{"id":"F2006B02439","name":"AD/APU/7 - High Pressure Turbine Disc","slug":"ad-apu-7-high-pressure-turbine-disc","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41695,"registerId":"commonwealth-F2006B02439-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/APU/7 - High Pressure Turbine Disc","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/7 High Pressure Turbine Disc 4/92\n\nApplicability: Garrett Auxiliary Power Division model TSCP700-4B auxiliary power units, prior to S/N 90697 and model TSCP700-5 auxiliary power units prior to S/N 80443.\n\n \n\nRequirement: Action in accordance with the technical requirements of FAA AD 91-25-04.\n\n \n\nNote: Garrett Service Bulletin TSCP700-49-5892 Revision 2 dated 10 October 1990, refers.\n\n \n\nCompliance: Within 24 months after the issue date of this Directive.\n\n \n\nBackground: This Directive has been raised due to reports of HPT disc ruptures. This condition, if not corrected, could lead to an uncontained HPT disc failure.\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 discrete safety directive targeting a specific mechanical defect in specific aircraft components. It has not expanded beyond its original purpose of addressing HPT disc ruptures in the identified Garrett APU models."},"complexity_factors":["Single, specific applicability clause (two APU models with serial number cutoffs)","Single requirement referencing external technical document (FAA AD 91-25-04)","Single compliance deadline (24 months)","No defined terms section","No cross-references to other legislation beyond the external FAA directive","Straightforward cause-and-effect background explanation"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific **Garrett auxiliary power units (APUs)** — essentially small jet engines that provide power to aircraft when the main engines are off — to inspect or replace their **High Pressure Turbine (HPT) discs**.\n\n**Who it affects:**\n- Owners and operators of aircraft using Garrett TSCP700-4B APUs with serial numbers below 90697, or TSCP700-5 APUs with serial numbers below 80443.\n\n**What it requires:**\n- Follow the technical instructions in **FAA AD 91-25-04** (a matching US safety order).\n- Reference **Garrett Service Bulletin TSCP700-49-5892 Revision 2** for the specific repair procedure.\n- Complete the work **within 24 months** of the directive's issue date.\n\n**Why it matters:**\nThere have been reports of **HPT discs rupturing** (breaking apart while spinning at high speed). If this happens, the disc can burst through its casing in an \"uncontained failure\" — potentially damaging the aircraft or injuring people nearby. This directive prevents catastrophic failures by forcing inspection or replacement of at-risk parts."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive's scope aligns with its stated purpose: it targets specified Garrett TSCP700-4B and TSCP700-5 APUs (by model and serial-number cutoff) and requires the FAA AD's technical actions within 24 months to address reported HPT disc ruptures (Applicability; Requirement; Compliance; Background). The text does not expand or narrow the stated safety concern beyond those measures."},"complexity_factors":["Cross-reference to an external technical document (FAA AD 91-25-04) rather than containing technical measures itself (Requirement).","Applicability limited by model and serial-number cutoffs (TSCP700-4B prior to S/N 90697; TSCP700-5 prior to S/N 80443) requiring operators to check serial records (Applicability).","Compliance deadline is a single fixed window (24 months) without internal staging or alternatives, which concentrates scheduling decisions (Compliance).","Technical detail is delegated to an external service bulletin and FAA AD, creating operational dependence on those documents (Note; Requirement).","Safety consequence described as risk of uncontained HPT disc failure, which implies urgency and potential operational disruption but the Directive does not quantify risk or prescribe mitigation timelines beyond the 24-month limit (Background; Compliance)."],"plain_english_summary":"This Directive requires owners/operators of specified Garrett TSCP700-4B and TSCP700-5 APUs (serials before stated cutoffs) to carry out the technical actions in FAA AD 91-25-04—as referenced—within 24 months. It was issued because of reported high‑pressure turbine disc ruptures; it creates a binding compliance obligation that affects maintenance scheduling, downtime and repair choices."}},"importantCases":[],"_links":{"self":"/api/acts/ad-apu-7-high-pressure-turbine-disc","history":"/api/acts/ad-apu-7-high-pressure-turbine-disc/history","analysis":"/api/acts/ad-apu-7-high-pressure-turbine-disc/analysis","conflicts":"/api/acts/ad-apu-7-high-pressure-turbine-disc/conflicts","importantCases":"/api/acts/ad-apu-7-high-pressure-turbine-disc/important-cases","documents":"/api/acts/ad-apu-7-high-pressure-turbine-disc/documents"}}