{"id":"F2006B04720","name":"AD/BELL 47/99 - Tail Rotor Blade Skin Material","slug":"ad-bell-47-99-tail-rotor-blade-skin-material","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44484,"registerId":"commonwealth-F2006B04720-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 47/99 - Tail Rotor Blade Skin Material","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 47 (All Variants) Series Helicopters\n\nAD/BELL 47/99 Tail Rotor Blade Skin Material 5/96\n\nTX\n\nApplicability: All models with tail rotor blade assembly P/N 047-642-117-105, S/Nos A-1943 to A-2068 inclusive, installed.\n\nRequirement: Action in accordance with BHTI ASB 47-96-21.\n\nNote 1. FAA AD 96-06-12 refers.\n\nNote 2. Installation of approved tail rotor blades, other than those specified in the Applicability, terminates this Directive.\n\nNote 3. Installation of tail rotor blades P/N 047-642-117-105M including those serial numbers specified in the Applicability terminates this Directive.\n\nCompliance: Prior to further flight after 22 March 1996, thereafter at each Daily Inspection, or at intervals not exceeding 10 hours time in service, whichever occurs first.\n\nNote: The Compliance of this Directive is at variance with that of the Requirement Document.\n\nBackground: The helicopter manufacturer has discovered that certain serial number tail rotor blades were skinned with the incorrect material. This may cause bond line separation and possible loss of the abrasion strip and/or blade tip block.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a specific helicopter part. It has not expanded beyond its original purpose of ensuring tail rotor blade integrity for the affected serial numbers."},"complexity_factors":["Single, specific mechanical defect addressed","Only 4 defined elements: specific part number, serial number range, reference to external document (ASB 47-96-21), and FAA AD cross-reference","Clear applicability test (serial number check)","Simple compliance timeline with two termination conditions","No nested exceptions or conditional logic — straightforward if-then structure","Background explanation provided in plain language"],"plain_english_summary":"This CASA airworthiness directive requires operators of Bell 47 helicopters with tail rotor blades P/N 047-642-117-105 (S/N A-1943–A-2068) to inspect for a manufacturing defect where the wrong skin material can separate in flight. Inspections must be done immediately and routinely per Bell Helicopter Alert Service Bulletin 47-96-21; the AD can be terminated by fitting approved replacement or modified (“-117-105M”) blades. It prevents blade loss that could cause loss of control or a crash."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope remains focused on the specific P/N and S/N range identified to correct the discovered skin-material defect. The directive requires inspections/corrective actions and ends on replacement with approved blades; there is no expansion beyond that safety-limited scope in the text provided."},"complexity_factors":["Applicability is serial-number and part-number specific (Applicability): requires checking P/N 047-642-117-105 and S/N A-1943 to A-2068.","Action is by reference to an external service bulletin (Requirement: BHTI ASB 47-96-21) — enforcement depends on reading another document.","Immediate and recurring timing: compliance required prior to further flight after 22 March 1996 and thereafter at each Daily Inspection or ≤10 hours TIS (Compliance) — operational scheduling constraint.","Termination conditions: installation of alternative approved tail rotor blades or P/N 047-642-117-105M (Notes 2–3) ends the obligation — creates a clear replacement pathway.","Regulatory ambiguity flag: directive states its Compliance is at variance with the Requirement Document (Note) — potential for interpretive or procedural mismatch.","Technical safety risk described requires remedial work: incorrect skin material may cause bond line separation and loss of abrasion strip/tip block (Background)."],"plain_english_summary":"Requires operators of Bell 47 helicopters fitted with tail rotor blade assembly P/N 047-642-117-105, S/N A-1943–A-2068, to follow Bell Helicopter ASB 47‑96‑21 immediately and at every daily inspection or every 10 flight hours. It mandates inspections and corrective action to address incorrectly skinned blades that can separate and shed components; replacing blades with approved part numbers terminates the directive. Operators pay for inspections, repairs and any blade replacement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-47-99-tail-rotor-blade-skin-material","history":"/api/acts/ad-bell-47-99-tail-rotor-blade-skin-material/history","analysis":"/api/acts/ad-bell-47-99-tail-rotor-blade-skin-material/analysis","conflicts":"/api/acts/ad-bell-47-99-tail-rotor-blade-skin-material/conflicts","importantCases":"/api/acts/ad-bell-47-99-tail-rotor-blade-skin-material/important-cases","documents":"/api/acts/ad-bell-47-99-tail-rotor-blade-skin-material/documents"}}