{"id":"F2006B10742","name":"AD/HU 369/78 - Four Bladed Tail Rotor Hubs","slug":"ad-hu-369-78-four-bladed-tail-rotor-hubs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116745,"registerId":"commonwealth-F2006B10742-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/78 - Four Bladed Tail Rotor Hubs","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 369/78 Four Bladed Tail Rotor Hubs 11/89\n\nDM\n\nApplicability: All MDHC 369D and 369E series helicopters fitted with four-bladed tail rotor hub P/N 369D21700-3 unless the currently fitted hub has been previously inspected in accordance with the Requirement Document.\n\nRequirement: Inspect the tail rotor hub in accordance with MDHC S.I.N. DN-160 or EN-50 as applicable.\n\nNote: Maintenance organisations will note MDHCs offer to replace unserviceable items free of charge and are urged to inspect their spares inventory forthwith.\n\nCompliance: 1. Helicopters with hub serial numbers 196 through 251 \\- before the accumulation of 10 hours component time in service after 11 September 1989.\n\n2. All other affected helicopters \\- before the accumulation of 100 hours component time in service after 11 September 1989.\n\nBackground: One hub has been returned from service with fatigue cracks. MDHC has determined that the cracks are a result of electrical arcing caused by poor anode contact during the Tiodize coating process during manufacture.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete airworthiness directive addressing a specific manufacturing defect in a specific helicopter part. It remains tightly scoped to its original safety purpose with no evidence of scope creep."},"complexity_factors":["Single, specific mechanical component targeted (tail rotor hub P/N 369D21700-3)","Only two compliance pathways based on serial number ranges","No defined terms section or interpretation provisions","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","Straightforward conditional logic (if serial 196-251, then 10 hours; else 100 hours)","Single-page directive with minimal procedural steps"],"plain_english_summary":"CASA orders urgent inspections of four‑bladed tail‑rotor hubs (P/N 369D21700‑3) on MDHC (Hughes) 369D/369E helicopters after fatigue cracks were found from a manufacturing defect (electrical arcing during Tiodize). Operators and maintenance organisations holding spares must inspect affected hubs — SNs 196–251 within 10 flying hours and others within 100 — and follow MDHC Service Information Notice DN‑160 or EN‑50. Cracked hubs risk catastrophic loss of control; MDHC is offering free replacements."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive, as written, targets a narrow set of helicopters fitted with a specific hub P/N and requires inspection per named service documents; it excludes hubs already inspected. There is no language in the text indicating an expansion or narrowing of that scope beyond these stated criteria."},"complexity_factors":["Technical inspection required to meet manufacturer's service instructions (MDHC S.I.N. DN‑160 or EN‑50).","Different compliance deadlines depending on hub serial numbers (SN 196–251 vs. all others).","Applicability limited to a specific part number (P/N 369D21700‑3) and excludes hubs already inspected.","Operational burden on operators to check spares inventory and schedule inspections within short component‑time windows.","Manufacturer involvement noted (offer to replace unserviceable items), introducing logistics/coordination considerations."],"plain_english_summary":"Requires operators of MDHC 369D and 369E helicopters fitted with four‑bladed tail‑rotor hub P/N 369D21700‑3 to inspect the hub in accordance with MDHC S.I.N. DN‑160 or EN‑50, unless that hub was already inspected. (Requirement)\n\nInspections must be done by specified component‑time limits—hub SN 196–251 before 10 component hours after 11 Sep 1989; all others before 100 hours. (Compliance) Operators bear inspection costs, must check spares stock, and act because a fatigue crack linked to a manufacturing coating fault was reported. (Background)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-78-four-bladed-tail-rotor-hubs","history":"/api/acts/ad-hu-369-78-four-bladed-tail-rotor-hubs/history","analysis":"/api/acts/ad-hu-369-78-four-bladed-tail-rotor-hubs/analysis","conflicts":"/api/acts/ad-hu-369-78-four-bladed-tail-rotor-hubs/conflicts","importantCases":"/api/acts/ad-hu-369-78-four-bladed-tail-rotor-hubs/important-cases","documents":"/api/acts/ad-hu-369-78-four-bladed-tail-rotor-hubs/documents"}}