{"id":"F2006B04753","name":"AD/BN-2/42 Amdt 3 - Elevator Trim Tab Cracking","slug":"ad-bn-2-42-amdt-3-elevator-trim-tab-cracking","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44517,"registerId":"commonwealth-F2006B04753-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/42 Amdt 3 - Elevator Trim Tab Cracking","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)  Pilatus Britten-Norman BN-2 Series Aeroplanes\n\n \n\nAD/BN-2/42\n\nAmdt 3\n\n\nElevator Trim Tab Cracking 4/86\n\n \n\nApplicability: All models listed in the Requirement Document.\n\n \n\nRequirement: Action in accordance with Pilatus Britten-Norman BN-2/S.B 142 Issue 4. Compliance:               1. Modify prior to the issue of a Certificate of Airworthiness.\n\n2. Inspect in accordance with the Requirement Document.\n\n \n\nBackground: Issue 4 of the Requirement Document has extended the post mod. inspection out to every 100 hours T.I.S.\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\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":true,"description":"The directive adopts Pilatus Britten‑Norman BN‑2/S.B 142 Issue 4 and the Background notes that Issue 4 \"has extended the post mod. inspection out to every 100 hours T.I.S.\" This is a change in inspection frequency from the prior Requirement Document issue, so the ongoing inspection scope/frequency has been altered (Background)."},"complexity_factors":["Mandates compliance with an external technical document (Pilatus Britten‑Norman BN‑2/S.B 142 Issue 4) rather than containing full technical instructions (Requirement).","Requires a modification before issuing a Certificate of Airworthiness, which creates a clear enforcement hook but requires coordination between operators, maintenance organisations, and the regulator (Compliance: 1).","Specifies ongoing inspections tied to the Requirement Document rather than fixed inspection language in the AD, meaning operators must interpret and apply that document for frequency, method and acceptance criteria (Compliance: 2).","Changes to inspection interval in Issue 4 (extended to every 100 hours T.I.S.) alter ongoing maintenance planning and costs relative to prior issues (Background).","Applicability refers to models listed in the Requirement Document, so affected fleet scope depends on that separate listing rather than being fully self-contained in the AD (Applicability)."],"plain_english_summary":"What this directive does\n\n- Requires owners/operators of Pilatus Britten‑Norman BN‑2 series aeroplanes listed in the Requirement Document to follow a specific modification and inspection regime for the elevator trim tab (\"Applicability\").\n- Directs compliance with the manufacturer/service document Pilatus Britten‑Norman BN‑2/S.B 142 Issue 4 (\"Requirement\").\n- Makes two concrete compliance steps mandatory: (1) the modification must be carried out before a Certificate of Airworthiness is issued for the affected aircraft, and (2) inspections must be carried out in the manner set out in the Requirement Document (\"Compliance: 1\" and \"Compliance: 2\").\n\nWho this affects and who pays\n\n- Affected parties: owners and operators of the BN‑2 models listed in the Requirement Document (Applicability). These parties must arrange and pay for the modification and the continuing inspections (Compliance: 1; Compliance: 2).\n- The regulator enforces the rule by conditioning certification on completion of the required modification (Compliance: 1).\n\nHow it works mechanically\n\n- The AD points operators to Pilatus Britten‑Norman BN‑2/S.B 142 Issue 4 as the technical specification to follow for both the modification and the inspections (Requirement).\n- The modification is a precondition for issuing a Certificate of Airworthiness for the affected aeroplane (Compliance: 1).\n- After modification, inspections must be performed according to the Requirement Document; Issue 4 of that document extends the post‑modification inspection interval to every 100 hours time in service (T.I.S.) (Compliance: 2; Background).\n\nWhy it matters (tracked mechanics, incentives, and trade‑offs)\n\n- Upfront cost vs ongoing cost: The AD creates an immediate compliance cost because the required modification must be completed before certification (Compliance: 1). The Background notes the Issue 4 change increases the interval to every 100 hours T.I.S., which lowers the frequency of post‑mod inspections compared with the prior interval; that can reduce ongoing inspection costs but only after the upfront modification cost is incurred (Background).\n- Operational scheduling and cashflow: Operators must schedule the modification into any certification process and thereafter incorporate 100‑hour T.I.S. inspections into maintenance planning (Compliance: 1; Compliance: 2; Background).\n- Reliance on an external technical document: The AD delegates the technical detail to Pilatus Britten‑Norman BN‑2/S.B 142 Issue 4. Operators must obtain and apply that document correctly; compliance depends on following its procedures (Requirement).\n- Enforcement lever: Conditioning the Certificate of Airworthiness on completion of the modification gives the regulator a clear compliance mechanism (Compliance: 1).\n\nPractical implementation risks and administrative burdens\n\n- Access and interpretation: Operators must obtain the specific Issue 4 Service Bulletin/Requirement Document and apply its instructions; errors or misunderstandings of that external document create implementation risk (Requirement).\n- Scheduling: The need to perform the modification before certification may delay entry-to-service and impose opportunity costs in aircraft utilisation (Compliance: 1).\n- Recordkeeping and proof of compliance: The AD requires inspections “in accordance with the Requirement Document” (Compliance: 2). While this AD does not list recordkeeping steps, demonstrating compliance to the regulator will typically require maintenance records tied to the Requirement Document procedures.\n\nNet behavioural effect\n\n- Owners/operators will incur an upfront modification cost prior to certification and will perform periodic inspections at the interval specified in Issue 4 (every 100 hours T.I.S.) thereafter (Compliance: 1; Compliance: 2; Background). The directive shifts a discrete technical obligation (modify and inspect per Issue 4) onto aircraft operators and maintenance organisations, enforced via the certification process."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a routine amendment to an existing Airworthiness Directive. The background note indicates the only change is extending the inspection interval from a more frequent schedule to every 100 hours T.I.S. This is a technical adjustment within the original safety purpose (addressing trim tab cracking), not an expansion of scope."},"complexity_factors":["Extremely short document (under 200 words)","Only 2 defined compliance actions (modification and inspection)","Single cross-reference to external technical document (Service Bulletin 142 Issue 4)","No nested conditional logic or exceptions","Straightforward applicability (all models in one aircraft series)","Minimal regulatory language — mostly procedural instructions"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on certain aircraft.\n\n**What it does:**\n- Requires owners and operators of **Pilatus Britten-Norman BN-2 series aeroplanes** (small twin-engine utility aircraft commonly used for regional transport and island hopping) to address a safety issue with **elevator trim tab cracking**.\n- An elevator trim tab is a small movable surface on the tail of the aircraft that helps the pilot maintain steady flight without constantly holding the control column. Cracking in this component could lead to loss of control.\n\n**Who must act:**\n- Anyone who owns, operates, or maintains a BN-2 aircraft.\n\n**What must be done:**\n1. **Modification:** Install a specific fix (detailed in Pilatus Britten-Norman Service Bulletin 142, Issue 4) before the aircraft can be issued a Certificate of Airworthiness (the official document allowing it to fly).\n2. **Ongoing inspections:** After the modification, inspect the trim tab every **100 hours Time In Service (T.I.S.)** — meaning every 100 hours the aircraft actually spends flying, not just sitting on the ground.\n\n**Why it matters:**\nThis directive prevents potentially catastrophic structural failure. The \"Amdt 3\" (Amendment 3) and \"Issue 4\" of the service bulletin show this safety requirement has been updated over time — in this case, extending the inspection interval from a more frequent schedule to every 100 hours, likely because data showed the modification was holding up well."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bn-2-42-amdt-3-elevator-trim-tab-cracking","history":"/api/acts/ad-bn-2-42-amdt-3-elevator-trim-tab-cracking/history","analysis":"/api/acts/ad-bn-2-42-amdt-3-elevator-trim-tab-cracking/analysis","conflicts":"/api/acts/ad-bn-2-42-amdt-3-elevator-trim-tab-cracking/conflicts","importantCases":"/api/acts/ad-bn-2-42-amdt-3-elevator-trim-tab-cracking/important-cases","documents":"/api/acts/ad-bn-2-42-amdt-3-elevator-trim-tab-cracking/documents"}}