{"id":"F2006B03600","name":"AD/BEA 121/6 - Fuel Tank Non-Return Valves","slug":"ad-bea-121-6-fuel-tank-non-return-valves","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43191,"registerId":"commonwealth-F2006B03600-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BEA 121/6 - Fuel Tank Non-Return Valves","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 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Beagle B121 (Pup) Series Aeroplanes\n\n \n\nAD/BEA 121/6 Fuel Tank Non-Return Valves 2/71\n\nApplicability: All Series 1, 2 and 3 aircraft which do not have non-return valve P/N 703-AA-25 fitted to each fuel cell outlet connection.\n\n \n\nRequirement: Action in accordance with Beagle SB B121/21. Compliance:  Within 100 hours time in service after 26 February 1971.\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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive’s scope is limited and explicit in the source: it applies to Beagle B121 Series 1–3 aircraft that do not have non‑return valve P/N 703‑AA‑25 fitted, requires action per Beagle SB B121/21, and sets a 100‑hour compliance window after 26 February 1971. The text does not indicate any expansion or narrowing beyond those stated conditions, so there is no change from the scope set out in the instrument itself."},"complexity_factors":["Narrow applicability tied to specific airframe series and absence of a specific part number (Applicability).","Mandates compliance with an external manufacturer Service Bulletin for the method of work (Requirement), creating dependence on that document for technical details.","A short, fixed compliance window measured in hours time in service (100 hours after 26 February 1971) (Compliance).","Requires procurement of a specific part number (703‑AA‑25), which can introduce supply constraints or lead times (Applicability).","Enforcement occurs under existing Civil Aviation Regulations and the Schedule of Airworthiness Directives, requiring regulatory oversight and record-keeping (Schedule heading)."],"plain_english_summary":"What this directive does\n\n- This is an Airworthiness Directive issued under the Civil Aviation Regulations requiring a hardware change to certain Beagle B121 (Pup) aeroplanes. (See heading and Schedule of Airworthiness Directives.)\n\nWho it affects\n\n- Owners and operators of Beagle B121 Series 1, 2 and 3 aircraft that do not already have non-return valve part number 703‑AA‑25 fitted to each fuel cell outlet connection. (Applicability)\n\nWhat it requires, mechanically\n\n- Those aircraft must have the specified non-return valve fitted to each fuel cell outlet connection by following the procedures in Beagle Service Bulletin B121/21. The AD makes compliance with that Service Bulletin mandatory for the affected aircraft. (Requirement)\n\nWhen it must be done\n\n- The installation must be completed within 100 hours time in service after 26 February 1971. (Compliance)\n\nWho pays and who decides\n\n- The aircraft owner/operator is responsible for arranging and paying for the parts and work required to comply. (Applicability; Requirement)\n- The Civil Aviation Safety Authority enforces the Airworthiness Directive under the Civil Aviation Regulations framework. (Schedule heading)\n\nIncentives, costs and trade-offs\n\n- The immediate private cost is the purchase price of valve P/N 703‑AA‑25 and the labour (and any downtime) to install it in each fuel cell outlet connection. (Applicability; Requirement; Compliance)\n- The AD narrows the acceptable solution by pointing to a specific part number and the manufacturer’s Service Bulletin as the required method, which reduces flexibility to adopt alternative solutions unless those alternatives are separately approved. (Applicability; Requirement)\n- Work to comply creates demand for parts and maintenance services; independent maintenance providers can perform the installation if they follow the Service Bulletin’s instructions. (Requirement)\n\nImplementation risk and compliance burden\n\n- Compliance depends on access to part P/N 703‑AA‑25 and on following the procedures in Beagle SB B121/21; if parts are scarce or the Service Bulletin requires specialist skills, owners may face delay and higher costs. (Applicability; Requirement)\n- The AD imposes a defined time window (100 hours TIS) for compliance, which creates scheduling pressure and potential opportunity cost from aircraft downtime. (Compliance)\n\nConcrete behavioural effect\n\n- Owners/operators must alter their aircraft (install the specified non-return valves) within the stated period or face non‑compliance with the AD. Maintenance organisations must carry out the installation in accordance with the Service Bulletin if they are engaged to do the work. (Applicability; Requirement; Compliance)\n\nSource references\n\n- Applicability: identifies which airframes are covered and the required part number condition. (Applicability)\n- Requirement: makes adherence to Beagle SB B121/21 mandatory. (Requirement)\n- Compliance: sets the 100‑hour time limit after 26 February 1971 for completing the work. (Compliance)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a historical Airworthiness Directive from 1971 with a tightly scoped, one-off safety mandate. It has not expanded beyond its original purpose of addressing a specific fuel valve deficiency in a particular aircraft model."},"complexity_factors":["Single, specific aircraft type (Beagle B121 Pup) with narrow applicability","Only one technical requirement referencing an external document (Service Bulletin B121/21)","Simple compliance deadline (100 hours time in service from fixed date)","No defined terms section, no cross-references to other legislation","Binary applicability test (valve P/N 703-AA-25 fitted or not)","Total length: approximately 150 words of substantive content"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to **Beagle B121 'Pup' series aeroplanes** (small British-made aircraft from the 1960s–70s).\n\n**What it does:**\n- **The problem:** Certain fuel tank outlet connections on these aircraft lack a specific non-return valve (part number 703-AA-25). Without this valve, fuel could potentially flow the wrong way or leak, creating a fire or engine failure risk.\n- **The fix:** Owners/operators must follow **Service Bulletin B121/21** issued by the manufacturer (Beagle) to install the correct valves.\n- **The deadline:** Complete the work within **100 hours of flying time** after 26 February 1971.\n\n**Who it affects:**\n- Owners and operators of Beagle B121 Series 1, 2, and 3 aircraft that don't already have the specified valve installed.\n\n**Why it matters:**\nAirworthiness Directives are legally binding. Ignoring this directive means the aircraft cannot be considered airworthy (safe to fly). This particular AD addresses a critical fuel system vulnerability that could cause engine stoppage or fire."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bea-121-6-fuel-tank-non-return-valves","history":"/api/acts/ad-bea-121-6-fuel-tank-non-return-valves/history","analysis":"/api/acts/ad-bea-121-6-fuel-tank-non-return-valves/analysis","conflicts":"/api/acts/ad-bea-121-6-fuel-tank-non-return-valves/conflicts","importantCases":"/api/acts/ad-bea-121-6-fuel-tank-non-return-valves/important-cases","documents":"/api/acts/ad-bea-121-6-fuel-tank-non-return-valves/documents"}}