{"id":"F2006B04327","name":"AD/BELL 204/21 - Main Rotor Blades - Inspection","slug":"ad-bell-204-21-main-rotor-blades-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44142,"registerId":"commonwealth-F2006B04327-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 204/21 - Main Rotor Blades - Inspection","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)  \nBell Helicopter Textron 204 Series Helicopters\n\nAD/BELL 204/21 Main Rotor Blades \\- Inspection NK\n\nApplicability: All models 204B with main rotor blades P/Nos. 204-012-001 (all dash numbers) and 204-011-250 (all dash numbers) which have achieved 600 hours’ time in service.\n\nRequirement: To detect cracks in the main rotor blades, perform the following:\n\n    Visually inspect the upper surface of each blade in the area of the spare particularly between stations 110 and 165.\n\n    2. Cone each blade by inserting a wooden wedge between the mast and the static stop and raise the tip of the blade sufficiently to eliminate blade droop and obtain approx. 6 ins. (15 cms) blade cone at the tip; and\n\n    3. Visually inspect the undersurface of each blade particularly in the area of the spare between stations 110 and 165.\n\nNote: Refer to the Maintenance Manual Section 1, Page 1-23 and 1-24 Section II, Page 2-6, Para 2-7B for inspection requirements.\n\nCompliance: At each daily or overnight inspection after 11 November 1975.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused specifically on inspection requirements for particular helicopter rotor blades. It has not expanded beyond its original purpose of ensuring airworthiness through crack detection."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 defined part numbers in the applicability section","Simple three-step procedural requirement with no nested conditions","Single compliance trigger (daily/overnight inspections after a fixed date)","No cross-references to other legislation or complex conditional logic","One external reference to maintenance manual (non-legislative document)"],"plain_english_summary":"Owners and operators of Bell 204B helicopters with main rotor blades P/N 204-012-001 or 204-011-250 (any dash variant) must perform repetitive daily/overnight visual inspections once those blades reach 600 flight hours. The AD targets spar-area cracks between stations 110–165 and references the maintenance manual for procedure details.\n\nThe required check sequence (upper-surface inspection, coning the blade to remove droop, then underside inspection) aims to detect cracks early to prevent catastrophic blade failure."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"Scope has not changed from the instrument's stated terms: it applies to all Bell 204B helicopters with the two listed blade part numbers once a blade reaches 600 hours TIS, and requires daily/overnight inspections per the Maintenance Manual references."},"complexity_factors":["Narrow technical scope: applies only to Bell 204B blades with two specific part numbers and a 600‑hour threshold (simple applicability).","Procedural requirement to 'cone' blades (insertion of a wedge and raising tip) requires specific technique/tools and access to the mast/static stop.","Inspection targets a defined structural zone ('between stations 110–165') requiring familiarity with blade station numbering.","High-frequency compliance: required at each daily or overnight inspection, creating recurring operational and administrative burden.","Reliance on cross-referenced Maintenance Manual pages for method detail increases a need to consult external documents.","Text ambiguity: phrase 'area of the spare' appears in source (likely 'spar'), which could cause interpretive uncertainty in implementation."],"plain_english_summary":"Mechanically, this Directive requires Bell 204B operators to carry out specific visual inspections of main rotor blades (P/N 204-012-001 and 204-011-250) and to \"cone\" each blade daily once a blade has reached 600 hours' time-in-service. Its stated purpose is to detect cracks in the blade spar between stations 110–165; operators bear the inspection burden and must follow the Maintenance Manual procedures, creating recurring operational and record-keeping costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-204-21-main-rotor-blades-inspection","history":"/api/acts/ad-bell-204-21-main-rotor-blades-inspection/history","analysis":"/api/acts/ad-bell-204-21-main-rotor-blades-inspection/analysis","conflicts":"/api/acts/ad-bell-204-21-main-rotor-blades-inspection/conflicts","importantCases":"/api/acts/ad-bell-204-21-main-rotor-blades-inspection/important-cases","documents":"/api/acts/ad-bell-204-21-main-rotor-blades-inspection/documents"}}