{"id":"F2006B10763","name":"AD/HU 369/99 - Four-Bladed Tail Rotor Fork","slug":"ad-hu-369-99-four-bladed-tail-rotor-fork","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":56212,"registerId":"commonwealth-F2006B10763-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 369/99 - Four-Bladed Tail Rotor Fork","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 369/99 Four-Bladed Tail Rotor Fork 8/99\n\nDM\n\nApplicability: Model 369D and E helicopters, with four-bladed tail rotor fork assemblies, part numbers 369D21701-21, installed.\n\nRequirement: Inspect in accordance with MD Helicopters Inc. Service Bulletin 369D-198 or 369E- 092, as applicable.\n\nNote: FAA Priority Letter AD 99-13-09 refers.\n\nCompliance: Unless the initial inspection is already accomplished, before further flight after\n\n30 June 1999; and if affected, thereafter at intervals not to exceed 50 hours time in service.\n\nIf no ridges are found on the initial inspection, raise an MDR quoting this directive, and include action under para 1E of the requirement document if necessary.\n\nThis Airworthiness Directive becomes effective on 30 June 1999.\n\nBackground: The FAA received reports from the manufacturer of the discovery of a discrepant part.\n\nDuring the manufacturing process, an unknown number of certain four-bladed tail rotor fork assemblies were incorrectly machined in critical areas after the shot-peening process. The two ridges on each of the arms of the fork assemblies were incorrectly machined off. This condition, if not corrected, could result in failure which could cause loss of a tail rotor blade and subsequent loss of control of the helicopter.","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific manufacturing defect in a specific helicopter part. It has not expanded beyond its original purpose of mandating inspection and reporting for this single airworthiness issue."},"complexity_factors":["Single, specific mechanical defect addressed","Only 1 defined term implicitly used ('time in service' — standard aviation term for flight hours)","Clear applicability criteria (2 specific helicopter models, 1 specific part number)","Straightforward compliance timeline (before 30 June 1999, then every 50 hours)","Single cross-reference to FAA directive for background context only","No nested exceptions or conditional logic beyond the standard 'unless already done' clause"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections of the four‑bladed tail rotor fork (P/N 369D21701‑21) on McDonnell Douglas (Hughes) and Kawasaki 369D/369E helicopters because some units were mis‑machined, missing two critical ridges. Without the ridges the fork can crack or fail, risking loss of the tail rotor and control.\n\nInspections per the manufacturer’s service bulletin must be done before next flight after 30 June 1999 and every 50 flight hours if affected; a Mandatory Defect Report is required when the fault is found."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The directive applies to the specific defect and listed parts/models disclosed by the manufacturer and requires inspection, reporting and repair per the Service Bulletin. It does not broaden coverage beyond those identified assemblies or add unrelated obligations."},"complexity_factors":["Narrow applicability tied to specific airframe models and part numbers (requires accurate parts tracking and configuration control).","Technical compliance depends on external documents (MD Helicopters Service Bulletin 369D-198 / 369E-092) for the inspection and repair steps.","Time-critical compliance: mandatory initial inspection before further flight after a fixed date and recurring inspections at ≤50 hours TIS, which affects maintenance planning.","Reporting obligation to raise a Mandatory Defect Report (MDR) quoting the directive and to follow para 1E actions introduces administrative burden and potential follow-up inspections/repairs.","Cross-reference to FAA Priority Letter AD 99-13-09 adds inter-jurisdictional coordination and potential interpretation issues for international operators."],"plain_english_summary":"Requires operators of McDonnell Douglas (Hughes) and Kawasaki 369D/E helicopters fitted with specified four‑bladed tail‑rotor fork assemblies (PN 369D21701‑21) to inspect those forks per the MD Helicopters Service Bulletin. Inspections must occur before further flight after 30 June 1999 and, if affected, at intervals not exceeding 50 flight hours; operators must lodge an MDR and follow repair instructions where directed. The measure addresses a manufacturing error that removed critical ridges and shifts inspection, repair and reporting costs and scheduling onto operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-99-four-bladed-tail-rotor-fork","history":"/api/acts/ad-hu-369-99-four-bladed-tail-rotor-fork/history","analysis":"/api/acts/ad-hu-369-99-four-bladed-tail-rotor-fork/analysis","conflicts":"/api/acts/ad-hu-369-99-four-bladed-tail-rotor-fork/conflicts","importantCases":"/api/acts/ad-hu-369-99-four-bladed-tail-rotor-fork/important-cases","documents":"/api/acts/ad-hu-369-99-four-bladed-tail-rotor-fork/documents"}}