{"id":"F2006B04823","name":"AD/CA21/4 - Tail Wheel Springs","slug":"ad-ca21-4-tail-wheel-springs","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44624,"registerId":"commonwealth-F2006B04823-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CA21/4 - Tail Wheel Springs","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/CA21/4 Tail Wheel Springs 1/96\n\nApplicability: CA21 and CA22A aircraft.\n\nRequirement: Inspect the tail wheel springs for deformation in accordance with Skyfox Aviation Service Bulletin No.8.\n\nCompliance: Before the first flight of each day after 4 January 1996.\n\nThis Directive must be entered onto the Maintenance Release as maintenance required. The inspection may be performed by the pilot in command, in which case a certification is to be made by entering AD/CA21/4 against the Daily Inspection certification on the Maintenance Release. A copy of this Directive and of the Requirement Document must be carried in the aircraft.\n\nBackground: Several instances have been reported of fractured tail wheel springs. This AD requires the tail wheel springs to be inspected on a daily basis by the pilot, with replacement of the springs if deformation is discovered.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical failure mode in specific aircraft models. It has not expanded beyond its original purpose of mandating daily tail wheel spring inspections."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined terms implicitly referenced (Maintenance Release, Service Bulletin)","Single, unambiguous compliance requirement with clear deadline","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","No conditional logic or exceptions — applies uniformly to all CA21/CA22A aircraft","Straightforward procedural steps (inspect, record, carry documents)"],"plain_english_summary":"This is a **safety instruction** (called an \"Airworthiness Directive\") for owners and pilots of specific light aircraft models: the **Skyfox Aviation CA21 and CA22A** series.\n\n**What it requires:**\n- **Daily inspection of tail wheel springs** — Before the first flight each day, pilots must check the springs on the tail wheel for any bending, warping, or damage (\"deformation\").\n- **How to do it:** Follow the instructions in \"Skyfox Aviation Service Bulletin No.8\" (a technical notice from the manufacturer).\n- **Record-keeping:** This inspection must be written down on the aircraft's **Maintenance Release** (the official document showing the plane is safe to fly). If the pilot does the check themselves, they write \"AD/CA21/4\" next to their daily inspection entry.\n- **Paperwork to carry:** The aircraft must have a copy of this Directive and the Service Bulletin on board.\n\n**Why it exists:**\nSeveral tail wheel springs have **broken** on these aircraft models. Because a failed tail wheel could affect ground handling and safety, the aviation regulator (CASA) mandated daily checks to catch problems early and replace damaged springs before they fail.\n\n**Who it affects:**\n- Pilots flying CA21 or CA22A aircraft\n- Aircraft owners and maintenance engineers\n- Anyone responsible for ensuring these planes are airworthy\n\n**Key point:** This is an urgent safety measure — the daily check can be done by the pilot (not just a mechanic), but it must be documented properly."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text presents a single, focused airworthiness directive setting a daily inspection and related record-keeping and document-carrying obligations for CA21 and CA22A aircraft. The Directive states its rationale (reported fractured springs) and prescribes inspection and replacement where deformation is discovered. There is no material in the instrument suggesting the scope has been broadened or narrowed relative to the Directive’s own stated effect; therefore there is no evidence in the source that the scope has changed from its original stated intent."},"complexity_factors":["Narrow applicability (only CA21 and CA22A) reduces scope complexity (Applicability).","Simple, high-frequency compliance timing: daily pre-flight inspections (Compliance).","Reference to an external Requirement Document (Skyfox Service Bulletin No.8) adds minor complexity because inspection steps are not reproduced in the Directive (Requirement).","Record-keeping and certification obligations (Maintenance Release entry; pilot certification) add administrative burden.","Ambiguity about who must perform replacement work when deformation is found introduces implementation risk and modest legal uncertainty (Background; Maintenance record and certification).","Requirement to carry copies of the Directive and Requirement Document on board creates a discrete logistical obligation."],"plain_english_summary":"This Directive applies to Skyfox CA21 and CA22A aeroplanes and mandates a daily, pre‑flight inspection of tail‑wheel springs per Skyfox Service Bulletin No.8, effective 4 Jan 1996. The inspection must be recorded on the Maintenance Release (entry “AD/CA21/4”), copies of the Directive and Service Bulletin carried on board, and any deformed spring must be replaced before further flight.\n\nOwners/operators and pilots bear the time, administrative and repair costs; the pilot in command may perform and certify the inspection."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ca21-4-tail-wheel-springs","history":"/api/acts/ad-ca21-4-tail-wheel-springs/history","analysis":"/api/acts/ad-ca21-4-tail-wheel-springs/analysis","conflicts":"/api/acts/ad-ca21-4-tail-wheel-springs/conflicts","importantCases":"/api/acts/ad-ca21-4-tail-wheel-springs/important-cases","documents":"/api/acts/ad-ca21-4-tail-wheel-springs/documents"}}