{"id":"F2006B06773","name":"AD/SA-TP/24 - Engine Nacelle Upper Longerons","slug":"ad-sa-tp-24-engine-nacelle-upper-longerons","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114613,"registerId":"commonwealth-F2006B06773-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SA-TP/24 - Engine Nacelle Upper Longerons","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)  British Aerospace (Scottish Aviation) Twin Pioneer Series Aeroplanes\n\n \n\nAD/SA-TP/24 Engine Nacelle Upper Longerons NK\n\nApplicability: All models.\n\n \n\nDocument: Scottish Aviation TNS No. 45 and Mod. No. C759.\n\n \n\nCompliance: Inspect at intervals not exceeding 200 hours time in service. Modify - 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\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 standard, narrow airworthiness directive targeting a specific structural component on a specific aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 2 substantive requirements (inspect and modify)","No defined terms section","No cross-references to other legislation beyond the enabling regulation (CAR 1998 Part 39)","Simple unconditional language ('Forthwith', 'not exceeding 200 hours')","Single applicability criterion ('All models')","References only one external technical document (Scottish Aviation TNS No. 45)"],"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) under the Civil Aviation Regulations 1998.\n\n**What it does:** It requires owners and operators of **British Aerospace (Scottish Aviation) Twin Pioneer series aeroplanes** to take specific safety actions regarding the **engine nacelle upper longerons** (structural support beams that run along the top of the engine housing).\n\n**Who it affects:** Anyone who owns, operates, or maintains any model of the Twin Pioneer aircraft.\n\n**What must be done:**\n- **Inspections:** Check the engine nacelle upper longerons at least every 200 hours of flight time (\"time in service\").\n- **Modification:** Install a specific design change (Modification No. C759, described in Scottish Aviation Technical Note No. 45) **immediately** (\"forthwith\" means without delay).\n\n**Why it matters:** This AD addresses a structural safety issue. The upper longerons are critical load-bearing components. If they fail, it could compromise the engine mounting structure, potentially leading to engine separation or other catastrophic failures. The mandatory inspection schedule and immediate modification requirement suggest CASA identified a serious defect or fatigue risk that requires urgent remediation."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"There is no indication in the text that the scope of affected aircraft or the required actions has been altered from an earlier or original intent. The AD explicitly states applicability to 'All models' and sets two required actions: periodic inspection at intervals not exceeding 200 hours and an immediate modification ('Forthwith'). The AD delegates procedural detail to Scottish Aviation TNS No. 45 and Mod. No. C759; that externalisation does not in the AD text itself change scope but does delegate how the actions are to be carried out. (Applicability: All models.; Document: Scottish Aviation TNS No. 45 and Mod. No. C759.; Compliance: Inspect... Modify - Forthwith.)"},"complexity_factors":["Short, focused directive with only two mandatory actions (recurring inspection and immediate modification). (Compliance: Inspect at intervals not exceeding 200 hours time in service. Modify - Forthwith.)","Applicability is broad but unambiguous: 'All models', which increases the number of affected operators but not technical complexity. (Applicability: All models.)","Key procedural detail is externalised to referenced documents (Scottish Aviation TNS No. 45 and Mod. No. C759), requiring users to obtain and interpret another source. (Document: Scottish Aviation TNS No. 45 and Mod. No. C759.)","The term 'Forthwith' mandates immediacy but provides no explicit scheduling window or conditions in the AD text, creating potential operational uncertainty.","No penalties, inspection standards, or acceptance criteria are stated in the AD text itself; those will be found in the referenced documents or by regulator enforcement practice.","Operational complexity stems from logistics (parts, technician availability, downtime) rather than legal or interpretive complexity."],"plain_english_summary":"This Airworthiness Directive requires owners/operators of all British Aerospace (Scottish Aviation) Twin Pioneer aircraft to carry out recurring inspections of the engine nacelle upper longerons at intervals no greater than 200 flight hours and to perform an immediate modification as directed. Compliance follows Scottish Aviation TNS No. 45 and Mod. No. C759, with costs and downtime borne by operators; it’s a mandatory safety action by the Civil Aviation Safety Authority."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sa-tp-24-engine-nacelle-upper-longerons","history":"/api/acts/ad-sa-tp-24-engine-nacelle-upper-longerons/history","analysis":"/api/acts/ad-sa-tp-24-engine-nacelle-upper-longerons/analysis","conflicts":"/api/acts/ad-sa-tp-24-engine-nacelle-upper-longerons/conflicts","importantCases":"/api/acts/ad-sa-tp-24-engine-nacelle-upper-longerons/important-cases","documents":"/api/acts/ad-sa-tp-24-engine-nacelle-upper-longerons/documents"}}