{"id":"F2006B07530","name":"AD/UH-1/18 - Main Rotor Tension-Torsion Strap","slug":"ad-uh-1-18-main-rotor-tension-torsion-strap","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50079,"registerId":"commonwealth-F2006B07530-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.001.png)\n\n![](image.001.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.\n\nBell UH-1 Series Helicopters","sortOrder":0},{"sectionNumber":"AD/UH-1/18 Main Rotor Tension-Torsion St","sectionType":"part","heading":"AD/UH-1/18 Main Rotor Tension-Torsion Strap 13/2002","content":"# AD/UH-1/18 Main Rotor Tension-Torsion Strap 13/2002\n\nDM\n\nApplicability: Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L,\n\nand UH-1P; and Southwest Florida Aviation Model SW204, SW204HP, SW205 and SW205A-1 helicopters, manufactured by Bell Helicopter Textron Inc. (BHTI) for the armed forces of the United States, with main rotor tension-torsion (TT) strap, part number 204-012-122-1, 204-012-122-5, 2601399, or 2606650, installed.\n\nRequirement: Remove and replace any TT strap with 1,200 hours total time in service or 24 months since the initial installation, whichever occurs first.\n\nNote: FAA AD 2002-20-01 Amdt 39-12895 refers.\n\nCompliance: Before further flight after 30 October 2002.\n\nThis Airworthiness Directive becomes effective on 30 October 2002.\n\nBackground: This Directive is prompted by the FAA requirement to update the product identification, extend the application to other models, continuing the existing retirement time for certain main rotor TT straps, and adding TT strap part numbers to the applicability. The actions required by this Directive are intended to prevent failure of a TT strap, loss of a main rotor blade, and subsequent loss of control of the helicopter.\n\n![Signature of David Alan Villiers Delegate of the Civil Aviation Safety Authority](image.002.jpeg)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 24 October 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 30 October 2002.","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"According to the AD’s Background, the directive updates product identification, extends the applicability to additional helicopter models, and adds TT strap part numbers while continuing the existing retirement time for those straps. In other words, the scope was widened to cover more aircraft and specific part numbers compared with the prior material the AD references (Background)."},"complexity_factors":["Clear, single prescriptive action: remove and replace TT straps at 1,200 hours or 24 months (Requirement).","Immediate compliance deadline: no further flight after 30 October 2002 unless complied with (Compliance).","Multiple affected helicopter models and multiple TT strap part numbers increase administrative tracking (Applicability).","Requirement depends on reliable records of initial installation date and time-in-service, which can complicate verification for older aircraft (Requirement).","Reference to an external FAA AD for related identification and context introduces a cross-jurisdictional reference point (Note).","Regulatory basis delegated to a CASA delegate under subregulation 39.1(1) establishes mandatory effect but provides little procedural detail in the AD text (first paragraph)."],"plain_english_summary":"This AD, issued by a CASA delegate and referencing FAA AD 2002-20-01, requires operators of the listed Bell and Southwest Florida Aviation helicopters to remove and replace specified main-rotor tension‑torsion (TT) straps at 1,200 hours TIS or 24 months after installation, whichever is earlier. It aims to prevent TT strap failure and loss of control. Operators bear replacement costs, must track strap hours/installation dates, and may not fly affected aircraft after 30 October 2002 unless compliant."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope as a targeted safety intervention for a specific fatigue-critical component. The background notes this updates product identification and extends to additional models, but this represents normal evolutionary maintenance of an existing safety regime rather than scope creep. The core purpose—preventing TT strap failure through mandatory retirement—remains unchanged from the original regulatory intent."},"complexity_factors":["Single, unambiguous requirement with clear numerical thresholds (1,200 hours or 24 months)","Limited applicability: only 9 specific helicopter models and 4 specific part numbers","No nested exceptions or conditional logic—compliance is absolute and time-bound","No cross-references to other legislation (only a non-binding note referencing the related FAA directive)","Short document (under 300 words of substantive text)","Only one defined term used (TT strap, immediately explained as 'tension-torsion')","Binary compliance trigger: whichever occurs first of two objective metrics"],"plain_english_summary":"This is a **safety order for specific military helicopters** that have been converted for civilian use in Australia.\n\n**What it does:**\nOrders owners and operators of certain Bell UH-1 \"Huey\" helicopters (and similar models) to **replace a critical rotor component** called the \"tension-torsion strap\" (or TT strap). This part helps hold the main rotor blades in place.\n\n**Who it affects:**\n- Owners and operators of specific Bell helicopter models (UH-1A, UH-1B, UH-1H, etc.) and Southwest Florida Aviation variants\n- Only applies to helicopters originally built for the US armed forces that now have specific part numbers installed (204-012-122-1, 204-012-122-5, 2601399, or 2606650)\n\n**What must be done:**\n- **Remove and replace** any affected TT strap that has either:\n  - **1,200 flight hours** of use, OR\n  - **24 months** since it was first installed\n- Whichever comes **first** triggers the replacement\n\n**When:**\n- Must be done **before the helicopter flies again after 30 October 2002**\n\n**Why it matters:**\nThe TT strap can fail from fatigue (wear and tear). If it breaks, a main rotor blade can detach, causing **total loss of control** and likely a fatal crash. This directive prevents that by forcing replacement before the part reaches a dangerous age."}},"importantCases":[],"_links":{"self":"/api/acts/ad-uh-1-18-main-rotor-tension-torsion-strap","history":"/api/acts/ad-uh-1-18-main-rotor-tension-torsion-strap/history","analysis":"/api/acts/ad-uh-1-18-main-rotor-tension-torsion-strap/analysis","conflicts":"/api/acts/ad-uh-1-18-main-rotor-tension-torsion-strap/conflicts","importantCases":"/api/acts/ad-uh-1-18-main-rotor-tension-torsion-strap/important-cases","documents":"/api/acts/ad-uh-1-18-main-rotor-tension-torsion-strap/documents"}}