{"id":"F2006B09597","name":"AD/ENST 28/7 Amdt 1 - Main Rotor Transmission Attachment Bolts - Inspection and Replacement","slug":"ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54319,"registerId":"commonwealth-F2006B09597-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/7 Amdt 1 - Main Rotor Transmission Attachment Bolts - Inspection and Replacement","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 28/7\n\nAmdt 1\n\nApplicability: All models.\n\n\nMain Rotor Transmission Attachment Bolts - Inspection and Replacement\n\n\n4/77\n\n \n\nRequirement: 1. Inspect the 4 bolts attaching the main rotor transmission assembly to the fuselage frame for a torque preloading of 100-110 inch pounds.\n\n \n\n2. Modify the attachment of the main rotor transmission assembly to fuselage attachment as per Enstrom Service Information Letter No. 0057.\n\n \n\nCompliance: For Para. 1: At intervals not exceeding 50 hours time in service until modified and then once only within 100 hours time in service after modification as per SIL No. 0057.\n\n \n\nFor Para. 2: Modify within 300 hours time in service after 1 June 1977.\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 Amendment 1 to an existing Airworthiness Directive (AD/ENST 28/7). The document appears to be a complete, standalone directive with clear scope limited to specific maintenance actions on Enstrom F-28 helicopters. There is no indication of scope creep beyond the original safety purpose of ensuring main rotor transmission attachment integrity."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 substantive requirements (inspection and modification)","No defined terms section","Minimal cross-referencing (only to external manufacturer document SIL No. 0057)","Simple conditional logic (time-based compliance intervals)","Single applicability clause covering all models"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to all models of **Enstrom F-28 Series Helicopters**.\n\n**What it requires:**\n- **Inspection:** Check 4 specific bolts that hold the main rotor transmission (the gearbox that drives the helicopter's main rotor) to the fuselage frame. These bolts must be tightened to a specific torque (twisting force) of 100-110 inch-pounds.\n- **Modification:** Change how the transmission attaches to the fuselage, following instructions in \"Enstrom Service Information Letter No. 0057\" (a technical bulletin from the helicopter manufacturer).\n\n**When it must be done:**\n- **Inspections:** Every 50 hours of flight time until the modification is done. After modification, one final inspection within 100 hours of flight time.\n- **Modification:** Within 300 hours of flight time after 1 June 1977.\n\n**Why it matters:** Loose or improperly tightened bolts on the main rotor transmission could cause the transmission to detach in flight, leading to catastrophic loss of control. This AD prevents mechanical failure by ensuring proper bolt tension and a design improvement."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text as provided applies to 'All models' and specifies inspection and modification requirements; it does not show any narrowing or expansion of applicability beyond that statement, so no change of scope is evident from this instrument alone (Applicability; Requirements; Compliance)."},"complexity_factors":["Technical specification of torque preload (100–110 in·lb) requires calibrated tooling and trained maintenance personnel (Requirement 1).","Recurring inspection interval until modification (every 50 flight hours) then a one‑time post‑modification check (Compliance for Para. 1) adds ongoing planning and labour costs.","Mandatory modification references an external document (Enstrom Service Information Letter No. 0057), so operators must obtain and follow that SIL to comply (Requirement 2).","Compliance timeframes tied to flight hours (300 hours after 1 June 1977) require tracking of aircraft utilisation and maintenance scheduling.","Applicability to 'All models' broadens universe of affected aircraft but keeps the directive uniform across the fleet (Applicability)."],"plain_english_summary":"This airworthiness directive requires owners/operators of Enstrom F‑28 helicopters to inspect the four bolts that attach the main rotor transmission to the fuselage for a preload torque of 100–110 inch‑pounds and to modify that attachment following Enstrom Service Information Letter No. 0057. Inspections are periodic (every 50 flight hours until modified; one check within 100 hours after modification) and the modification must be completed within 300 flight hours of 1 June 1977. The directive shifts inspection, modification and recordkeeping costs and scheduling decisions to aircraft operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement","history":"/api/acts/ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement/history","analysis":"/api/acts/ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement/analysis","conflicts":"/api/acts/ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement/conflicts","importantCases":"/api/acts/ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement/important-cases","documents":"/api/acts/ad-enst-28-7-amdt-1-main-rotor-transmission-attachment-bolts-inspection-and-replacement/documents"}}