{"id":"F2006B02092","name":"AD/AC/34 - Main Landing Gear Upper Bearing - Modification","slug":"ad-ac-34-main-landing-gear-upper-bearing-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41322,"registerId":"commonwealth-F2006B02092-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AC/34 - Main Landing Gear Upper Bearing - Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-description: CASA Airworthiness Directive\nmeta-generator: Aspose.Words for .NET 22.10.0\nmeta-keywords: Issue 12/1967,Aircraft below 5700 kg,Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes,Main Landing Gear Upper Bearing - Modification,34\ntitle: Airworthiness Directive - AD/AC/34 - Main Landing Gear Upper Bearing - Modification\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)  Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes\n\n \n\nAD/AC/34 Main Landing Gear Upper Bearing - Modification 12/67\n\nApplicability: Models 500A, 500B, 560F, 680F, 680FL and 680FL(P) with S/Nos. 871, 875, 893 to 1535 except 1496, 1515, 1517, 1527, 1531, 1532 and 1534.\n\n \n\nDocument: Aero Commander SB No. 83, Rev. A. Compliance:  Forthwith.\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":false,"description":"The AD as published sets a clear, narrow scope by model and serial number and prescribes a single remedial document (Aero Commander SB No. 83, Rev. A) with an immediate compliance time. There is no indication within the supplied text that the scope departs from an earlier stated intent; the directive lists affected serial numbers and specific exclusions, and requires the modification \"Forthwith.\""},"complexity_factors":["Narrow and explicit applicability list (specific models and serial numbers), which reduces legal ambiguity but requires serial-number checks.","Single mandatory technical remedy referenced (Aero Commander SB No. 83, Rev. A) simplifies legal interpretation but shifts technical complexity to the service bulletin.","Immediate compliance time — 'Forthwith' — raises operational urgency and logistical complexity for owners/operators.","No phased compliance schedule or conditional exemptions in the text — few regulatory complexity layers but operational pressure for prompt action.","Dependence on availability of parts, qualified maintenance personnel and maintenance facilities introduces practical/operational complexity not described in the AD itself."],"plain_english_summary":"This AD mandates an immediate physical modification to the main landing‑gear upper bearing on specified Twin Commander (Aero/Rockwell/Gulfstream) models, to be carried out exactly per Aero Commander SB No. 83, Rev. A. It affects owners/operators of the listed serial‑numbered aircraft and the maintenance organisations that will perform the work. It matters because compliance is mandatory \"forthwith,\" imposing direct parts, labour and downtime costs on operators while restoring required airworthiness."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical issue on specific aircraft. It has not expanded beyond its original purpose of mandating a landing gear modification for safety reasons."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined applicability criterion (specific aircraft models and serial numbers)","No cross-references to other legislation beyond the enabling Civil Aviation Regulations 1998","Single, unambiguous compliance requirement ('Forthwith')","No conditional logic, exceptions, or nested provisions","Straightforward reference to external technical document (Service Bulletin No. 83, Rev. A)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA). It is a mandatory safety order for specific aircraft owners and operators.\n\n**What it does:**\n- Requires owners of certain **Twin Commander aircraft** (specifically models 500A, 500B, 560F, 680F, 680FL and 680FL(P) with particular serial numbers) to modify the **main landing gear upper bearing**.\n- The modification must follow the manufacturer's Service Bulletin No. 83, Revision A.\n\n**Who it affects:**\n- Owners and operators of the specified Twin Commander aircraft models (Gulfstream/Rockwell/Aero Commander 500, 600 and 700 series).\n- Only applies to aircraft with specific serial numbers listed in the directive.\n\n**Why it matters:**\n- Airworthiness Directives are legally enforceable safety instructions. Non-compliance means the aircraft cannot legally fly in Australian airspace.\n- This particular directive addresses a potential safety issue with the main landing gear upper bearing that could affect flight safety if not corrected.\n- The word **\"Forthwith\"** means the modification must be done immediately — there is no grace period.\n\n**Key terms explained:**\n- **Airworthiness Directive (AD):** A mandatory regulatory notice requiring aircraft owners to complete specific maintenance or modifications to address unsafe conditions.\n- **Service Bulletin (SB):** Technical instructions issued by an aircraft manufacturer describing recommended or required modifications.\n- **Compliance: Forthwith:** Must be completed immediately before further flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ac-34-main-landing-gear-upper-bearing-modification","history":"/api/acts/ad-ac-34-main-landing-gear-upper-bearing-modification/history","analysis":"/api/acts/ad-ac-34-main-landing-gear-upper-bearing-modification/analysis","conflicts":"/api/acts/ad-ac-34-main-landing-gear-upper-bearing-modification/conflicts","importantCases":"/api/acts/ad-ac-34-main-landing-gear-upper-bearing-modification/important-cases","documents":"/api/acts/ad-ac-34-main-landing-gear-upper-bearing-modification/documents"}}