{"id":"F2006B04647","name":"AD/BELL 412/12 Amdt 5 - Vertical Fin Forward Spar","slug":"ad-bell-412-12-amdt-5-vertical-fin-forward-spar","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44399,"registerId":"commonwealth-F2006B04647-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 412/12 Amdt 5 - Vertical Fin Forward Spar","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\n# AD/BELL412/12\n\nAmdt 5\n\nApplicability: All models.\n\n\n# Vertical Fin Forward Spar 6/93 DM\n\n \n\nRequirement:  1. For helicopters fitted with fin spar cap P/N 212-030-447-001: Inspect the spar cap for cracks, corrosion and doubler debonding in accordance with Bell ASB 412-92- 65.\n\n \n\nNote: FAA AD 93-02-07 refers.\n\n \n\nNote: All fin spar caps P/N 212-030-447-001 should have been modified with a cold bonded doubler in accordance with Bell ASB 412-85-20 not later than 31 March 1986. Amendment 2 to this AD referred.\n\n \n\n2.    For helicopters fitted with fin spar cap P/N 212-030-447-101:\n\n \n\n1. If cap thickness is greater than or equal to 0.190 inches when measured as shown in Bell ASB 412-86-24, no further action is required by this AD;\n\n\n \n\nb.    If cap thickness is less than 0.190 inches and the cap has been modified with a cold bonded doubler in accordance with Bell ASB 412-86-24, inspect for cracks, corrosion and doubler debonding using the inspection technique described in Part I of Bell ASB 412-92-65. Inspect at intervals not exceeding 100 hours time in service or 25 flight operation days, whichever occurs earlier, until replaced by a new cap P/N 212-030-447-101 in accordance with Bell ASB 412-92-65;\n\n \n\nc.    If cap thickness is less than 0.190 inches, but not less than 0.155 inches, and the cap has not been modified with a cold bonded doubler in accordance with Bell ASB 412-86-24, inspect for cracks in accordance with the inspection technique described in Part I of Bell ASB 412-85-20 Revision B. Inspect at intervals not exceeding 20 hours time in service or 5 flight operation days, whichever occurs earlier, until replaced with a new cap P/N 212-030-447-101 in accordance with Bell ASB 412-92-65.\n\n \n\nNote: All fin spar caps P/N 212-030-447-101 that were less than 0.155 inches thick should have been modified with a cold bonded doubler in accordance with Bell ASB 412-86-24 not later than 31 December 1986. AD/BELL 412/16 (incorporated into this AD at Amendment 3) referred.\n\n \n\nCompliance: Inspect within 25 hours time in service from 26 March 1993.\n\n \n\nRe-inspect at intervals not to exceed 25 hours time in service, until replaced with a new cap P/N 212-030-447-101 in accordance with Bell ASB 412-92-65.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\nBackground:  P/N 212-030-447-001 fin spar caps with a cold bonded doubler fitted in accordance with Bell ASB 412-85-20, and undersized P/N 212-030-447-101 fin spar caps with a cold bonded doubler fitted in accordance with Bell ASB 412-86-24, require inspections because of reports of cracks originating from corrosion under the doublers.\n\n \n\nP/N 212-030-447-101 fin spar caps with thicknesses between 0.155 inches and 0.190 inches, and which have not had a cold bonded doubler fitted, require inspection because the fatigue strength of this size cap has not been demonstrated.\n\n \n\nThe format of this AD has changed to improve clarity; the only technical change is a reduction of the inspection interval for modified -001 spar caps from 100 hours to 25 hours, introduced by Bell Alert Service Bulletin 412-92-65.\n","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":6,"scope_assessment":{"changed":true,"description":"Originally issued in March 1993 (6/93), this directive has expanded through five amendments. The current version incorporates at least one entire previous directive (AD/BELL 412/16 at Amendment 3) and has tightened inspection intervals (reduced from 100 hours to 25 hours for modified -001 spar caps). The format was also revised 'to improve clarity,' suggesting the original structure became unwieldy as conditions accumulated. What began as a straightforward inspection requirement has evolved into a complex decision tree accounting for multiple part variants, modification histories, and measurement thresholds."},"complexity_factors":["Multiple conditional branches based on part numbers, thickness measurements, and modification history","Cross-references to four separate Bell Alert Service Bulletins (ASB 412-92-65, ASB 412-85-20, ASB 412-86-24, and Revision B of ASB 412-85-20)","Nested measurement thresholds (≥0.190 inches, <0.190 inches, ≥0.155 inches, <0.155 inches) creating four distinct compliance paths","Dual interval systems (hours time in service vs flight operation days) with 'whichever occurs earlier' logic","Historical compliance deadlines referenced but not fully explained (31 March 1986, 31 December 1986)","Incorporation of previous directives (AD/BELL 412/16) by reference without reproducing their text","Amendment history (Amendment 5) implies layered changes over time, with only the most recent technical change explicitly noted"],"plain_english_summary":"This rule requires Bell 412 operators and maintenance organisations to perform recurring inspections of the vertical fin forward spar cap for cracks, corrosion, and bonding failures, and to replace defective or undersized parts on a mandated timetable. Different inspection and replacement requirements apply depending on installed part variants and whether cold-bonded repair doublers or other modifications are present.\n\nIt addresses hidden cracking under bonded doublers that could cause structural failure, protecting flight safety."},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"The AD notes a format change for clarity and states the only technical change is a reduction of the inspection interval for modified P/N 212-030-447-001 fin spar caps from 100 hours to 25 hours (Background). Other inspection and replacement requirements remain as previously set and continue to reference Bell ASBs."},"complexity_factors":["Multiple part numbers targeted (P/N 212-030-447-001 and P/N 212-030-447-101) with different treatments","Thickness-based branching rules (<0.155, 0.155–0.190, ≥0.190 inches) that change required action","Different inspection intervals depending on part, thickness and whether a cold-bonded doubler is fitted (25 hours, 20 hours, previously 100 hours)","References to multiple external technical documents (Bell ASB 412-85-20, 412-86-24, 412-92-65, 412-85-20 Revision B and FAA AD 93-02-07) creating dependency on service bulletin content","Historic mandatory modification deadlines and prior amendments reflected in notes (deadlines in 1986) increasing compliance-check complexity","Requirement to replace with a new cap per Bell ASB 412-92-65 once identified, adding procurement/repair steps","Technical inspection tasks (detecting corrosion under doublers, debonding and fatigue cracks) that may require specialised inspection techniques","Applicability stated as 'All models' but practically affects only helicopters fitted with the specified P/Ns, creating identification burden for operators","Amendments and a format change in the AD that alter intervals without changing other substantive requirements"],"plain_english_summary":"This Airworthiness Directive requires operators of Bell 412 helicopters to inspect and, where prescribed, replace the vertical fin forward spar cap parts (specific P/Ns) and to inspect for cracks, corrosion and doubler debonding following Bell service bulletins. Inspections must begin within 25 hours time in service and recur at specified short intervals until replacement is done.\n\nCASA cites reports of cracks under cold-bonded doublers and reduced the inspection interval for modified P/N 212-030-447-001 from 100 to 25 hours; operators bear inspection and replacement costs and must follow Bell ASBs referenced."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-12-amdt-5-vertical-fin-forward-spar","history":"/api/acts/ad-bell-412-12-amdt-5-vertical-fin-forward-spar/history","analysis":"/api/acts/ad-bell-412-12-amdt-5-vertical-fin-forward-spar/analysis","conflicts":"/api/acts/ad-bell-412-12-amdt-5-vertical-fin-forward-spar/conflicts","importantCases":"/api/acts/ad-bell-412-12-amdt-5-vertical-fin-forward-spar/important-cases","documents":"/api/acts/ad-bell-412-12-amdt-5-vertical-fin-forward-spar/documents"}}