{"id":"F2006B08304","name":"AD/CESSNA 400/17 - Engine Exhaust System Manifold Tube Assembly - Life Limitation","slug":"ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115698,"registerId":"commonwealth-F2006B08304-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 400/17 - Engine Exhaust System Manifold Tube Assembly - Life Limitation","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)  Cessna 400 Series Aeroplanes\n\n \n\nAD/CESSNA 400/17 Engine Exhaust System Manifold Tube\n\nAssembly - Life Limitation\n\n\n4/70\n\n \n\nApplicability: All 401 and 402 series.\n\n \n\nRequirement: Retire from service exhaust manifold tube assemblies P/Nos. 0850712-5; 0850712-6; 0850712-32 and 0850712-33.\n\n \n\nCompliance: 1. For assemblies with more than 1700 hours time in service at 29 May 1971 - within 100 hours time in service.\n\n \n\n2. For assemblies with less than 1700 hours time in service - before achieving 1800 hours time in service.\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, as presented, sets a life-limitation for specific exhaust manifold tube assemblies and applies to all Cessna 401 and 402 series. The text contains no indication that the applicability or required retirements alter or expand beyond what is stated (Applicability; Requirement; Compliance)."},"complexity_factors":["Narrow applicability (only Cessna 401 and 402 series) as stated in the Applicability section","Specific part numbers listed (0850712-5; 0850712-6; 0850712-32; 0850712-33) reduce ambiguity (Requirement)","Simple, discrete compliance rules tied to hours-in-service with two clear thresholds and a fixed reference date (Compliance 1 and 2)","No technical procedures, exception mechanisms, or multiple compliance options included in the text (Requirement; Compliance)","Implementation depends on accurate maintenance records for hours-in-service, creating a practical compliance dependency absent from the directive text (Compliance)"],"plain_english_summary":"What this directive does (mechanically)\n\n- Applicability: applies to all Cessna 401 and 402 series aeroplanes. (Applicability)\n- Requirement: operators must remove (retire from service) exhaust manifold tube assemblies with part numbers 0850712-5, 0850712-6, 0850712-32 and 0850712-33. (Requirement)\n- Compliance timing: there are two deadlines based on the assemblies' recorded hours in service: (Compliance)\n  - If an affected assembly had more than 1,700 hours in service as of 29 May 1971, it must be retired within 100 hours time in service after that date. (Compliance 1)\n  - If an affected assembly had less than 1,700 hours in service as of that date, it must be retired before it reaches 1,800 hours time in service. (Compliance 2)\n\nWho decides and who pays\n\n- The Civil Aviation Safety Authority issued this item as an Airworthiness Directive (header: \"Civil Aviation Regulations 1998, PART 39 ... SCHEDULE OF AIRWORTHINESS DIRECTIVES\"). Operators of the specified aeroplanes must follow the directive. (header)\n- Financially, the explicit action required is removal of parts from service; the directive does not state who supplies replacements or how costs are funded. Reasonably, the aircraft operator will bear the direct costs and operational consequences of removing and replacing the retired assemblies because they are responsible for maintaining airworthiness. (Requirement)\n\nHow the rule changes behaviour and the immediate mechanics\n\n- Operators must check maintenance records to determine hours in service for each listed part number and then schedule retirement and replacement work to meet the deadlines in (Compliance 1) and (Compliance 2).\n- The rule removes the option to continue operating an affected manifold assembly beyond the specified hours: once the applicable threshold is reached (or the short-term deadline after 29 May 1971 for already-aged parts), the assembly must be retired. (Requirement; Compliance)\n\nCosts, incentives, and trade-offs (source-grounded)\n\n- Direct cost: the directive creates a requirement to remove specified assemblies from service. The source does not quantify replacement part prices, labour, or downtime; those are borne by the party that furnishes and maintains the aircraft. (Requirement)\n- Administrative/compliance burden: operators must determine and record each assembly's time in service and ensure retirement occurs within the specified hours; this imposes record-keeping and scheduling obligations. (Compliance)\n- Incentives: because retirement is tied to hours in service, operators have an incentive to track component hours precisely and to schedule replacements before reaching mandated limits. The directive does not create a choice about whether to comply: retirement is mandated by the compliance rules. (Compliance)\n- Market effects: the directive concentrates demand for replacement manifold assemblies among operators of Cessna 401/402 aircraft that use these part numbers. The source does not describe supply arrangements or approvals for replacement parts. (Requirement)\n\nImplementation risk and discretion\n\n- The directive gives little operational discretion to operators about whether and when to retire the listed assemblies beyond the hour thresholds; the timing rules are fixed. (Compliance)\n- Implementation risk centers on accurate records of time in service and timely scheduling of replacement work. The directive does not specify enforcement mechanisms or penalties in this text. (Compliance)\n\nPurpose claims and testing them against costs and trade-offs\n\n- The document functions as an Airworthiness Directive that imposes a life limit on specific exhaust manifold tube assemblies by part number. That is its explicit operational effect: mandatory retirement by specified hours. (Requirement; Compliance)\n- The directive does not provide cost estimates, replacement procedures, or details about certification/approved replacements in this text. Therefore, anyone evaluating the full economic effect must obtain or estimate replacement costs, labour time, and availability of parts outside this document. (Requirement)\n\nBottom line\n\n- This is a narrowly targeted Airworthiness Directive requiring operators of Cessna 401/402 aeroplanes to retire four specified exhaust manifold tube assembly part numbers by fixed hours-in-service thresholds. The directive shifts the immediate operational and financial burden of retirement and replacement to the aircraft operators and requires them to track parts' hours to ensure compliance. (Applicability; Requirement; Compliance)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a vintage 1971 airworthiness directive with a tightly focused, single-purpose scope: mandating retirement of specific exhaust components on specific aircraft models. There is no evidence of scope creep — the directive does exactly what its title suggests and nothing more."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 4 specific part numbers identified","Simple binary compliance condition based on hours in service","No defined terms section","No cross-references to other legislation","Single applicability criterion (aircraft series)","Straightforward retirement requirement with no exceptions or exemptions mentioned"],"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 specific **Cessna 401 and 402 series aircraft** (twin-engine propeller planes commonly used for small charter flights, freight, and aerial work).\n\n**What it does:**\nThe directive forces owners and operators to permanently remove and replace certain **exhaust manifold tube assemblies** — the metal piping that carries hot exhaust gases away from the engine. The specific part numbers affected are: 0850712-5, 0850712-6, 0850712-32, and 0850712-33.\n\n**Why it matters:**\nExhaust manifolds operate under extreme heat and pressure. Over time, they can crack or fail, potentially leading to:\n- **Carbon monoxide leaks** into the cabin (deadly for occupants)\n- **Engine fires**\n- **Loss of engine power**\n\n**The deadlines:**\n- If your aircraft's exhaust tubes already had **more than 1,700 flight hours** by 29 May 1971: you had **100 hours** to replace them.\n- If they had **fewer than 1,700 hours**: you must replace them **before they hit 1,800 hours total**.\n\nThis is a **life limit** rule — meaning these parts cannot be repaired or overhauled; they must be scrapped once they reach the hour threshold."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation","history":"/api/acts/ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation/history","analysis":"/api/acts/ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation/analysis","conflicts":"/api/acts/ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation/conflicts","importantCases":"/api/acts/ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation/important-cases","documents":"/api/acts/ad-cessna-400-17-engine-exhaust-system-manifold-tube-assembly-life-limitation/documents"}}