{"id":"F2006B07310","name":"AD/TB10/8 - Engine Mounts","slug":"ad-tb10-8-engine-mounts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49313,"registerId":"commonwealth-F2006B07310-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB10/8 - Engine Mounts","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)  Aerospatiale (Socata) TB9 and TB10 (Tobago) Series Aeroplanes\n\n \n\nAD/TB10/8 Engine Mounts 1/87 DM\n\nApplicability: All aircraft with engine mounts TB 10.51.000.000. Requirement:  Action in accordance with Aerospatiale Socata SB 16/1.\n\nCompliance: Within 50 hours time in service after 17 December 1986 and thereafter at intervals not exceeding 50 hours time in service until modified.\n\n \n\nBackground: The manufacturer reports cracking of the engine mount weld clusters.\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":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument's scope is stated in the AD and confines obligations to aircraft with engine mounts TB 10.51.000.000. The AD prescribes mandatory action per SB 16/1 and a 50-hour compliance interval until modification. There is no text in the AD indicating any change to that scope from its stated purpose (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Narrow applicability: limited to aircraft with a single engine mount part number (Applicability).","Simple procedural requirement: mandates compliance with a single manufacturer Service Bulletin (Requirement).","Short, repeating compliance interval (50 hours) until modification increases operational burden despite legal simplicity (Compliance).","Dependence on an external document (SB 16/1) for technical detail creates an implementation dependency outside the AD text (Requirement).","Clear trigger date for initial compliance (17 December 1986) makes timing rules explicit and simple (Compliance)."],"plain_english_summary":"What this instrument does (mechanically)\n\n- This is an Airworthiness Directive (AD) issued under the Civil Aviation Safety Authority for Aerospatiale (Socata) TB9 and TB10 (Tobago) series aeroplanes. It applies to every aircraft that has the engine mount part number TB 10.51.000.000. (Applicability)\n- It requires operators to carry out the work set out in the manufacturer's Service Bulletin Aerospatiale Socata SB 16/1. (Requirement)\n- The first action must be completed within 50 hours time in service after 17 December 1986, and then repeated at intervals not exceeding 50 hours time in service until the engine mount is modified as described. (Compliance)\n\nWhy it was issued (stated reason)\n\n- The manufacturer reported cracking of the engine mount weld clusters. That report is stated as the background for the AD. (Background)\n\nWho pays and who decides\n\n- Aircraft owners/operators are the ones who must carry out the inspections/repairs/modifications required by the Service Bulletin and therefore bear the direct costs and downtime. (Requirement; Compliance)\n- The Civil Aviation Safety Authority has issued the AD and prescribes the timing and mandatory nature of the actions. The detailed method of compliance is delegated to the manufacturer's Service Bulletin SB 16/1. (header; Requirement)\n\nWhat behaviour changes\n\n- Operators must inspect/repair/modify the specified engine mounts per SB 16/1 within the initial 50 hours after 17 December 1986 and then at no more than 50-hour intervals until the mount is modified. This increases inspection frequency and may require parts, labour and aircraft out-of-service time. (Compliance; Requirement)\n\nCosts, incentives and trade-offs (mechanical and economic effects)\n\n- Direct costs and downtime: Repeated 50-hour-interval actions impose recurring maintenance costs and aircraft availability loss until the mount is modified. Those costs fall on the aircraft owners/operators. (Compliance)\n- Incentive to modify: Because the 50-hour interval repeats “until modified”, operators have a clear incentive to perform the modification described in SB 16/1 to stop the recurring inspections; the AD therefore creates a trade-off between an upfront modification cost and ongoing inspection costs and downtime. (Compliance; Requirement)\n- Reliance on manufacturer method: The AD mandates compliance with SB 16/1, so technical choices about how to inspect or fix the mounts are determined by the manufacturer’s bulletin rather than by individual operators or independent engineers. That channels implementation through the manufacturer’s prescribed procedure. (Requirement)\n\nImplementation risk and compliance burden\n\n- Repeated short-interval compliance creates higher administrative and operational burden for operators (tracking repeated 50‑hour inspections and arranging work within short service intervals). (Compliance)\n- The AD does not itself describe the technical fix; implementers must consult SB 16/1 to know exactly what work is required. That external dependence means the AD’s practical effect depends on the content and availability of SB 16/1. (Requirement)\n\nEffects on market and private choice (focused observations)\n\n- Independent maintenance providers can perform the work only if they can lawfully and practically follow SB 16/1; the AD does not open or close market access explicitly but channels required activity through the service bulletin. (Requirement)\n- The directive raises operating costs for owners of affected aircraft while providing a prescribed technical route to address a structural safety issue. (Applicability; Requirement; Background)\n\nSource citations\n\n- Applicability: \"All aircraft with engine mounts TB 10.51.000.000.\" (Applicability)\n- Requirement: \"Action in accordance with Aerospatiale Socata SB 16/1.\" (Requirement)\n- Compliance: \"Within 50 hours time in service after 17 December 1986 and thereafter at intervals not exceeding 50 hours time in service until modified.\" (Compliance)\n- Background: \"The manufacturer reports cracking of the engine mount weld clusters.\" (Background)\n"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive addressing a specific safety defect in specific aircraft. It has not expanded beyond its original purpose of mandating inspections for cracked engine mounts."},"complexity_factors":["Extremely short document (under 200 words)","Only 4 defined elements: applicability, requirement, compliance, and background","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Single, clear compliance pathway with straightforward time-in-service calculation","No conditional logic, exceptions, or nested provisions","Technical content limited to a single manufacturer's service bulletin reference"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:** Orders owners and operators of certain Socata Tobago aeroplanes (models TB9 and TB10) to inspect their **engine mounts** (the metal framework that holds the engine to the aircraft body) for dangerous cracking.\n\n**Who it affects:** Anyone who owns or operates an Aerospatiale (Socata) TB9 or TB10 aircraft with engine mount part number TB 10.51.000.000.\n\n**What must be done:**\n- **First inspection:** Within 50 hours of flying time after 17 December 1986\n- **Ongoing inspections:** Every 50 hours of flying time thereafter\n- **How:** Follow the manufacturer's Service Bulletin SB 16/1 (a technical instruction document)\n- **When it stops:** Once the engine mount is permanently modified to fix the problem\n\n**Why it matters:** Cracked engine mounts can cause the engine to detach from the aircraft in flight — obviously catastrophic. This AD was triggered after the manufacturer reported weld cracks appearing in these mounts."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb10-8-engine-mounts","history":"/api/acts/ad-tb10-8-engine-mounts/history","analysis":"/api/acts/ad-tb10-8-engine-mounts/analysis","conflicts":"/api/acts/ad-tb10-8-engine-mounts/conflicts","importantCases":"/api/acts/ad-tb10-8-engine-mounts/important-cases","documents":"/api/acts/ad-tb10-8-engine-mounts/documents"}}