{"id":"F2006B02598","name":"AD/B-2/26 - Main Rotor Mast Upper Bearing - Replacement","slug":"ad-b-2-26-main-rotor-mast-upper-bearing-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41875,"registerId":"commonwealth-F2006B02598-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B-2/26 - Main Rotor Mast Upper Bearing - Replacement","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)  Brantly B-2 Series Helicopters\n\n \n\nAD/B-2/26 Main Rotor Mast Upper Bearing - Replacement 7/67\n\nApplicability: All model B-2, B-2A and B-2B with P/N B2-324 transmission with S/Nos. prior to 307.\n\n \n\nDocument: Brantly SB No. 21.\n\n \n\nCompliance: Within 100 hours time in service after 15 August 1967.\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\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive from 1967 addressing a specific mechanical defect in a narrow class of helicopters. It has not expanded beyond its original purpose of mandating a particular safety-critical replacement."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 3 defined applicability criteria (model, part number, serial number range)","Single compliance requirement with clear deadline","No cross-references to other legislation or regulations beyond citation of parent Civil Aviation Regulations 1998","No conditional logic, exceptions, or nested provisions","Straightforward command structure: applicability → document reference → compliance deadline"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order — issued by Australia's Civil Aviation Safety Authority (CASA) for certain Brantly helicopters.\n\n**What it does:**\nOrders owners and operators of specific Brantly B-2 series helicopters to **replace the main rotor mast upper bearing** — a critical component that supports the main rotor system.\n\n**Who it affects:**\n- All **B-2, B-2A, and B-2B** model helicopters\n- That have a **P/N B2-324 transmission** (a specific part number)\n- With **serial numbers before 307**\n\n**Why it matters:**\nThe main rotor mast bearing is essential for safe flight. If it fails, the rotor system could malfunction with catastrophic consequences. This directive was issued after the manufacturer (Brantly) identified a safety problem through **Service Bulletin No. 21** — a technical notice alerting operators to defects or required maintenance.\n\n**What operators must do:**\nReplace the bearing **within 100 hours of flight time** after 15 August 1967. This is a hard deadline — no extensions, no exceptions for this specific directive.\n\n**Key point:** This is not optional maintenance advice. It's a **legally enforceable safety requirement**. Non-compliance can ground an aircraft and expose operators to penalties."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The provided directive sets a specific and limited scope (models B‑2, B‑2A, B‑2B with P/N B2‑324 transmissions S/N prior to 307) and a single compliance requirement. There is no indication in the text supplied that the scope was changed from any earlier or different intent."},"complexity_factors":["Narrow applicability defined by model, transmission part number and transmission serial number (Applicability)","Single, clear mandated action with a fixed compliance time (Compliance)","Dependence on an external technical document (Brantly SB No. 21) for the procedural details (Document)","Requirement to identify affected airframes by serial number, which can create administrative work for operators (Applicability)","No alternative compliance routes or exemptions stated in the provided text, making the directive straightforward but binary (Compliance)"],"plain_english_summary":"This AD mandates replacement of the main rotor mast upper bearing on Brantly B‑2, B‑2A and B‑2B helicopters with transmission P/N B2‑324 and S/Ns before 307, following Brantly Service Bulletin No. 21.  \n\nAffected owners/operators must obtain parts and complete the replacement within 100 hours time‑in‑service after 15 August 1967, bearing all cost and scheduling responsibility."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b-2-26-main-rotor-mast-upper-bearing-replacement","history":"/api/acts/ad-b-2-26-main-rotor-mast-upper-bearing-replacement/history","analysis":"/api/acts/ad-b-2-26-main-rotor-mast-upper-bearing-replacement/analysis","conflicts":"/api/acts/ad-b-2-26-main-rotor-mast-upper-bearing-replacement/conflicts","importantCases":"/api/acts/ad-b-2-26-main-rotor-mast-upper-bearing-replacement/important-cases","documents":"/api/acts/ad-b-2-26-main-rotor-mast-upper-bearing-replacement/documents"}}