{"id":"F2006B06359","name":"AD/PT6A/19 - Fuel Control Bypass Valve Diaphragm","slug":"ad-pt6a-19-fuel-control-bypass-valve-diaphragm","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47591,"registerId":"commonwealth-F2006B06359-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PT6A/19 - Fuel Control Bypass Valve Diaphragm","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)  Pratt and Whitney Canada Turbine Engines - PT6A Series\n\n \n\nAD/PT6A/19 Fuel Control Bypass Valve Diaphragm 10/85\n\nApplicability: PT6A-38, -41 and 45A engines fitted with Aviation Electric Fuel Control Units P/No 3244723-3 thru -10, 3244738-5, 3244738-6, 3244752-6 thru -10, and 3244755-7 thru-\n\n11.\n\n \n\nDocument: 1. Pratt & Whitney Aircraft of Canada SB No. 3103; 2. FAA AD 78-17-07, Amendment 39-3287; or\n\n3. AD/UAC-T/31.\n\n \n\nCompliance: Within the next 100 hours time in service after 30 November 1978.\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":4,"scope_assessment":{"changed":false,"description":"The directive’s scope is explicit in the source text: it targets PT6A-38, -41 and -45A engines fitted with the specifically listed Aviation Electric Fuel Control Unit part numbers (Applicability) and requires compliance with the listed documents within a defined 100‑hour window (Document; Compliance). Nothing in the instrument text indicates a change from that stated, broader or narrower, than the original stated applicability and compliance requirement."},"complexity_factors":["Technical specificity of applicability: exact engine models and multiple fuel control unit part‑number ranges must be checked (Applicability).","Mandated compliance depends on external documents (Pratt & Whitney SB No. 3103; FAA AD 78-17-07; AD/UAC-T/31), requiring cross‑referencing to find the required technical actions (Document).","Tight, time‑bound compliance window (100 hours time in service after 30 November 1978) creates scheduling and operational complexity for affected operators (Compliance).","Limited text in the AD itself—absence of detailed corrective steps—shifts implementation complexity to maintenance organisations and the referenced material (Document).","Historical dating and placement in a broader regulatory schedule may complicate locating the operative version and any subsequent amendments (Schedule header)."],"plain_english_summary":"What this instrument does, mechanically:\n\n- This Airworthiness Directive (AD/PT6A/19) requires operators of certain Pratt & Whitney Canada PT6A turbine engines to follow specified corrective actions that are set out in referenced technical documents. The directive does not itself list detailed actions; instead it directs compliance with the listed documents (Pratt & Whitney Service Bulletin No. 3103; FAA AD 78-17-07; or AD/UAC-T/31) (Document).  \n\nWho is affected:\n\n- The AD applies to PT6A-38, PT6A-41 and PT6A-45A engines that are fitted with Aviation Electric Fuel Control Units having part numbers in the specific ranges listed in the directive (Applicability). Owners and operators of aircraft with those engines, and the maintenance organisations that service them, are the parties required to respond. The instrument is published under the Civil Aviation Safety Authority schedule of airworthiness directives (Schedule header).  \n\nWhen it must be done:\n\n- The actions required by the referenced documents must be completed within the next 100 hours time in service after 30 November 1978 (Compliance). The AD therefore creates a near-term, time‑bound compliance window measured in flight/engine hours.  \n\nWhy it matters (officially stated and how that creates incentives and costs):\n\n- The directive’s placement and title (Fuel Control Bypass Valve Diaphragm) indicate the technical focus is the fuel control bypass valve diaphragm; the directive points operators to the referenced service/airworthiness documents for the corrective measures (Document). The official purpose-claim (embedded in the choice of documents to follow) is to address an identified problem with that component. Mechanically, this creates an obligation for operators to (a) determine which engines have the listed fuel control unit part numbers (Applicability), and (b) carry out the inspections/repairs/modifications specified in the referenced documents within the 100‑hour window (Document; Compliance).\n\nWho pays, who decides, and how behaviour changes:\n\n- Operators and aircraft owners pay for the inspections, parts and labour needed to meet the actions in the referenced documents (Document; Compliance). Maintenance organisations will perform the work to meet the AD. The Civil Aviation Safety Authority (through its published schedule of ADs) is the issuing authority that sets the requirement (Schedule header). The immediate behavioural change required is that operators must identify affected engines and implement the required service actions in the specified timeframe rather than following usual maintenance intervals (Applicability; Compliance).\n\nCosts, compliance burden and discretion:\n\n- The directive delegates the exact technical steps to external documents (Document). That creates a compliance burden of locating and following those documents and bearing their associated costs (parts, labour, downtime). The AD itself prescribes who must comply and the deadline but not the technical details; implementing discretion is therefore held by maintenance organisations following the prescribed service bulletin or airworthiness directive text (Document).  \n\nTrade‑offs and risks (implementation/operational):\n\n- The instrument concentrates obligations on owners/operators of the small set of engine models and specified fuel control unit part numbers (Applicability). The main administrative and operational costs are: identifying affected units, taking engines or aircraft out of service for maintenance, and acquiring any replacement parts or performing repairs per the referenced documents (Document; Compliance). Because the AD requires action within a fixed short window (100 hours after 30 November 1978), operators face scheduling and potential short‑term availability costs. The directive does not itself create or describe alternative means of compliance; such details would be found in the referenced documents or in further CASA guidance (Document)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific engine configurations. It has not expanded beyond its original purpose of mandating fuel control bypass valve diaphragm maintenance."},"complexity_factors":["Single, specific technical requirement (diaphragm inspection/replacement)","Limited applicability — only 3 engine models with specific part number ranges","No nested exceptions or conditional logic","Simple compliance deadline (100 hours time-in-service after fixed date)","Only 3 reference documents cited","No defined terms section or interpretive provisions","Total length is approximately 150 words"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires specific maintenance action on certain aircraft engines.\n\n**What it does:**\n- Orders owners and operators of Pratt & Whitney Canada PT6A-38, -41, and 45A turbine engines to inspect or replace the **fuel control bypass valve diaphragm** (a rubber or synthetic membrane that helps regulate fuel flow).\n\n**Who it affects:**\n- Anyone operating aircraft with these specific engine models **AND** fitted with particular Aviation Electric fuel control units (identified by part numbers 3244723-3 through -10, 3244738-5, 3244738-6, 3244752-6 through -10, and 3244755-7 through -11).\n\n**Why it matters:**\n- Fuel control bypass valve diaphragm failures can cause engine power loss or uncommanded engine shutdown — a serious safety risk during flight. This AD mandates corrective action to prevent accidents.\n\n**What must be done:**\n- Compliance is required within **100 hours of flight time** after 30 November 1978.\n- Operators must follow the technical instructions in one of three referenced documents: a Pratt & Whitney service bulletin, an American FAA airworthiness directive, or an earlier Australian directive.\n\n**Key point:** This is a **time-critical safety mandate**. Non-compliance means the aircraft cannot legally fly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pt6a-19-fuel-control-bypass-valve-diaphragm","history":"/api/acts/ad-pt6a-19-fuel-control-bypass-valve-diaphragm/history","analysis":"/api/acts/ad-pt6a-19-fuel-control-bypass-valve-diaphragm/analysis","conflicts":"/api/acts/ad-pt6a-19-fuel-control-bypass-valve-diaphragm/conflicts","importantCases":"/api/acts/ad-pt6a-19-fuel-control-bypass-valve-diaphragm/important-cases","documents":"/api/acts/ad-pt6a-19-fuel-control-bypass-valve-diaphragm/documents"}}