{"id":"F2006B02427","name":"AD/APU/1 - Turbine Blade Containment Ring - Installation","slug":"ad-apu-1-turbine-blade-containment-ring-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41676,"registerId":"commonwealth-F2006B02427-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/APU/1 - Turbine Blade Containment Ring - Installation","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 - 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Auxiliary Power Units\n\n \n\nAD/APU/1 Turbine Blade Containment Ring - Installation NK\n\nApplicability: Airesearch Model No\n\n \n\nGTCP85-98D with Serial No. prior to 28008.\n\n \n\n-98W with Serial No. prior to 30734.\n\n \n\n-99 with Serial No. prior to 14744.\n\n \n\n-115 with Serial No. prior to 18801.\n\n \n\n-115C with Serial No. prior to 35975.\n\n \n\nDocument: Airesearch SB No. 49-1790.\n\n \n\nCompliance: Before installation in an aircraft following next reconditioning or hot end repair after 30 November 1971.\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, as presented, sets a narrowly targeted requirement limited to the listed Airesearch APU models and serial-number ranges and prescribes compliance timing tied to next reconditioning or hot-end repair after 30 November 1971. There is no text in the instrument indicating a change to that scope from a prior stated intent."},"complexity_factors":["Narrow, explicit applicability by model and serial-number cutoffs (requires precise record checks)","Compliance trigger tied to maintenance events (next reconditioning or hot-end repair) rather than a fixed calendar retrofit date","Dependence on an external technical document (Airesearch SB No. 49-1790) for the detailed procedure","Administrative enforcement under the Civil Aviation Regulations / CASA airworthiness directives framework"],"plain_english_summary":"What this instrument does (mechanically)\n\n- It mandates the installation of a turbine blade containment ring on a set of specific Airesearch auxiliary power unit (APU) models and serial-number ranges. (See \"Applicability\".)\n- The installation must be carried out in accordance with the manufacturer's paperwork referenced: Airesearch Service Bulletin No. 49-1790. (See \"Document\".)\n- The required timing is: before the APU is next installed in an aircraft after its next reconditioning or after a hot-end repair that occurs following 30 November 1971. (See \"Compliance\".)\n\nWho is affected\n\n- Owners and operators of aircraft that use the listed Airesearch APU models with the specified serial numbers. (See \"Applicability\".)\n- Maintenance organisations and technicians who perform reconditioning, hot-end repair, or installation work on those APUs, because they must ensure the containment ring is installed before re-installation in an aircraft. (See \"Compliance\" and \"Document\".)\n\nWhy it matters (procedural and economic effects)\n\n- The directive creates a mandatory maintenance action that must be completed before re-installation in service. That converts a discretionary retrofit into a condition precedent for installation after certain maintenance events. (See \"Compliance\".)\n- Practically, the parties arranging and performing the reconditioning or hot-end repair must ensure the containment ring is fitted and documented per the Airesearch service bulletin. That imposes a compliance task and an operational timing constraint on maintenance schedules. (See \"Compliance\" and \"Document\".)\n\nWho pays and who decides (derived from the instrument)\n\n- The directive does not name a payer; by its terms the actor who controls reconditioning and installation (typically the APU/aircraft owner or their contracted maintenance provider) must ensure compliance before installing the APU in an aircraft. Those actors will therefore bear the direct costs of parts, labour and any additional downtime needed to fit the containment ring. (See \"Compliance\" and \"Applicability\".)\n- The Civil Aviation Safety Authority (CASA) is the issuing authority under the Civil Aviation Regulations framework that places this item in the Schedule of Airworthiness Directives. CASA enforces compliance under the statutory airworthiness system. (See header: \"Civil Aviation Regulations 1998, PART 39\" and \"Civil Aviation Safety Authority\".)\n\nImplementation, incentives and trade-offs (practical considerations)\n\n- Compliance burden: maintenance planners must track which APUs fall inside the listed serial-number ranges and ensure the containment ring is fitted at the next qualifying maintenance event. The directive ties compliance to the event of reconditioning or hot-end repair, which may create scheduling pressures to combine or defer work to fit the requirement. (See \"Applicability\" and \"Compliance\".)\n- Operational cost and downtime: the entity responsible for the APU installation must absorb the parts, labour and potential aircraft downtime needed to fit the containment ring according to the service bulletin. (See \"Document\" and \"Compliance\".)\n- Technical discretion and documentation: the directive points to the manufacturer’s service bulletin for the technical method; adherence to that bulletin will determine the exact scope of work and recorded evidence of compliance. That concentrates technical discretion in the service-bulletin content and in the hands of the maintenance organisation executing it. (See \"Document\".)\n- Concentrated benefits, diffuse costs: the directive creates a narrowly targeted requirement (specific APU models/serial numbers). The safety or performance upside (as asserted by issuing authorities or the manufacturer) will accrue to aircraft operators using those APUs; the costs (parts, labour, scheduling) are borne by the same operators and their contracted maintainers. (See \"Applicability\" and \"Compliance\".)\n\nSource references\n\n- Applicability (listed models and serial-number cutoffs): \"Applicability: Airesearch Model No ... GTCP85-98D with Serial No. prior to 28008 ... -98W with Serial No. prior to 30734 ... -99 with Serial No. prior to 14744 ... -115 with Serial No. prior to 18801 ... -115C with Serial No. prior to 35975.\" (See \"Applicability\".)\n- Required action timing: \"Compliance: Before installation in an aircraft following next reconditioning or hot end repair after 30 November 1971.\" (See \"Compliance\".)\n- Technical reference: \"Document: Airesearch SB No. 49-1790.\" (See \"Document\".)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in specific equipment. It has not expanded beyond its original purpose of mandating containment ring installation."},"complexity_factors":["Single, specific technical requirement (install one component)","Limited applicability (5 specific APU models with serial number cutoffs)","No defined terms section","Single compliance trigger (next reconditioning/hot end repair after fixed date)","No cross-references to other legislation or regulations","References only one technical document (manufacturer Service Bulletin 49-1790)","Total length under 200 words"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA). It mandates a safety modification for specific models of Airesearch auxiliary power units (APUs) — small turbine engines used to power aircraft systems when the main engines aren't running.\n\n**What it requires:**\nOperators must install a **turbine blade containment ring** — a protective metal band around the turbine — before installing any affected APU into an aircraft. This ring prevents broken turbine blades from flying out and damaging the aircraft or injuring people.\n\n**Who it affects:**\nOwners and operators of aircraft using specific Airesearch GTCP85 and GTCP99 series APUs with serial numbers below certain thresholds (essentially older units manufactured before the early 1970s).\n\n**When compliance is required:**\nBefore the APU is installed in an aircraft following its next reconditioning or \"hot end repair\" (major overhaul of the hot section) after 30 November 1971.\n\n**Why it matters:**\nTurbine blades can fail catastrophically at high speeds. Without a containment ring, a blade failure could penetrate the APU casing, potentially causing fires, structural damage, or loss of aircraft systems. This directive prevents that by ensuring older APUs get retrofitted with protective hardware."}},"importantCases":[],"_links":{"self":"/api/acts/ad-apu-1-turbine-blade-containment-ring-installation","history":"/api/acts/ad-apu-1-turbine-blade-containment-ring-installation/history","analysis":"/api/acts/ad-apu-1-turbine-blade-containment-ring-installation/analysis","conflicts":"/api/acts/ad-apu-1-turbine-blade-containment-ring-installation/conflicts","importantCases":"/api/acts/ad-apu-1-turbine-blade-containment-ring-installation/important-cases","documents":"/api/acts/ad-apu-1-turbine-blade-containment-ring-installation/documents"}}