{"id":"F2006B07528","name":"AD/UH-1/16 - Main Rotor Mast P/N 204-011-450-001 & -005","slug":"ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50075,"registerId":"commonwealth-F2006B07528-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.","sortOrder":0},{"sectionNumber":"AD/UH-1/16 Main Rotor Mast P/N 204-011-4","sectionType":"part","heading":"AD/UH-1/16 Main Rotor Mast P/N 204-011-450-001 & -005 10/2000","content":"# AD/UH-1/16 Main Rotor Mast P/N 204-011-450-001 & \\-005 10/2000\n\nDM\n\nApplicability: Models UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, and HH-1K, TH-\n\n1F, TH-1L, and Southwest Florida Aviation SW204, SW204HP, SW205, and SW205A-1 helicopters with a main rotor mast assembly part number 204-011-450- 001 or -005 installed.\n\nRequirement: Remove the main rotor mast assembly from service. Replace with a serviceable mast assembly that is neither a 204-011-450-001 nor a -005.\n\nNote: FAA AD 2000-15-21 refers.\n\nCompliance: Within 25 hours time in service after 30 August 2000.\n\nThis Airworthiness Directive becomes effective on 30 August 2000.\n\nBackground: The FAA received a report of a BHTI-manufactured Model UH-1B accident that was attributed to fatigue failure of a thin-walled mast installed on the helicopter.\n\n![Signature of Steve Swift Delegate of the Civil Aviation Safety Authority](image.003.png)  \n\nSteve Swift\n\nDelegate of the Civil Aviation Safety Authority 24 August 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 30 August 2000.","sortOrder":1}],"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD maintains a narrowly targeted scope consistent with its stated purpose: mandatory removal and replacement of two specified mast part numbers from listed helicopter models due to a reported fatigue failure. It does not expand applicability beyond the named models/part numbers or add broader inspection or monitoring obligations; it references the FAA AD but does not alter the original target population or required corrective action."},"complexity_factors":["Narrow technical scope: applies only to specific helicopter models and two exact part numbers (Applicability).","Single mandatory action: remove and replace the mast with a non‑listed serviceable part (Requirement) — no alternative compliance routes provided.","Short compliance window: 25 hours time in service after 30 August 2000 creates logistical pressure (Compliance).","Safety justification is event‑based: based on an FAA‑reported fatigue failure of a thin‑walled mast (Background), not a broad fleet inspection regime.","Low regulatory discretion: delegate issues AD under CAR 1998 subregulation 39.1(1), setting mandatory instructions rather than guidance.","Operational and cost burden concentrated on operators: must source and install replacement masts, potentially grounding aircraft temporarily (Requirement/Compliance).","Reference to external instrument (FAA AD 2000‑15‑21) without expanding scope introduces cross‑jurisdictional linkage but not additional complex procedures (Note)."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of the listed UH‑1, TH‑1 and certain Southwest Florida Aviation helicopters to remove main rotor mast assemblies P/N 204‑011‑450‑001 and P/N 204‑011‑450‑005 and install a serviceable mast that is not one of those two parts. The replacement must be done within 25 hours time in service after 30 August 2000. CASA cites an FAA report of a fatigue failure of a thin‑walled mast as the safety reason. Operators pay for grounding, parts and replacement and must decide how to source compliant masts."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete safety directive addressing a specific airworthiness issue. It has not expanded beyond its original purpose of addressing the fatigue failure risk in these specific part numbers."},"complexity_factors":["Single, unambiguous operative requirement (remove and replace)","Only 2 defined part numbers in applicability","Clear compliance deadline (25 hours TIS after effective date)","No nested exceptions or conditional logic","No cross-references to other legislation (only a note referencing related FAA AD)","Short document (approximately 250 words of substantive text)","Straightforward cause-and-effect: unsafe condition → mandatory action"],"plain_english_summary":"CASA has issued a safety order grounding specific Bell UH-1 main rotor masts (part nos. 204-011-450-001 and 204-011-450-005), banning their use and requiring immediate replacement with approved parts within 25 flight hours after 30 August 2000. \n\nIt affects owners, operators and maintenance organisations of UH-1 variants (civil and military, including certain modified versions). The measure prevents catastrophic rotor separation from thin-walled mast fatigue and mirrors FAA AD 2000-15-21."}},"importantCases":[],"_links":{"self":"/api/acts/ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005","history":"/api/acts/ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005/history","analysis":"/api/acts/ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005/analysis","conflicts":"/api/acts/ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005/conflicts","importantCases":"/api/acts/ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005/important-cases","documents":"/api/acts/ad-uh-1-16-main-rotor-mast-p-n-204-011-450-001-005/documents"}}