{"id":"F2006B10716","name":"AD/HU 369/53 Amdt 2 - Main Rotor Drive Shaft","slug":"ad-hu-369-53-amdt-2-main-rotor-drive-shaft","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116694,"registerId":"commonwealth-F2006B10716-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/53 Amdt 2 - Main Rotor Drive Shaft","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nMcDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters\n\nAD/HU 369/53\n\nAmdt 2\n\n  \n\nMain Rotor Drive Shaft 1/91 DM\n\nApplicability: All 369 series helicopters equipped with main rotor drive shaft P/N 369D25510.\n\nRequirement: Visually inspect the spherical spline and adjacent shaft area of the drive shaft P/N 369D25510.\n\nIn accordance with Hughes Service Information Notices DN-99, FN-4 or EN-4.\n\nNote: FAA AD 81-26-01 R1 Amdt 39-4275 revised by 39-6689 refers.\n\nCompliance: Within 300 hours time in service since new or from date of last inspection. Re- inspect at intervals not exceeding 300 hours time in service. Helicopters with shafts that have exceeded 300 hours time in service and were previously exempted from this Directive must be inspected within 25 hours time in service from 7 December 1990.\n\nBackground: This Directive is further amended to include all 369 models in its applicability.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The Directive's scope was expanded. The Background states the Directive was \"further amended to include all 369 models in its applicability,\" meaning the class of helicopters covered by the inspection requirement was broadened to encompass every 369 series model fitted with drive shaft P/N 369D25510. (Background; Applicability)"},"complexity_factors":["Single, narrowly-specified technical trigger (specific part number P/N 369D25510) reduces breadth but requires accurate parts identification.","Cross-reference to external manufacturer documents (Hughes Service Information Notices DN-99, FN-4 or EN-4) places procedural detail outside the Directive and requires operators to obtain and follow those notices.","Time-based compliance schedule (300-hour intervals and a 25-hour short-term deadline for previously exempted shafts) requires operational tracking of flight hours and rapid scheduling for some operators.","Amendment expanding applicability to all 369 models increases the affected population compared with prior versions (explicitly stated in Background).","Absence of procedural text on record-keeping, verification, or enforcement in the Directive itself means those implementation details must be handled by regulators or other documents, adding practical ambiguity."],"plain_english_summary":"This directive requires owners/operators of McDonnell Douglas (Hughes)/Kawasaki 369 series helicopters fitted with main rotor drive shaft P/N 369D25510 to visually inspect the spherical spline and adjacent shaft area per Hughes Service Information Notices DN-99, FN-4 or EN-4. Inspections are due within 300 hours TIS and every 300 hours thereafter, with a 25‑hour short‑term requirement for previously exempted shafts. CASA mandates compliance; inspection time and service costs fall to operators."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"This is Amendment 2 to the original directive. The background explicitly states this amendment expands the applicability to 'include all 369 models' — meaning the scope has grown from a more limited subset of helicopters to cover the entire 369 series. This is a deliberate expansion of regulatory reach based on evolving safety data."},"complexity_factors":["Very short document (approximately 200 words)","Only 1 defined term implicitly referenced (P/N = Part Number)","Single, clear applicability criterion (specific helicopter series and part number)","Straightforward compliance timeline (300 hours/25 hours with one exception)","No cross-references to other legislation sections — only references to manufacturer service notices and FAA directive for background","Simple conditional logic (only one exemption catch-up clause for previously exempted aircraft)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on certain helicopters.\n\n**What it does:**\n- Requires owners and operators of **McDonnell Douglas (Hughes) and Kawasaki 369 series helicopters** to visually inspect a specific part — the **main rotor drive shaft** (part number 369D25510).\n- The inspection focuses on the \"spherical spline\" and nearby areas of the shaft. A spherical spline is a type of mechanical connection that allows rotation while accommodating some angular movement — critical for transferring power from the engine to the main rotor.\n\n**Who it affects:**\n- Anyone who owns, operates, or maintains **369 series helicopters** fitted with this specific drive shaft part number.\n\n**What must be done:**\n- **First inspection:** Within 300 hours of flight time since the shaft was new, or since it was last inspected.\n- **Ongoing:** Re-inspect at least every 300 flight hours thereafter.\n- **Special case:** If a helicopter was previously exempted and has already flown more than 300 hours, it must be inspected within **25 flight hours** starting from 7 December 1990.\n\n**Why it matters:**\n- The main rotor drive shaft is what keeps the helicopter's blades spinning. If it fails, the helicopter loses lift and crashes. This AD exists because there was likely a safety concern about cracks or wear in this specific shaft design that could lead to catastrophic failure.\n\n**Technical note:** The directive references Hughes Service Information Notices and an FAA (American) Airworthiness Directive, showing this is based on international safety data and manufacturer guidance."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-53-amdt-2-main-rotor-drive-shaft","history":"/api/acts/ad-hu-369-53-amdt-2-main-rotor-drive-shaft/history","analysis":"/api/acts/ad-hu-369-53-amdt-2-main-rotor-drive-shaft/analysis","conflicts":"/api/acts/ad-hu-369-53-amdt-2-main-rotor-drive-shaft/conflicts","importantCases":"/api/acts/ad-hu-369-53-amdt-2-main-rotor-drive-shaft/important-cases","documents":"/api/acts/ad-hu-369-53-amdt-2-main-rotor-drive-shaft/documents"}}