{"id":"F2006B09577","name":"AD/ENST 28/21 - Tail Rotor Blade Grip - Inspection and Modification","slug":"ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54266,"registerId":"commonwealth-F2006B09577-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/21 - Tail Rotor Blade Grip - Inspection and Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Enstrom F-28 Series Helicopters\n\n \n\nAD/ENST 28/21 Tail Rotor Blade Grip - Inspection\n\nand Modification\n\n\n5/79\n\n \n\nApplicability: All models F-28C and 280C with Tail Rotor Blade Grip P/N 28-150013-1 wide chord.\n\n \n\nDocument: Enstrom Service Directive Bulletin No. 0048. Compliance: As per requirement document.\n\nThe Preflight Inspections may be carried out by the pilot in command in which case certification is not required.\n\n \n\nBackground:  The manufacturer has received several field reports of crack indications being found in the wide chord tail rotor blade retentions grip.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive targeting a specific safety defect in a specific helicopter part. It has not expanded beyond its original purpose of addressing cracked tail rotor blade grips."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 1 defined applicability criterion (specific part number)","Single cross-reference to external technical document (Enstrom Service Directive Bulletin No. 0048)","No nested exceptions or conditional logic","No interpretation section or defined terms","Simple binary applicability test (model + part number match = applies)","Explicit delegation of inspection authority to pilots (unusual but clearly stated)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for specific Enstrom helicopters.\n\n**What it does:**\n- Requires owners and operators of certain Enstrom F-28C and 280C helicopters to inspect and modify the **tail rotor blade grip** (the part that holds the tail rotor blade to the helicopter).\n- The specific part affected is part number 28-150013-1, known as the \"wide chord\" tail rotor blade grip.\n\n**Who it affects:**\n- Anyone who owns or operates an Enstrom F-28C or 280C helicopter with the specified tail rotor blade grip.\n- Pilots can perform the preflight inspections themselves without needing a mechanic to sign off on it (unusual flexibility for aviation safety rules).\n\n**Why it matters:**\n- The manufacturer received multiple reports of **cracks** appearing in this critical component. The tail rotor keeps the helicopter from spinning uncontrollably — if the grip fails, the helicopter could crash.\n- This directive forces action before a failure occurs, rather than waiting for an accident.\n\n**What must be done:**\n- Follow the instructions in **Enstrom Service Directive Bulletin No. 0048** (the manufacturer's technical document referenced here).\n- Compliance is mandatory \"as per requirement document\" — meaning the bulletin sets the specific deadlines and procedures."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The supplied text contains no information indicating a change of scope from an earlier or original instrument. The directive as presented applies to the specified models and part number and requires compliance with Enstrom Service Directive Bulletin No. 0048; there is no statement within the supplied text that the scope has been expanded or narrowed relative to an earlier version."},"complexity_factors":["Narrow technical scope — applies only to F-28C and 280C helicopters with tail rotor blade grip P/N 28-150013-1 (Applicability).","Delegation to an external technical document — compliance requires obtaining and following Enstrom Service Directive Bulletin No. 0048, so the directive’s operational detail is in another document (Document; Compliance).","Operational flexibility — permits pilots in command to perform preflight inspections without certification, introducing a simple procedural exception (Preflight Inspections).","Limited procedural content in the directive itself — absence of inspection intervals, methods, or modification steps in the directive increases reliance on the service bulletin for substantive instructions (Document; Compliance)."],"plain_english_summary":"This AD requires owners/operators of Enstrom F‑28C and 280C helicopters with the wide‑chord tail rotor blade grip (P/N 28‑150013‑1) to inspect and, if necessary, modify or replace that grip by following Enstrom Service Directive Bulletin No. 0048 because of reported crack indications. It shifts technical detail to the manufacturer’s bulletin, leaves compliance costs to operators, and allows pilots to perform the preflight check without certification."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification","history":"/api/acts/ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification/history","analysis":"/api/acts/ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification/analysis","conflicts":"/api/acts/ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification/important-cases","documents":"/api/acts/ad-enst-28-21-tail-rotor-blade-grip-inspection-and-modification/documents"}}