{"id":"F2006B07588","name":"AD/VIPER/6 - Blow-Off Valve Operating Limit","slug":"ad-viper-6-blow-off-valve-operating-limit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50231,"registerId":"commonwealth-F2006B07588-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/VIPER/6 - Blow-Off Valve Operating Limit","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 - 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Rolls Royce Turbine Engines - Viper Series\n\n \n\nAD/VIPER/6 Blow-Off Valve Operating Limit 4/90\n\nApplicability: Viper Mk 601-22.\n\n \n\nRequirement: Action in accordance with Rolls Royce SB Viper Mk 601-22 75-All. Compliance: Effective 19 April 1990.\n\nBackground: This Directive has been issued to require a revised blow-off valve operating point.\n\nThe Requirement reduces the possibility of engine surge or stall.\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 directive applies specifically to Viper Mk 601-22 engines and requires compliance with a Rolls Royce service bulletin to revise the blow-off valve operating point. The instrument does not expand applicability beyond the named engine model nor introduce additional categories of affected parties; it prescribes a technical remedy by reference. Therefore, based on the text of the instrument, the scope has not changed from the described purpose — it remains a targeted requirement for the specified engine type. (Applicability; Requirement; Background)"},"complexity_factors":["Single, narrowly defined applicability (Viper Mk 601-22) reduces scope complexity. (Applicability)","Primary requirement is a cross-reference to an external document (Rolls Royce SB Viper Mk 601-22 75-All), which requires users to consult the service bulletin for technical detail. (Requirement)","Directive text contains no technical steps, parts lists, or labour estimates, shifting implementation complexity to the service bulletin and maintenance providers. (Requirement)","Clear compliance date (19 April 1990) reduces temporal ambiguity. (Compliance)","Stated outcome (reduction of surge or stall) is qualitative; absence of test/verification procedures in the AD increases dependence on ancillary documents or oversight. (Background)"],"plain_english_summary":"This airworthiness directive (effective 19 April 1990) mandates owners/operators and maintenance organisations of Viper Mk 601-22 engines to comply with Rolls Royce SB Viper Mk 601-22 75‑All, which revises the blow-off valve operating point to reduce the risk of engine surge or stall. Compliance is compulsory; the operator bears costs and must rely on the manufacturer’s bulletin for the technical work and practical implementation."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope — a specific safety modification for a single engine model. There is no evidence of scope creep; it addresses exactly what it was issued for: preventing engine surge through a blow-off valve adjustment."},"complexity_factors":["Extremely short document (under 150 words)","Only one defined applicability (single engine model)","Single requirement referencing an external technical document (Rolls Royce Service Bulletin)","No conditional logic, exceptions, or nested provisions","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Straightforward compliance date with no alternative methods or phased implementation"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance or operational changes to aircraft.\n\n**What it does:**\n- Requires owners or operators of **Rolls Royce Viper Mk 601-22 turbine engines** to adjust the \"blow-off valve operating point\" (a pressure relief mechanism that prevents engine damage).\n- The change must follow the manufacturer's instructions in **Rolls Royce Service Bulletin Viper Mk 601-22 75-All**.\n\n**Who it affects:**\n- Anyone operating aircraft with these specific Rolls Royce Viper engines (typically older business jets or military aircraft conversions).\n\n**Why it matters:**\n- The adjustment **reduces the risk of engine surge or stall** — dangerous conditions where airflow through the engine becomes unstable, potentially causing sudden power loss or engine damage.\n- Compliance became mandatory from **19 April 1990**.\n\n**In short:** If you fly or maintain an aircraft with this engine, you had to recalibrate a safety valve by April 1990 to prevent the engine from stalling mid-flight."}},"importantCases":[],"_links":{"self":"/api/acts/ad-viper-6-blow-off-valve-operating-limit","history":"/api/acts/ad-viper-6-blow-off-valve-operating-limit/history","analysis":"/api/acts/ad-viper-6-blow-off-valve-operating-limit/analysis","conflicts":"/api/acts/ad-viper-6-blow-off-valve-operating-limit/conflicts","importantCases":"/api/acts/ad-viper-6-blow-off-valve-operating-limit/important-cases","documents":"/api/acts/ad-viper-6-blow-off-valve-operating-limit/documents"}}