{"id":"F2006B09578","name":"AD/ENST 28/22 - Main Rotor Transmission Mount Bolts - Inspection","slug":"ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54270,"registerId":"commonwealth-F2006B09578-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/22 - Main Rotor Transmission Mount Bolts - 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 28/22 Main Rotor Transmission Mount\n\nBolts - Inspection\n\n\n5/79\n\n \n\nApplicability: All model F-28C with S/Nos. 451-2, 452-2, 453, 454-2, 455-2, 456-2, 457, 458, 459,\n\n460-2, 462, 463-2 and 464-2.\n\n \n\nAll model 280C with S/Nos. 1145, to 1169.\n\n \n\nDocument: Enstrom Service Directive Bulletin No. 0049. Compliance: Within 100 hours time in service after 31 July 1979.\n\nBackground: It has been found that several of the NAS 146R-57 main rotor transmission mount bolts have defectively formed heads.\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":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1742},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive maintains a narrow, targeted scope focused solely on addressing a specific manufacturing defect in particular helicopter models. It does not expand beyond the original safety purpose of inspecting defective transmission mount bolts."},"complexity_factors":["Very short length (single compliance requirement)","Limited applicability restricted to specific aircraft serial numbers","Single reference document (Enstrom Service Directive Bulletin No. 0049)","Simple time-based compliance trigger (100 hours after specific date)","No exceptions, conditional clauses, or nested provisions"],"plain_english_summary":"**What this does:** This Airworthiness Directive (AD) mandates an inspection of the main rotor transmission mount bolts on specific Enstrom F-28C and 280C helicopters.\n\n**Who it affects:** Owners and operators of Enstrom F-28C helicopters with serial numbers 451-2, 452-2, 453, 454-2, 455-2, 456-2, 457, 458, 459, 460-2, 462, 463-2, and 464-2; and Enstrom 280C helicopters with serial numbers 1145 through 1169.\n\n**What must be done:** The helicopters must be inspected in accordance with Enstrom Service Directive Bulletin No. 0049. This inspection must be completed within 100 hours of flight time after 31 July 1979.\n\n**Why it matters:** The bolts that hold the main rotor transmission in place were found to have defectively formed heads during manufacturing. This creates a safety risk because if these bolts fail, the main rotor transmission could detach, causing catastrophic failure of the helicopter."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection","history":"/api/acts/ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection/history","analysis":"/api/acts/ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection/analysis","conflicts":"/api/acts/ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection/conflicts","importantCases":"/api/acts/ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection/important-cases","documents":"/api/acts/ad-enst-28-22-main-rotor-transmission-mount-bolts-inspection/documents"}}