{"id":"F2006B04595","name":"AD/BELL 212/62 - Tail Rotor Counterweight Bellcrank Retention Nut","slug":"ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44338,"registerId":"commonwealth-F2006B04595-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 212/62 - Tail Rotor Counterweight Bellcrank Retention Nut","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 Helicopter Textron 212 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 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\nAD/BELL 212/62 Tail Rotor Counterweight Bellcrank Retention Nut\n\n  \n9/2001\n\nDM\n\nApplicability: Model 212 helicopters.\n\nRequirement: 1. Remove the two existing retention nuts retaining the bellcranks, part number 212- 010-709-001 or 212-011-705-001, and install retention nuts, part number MS14145L6 or MS17826-6, in accordance with paragraphs (1) through (5) of the Accomplishment Instructions in Bell Helicopter Textron Alert Service Bulletin (ASB) 212-00-107 Revision A, dated 13 September 2000. A used retention nut must not be installed.\n\n2. Inspect the retention nuts and corrosion preventive compound (CPC) coating in accordance with paragraph (6) of the Accomplishment Instructions in ASB 212- 00-107 Revision A. Reapply the CPC coating if deficiencies are found in the coverage and protection of the area. Replace any retention nut found with any corrosion, mechanical damage, a crack, or looseness, with a serviceable nut before further flight.\n\nNote: FAA AD 2001-13-01 Amdt 39-12281 refers.\n\nCompliance: 1. Within 100 hours time in service or 90 days after 1 August 2001, whichever occurs first; unless already accomplished.\n\n2. At intervals not to exceed 100 hours time in service after accomplishing Requirement 1.\n\nThis Airworthiness Directive becomes effective on 1 August 2001.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBackground: The FAA received a report of an in-flight loss of a tail rotor counterweight bellcrank due to failure of the retention nut. Failure of the retention nut could result in the bellcrank migrating off the crosshead spindle, loss of tail rotor control, and subsequent loss of control of the helicopter.\n\n![](image.003.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 25 July 2001\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 1 August 2001.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive remains narrowly focused on correcting a single unsafe condition: preventing retention-nut failure on the tail-rotor counterweight bellcrank of Bell 212 helicopters. It prescribes a specific replacement part, inspection procedure and periodic inspection interval. It does not expand beyond that original technical safety purpose."},"complexity_factors":["Short, single-issue AD focused on one component (tail-rotor counterweight bellcrank retention nut).","Two principal mandatory actions: one-time replacement of specific part numbers and recurring inspections.","Conditional compliance timing (within 100 hours TIS or 90 days, whichever occurs first).","Mandatory reliance on an external document (Bell ASB 212-00-107 Revision A, paragraphs 1–6) for procedural detail.","Prohibition on installing used retention nuts (a clear absolute requirement).","Recurring inspection interval (every 100 hours TIS) introduces ongoing compliance obligation.","Cross-reference to FAA AD (2001-13-01) but no alternative-method text included in this AD.","Some practical ambiguity left to implementers (e.g. definition of \"serviceable\" parts resolved in maintenance practice/ASB)."],"plain_english_summary":"**What this directive does (plain mechanical effect)**\n\n- Applies to: Bell Helicopter Textron Model 212 series helicopters.\n- Mandatory change: Remove the two existing retention nuts that hold each tail-rotor counterweight bellcrank (part numbers 212-010-709-001 or 212-011-705-001) and install new retention nuts of a specified type (part numbers MS14145L6 or MS17826-6). Used retention nuts are not allowed to be installed.\n- Inspection and protection: Inspect the installed retention nuts and the corrosion preventive compound (CPC) coating as specified in the Bell Helicopter Textron Alert Service Bulletin (ASB) 212-00-107 Revision A (paragraph 6). Reapply CPC where coverage is deficient. If a nut shows corrosion, mechanical damage, a crack, or looseness, it must be replaced with a serviceable nut before the helicopter flies again.\n- Timing: Replace the nuts within 100 hours time-in-service (TIS) or 90 days after 1 August 2001, whichever comes first (unless already done). After the replacement, repeat the inspection at intervals not exceeding 100 hours TIS.\n- How it must be done: Follow the Accomplishment Instructions (paragraphs 1–6) in ASB 212-00-107 Revision A for removal, installation, inspection and CPC reapplication.\n\n**Why the regulator says this is required (official rationale)**\n\n- The FAA reported an in-flight loss of a tail rotor counterweight bellcrank caused by failure of the retention nut. If a bellcrank migrates off its spindle, it can lead to loss of tail-rotor control and loss of control of the helicopter. The AD adopts corrective action (replacement and inspection) intended to eliminate that unsafe condition.\n\n**Who is affected and who pays**\n\n- Affected parties: Owners and operators of Bell 212 helicopters, and the maintenance organisations that service them.\n- Who pays: Operators pay for the new nuts, CPC materials, required labour, and any downtime while the aircraft is removed from service for the work.\n\n**Who decides and who must act**\n\n- The Civil Aviation Safety Authority (CASA) delegate issued the AD; aircraft owners/operators and their certificated maintenance personnel must comply. The actual work must be carried out to the ASB instructions by appropriately authorised maintenance personnel.\n\n**Trade-offs, practical considerations and implementation risks**\n\n- Immediate costs: Purchase of specified MS-series nuts (new, not used) and labour to remove/install bearings and apply CPC.\n- Recurring cost and operational impact: A mandated recurring inspection every 100 hours TIS adds ongoing maintenance time and cost, and may increase aircraft downtime.\n- Supply risk: The AD mandates specific replacement part numbers. If those exact MS parts are scarce, operators may need to source equivalents or apply to the regulator for an alternative means of compliance (AMOC), which takes time and regulatory interaction.\n- Compliance clarity and reliance on external document: The AD requires following specific paragraphs in Bell Helicopter ASB 212-00-107 Revision A. Operators must have and correctly follow that ASB; any ambiguity in the ASB could affect implementation. The AD does not itself set out step-by-step instructions beyond referencing the ASB.\n- Safety benefit vs cost: The intervention targets a single mechanical failure mode (retention nut failure) that, if it occurs, can have severe consequences. Costs are concentrated on Model 212 operators; safety benefits accrue primarily to those operators and their passengers/crew.\n\n**Notes and cross-references**\n\n- The AD explicitly refers to the related FAA Airworthiness Directive (FAA AD 2001-13-01) for context. The CASA AD requires the actions and compliance times set out above and becomes effective on 1 August 2001.\n\n(References: AD/BELL 212/62; Bell Helicopter Textron ASB 212-00-107 Revision A, paragraphs 1–6.)"},"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":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope. It addresses a specific safety-critical hardware defect identified by the FAA and applies only to Bell 212 helicopters. The requirements remain tightly focused on the identified unsafe condition (retention nut failure) without expanding to unrelated systems or aircraft types."},"complexity_factors":["Single, specific mechanical component addressed (tail rotor counterweight bellcrank retention nut)","Only 2 substantive requirements with clear, sequential steps","References external technical document (Bell Helicopter Service Bulletin) but provides specific paragraph citations","Minimal defined terms (only standard aviation terminology like 'time in service')","Simple compliance structure: one-time action plus recurring inspection interval","No nested exceptions or conditional logic beyond standard 'unless already accomplished' clause","Short document (approximately 300 words of substantive text)"],"plain_english_summary":"This CASA safety order for Bell 212 helicopters mandates replacing two nuts that secure the tail-rotor bellcrank with approved parts (MS14145L6 or MS17826-6), banning reuse of the originals, and requiring inspections every 100 flight hours (reapplying protective coating if worn).  \n\nEffective 1 August 2001, operators had 90 days or 100 flight hours to comply. The measure prevents nut failure that can lead to loss of tail-rotor control and catastrophic loss of the aircraft."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut","history":"/api/acts/ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut/history","analysis":"/api/acts/ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut/analysis","conflicts":"/api/acts/ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut/conflicts","importantCases":"/api/acts/ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut/important-cases","documents":"/api/acts/ad-bell-212-62-tail-rotor-counterweight-bellcrank-retention-nut/documents"}}