{"id":"F2006B09580","name":"AD/ENST 28/24 - Main Rotor Retention Assembly - Inspection","slug":"ad-enst-28-24-main-rotor-retention-assembly-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54275,"registerId":"commonwealth-F2006B09580-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/24 - Main Rotor Retention Assembly - Inspection","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 28/24 Main Rotor Retention Assembly - Inspection 10/82\n\nApplicability: All model F-28A, F-28C, F-28F, 280, 280C and 280F. Document:  Enstrom Service Directive Bulletin No. 0057.\n\nNote: FAA AD 82-16-09 Amdt. 39-4429 refers.\n\n \n\nCompliance: Within 100 hours time in service after 31 October 1982, and thereafter at intervals not exceeding 200 hours time in service.\n\n \n\nBackground:  Manufacture reports misalignment of the nylon shims has worn grooves in the inner surfaces of the blade 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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive, as presented, sets inspection requirements for the specified Enstrom models and prescribes timing and a referenced service bulletin. There is no indication in the text that the scope has been widened or narrowed from an earlier version; the AD explicitly lists applicability, compliance intervals, and the supporting document. (Applicability; Compliance; Document)"},"complexity_factors":["Narrow technical subject limited to main rotor retention assembly of specific Enstrom F‑28 models (Applicability)","Simple, time‑based inspection schedule with fixed intervals (Compliance)","Reliance on an external manufacturer service bulletin for inspection procedure (Document)","Cross‑reference to FAA AD increases cross‑jurisdictional coordination but does not add procedural layers (Note)","Potential procedural ambiguity if the referenced service bulletin is unavailable or interpreted differently by maintenance providers (Document)"],"plain_english_summary":"What this instrument does (mechanically)\n\n- Requires regular inspections of the main rotor retention assembly on certain Enstrom F‑28 family helicopters. (Applicability; Compliance)\n- Applies to all Enstrom models F‑28A, F‑28C, F‑28F, 280, 280C and 280F. (Applicability)\n- Specifies an initial inspection \"within 100 hours time in service after 31 October 1982\" and repeat inspections thereafter at intervals not exceeding 200 hours time in service. (Compliance)\n- Directs operators to the manufacturer document \"Enstrom Service Directive Bulletin No. 0057\" for the inspection procedure. (Document)\n- Cross‑references FAA AD 82‑16‑09. (Note)\n\nWhy the requirement was issued (official rationale)\n\n- The manufacturer reported that misalignment of nylon shims has caused wear grooves in the inner surfaces of the blade grip. The AD implements inspections to identify that wear. (Background)\n\nWho is affected and who pays\n\n- Affected parties: owners and operators of the listed Enstrom F‑28 series helicopters. (Applicability)\n- Who pays: aircraft owners/operators pay the direct costs of conducting the inspections (labour, maintenance facility time, possible parts/repairs if wear is found). (Compliance; Document)\n\nWhat behaviour changes and decisions are required\n\n- Operators must schedule and perform the initial inspection within the specified 100‑hour window after 31 October 1982 and then perform follow‑up inspections at intervals not exceeding 200 hours TIS. (Compliance)\n- Operators must obtain and follow Enstrom Service Directive Bulletin No. 0057 for the inspection method and criteria. If corrective action is needed, operators must carry out whatever repairs or replacements the service bulletin or maintenance authority requires. (Document)\n\nImplementation details, risks and trade‑offs\n\n- The AD sets a time‑based inspection frequency (100 hours initial, then every 200 hours). That creates recurring maintenance costs and aircraft downtime proportional to flight hours. (Compliance)\n- The AD relies on an external manufacturer document for the inspection procedure. If that document is not on hand or is interpreted differently by different maintenance providers, there is potential variation in how inspections are performed. (Document)\n- The background statement identifies a specific manufacturing/assembly issue (misaligned nylon shims) and a resulting wear pattern (grooves in the blade grip inner surface). The inspection requirement targets that observed failure mode. (Background)\n- The AD cross‑references a FAA airworthiness directive, indicating alignment with a foreign regulator’s action; operators and maintenance organisations may use both documents when determining compliance steps. (Note)\n\nOpportunity costs and compliance burden\n\n- Time spent on periodic inspections is time not spent flying; the compliance intervals (200 hours) determine how often that opportunity cost recurs. (Compliance)\n- If inspections find wear requiring repair, operators incur additional parts and labour costs and possible extended aircraft downtime. (Document; Background)\n\nSummary statement\n\nThis airworthiness directive mandates that owners/operators of specified Enstrom F‑28 series helicopters carry out an initial inspection of the main rotor retention assembly within 100 hours TIS after 31 October 1982 and then every 200 hours TIS, following Enstrom Service Directive Bulletin No. 0057, because of manufacturer reports of wear caused by misaligned nylon shims. (Applicability; Compliance; Document; Background; Note)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-limited airworthiness directive with a narrow, specific scope addressing a known mechanical defect in a particular helicopter series. It has not expanded beyond its original purpose of ensuring rotor assembly safety through periodic inspection."},"complexity_factors":["Single, specific mechanical component addressed (main rotor retention assembly)","Straightforward compliance timeline (100 hours initial, 200 hours recurring)","Only 6 helicopter models affected, clearly listed","No defined terms section or complex conditional logic","Single external reference document (Enstrom Service Directive Bulletin No. 0057)","No nested exceptions or cross-references to other legislation","Total length is approximately 200 words"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) that mandates safety inspections for specific Enstrom helicopter models.\n\n**What it does:**\n- Requires owners and operators of Enstrom F-28 series helicopters (models F-28A, F-28C, F-28F, 280, 280C, and 280F) to inspect the **main rotor retention assembly** — the critical hardware that keeps the helicopter's main rotor blades attached to the aircraft.\n\n**Why it matters:**\n- The directive was issued because the manufacturer discovered that **misaligned nylon shims** (thin plastic washers used as spacers) were wearing grooves into the inner surfaces of the blade grip. This wear could potentially compromise the structural integrity of the rotor system, creating a serious flight safety risk.\n\n**What must be done:**\n- **First inspection:** Must be completed within 100 hours of flight time after 31 October 1982\n- **Ongoing inspections:** Must be repeated every 200 hours of flight time thereafter\n\n**Who it affects:**\n- Owners, operators, and maintenance organisations responsible for the affected Enstrom helicopter models\n\n**Key reference:**\n- The directive references **Enstrom Service Directive Bulletin No. 0057** for the detailed inspection procedure, and notes the corresponding US Federal Aviation Administration (FAA) directive AD 82-16-09."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-24-main-rotor-retention-assembly-inspection","history":"/api/acts/ad-enst-28-24-main-rotor-retention-assembly-inspection/history","analysis":"/api/acts/ad-enst-28-24-main-rotor-retention-assembly-inspection/analysis","conflicts":"/api/acts/ad-enst-28-24-main-rotor-retention-assembly-inspection/conflicts","importantCases":"/api/acts/ad-enst-28-24-main-rotor-retention-assembly-inspection/important-cases","documents":"/api/acts/ad-enst-28-24-main-rotor-retention-assembly-inspection/documents"}}