{"id":"F2006B04817","name":"AD/CA21/1 - Air Filter Box Rear Mounting Bracket","slug":"ad-ca21-1-air-filter-box-rear-mounting-bracket","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44615,"registerId":"commonwealth-F2006B04817-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CA21/1 - Air Filter Box Rear Mounting Bracket","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nSkyfox Aviation (Calair/Hedaro) CA21 and CA22A Series Aeroplanes\n\nAD/CA21/1 Air Filter Box Rear Mounting Bracket 1/96\n\nApplicability: CA 22A aircraft.\n\nRequirement: 1. Visually inspect the rivets securing the air filter box rear mounting bracket. If the rivets are loose, broken or missing, replace with MS20470AD4-4 solid rivets.\n\n2. Remove the air filter box from the aircraft and replace the pop rivets securing the rear mounting bracket with MS20470AD4-4 or MS20470AD5-4 solid rivets.\n\nNote: Skyfox Aviation Service Bulletin 9 Iss.2 refers.\n\nCompliance: For Requirement 1, before next flight after 4 January 1996.\n\nFor Requirement 2, at the next inspection for issue of a Maintenance Release or within 100 hours time in service, whichever occurs first.\n\nBackground: The pop rivets originally fitted could work loose and be ingested into the engine.\n\nThis AD requires fitment of solid rivets.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The directive changes maintenance requirements for CA22A aircraft by mandating inspection and replacement of pop rivets with specified solid rivets for the air filter box rear mounting bracket. Mechanically, it replaces the originally fitted pop rivets with MS20470AD4-4 or MS20470AD5-4 solid rivets and imposes a two-step compliance schedule (Requirement 1; Requirement 2; Background)."},"complexity_factors":["Narrow applicability — applies only to Skyfox CA22A aircraft (Applicability)","Two-step compliance schedule with different deadlines (Requirement 1; Requirement 2; Compliance)","Specific hardware mandates — exact rivet part numbers prescribed (MS20470AD4-4, MS20470AD5-4) (Requirement 1; Requirement 2)","Physical work required (removal of air filter box) increases labour and downtime (Requirement 2)","Reference to manufacturer service bulletin for further detail (Note)","Regulatory enforcement and record-keeping obligations for operators/maintainers (Compliance)"],"plain_english_summary":"Owners/operators and maintenance organisations of Skyfox CA22A aeroplanes must inspect the rear mounting rivets of the air filter box for loose, broken or missing fasteners and replace any defective ones with MS20470AD4-4 solid rivets before the next flight. They must then remove the air filter box and replace all pop rivets with MS20470AD4-4 or MS20470AD5-4 solid rivets at the next Maintenance Release or within 100 flight hours. Costs and work fall to operators."},"summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"Applies to CA 22A aircraft as originally issued."},"complexity_factors":["aviation maintenance directives","specific compliance deadlines","technical component specifications"],"plain_english_summary":"**AD/CA21/1 - Air Filter Box Rear Mounting Bracket**\n\nThis is an Airworthiness Directive issued by the Civil Aviation Safety Authority (CASA) in Australia. It applies to CA 22A aeroplanes in the Skyfox Aviation CA21 and CA22A series.\n\nThe directive addresses a safety issue with the air filter box rear mounting bracket. The original pop rivets could work loose and be ingested by the engine, which might cause damage.\n\nIt requires the following actions:\n\n- Visually inspect the rivets before the next flight after 4 January 1996. Replace any that are loose, broken or missing with MS20470AD4-4 solid rivets.\n\n- Remove the air filter box and replace the pop rivets with MS20470AD4-4 or MS20470AD5-4 solid rivets at the next Maintenance Release inspection or within 100 hours time in service, whichever comes first.\n\nThis affects owners, operators and maintainers of these specific aircraft. The practical point is to ensure the bracket is securely fixed using solid rivets instead of pop rivets to prevent foreign object damage to the engine.\n\nReference Skyfox Aviation Service Bulletin 9 Issue 2 for details on the procedure.\n\nThis is a narrow instrument in the form of an airworthiness directive that sets mandatory compliance requirements for affected aeroplanes."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive (AD) — a targeted safety notice for a specific mechanical defect on a specific aircraft model. It has not expanded beyond its original purpose of addressing the rivet failure risk."},"complexity_factors":["Single, specific aircraft type (CA 22A) with narrow applicability","Only two requirements with clear, sequential compliance deadlines","Minimal defined terms (only references specific rivet part numbers and one service bulletin)","No cross-references to other legislation or complex conditional logic","Straightforward background explanation with single causal chain (pop rivets → loosening → engine ingestion)","Total length under 200 words"],"plain_english_summary":"This is a **safety directive for a specific aircraft part** on certain light aeroplanes.\n\n**What it does:**\nThis document orders owners and operators of **CA 22A aircraft** (a type of light sport/training plane made by Skyfox Aviation) to fix a potentially dangerous problem with the **air filter box rear mounting bracket**.\n\n**The problem:**\nThe original \"pop rivets\" (a type of fastener) used to attach this bracket can work loose over time. If they break off, they can get sucked into the engine and cause serious damage or engine failure.\n\n**What must be done:**\n- **Immediate check:** Before flying after 4 January 1996, visually inspect the rivets. If any are loose, broken or missing, replace them with specific solid rivets (MS20470AD4-4).\n- **Full replacement:** At the next scheduled maintenance check or within 100 flight hours (whichever comes first), remove the entire air filter box and replace all the pop rivets with solid rivets.\n\n**Who it affects:**\nOwners, operators and maintenance engineers of CA 22A Skyfox aircraft.\n\n**Why it matters:**\nLoose rivets can destroy an engine mid-flight. This directive prevents that by mandating stronger, more reliable solid rivets."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ca21-1-air-filter-box-rear-mounting-bracket","history":"/api/acts/ad-ca21-1-air-filter-box-rear-mounting-bracket/history","analysis":"/api/acts/ad-ca21-1-air-filter-box-rear-mounting-bracket/analysis","conflicts":"/api/acts/ad-ca21-1-air-filter-box-rear-mounting-bracket/conflicts","importantCases":"/api/acts/ad-ca21-1-air-filter-box-rear-mounting-bracket/important-cases","documents":"/api/acts/ad-ca21-1-air-filter-box-rear-mounting-bracket/documents"}}