{"id":"F2006B07586","name":"AD/VIPER/4 - Blow-Off Valve","slug":"ad-viper-4-blow-off-valve","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50223,"registerId":"commonwealth-F2006B07586-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/VIPER/4 - Blow-Off Valve","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/4 Blow-Off Valve 3/90\n\nApplicability: Viper Mk. 521, 522 engines.\n\n \n\nRequirement: 1. Action in accordance with Rolls Royce Service Bulletin No. 75-31, or\n\n \n\n2. CAO 106 AD/RRT-V/14. Compliance: Effective 22 March 1990.\n\nBackground: This Directive has been reissued to require repetitive inspection of the blow-off valve.\n\nEngine surge/stall events have been attributed, in part, to stiction of the blow-off valve.\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":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1412},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive remains tightly focused on its original purpose: addressing blow-off valve stiction in specific Viper engines through repetitive inspection requirements."},"complexity_factors":["Very short document containing a single requirement","Limited applicability (only two specific engine models: Mk. 521 and 522)","Single compliance pathway (reference to external service bulletin)","No nested exceptions, defined terms, or conditional logic"],"plain_english_summary":"**What this does:** This rule requires regular inspections of the blow-off valve on specific Rolls Royce Viper jet engines.\n\n**Who it affects:** Anyone operating or maintaining aircraft with **Viper Mk. 521 or 522 engines**.\n\n**What you must do:** Follow the instructions in Rolls Royce Service Bulletin No. 75-31 (or an alternative Civil Aviation Order) to inspect the blow-off valve. This isn't a one-off fix—you need to keep checking it repeatedly.\n\n**Why it matters:** If these valves get stuck (a problem called \"stiction\"), it can cause the engine to surge or stall mid-flight. This directive was reissued specifically to make sure operators keep checking this part, not just fix it once."}},"importantCases":[],"_links":{"self":"/api/acts/ad-viper-4-blow-off-valve","history":"/api/acts/ad-viper-4-blow-off-valve/history","analysis":"/api/acts/ad-viper-4-blow-off-valve/analysis","conflicts":"/api/acts/ad-viper-4-blow-off-valve/conflicts","importantCases":"/api/acts/ad-viper-4-blow-off-valve/important-cases","documents":"/api/acts/ad-viper-4-blow-off-valve/documents"}}