{"id":"F2006B07591","name":"AD/VIPER/9 - Engine Centre Section","slug":"ad-viper-9-engine-centre-section","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50242,"registerId":"commonwealth-F2006B07591-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/VIPER/9 - Engine Centre Section","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nRolls Royce Turbine Engines \\- Viper Series\n\nAD/VIPER/9 Engine Centre Section 9/90\n\nApplicability: Viper Mk 601-22 and Viper Mk 520, 521 and 522 engines.\n\nRequirement: Inspect engine compressor casing/centre section joint flange in accordance with and as applicable:\n\nRolls Royce Viper Mk 601-22 Service Bulletin No 72-A173; or\n\nRolls Royce Viper Mk 520, 521, and 522 Service Bulletin No 72-A388.\n\nCompliance: (1) Engines in service \\- Prior to 6 August 1990.\n\n(2) Uninstalled engines \\- Prior to installation in an aircraft.\n\nBackground: Investigation of an engine established that the compressor casing/centre section joint had parted at the top, causing heavy bending loads on the turbine mainshaft causing spline failure. Parting of the compressor casing/centre section has been attributed to thermal stress pulling fastener inserts from the centre section.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical failure mode in specific engine models. It has not expanded beyond its original purpose of mandating inspection of the compressor casing/centre section joint flange."},"complexity_factors":["Extremely short document (under 200 words)","Only 4 defined engine models in applicability section","Simple binary compliance structure: (1) in-service engines, (2) uninstalled engines","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","No nested conditions or exceptions — straightforward mandatory inspection requirement","Single technical cause-and-effect explanation in background section"],"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). Think of it as a \"recall notice\" for aircraft engines, but with legal force. Owners and operators must comply or the aircraft cannot fly legally.\n\n**What it requires:** Anyone operating specific Rolls-Royce Viper jet engines (models Mk 601-22, 520, 521, and 522) must inspect a critical joint where the compressor casing meets the centre section of the engine. This inspection must follow specific technical instructions laid out in two Rolls-Royce Service Bulletins (official repair notices from the manufacturer).\n\n**Who must act:**\n- **For engines already in use:** The inspection must be done before 6 August 1990.\n- **For spare engines not yet installed:** The inspection must be done before the engine goes into any aircraft.\n\n**Why it matters:** An investigation found that this engine joint can fail due to heat stress pulling out fasteners. When this joint fails, it puts massive bending force on the turbine shaft, which can cause the shaft to break (\"spline failure\"). A broken turbine shaft means catastrophic engine failure — potentially causing loss of aircraft and life.\n\n**The bottom line:** This directive prevents engines from disintegrating in flight by catching a specific thermal fatigue problem before it causes catastrophic failure."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive confines itself to the specific Rolls-Royce Viper engine models listed and prescribes inspection of the compressor casing/centre section joint flange in accordance with specified service bulletins, with time limits for in-service and uninstalled engines. That scope aligns with the stated safety purpose (investigation of a joint separation attributed to thermal stress) and does not expand beyond the engine types, the joint area, and the inspection measures required in the source text (Applicability; Requirement; Compliance; Background)."},"complexity_factors":["Technical specificity limited to a small set of engine models (Viper Mk 601-22; Mk 520, 521, 522) (Applicability)","Dependency on external manufacturer documents (two Rolls-Royce service bulletins referenced for inspection procedures) (Requirement)","Distinct compliance deadlines for in-service engines versus uninstalled engines, creating scheduling constraints (Compliance)","Safety-technical cause described (thermal stress pulling fastener inserts causing joint separation and shaft spline failure), requiring technically competent inspection (Background)","Regulatory form is prescriptive (an airworthiness directive) with little scope for substitution unless the service bulletins provide alternatives (Requirement)"],"plain_english_summary":"Mandates inspection of the compressor casing/centre‑section joint flange on Rolls‑Royce Viper Mk 601‑22 and Mk 520/521/522 engines, to be performed exactly per the cited Rolls‑Royce service bulletins. The requirement responds to an investigation finding flange separation (attributed to thermal‑stress pull‑out of fastener inserts) that led to turbine shaft spline failure.\n\nIt affects engine owners/operators and maintenance organisations, who must pay for and schedule the inspection—before 6 Aug 1990 for in‑service engines, or before installation for uninstalled engines."}},"importantCases":[],"_links":{"self":"/api/acts/ad-viper-9-engine-centre-section","history":"/api/acts/ad-viper-9-engine-centre-section/history","analysis":"/api/acts/ad-viper-9-engine-centre-section/analysis","conflicts":"/api/acts/ad-viper-9-engine-centre-section/conflicts","importantCases":"/api/acts/ad-viper-9-engine-centre-section/important-cases","documents":"/api/acts/ad-viper-9-engine-centre-section/documents"}}