{"id":"F2006B04662","name":"AD/BELL 412/27 - Tailboom Upper Longeron","slug":"ad-bell-412-27-tailboom-upper-longeron","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44414,"registerId":"commonwealth-F2006B04662-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 412/27 - Tailboom Upper Longeron","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Bell Helicopter Textron 412 Series Helicopters\n\n \n\nAD/BELL 412/27 Tailboom Upper Longeron 12/90\n\nDM\n\n \n\nApplicability: Model 412 with serial numbers:\n\n \n\n33001 through 33211\n\n \n\n34001 through 34013\n\n \n\n36001 through 36013\n\n \n\nRequirement: 1. Action in accordance with Part 1 of Bell Alert Service Bulletin No 412-90-49.\n\n \n\n2. Action in accordance with Part II of Bell Alert Service Bulletin No 412-90-49. Compliance:              1. Prior to 30 November 1990.\n\n2. At intervals not exceeding 300 hours time in service after incorporation of Requirement 1.\n\n \n\nBackground:  Incidents of cracked longeron splices have created a requirement for additional access to inspect upper longeron splices, and modification action to increase structural integrity.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope matches its stated purpose: to add inspection access and a modification to address cracked upper longeron splices. It applies only to the listed serial numbers and requires the actions set out in Bell Alert Service Bulletin No. 412-90-49, with the initial deadline (30 Nov 1990) and 300-hour recurring interval (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Limited applicability defined by explicit serial number ranges (Applicability).","Mandates actions by reference to an external manufacturer document (Bell Alert Service Bulletin No. 412-90-49) (Requirement).","Two-step regime: initial action with a hard due date and recurring inspections/modification tied to flight hours (Compliance).","Technical work (inspection/access and structural modification) imposes direct cost and downtime on owners/operators (Requirement/Background).","Low administrative discretion: CASA prescribes the bulletin actions and fixed intervals; enforcement is categorical (Requirement/Compliance)."],"plain_english_summary":"Requires operators of specified Bell 412 helicopters (listed serial numbers) to carry out the actions in Bell Alert Service Bulletin No. 412‑90‑49: an initial access/inspection and a follow‑up structural modification. The initial action must be done by 30 November 1990, then inspections recur every 300 flight hours. The directive responds to reports of cracked upper longeron splices. Aircraft owners/operators pay for and arrange the work; the Civil Aviation Safety Authority requires and enforces compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive issued in 1990 for a specific airworthiness issue. It has not expanded beyond its original purpose of addressing cracked tailboom longerons in Bell 412 helicopters."},"complexity_factors":["Single, specific technical requirement referencing an external manufacturer document (Bell Alert Service Bulletin 412-90-49)","Only 2 compliance deadlines: one fixed calendar date and one recurring flight hour interval","Limited applicability — only 3 specific serial number ranges affected","No defined terms section, no cross-references to other legislation, no conditional exceptions","Document is essentially a 1-page safety notice with minimal legal machinery"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998.\n\n**What it does:**\nThis directive requires owners and operators of specific **Bell 412 helicopters** to inspect and modify the **tailboom upper longeron** (a structural beam running along the top of the helicopter's tail section). The longeron had been cracking where sections are joined together (\"splices\"), creating a safety risk.\n\n**Who it affects:**\n- Owners and operators of Bell 412 helicopters with specific serial numbers (roughly 250 aircraft in the listed ranges)\n- Maintenance organisations servicing these helicopters\n\n**What must be done:**\n1. **Immediate action:** Follow Part 1 of Bell's Alert Service Bulletin 412-90-49 before 30 November 1990 — this likely involves creating better access to inspect the longeron splices\n2. **Ongoing inspections:** Follow Part 2 of the same bulletin every 300 flight hours thereafter — this likely involves the actual structural modifications to strengthen the area\n\n**Why it matters:**\nCracks in the tailboom structure can lead to catastrophic failure in flight. This AD mandates proactive fixes to prevent accidents rather than waiting for failures to occur. Non-compliance grounds the aircraft — it cannot legally fly until the work is done."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-27-tailboom-upper-longeron","history":"/api/acts/ad-bell-412-27-tailboom-upper-longeron/history","analysis":"/api/acts/ad-bell-412-27-tailboom-upper-longeron/analysis","conflicts":"/api/acts/ad-bell-412-27-tailboom-upper-longeron/conflicts","importantCases":"/api/acts/ad-bell-412-27-tailboom-upper-longeron/important-cases","documents":"/api/acts/ad-bell-412-27-tailboom-upper-longeron/documents"}}