, whichever occurs first, unless already accomplished within the last 6 months.\n\nDisbonds found to be beyond the local disbond limits defined in de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01, shall be repaired before further flight.\n\nThis airworthiness directive becomes effective on 25 February 1998.\n\nBackground: Transport Canada has received two reports of cases of disbonding of the doubler and stringers on the upper and lower skin panels of the horizontal stabiliser, on two separate aircraft. This condition, if not detected and corrected, could result in structural failure of the horizontal stabiliser and possible loss of control of the aircraft.","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, time-bound safety directive with a narrow, specific scope (inspection of one component on 47 specific aircraft). It has not expanded beyond its original purpose of addressing the identified disbonding risk."},"complexity_factors":["Short, single-purpose document (1 page)","Only 2 defined applicability groups (serial number ranges)","Simple conditional compliance structure (two-tier deadline system based on serial numbers)","Single cross-reference to manufacturer technical document (PSM 1-8-7A)","No nested exceptions or complex definitional sections","Clear, imperative language throughout"],"plain_english_summary":"This mandatory Airworthiness Directive requires urgent ultrasonic inspections of the upper and lower horizontal‑stabiliser skins on 47 Bombardier DHC‑8‑100/300 aeroplanes (serials 003–050) to detect skin disbonding. It affects operators, maintenance crews and pilots and sets short compliance windows for higher‑ and lower‑risk serials; aircraft with excessive disbonding are grounded until repaired to prevent structural failure and potential loss of control."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive implements a targeted, one‑time inspection and repair requirement for a defined set of serial‑numbered aircraft to address reported disbonding. It does not expand applicability beyond those aircraft, nor introduce recurring inspections or new regulatory powers beyond requiring inspection and repair as specified."},"complexity_factors":["Narrow applicability: applies only to DHC-8 models 102 and 103, serial numbers 003–050 (low scope breadth).","Single, one‑time action: requirement is a single ultrasonic inspection rather than ongoing monitoring (reduces procedural complexity).","Technical execution: inspection requires ultrasonic NDT equipment and trained personnel (specialist skill/equipment burden).","Staggered compliance windows: different flight‑cycle deadlines for subgroups (administrative scheduling burden).","External normative references: inspection limits and procedures are defined in de Havilland Document PSM 1-8-7A, Part 5, Section 55-00-01 (dependency on external documentation).","Immediate grounding risk: discovered disbonds beyond limits must be repaired before further flight (potential operational disruption and repair cost to operators).","Cross-reference to other authorities: notes Transport Canada AD and Bombardier AOM references (coordination/traceability factor)."],"plain_english_summary":"This airworthiness directive requires operators of Bombardier (DeHavilland) DHC-8 models 102 and 103, serial numbers 003–050, to carry out a one‑time ultrasonic inspection of the horizontal stabiliser upper and lower skin panels within short, specified flight‑cycle or calendar deadlines. If the inspection finds disbonds beyond the limits set in the manufacturer’s procedure, the stabiliser must be repaired before the aircraft flies again. The rule aims to detect and fix structural disbonding that could risk stabiliser failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-51-horizontal-stabiliser-skin-disbonding","history":"/api/acts/ad-dhc-8-51-horizontal-stabiliser-skin-disbonding/history","analysis":"/api/acts/ad-dhc-8-51-horizontal-stabiliser-skin-disbonding/analysis","conflicts":"/api/acts/ad-dhc-8-51-horizontal-stabiliser-skin-disbonding/conflicts","importantCases":"/api/acts/ad-dhc-8-51-horizontal-stabiliser-skin-disbonding/important-cases","documents":"/api/acts/ad-dhc-8-51-horizontal-stabiliser-skin-disbonding/documents"}}