{"id":"F2006B08314","name":"AD/CESSNA 400/29 - Engine Tachometer - Incorporation of Warning Arc and Placard","slug":"ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115721,"registerId":"commonwealth-F2006B08314-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 400/29 - Engine Tachometer - Incorporation of Warning Arc and Placard","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 400/29 Engine Tachometer - Incorporation\n\nof Warning Arc and Placard\n\nApplicability: Model 411 and 421 series with S/Nos. prior to 421B0148. Document:  Cessna SL ME71-16 Supplement No. 2.\n\nCompliance: Within 50 hours time in service after 6 March 1972.\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\n\n2/72\n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"There is no indication in the text supplied that the Directive changes the scope of which aircraft are covered beyond the stated applicability. The instrument prescribes an additional marking/modification for Model 411 and 421 aeroplanes with serial numbers prior to 421B0148 and points to the manufacturer's supplement for the method. The Directive does not, in this text, expand applicability to other models, change certification categories, or add unrelated regulatory obligations. (Applicability; Document; Compliance)"},"complexity_factors":["Narrow technical requirement: single physical change (warning arc and placard) identified in the title.","Clear, narrow applicability: specific models and serial-number cutoff reduce scope complexity. (Applicability)","Simple compliance timeline: single deadline measured in hours time-in-service after a calendar date. (Compliance)","Dependency on external document for procedure: detailed steps and parts are not in the Directive but in the referenced Cessna supplement, introducing a secondary source to consult. (Document)","Administrative calculation: ‘‘50 hours time in service’’ requires operators to track and schedule maintenance, which can introduce operational complexity.","Historic date reference (6 March 1972) may complicate record verification for older aircraft."],"plain_english_summary":"The Civil Aviation Safety Authority requires owners/operators of Cessna Model 411 and 421 aeroplanes (serials earlier than 421B0148) to fit a warning arc and placard to the engine tachometer.  \n\nThe modification must follow Cessna SL ME71‑16 Supplement No. 2 and be completed within 50 hours time in service after 6 March 1972. Owners/operators pay for parts, labour and downtime; technical details and implementation are governed by the referenced manufacturer supplement."},"kimi_summary":{"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on tachometer modifications for a limited aircraft population. It represents the original and sole intent of the instrument — to mandate a specific safety modification — with no evidence of scope creep or expansion beyond this narrow technical requirement."},"complexity_factors":["Extremely short document (approximately 100 words of substantive content)","No defined terms section","No cross-references to other legislation or regulations beyond the enabling authority (Civil Aviation Regulations 1998, Part 39)","Simple conditional logic: single applicability criterion (specific model and serial number range)","Single compliance requirement with straightforward deadline calculation","No exceptions, exemptions, or nested conditions","References only one external technical document (Cessna Service Letter ME71-16 Supplement No. 2)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety fix ordered by Australia's aviation regulator (CASA) for specific aircraft.\n\n**What it does:**\nRequires owners and operators of certain **Cessna 400 series aeroplanes** (specifically Model 411 and early Model 421 aircraft with serial numbers before 421B0148) to modify their **engine tachometers** (the gauge that shows engine speed/revolutions per minute).\n\nThe modification involves:\n- Adding a **warning arc** (a coloured zone on the dial indicating dangerous operating ranges)\n- Installing a **placard** (a warning label) on the instrument\n\n**Who it affects:**\n- Owners and operators of the specified Cessna aircraft models\n- Maintenance organisations servicing these aircraft\n\n**Why it matters:**\nWithout this modification, pilots might not have clear visual warnings about engine speeds that could cause damage or failure. The directive ensures critical safety information is visible during flight, reducing the risk of engine damage and potential accidents.\n\n**Compliance deadline:**\nThe work had to be completed within **50 hours of flight time** after 6 March 1972."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard","history":"/api/acts/ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard/history","analysis":"/api/acts/ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard/analysis","conflicts":"/api/acts/ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard/conflicts","importantCases":"/api/acts/ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard/important-cases","documents":"/api/acts/ad-cessna-400-29-engine-tachometer-incorporation-of-warning-arc-and-placard/documents"}}