{"id":"F2006B04722","name":"AD/BN-2/11 Amdt 1 - Elevator Trim Final Drive Lever - Inspection and Modification","slug":"ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44486,"registerId":"commonwealth-F2006B04722-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BN-2/11 Amdt 1 - Elevator Trim Final Drive Lever - Inspection and Modification","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-2/11\n\nAmdt 1\n\n\nElevator Trim Final Drive Lever - Inspection NK and Modification\n\n \n\nApplicability: All models not incorporating Modification No. NB/M/394. Document:  Britten-Norman SB No. BN-2/SB.24.\n\nCompliance: Inspect within 10 hours time in service after 23 February 1970 and thereafter at intervals not exceeding 25 hours time in service until modified.\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\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a narrow, targeted safety directive focused on a specific mechanical component in a specific aircraft series. It has not expanded beyond its original purpose of addressing a known defect in the elevator trim system."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only one defined term implied ('time in service' — standard aviation term)","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Simple conditional structure: inspect until modified, then stop","Single applicability criterion (all models not incorporating one specific modification)","Clear compliance deadline and recurring interval"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** It requires owners and operators of **Pilatus Britten-Norman BN-2 series aeroplanes** (small twin-engine aircraft commonly used for regional transport and island hopping) to:\n- **Inspect** the **elevator trim final drive lever** (a mechanical part that controls the up-down balance of the aircraft's tail) within 10 hours of flying time after 23 February 1970, and then every 25 hours of flying time after that\n- **Modify** the aircraft by installing **Modification No. NB/M/394** (a factory-approved design change) — once this modification is done, the repeated inspections can stop\n\n**Why it matters:** The elevator trim system helps pilots maintain steady flight without constant pressure on the controls. If the final drive lever fails, the pilot could lose control of the aircraft's pitch (nose-up/nose-down attitude), creating a serious safety risk. This AD ensures a known mechanical defect is found before it causes an accident.\n\n**Who must comply:** Anyone operating a BN-2 aircraft that hasn't already had Modification NB/M/394 installed. The technical reference is Britten-Norman Service Bulletin BN-2/SB.24."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The text contains no indication that the directive’s scope was altered from an original intent. It states a clear applicability (all BN-2 models not incorporating Modification No. NB/M/394) and a fixed compliance regimen (inspect within 10 hours after 23 February 1970 and then at intervals not exceeding 25 hours TIS until modified). There is no language in the document indicating an expansion or narrowing of that scope."},"complexity_factors":["Narrow, specific applicability limited to BN-2 models without Modification No. NB/M/394 (clear scope).","Single, simple compliance prescription with fixed time windows (inspect within 10 hours after specified date; then every ≤25 hours TIS until modified).","References an external technical document (Britten-Norman SB No. BN-2/SB.24) which requires implementers to consult further detail.","Operational complexity limited to scheduling frequent short-interval inspections or performing a one-off modification.","No multiple conditional branches, remedial options, or reporting/record-keeping requirements stated in the text provided."],"plain_english_summary":"What this instrument does mechanically\n\n- Requires Pilatus Britten-Norman BN-2 series aeroplanes that do not already have Modification No. NB/M/394 installed to undergo a prescribed inspection and then be modified. (See: “Applicability: All models not incorporating Modification No. NB/M/394.”)\n- Sets the inspection timing: inspect within 10 hours time in service after 23 February 1970 and then repeat inspections at intervals not exceeding 25 hours time in service until the aircraft has the modification installed. (See: “Compliance: Inspect within 10 hours time in service after 23 February 1970 and thereafter at intervals not exceeding 25 hours time in service until modified.”)\n- Directs maintainers/operators to the manufacturer’s service bulletin for the technical procedure: Britten-Norman SB No. BN-2/SB.24. (See: “Document: Britten-Norman SB No. BN-2/SB.24.”)\n- Is issued under the Civil Aviation Regulations 1998, Part 39 schedule of airworthiness directives. (See heading: “COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES.”)\n\nWho is affected\n\n- Owners and operators of Pilatus Britten-Norman BN-2 series aeroplanes that have not incorporated Modification No. NB/M/394. (Applicability line.)\n- Maintenance organisations and aircraft engineers who must perform the inspections and carry out the modification in accordance with the referenced service bulletin.\n\nWhy it matters (as stated and implied by the instrument)\n\n- The directive targets the elevator trim final drive lever by name (title: “Elevator Trim Final Drive Lever - Inspection NK and Modification”), so its stated purpose is to check and, if necessary, modify that component to address an airworthiness concern. That stated aim is the basis for the mandatory inspection/modification requirement in the compliance paragraph.\n\nPractical effects, incentives and trade-offs\n\n- Who pays: Aircraft owners/operators bear the direct costs of repeated inspections and of installing Modification NB/M/394 (costs are not set out in the text but follow from the mandatory work). (Compliance + Applicability.)\n- Behaviour change: Operators must either (a) carry out inspections every ≤25 hours time in service until the modification is installed, or (b) install Modification NB/M/394 to discontinue the repetitive inspections (the AD stops applying once the modification is incorporated). (Compliance: “until modified”; Applicability.)\n- Compliance burden: The inspection interval (within 10 hours after the specified date, then every ≤25 hours TIS) is frequent and will require scheduling maintenance around short service-hours windows. (Compliance.)\n- Discretion and decision points: The regulator prescribes the obligation and the manufacturer’s service bulletin supplies the technical method. The owner/operator decides when to install the modification (subject to the inspection schedule) and which approved maintenance provider performs the work. (Authority heading; Document reference; Compliance.)\n- Implementation risk and constraints: The AD presumes availability of the parts/engineering data and of maintenance capability described in Britten-Norman SB No. BN-2/SB.24; if those are not readily available, operators may face delays or additional costs. (Document reference.)\n- Opportunity cost and substitution: Installing the modification removes the need for repeated inspections; therefore operators balance the upfront modification cost and downtime against continuing inspection costs and scheduling impacts. (Compliance: “until modified”.)\n\nConcrete citation points\n\n- Applicability: “All models not incorporating Modification No. NB/M/394.”\n- Compliance timing: “Inspect within 10 hours time in service after 23 February 1970 and thereafter at intervals not exceeding 25 hours time in service until modified.”\n- Technical reference: “Document: Britten-Norman SB No. BN-2/SB.24.”\n- Issuing authority context: “COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES.”"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification","history":"/api/acts/ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification/history","analysis":"/api/acts/ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification/analysis","conflicts":"/api/acts/ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification/conflicts","importantCases":"/api/acts/ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification/important-cases","documents":"/api/acts/ad-bn-2-11-amdt-1-elevator-trim-final-drive-lever-inspection-and-modification/documents"}}