{"id":"F2006B07533","name":"AD/UH-1/5 Amdt 2 - Tailboom Vertical Fin Spar","slug":"ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50085,"registerId":"commonwealth-F2006B07533-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/UH-1/5 Amdt 2 - Tailboom Vertical Fin Spar","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)  \n![](image.002.png)  \nBell UH-1 Series Helicopters\n\nAIRWORTHINESS 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 revokes Airworthiness Directive (AD) AD/UH-1/5 Amdt 1 and issues the following 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 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\nAD/UH-1/5\n\nAmdt 2\n\n  \n\nTailboom Vertical Fin Spar 1/2001 TX\n\nApplicability: All UH1 Series, and UH1 derivatives with the USA FAA Type Certificate Data sheets (TCDS) listed in the Requirement document.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 99-25-12 Amdt 39-11455.\n\nNote: Replacement of the vertical fin spar in accordance with the Requirement document constitutes terminating action for the requirements of this Directive.\n\nCompliance: As specified in the Requirement document with a revised effective date of 20 November 2000.\n\nThis Amendment becomes effective on 20 November 2000.\n\nBackground: Following accident investigations, the FAA determined that a large number of high power events can cause fatigue cracking which will result in failure of the vertical fin spar, which in turn will result in loss of control of the helicopter.\n\nAmendment 1 was raised following an administrative error, and superseded AD/UH1/3 which was cancelled.\n\nAmendment 2 is issued in response to a superseding FAA AD which requires the same modification and inspections as the previous AD, and additionally, a further two inspections and replacement of the vertical fin spar. This further FAA action was prompted by reports of six accidents, two of which involved fatalities, and involved fatigue cracks in the vertical fin spar that have occurred since the issue of AD\n\n97-20-09.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![Signature of David Alan Villiers Delegate of the Civil Aviation Safety Authority](image.003.png)  \nAmendment 1 of this Directive became effective on 24 February 2000. The initial issue of this Directive became effective on 31 December 1999.\n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 17 November 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 20 November 2000.","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"},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Amendment 2 expands the previous directive by adopting the superseding FAA AD (99-25-12), which retains earlier modification/inspection requirements and adds two further inspections plus mandatory replacement of the vertical fin spar. The AD therefore increases operator obligations compared with the earlier amendment (Requirement; Background)."},"complexity_factors":["Cross-reference to an external FAA directive (FAA AD 99-25-12) for technical requirements rather than reproducing technical detail (Requirement).","Interplay of multiple amendments and revocation (revokes AD/UH-1/5 Amdt 1; Amendment 1 arose from an administrative error).","Safety‑critical engineering work (inspections, two additional inspections, and component replacement) requiring certified maintenance organisations and parts.","Applicability tied to FAA Type Certificate Data Sheets for certain derivatives, requiring operators to check model coverage (Applicability / Requirement).","Compliance timing and an explicit revised effective date (Compliance: revised effective date 20 November 2000).","Termination mechanic: replacement constitutes terminating action for the Directive (Requirement note).","Background links legal action to accident investigations and multiple crashes, which raises immediacy and enforcement implications (Background)."],"plain_english_summary":"This Airworthiness Directive (AD/UH-1/5 Amdt 2) requires operators of Bell UH‑1 series helicopters (and listed derivatives) to perform inspections and replace the tailboom vertical fin spar as specified by FAA AD 99‑25‑12. It revokes the prior amendment and takes effect from 20 November 2000.\n\nCASA says the actions address fatigue cracking from high‑power events that can cause fin‑spar failure and loss of control; compliance and replacement are mandatory, and replacement is terminating action."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"The legislation maintains its original narrow scope — addressing a specific structural fatigue issue in Bell UH-1 helicopter tail fins. Amendment 2 expands the technical requirements slightly (adding two more inspections and explicit replacement provisions compared to Amendment 1), but this is responsive to new accident data rather than scope creep. The directive remains tightly focused on the original safety problem."},"complexity_factors":["Short, single-purpose directive (approximately 400 words)","Only 1 defined term implicitly referenced (FAA AD 99-25-12, which contains the actual technical requirements)","Simple structure: Applicability → Requirement → Compliance → Background","No nested exceptions or conditional logic — compliance is mandatory with clear terminating action","Heavy reliance on external document (FAA AD 99-25-12) for actual technical content, reducing on-page complexity but creating dependency on US regulations","Clear effective dates and straightforward administrative history (explaining why Amendment 2 replaces Amendment 1)"],"plain_english_summary":"This Airworthiness Directive replaces the prior amendment and mandates that owners and operators of Bell UH-1 helicopters comply with FAA AD 99-25-12 to inspect and, if necessary, replace the vertical fin spar.  \n\nFatigue cracks in that tail spar have caused six accidents (two fatal); spar failure can lead to loss of control. Compliance is mandatory and effective 20 November 2000."}},"importantCases":[],"_links":{"self":"/api/acts/ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar","history":"/api/acts/ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar/history","analysis":"/api/acts/ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar/analysis","conflicts":"/api/acts/ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar/conflicts","importantCases":"/api/acts/ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar/important-cases","documents":"/api/acts/ad-uh-1-5-amdt-2-tailboom-vertical-fin-spar/documents"}}