{"id":"F2006B07585","name":"AD/VIPER/3 - Blow Off Valve Operation Limit","slug":"ad-viper-3-blow-off-valve-operation-limit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50220,"registerId":"commonwealth-F2006B07585-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/VIPER/3 - Blow Off Valve Operation 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/3 Blow Off Valve Operation Limit 3/90\n\nApplicability: Viper Mk. 521, 522 engines.\n\n \n\nRequirement: 1. Action in accordance with Rolls Royce Service Bulletin No. 75-A32, or\n\n \n\n2. CAO 106 AD/RRT-V/13. Compliance: Effective 22 March 1990.\n\nBackground:  This Directive has been reissued to require a revised blow-off valve operating point to reduce 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","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive focused on a specific mechanical component in specific engine models. It has not expanded beyond its original narrow technical purpose."},"complexity_factors":["Extremely short document (under 200 words)","Only 2 defined applicability criteria (engine models)","Simple binary compliance path (Option 1 OR Option 2)","No cross-references to other legislation beyond a single alternative directive","No conditional logic, exceptions, or defined terms section","Single technical requirement with clear effective date"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety fix ordered by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft engines.\n\n**What it does:** It requires owners or operators of Rolls Royce Viper Mk. 521 and 522 turbine engines to adjust the \"blow-off valve\" — a safety device that releases excess pressure from the engine. The directive mandates either following a specific Rolls Royce service bulletin (technical repair instruction) or complying with an older airworthiness directive (CAO 106 AD/RRT-V/13).\n\n**Who it affects:** Anyone operating aircraft with these specific Viper engine models — typically found in older military trainer or light jet aircraft (such as the BAC Jet Provost or similar types used in Australia).\n\n**Why it matters:** The blow-off valve prevents dangerous pressure build-up that can cause \"surge or stall\" — engine failures that could lead to sudden power loss in flight. The revised operating point reduces this risk, making flight safer.\n\n**When compliance was required:** From 22 March 1990."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The directive was reissued to require a revised blow‑off valve operating point compared with the prior issue. The Background explicitly states the reissue changes the operating point requirement to reduce the possibility of engine surge or stall, so the scope of required technical action has been altered from the earlier version (Background)."},"complexity_factors":["Narrow applicability to two engine models (Viper Mk. 521, 522) — limits scope but requires identification of affected units (Applicability).","Mandatory compliance by reference to external technical documents (Rolls Royce Service Bulletin No. 75-A32 or CAO 106 AD/RRT-V/13) — requires access to and correct application of those documents (Requirement).","Technical nature of the action (changing blow‑off valve operating point) — requires qualified maintenance personnel and appropriate tools/calibration (implied by requirement to follow service bulletin).","Directive was reissued to alter the operating point (Background) — operators must track and apply the revised requirement rather than any earlier version.","Fixed effective date for compliance (22 March 1990) — imposes a clear deadline for implementation (Compliance)."],"plain_english_summary":"This Airworthiness Directive applies to aircraft with Rolls‑Royce Viper Mk.521 and Mk.522 engines and requires operators to have maintenance follow either Rolls‑Royce Service Bulletin No. 75‑A32 or CAO 106 AD/RRT‑V/13 to reset the blow‑off valve operating point. The change, paid for and implemented by operators or their maintenance organisations, is intended to reduce the risk of engine surge or stall."}},"importantCases":[],"_links":{"self":"/api/acts/ad-viper-3-blow-off-valve-operation-limit","history":"/api/acts/ad-viper-3-blow-off-valve-operation-limit/history","analysis":"/api/acts/ad-viper-3-blow-off-valve-operation-limit/analysis","conflicts":"/api/acts/ad-viper-3-blow-off-valve-operation-limit/conflicts","importantCases":"/api/acts/ad-viper-3-blow-off-valve-operation-limit/important-cases","documents":"/api/acts/ad-viper-3-blow-off-valve-operation-limit/documents"}}