{"id":"F2006B05126","name":"AD/CESSNA 185/35 - Vertical Fin Rear Spar","slug":"ad-cessna-185-35-vertical-fin-rear-spar","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":45158,"registerId":"commonwealth-F2006B05126-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 185/35 - Vertical Fin Rear Spar","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 185 Series Aeroplanes\n\n \n\nAD/CESSNA 185/35 Vertical Fin Rear Spar 12/80\n\nApplicability: Model 185 with S/Nos. 18502311 to 18504070. Requirement:  Action in accordance with Cessna SIL No. SE80-85. Compliance:               Within 100 hours time in service after 31 December 1980.\n\nBackground: Overseas, cracks have been found in the flanges and web of the spar below the lower rudder hinge.\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 narrowly targets Cessna 185 aeroplanes with serial numbers 18502311 to 18504070 and requires action per Cessna SIL No. SE80-85 within a fixed time window (Applicability; Requirement; Compliance). The source text sets out the applicability, required action and compliance timeframe; nothing in the text indicates a change from that original specification."},"complexity_factors":["Narrow technical scope — applies only to specific serial-numbered Cessna 185 aircraft (Applicability).","Prescriptive compliance timeframe (must be done within 100 hours after 31 December 1980) adds scheduling constraint (Compliance).","Procedure delegated to an external technical document (Cessna SIL No. SE80-85), requiring access to and application of manufacturer guidance (Requirement).","Technical nature — inspection/repair of a structural spar requires specialised maintenance skills and possible parts, creating operational and logistical steps.","Limited administrative discretion — mandatory action reduces interpretive complexity but increases operational obligations for operators."],"plain_english_summary":"### What this directive does mechanically\n\nThis airworthiness directive requires owners/operators of certain Cessna 185 aeroplanes to carry out the action described in Cessna Service Information Letter No. SE80-85. The directive applies only to Cessna 185 aircraft with serial numbers 18502311 through 18504070 (Applicability). The required work must be completed within 100 hours time in service after 31 December 1980 (Compliance). The technical steps to be taken are set out in the referenced Cessna SIL (Requirement).\n\n### Why it was issued (official rationale)\n\nThe directive was issued because cracks were found overseas in the flanges and web of the vertical fin rear spar below the lower rudder hinge (Background). The stated purpose is to detect and address those cracks by following the manufacturer’s service information.\n\n### Who pays and who decides\n\n- Who pays: Owners/operators of the affected aircraft will bear the direct costs of inspection and any repairs called for by Cessna SIL No. SE80-85 (Requirement; Applicability).\n- Who decides what to do: The directive mandates following the manufacturer’s Service Information Letter; the civil aviation authority (Civil Aviation Safety Authority reference at head) enforces compliance with the AD, while Cessna’s SIL provides the technical procedure (Requirement).\n\n### What behaviour changes\n\nOperators must schedule and complete the inspection/repair procedures in the SIL within the specified 100-hour window after 31 December 1980. That will produce aircraft downtime for inspection and possible repair, and may require specialised maintenance personnel or parts depending on findings (Compliance; Requirement).\n\n### Costs, incentives and trade-offs\n\n- Direct costs: inspection labour, any parts and repairs, and aircraft out-of-service time. These costs are borne by owners/operators (Applicability; Requirement). \n- Incentives: compliance reduces the risk of undetected spar cracks continuing in service; non-compliance risks regulatory enforcement and continued structural risk. The AD creates a clear compliance incentive by specifying the action and timeframe (Requirement; Compliance).\n- Opportunity costs: time and resources spent complying cannot be used for other maintenance or operations during the aircraft downtime. \n- Implementation risk and practical constraints: adherence depends on availability of the SIL, qualified maintenance personnel and any parts or repair facilities needed to implement the SIL instructions. The AD itself delegates the technical method to the manufacturer’s SIL rather than setting the technical steps in the directive (Requirement).\n\n### Compliance burden and discretion\n\n- Bureaucratic discretion: the AD is prescriptive about the required action (follow Cessna SIL) and the timeframe (within 100 hours after 31 December 1980); it leaves little discretion to operators about whether to act, though technical judgement within the scope of the SIL may be exercised by qualified maintenance personnel (Requirement; Compliance). \n- Administrative burden: owners/operators must identify whether their aircraft fall within the listed serial-number range and ensure the SIL action is recorded and completed within the specified time window (Applicability; Compliance).\n\nSource citations: Applicability; Requirement (Cessna SIL No. SE80-85); Compliance (within 100 hours time in service after 31 December 1980); Background (cracks found overseas in spar below lower rudder hinge)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific airframe defect in a limited production run of aircraft. It has not expanded beyond its original purpose of mandating inspection and repair of the vertical fin rear spar."},"complexity_factors":["Extremely short document (under 150 words)","Only 4 operative provisions: applicability, requirement, compliance deadline, and background","Single cross-reference to external document (Cessna SIL No. SE80-85) — the actual technical work is outsourced to manufacturer guidance","No defined terms section","No nested conditions or exceptions","Simple temporal trigger (100 hours time in service after fixed date)","Narrow applicability (specific model and serial number range)"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA).\n\n**What it does:** Requires owners and operators of specific Cessna 185 aircraft to inspect and repair a structural defect in the tail section (the \"vertical fin rear spar\" — essentially the backbone of the tail fin).\n\n**Who it affects:** Anyone who owns or operates a Cessna 185 aircraft with serial numbers between 18502311 and 18504070.\n\n**What must be done:** Follow the instructions in Cessna Service Information Letter (SIL) No. SE80-85. This document details how to check for and fix cracks in the metal flanges and web of the spar located below the lower rudder hinge.\n\n**When it must be done:** Within 100 hours of flying time after 31 December 1980.\n\n**Why it matters:** Cracks had been discovered overseas in this exact location on similar aircraft. If left unchecked, structural failure in the tail could lead to loss of control of the aircraft. This directive ensures Australian operators address the problem before it becomes dangerous."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-185-35-vertical-fin-rear-spar","history":"/api/acts/ad-cessna-185-35-vertical-fin-rear-spar/history","analysis":"/api/acts/ad-cessna-185-35-vertical-fin-rear-spar/analysis","conflicts":"/api/acts/ad-cessna-185-35-vertical-fin-rear-spar/conflicts","importantCases":"/api/acts/ad-cessna-185-35-vertical-fin-rear-spar/important-cases","documents":"/api/acts/ad-cessna-185-35-vertical-fin-rear-spar/documents"}}