{"id":"F2006B11415","name":"AD/OPTICA/3 - A51 Fan Replacement","slug":"ad-optica-3-a51-fan-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57326,"registerId":"commonwealth-F2006B11415-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/OPTICA/3 - A51 Fan 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)  FLS Aerospace OA7 Optica Series Aeroplanes\n\n \n\nAD/OPTICA/3 A51 Fan Replacement 13/94 DM\n\nApplicability: All model OA7 Optica series aircraft.\n\n \n\nRequirement: Action in accordance with Brookland Aerospace Mandatory SB No 0A7/SB/0042 Issue 1.\n\n \n\nNote: UK CAA AD 004-05-90 refers.\n\n \n\nCompliance: Prior to issue of Certificate of Airworthiness.\n\n \n\nBackground: FLS Aerospace (Lovaux) Light Aircraft Division has advised that the A51 fan originally fitted to the OA7 Optica has suffered fatigue failure due to the fundamentally flawed design of the fan assembly. The A51 fan is therefore considered unsuitable for use on the aircraft.\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, targeted safety directive addressing a specific mechanical defect. It has not expanded beyond its original purpose of mandating fan replacement on affected aircraft."},"complexity_factors":["Single, specific mechanical requirement (fan replacement)","Only one defined applicability criterion (all OA7 Optica series aircraft)","No nested exceptions or conditional logic","Short document (approximately 150 words of substantive content)","Single cross-reference to a UK CAA directive and one service bulletin","No interpretation section or defined terms"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nOrders the replacement of a specific part (the \"A51 fan\") on all **FLS Aerospace OA7 Optica series aircraft**.\n\n**Why it matters:**\nThe A51 fan has a \"fundamentally flawed design\" that has caused **fatigue failures** (meaning the part cracks and breaks after repeated use). This is a serious safety risk — if the fan fails in flight, it could cause engine damage or loss of power.\n\n**Who must comply:**\nAnyone who owns or operates an OA7 Optica aircraft. They must replace the fan **before the aircraft can be issued a Certificate of Airworthiness** (the official document that says an aircraft is safe to fly).\n\n**What owners must do:**\nFollow the instructions in **Brookland Aerospace Mandatory Service Bulletin No 0A7/SB/0042 Issue 1** — this document tells mechanics exactly how to replace the faulty fan."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument’s scope is confined to all OA7 Optica series aircraft and requires replacement of the A51 fan according to a specified Mandatory Service Bulletin before a Certificate of Airworthiness is issued (Applicability; Requirement; Compliance). The text presents this as a corrective safety action due to fatigue failure of the A51 fan (Background). There is no indication within the document that the AD’s applicability, required action, or timing has been expanded or narrowed from the stated measures."},"complexity_factors":["Narrow technical scope: single, specific component (A51 fan) on a single aircraft family (Applicability).","Prescriptive external reference: requires compliance with a named Brookland Aerospace Mandatory Service Bulletin (Requirement).","Hard timing constraint tied to certification: work must be completed prior to issuance of Certificate of Airworthiness (Compliance).","Dependence on an external authority/document (Note refers to UK CAA AD) which may require cross-checking.","Low statutory ambiguity: clear mandatory action and timing reduce interpretive complexity but create operational/coordination complexity for affected parties."],"plain_english_summary":"What this changes, mechanically:\n\n- It requires that every OA7 Optica series aeroplane have the A51 fan replaced in accordance with Brookland Aerospace Mandatory Service Bulletin No 0A7/SB/0042 Issue 1 (\"Requirement\"), and that this work be completed before a Certificate of Airworthiness is issued for the aircraft (\"Compliance\").\n\nWho and what is affected:\n\n- Applicability: all model OA7 Optica series aircraft (\"Applicability\").\n- The persons or organisations responsible for putting an OA7 Optica into a condition to receive a Certificate of Airworthiness (for example, owners, registrants, or maintenance organisations) must ensure the replacement is carried out prior to issuance of that certificate (\"Compliance\").\n\nOfficial stated purpose:\n\n- The Background states that the A51 fan originally fitted to the OA7 Optica has suffered fatigue failure because of a fundamentally flawed design of the fan assembly, and that the A51 fan is therefore considered unsuitable for use on the aircraft (\"Background\"). The AD references a related UK Civil Aviation Authority airworthiness directive (\"Note\").\n\nOperational effects, costs and incentives (source-grounded observations):\n\n- Direct action required: the AD prescribes a specific maintenance action — replacement of the A51 fan following Brookland Aerospace Mandatory SB No 0A7/SB/0042 Issue 1 — rather than leaving the method to the discretion of operators (\"Requirement\").\n- Timing constraint and enforcement point: compliance must be demonstrated before the aircraft is granted a Certificate of Airworthiness, which ties enforcement to the certification process rather than in-service inspection cycles (\"Compliance\"). This creates a hard timing constraint: the work must be done before entry into service or before initial certification.\n- Who bears the immediate burden: the affected aircraft (all OA7 Optica series) and the parties responsible for preparing them for a Certificate of Airworthiness must carry out the replacement. Those parties will therefore incur the direct time and cost of parts and labour needed to comply (inferred from the \"Applicability\" and \"Compliance\" requirements and the prescriptive \"Requirement\").\n- Dependency on external technical guidance: the AD requires action in accordance with a named Brookland Aerospace Mandatory Service Bulletin. That ties the required method to an external document and to the availability and content of that bulletin (\"Requirement\").\n- Implementation and timing risk: because compliance is a precondition to issuing a Certificate of Airworthiness, any delay in performing the replacement, in obtaining the specified parts, or in accessing the service bulletin could delay certification (inferred from the conjunction of \"Requirement\" and \"Compliance\").\n- Administrative discretion and enforcement mechanism: the requirement is enforced at the point of airworthiness certification, so the civil aviation authority or its delegated certificating officers control whether the aircraft may be released to service without the A51 fan fitted (\"Compliance\").\n\nTrade-offs and opportunity costs (source-grounded):\n\n- The AD replaces continued use of the A51 fan with a mandatory replacement prior to certification. The Background frames this as a safety-driven change (\"Background\"). The trade-off is that operators must allocate resources (parts, maintenance labour, scheduling) to meet that safety requirement before the aircraft can be certified (inferred from \"Requirement\" and \"Compliance\").\n\nNotes and cross-references:\n\n- The AD explicitly refers to a related UK CAA AD (UK CAA AD 004-05-90) for further context or action (\"Note\").\n\nKey cited lines from the instrument: \"Applicability: All model OA7 Optica series aircraft.\"; \"Requirement: Action in accordance with Brookland Aerospace Mandatory SB No 0A7/SB/0042 Issue 1.\"; \"Compliance: Prior to issue of Certificate of Airworthiness.\"; \"Background: ... the A51 fan ... has suffered fatigue failure ... The A51 fan is therefore considered unsuitable for use on the aircraft.\""}},"importantCases":[],"_links":{"self":"/api/acts/ad-optica-3-a51-fan-replacement","history":"/api/acts/ad-optica-3-a51-fan-replacement/history","analysis":"/api/acts/ad-optica-3-a51-fan-replacement/analysis","conflicts":"/api/acts/ad-optica-3-a51-fan-replacement/conflicts","importantCases":"/api/acts/ad-optica-3-a51-fan-replacement/important-cases","documents":"/api/acts/ad-optica-3-a51-fan-replacement/documents"}}