{"id":"F2006B09587","name":"AD/ENST 28/30 Amdt 2 - Tail Rotor Spindle","slug":"ad-enst-28-30-amdt-2-tail-rotor-spindle","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54292,"registerId":"commonwealth-F2006B09587-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/30 Amdt 2 - Tail Rotor Spindle","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 28/30\n\nAmdt 2\n\n\nTail Rotor Spindle 3/93\n\n \n\nApplicability: All F-28F, 280F or 280FX model helicopters and any F-28C, F-28C-2, or 280C models that have been converted to use the 28-150064-11 or -13 spindle.\n\nRequirement: Action in accordance with Enstrom Service Directive Bulletin No 0077 Revision B. Compliance:               As specified in the requirement document but with a revised effective date of\n\n26 March 1992.\n\n \n\nBackground:  This amendment raised in sequence to add the -13 spindle to the AD requirements and to place a service life limit of 1200 hours on the 28-150064-11 and -13 spindles.\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\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original AD (issued 3/93) has expanded through amendments. Amendment 2 specifically broadened scope from covering only the -11 spindle to also include the -13 variant, and added a mandatory retirement life limit. This represents incremental expansion typical of airworthiness directives as operational experience reveals additional safety concerns."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined term implicitly referenced (the spindle part numbers)","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","Single, clear compliance requirement (follow the manufacturer's bulletin)","No nested exceptions or conditional logic — straightforward applicability and requirement","Background section provides plain explanation of the amendment's purpose"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). Think of it like a compulsory recall notice for aircraft parts, but with legal force.\n\n**What it does:** This directive applies to specific **Enstrom F-28 series helicopters** (models F-28F, 280F, 280FX, and certain converted C models). It requires owners and operators to follow **Enstrom Service Directive Bulletin No. 0077 Revision B** — essentially, a manufacturer's maintenance instruction.\n\n**The key safety issue:** The directive addresses problems with the **tail rotor spindle** — a critical component that connects the tail rotor to the helicopter. If this part fails, the pilot can lose control of the aircraft's yaw (directional control), which can be catastrophic.\n\n**What's new in this version (Amendment 2):**\n- Expands coverage to include the **-13 spindle** (not just the -11 version)\n- Imposes a **hard service life limit of 1,200 flight hours** on these spindles — meaning they must be replaced after reaching that time, regardless of condition\n- Sets a **new effective date of 26 March 1992** for compliance\n\n**Who must comply:** Anyone operating the affected helicopter models in Australia. Non-compliance means the aircraft cannot legally fly.\n\n**Why it matters:** This prevents in-flight failures of a critical rotating component. The 1,200-hour \"retirement life\" is a precautionary measure based on fatigue analysis — even if the spindle looks fine, it must come out after that time to prevent catastrophic failure."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The amendment expanded the directive's coverage by explicitly adding the 28-150064-13 spindle to the parts governed by the AD and by introducing a service life limit of 1,200 hours on the 28-150064-11 and -13 spindles. This alters the previous scope by increasing the set of affected components and imposing a numeric life limit that operators must monitor and enforce. (Background; Applicability)"},"complexity_factors":["Narrow technical scope: applies to a specific component (tail rotor spindle) on specified helicopter models (Applicability).","Dependence on an external technical document: compliance requires following Enstrom Service Directive Bulletin No 0077 Revision B (Requirement).","A single quantitative limit to track: the 1,200-hour service life on two spindle part numbers (Background).","Clear compliance deadline/effective date but no complex phased implementation: revised effective date given (Compliance)."],"plain_english_summary":"This directive requires owners/operators of specified Enstrom F‑28/280 helicopters to comply with Enstrom Service Directive Bulletin No. 0077 Rev B, making that bulletin the mandatory means of compliance. It adds the 28‑150064‑13 tail‑rotor spindle and sets a 1,200‑hour service‑life limit on both 28‑150064‑11 and ‑13 spindles.\n\nAffected operators bear inspection, removal and replacement costs and must track spindle hours; the civil aviation authority enforces the AD."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-30-amdt-2-tail-rotor-spindle","history":"/api/acts/ad-enst-28-30-amdt-2-tail-rotor-spindle/history","analysis":"/api/acts/ad-enst-28-30-amdt-2-tail-rotor-spindle/analysis","conflicts":"/api/acts/ad-enst-28-30-amdt-2-tail-rotor-spindle/conflicts","importantCases":"/api/acts/ad-enst-28-30-amdt-2-tail-rotor-spindle/important-cases","documents":"/api/acts/ad-enst-28-30-amdt-2-tail-rotor-spindle/documents"}}