{"id":"F2006B04824","name":"AD/CA21/5 - Wing Strut Carry Through Structure","slug":"ad-ca21-5-wing-strut-carry-through-structure","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44625,"registerId":"commonwealth-F2006B04824-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CA21/5 - Wing Strut Carry Through Structure","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/CA21/5 Wing Strut Carry Through Structure 2/96\n\nApplicability: All CA21 and CA22A aircraft, including CALAIR CA21 aircraft.\n\nNote: For CA22A/25, CA25 and CA25N models see AD/CA25/2.\n\nRequirement: 1. Remove the 3/32\" blind type sealing rivet from the wing strut carry through tube oiling hole. Check that corrosion preventive fluid is present in the tube, using a small diameter wire as a dipstick. Refill the tube with up to 100 ml of Shell ENSIS fluid, or similar corrosion preventive fluid. Refit a 3/32\" blind type sealing rivet in the oiling hole.\n\nNote: Skyfox Aviation Service Bulletin No 10 also refers to oiling of the wing strut carry through tube. Addition of a colour contrast dye to the preventive fluid may assist inspection with Requirement 2. Check before use to ensure the dye has no adverse effects on either the corrosion inhibitor properties of the fluid or on the tube material.\n\n2. Visually inspect the wing strut carry through tube and adjacent fabric in the area shown in the figure below. Inspect for cracks, evidence of fluid seepage from the tube or for any corrosion damage. The cause of any fluid seepage is to be determined and rectified before returning the aircraft to service. Repair cracks and corrosion before returning the aircraft to service.\n\n3.a. Gain access to the wing lift strut mount cross tube structure inboard of the lower lift strut attachments. Remove the paint from the wing lift strut mount cross tube, using a non abrasive method, in the area shown in the diagram below.\n\nNote: Gaining access to the wing lift strut mount cross tube for inspection in accordance with Requirement 3 may require cutting a hole in the fabric covering. A hole 50 mm in diameter should be sufficient.\n\n3.b. Inspect, using the dye penetrant method as per CAO 108.10, the wing lift strut mount cross tube inboard of the strut attachment lugs for signs of cracks. Inspect both port and starboard fittings. Pay particular attention to the inboard end of the strut attachment lug weld as indicated in the diagram below. Repair cracks found before further flight. Repaint the cross tube before returning aircraft to service.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.002.png)  \n\nCompliance: 1. Action in accordance with Requirement 1 before 500 hours aircraft time in service or 50 hours time in service after 1 February 1996, whichever occurs later. Re- inspect at intervals not to exceed 100 hours time in service.\n\n    2. Inspect in accordance with Requirement 2 before 500 hours aircraft time in service or 50 hours time in service after 1 February 1996, whichever occurs later. Re- inspect at intervals not to exceed 100 hours time in service.\n\n    3. Inspect in accordance with Requirement 3 before further flight if no fluid is found in the tube as a result of Requirement 1.\n\nBackground: A CA22 Skyfox aircraft registered to the Australian Ultralight Federation experienced on inflight failure of the wing lift strut mount cross tube. The aircraft had previously been involved a landing accident and repaired. Failure occurred at a time well below the retirement life. The area of the failure is subject to a combination of tensile and bending stress.\n\nA once off dye penetrant inspection of the wing lift strut mount cross tube was required by the issue of Directive AD/CA25/2. A laboratory examination of the failed tube has indicated that failure had resulted from fatigue initiating at the toe of the weld. The examination indicated that there was no eivdence of crack initiation from the earlier accident.\n\nThis Directive, specifically for the CA21 and CA22A aircraft, sets a threshold for inspection and requires repeat visual inspections to be made. The dye penetrant inspection is conditional on the findings of the visual inspections.\n\nThis Directive does not remove the life limitation of the wing lift strut mount cross tube in AD/CA21/6.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Moves from a prior once‑off dye‑penetrant inspection (AD/CA25/2 referenced in Background) to a regime that sets an inspection threshold, mandates topping up of corrosion inhibitor and repeat visual inspections at fixed intervals, and makes dye‑penetrant testing conditional; applies specifically to all CA21 and CA22A aircraft while preserving the existing life‑limit in AD/CA21/6."},"complexity_factors":["Multiple inspection methods required: visual inspections and conditional dye‑penetrant testing per CAO 108.10.","Conditional workflow: dye‑penetrant inspection only if fluid is absent (Requirement 3 tied to Requirement 1).","Access complications: inspection of the cross tube may require cutting a ~50 mm hole in fabric covering (Requirement 3 note).","Material and procedure specifications: remove a 3/32\" blind rivet, use a small wire dipstick, refill up to 100 ml of Shell ENSIS or similar, and refit a rivet (Requirement 1).","Surface treatment steps: remove paint by non‑abrasive methods, then repaint after inspection (Requirement 3a/b).","Strict compliance timing: initial action before 500 hours or 50 hours after 1 Feb 1996 (whichever later) and repeat inspections at intervals not to exceed 100 hours (Compliance).","Operational constraint: repairs and rectification of seepage causes are mandatory before further flight, creating potential grounding and maintenance costs (Requirements 2 and 3b).","Interactions with other directives: references AD/CA25/2 for related models and explicitly does not remove the life limitation in AD/CA21/6 (Background)."],"plain_english_summary":"Requires owners/operators of Skyfox CA21 and CA22A aeroplanes to open the wing strut carry‑through tube, check and refill it with a corrosion‑preventive fluid (refit the sealing rivet), and carry out recurring visual inspections for cracks, corrosion or fluid seepage; a dye‑penetrant inspection is required if no fluid is found. Repairs and cause‑finding for any seepage must be completed before the aircraft returns to service. This shifts specific inspection, access (including cutting fabric) and repair obligations onto operators under set time thresholds."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific structural failure mode in a specific aircraft type. The scope remains precisely focused on the wing strut carry-through structure of CA21/CA22A aircraft, consistent with the original intent of preventing catastrophic structural failure. The background section confirms this originated from a specific incident investigation and maintains the original safety purpose."},"complexity_factors":["Multiple conditional triggers: inspections are required based on flight hours OR calendar date, whichever is later, with different thresholds for initial vs. repeat inspections","Nested conditional logic: Requirement 3 (dye penetrant inspection) is only triggered if Requirement 1 finds no fluid","Cross-reference to another directive: notes relationship to AD/CA25/2 for related aircraft models and AD/CA21/6 for life limitations","Technical aviation terminology requiring specialized knowledge: \"dye penetrant method,\" \"blind type sealing rivet,\" \"time in service,\" \"retirement life\"","Specific material and dimensional requirements: 3/32\" rivet size, 100 ml fluid volume, Shell ENSIS fluid specification, 50 mm hole diameter","Reference to external technical standards: CAO 108.10 (Civil Aviation Order)","Multiple inspection methods required: visual, dipstick/wire check, dye penetrant, non-abrasive paint removal"],"plain_english_summary":"This Airworthiness Directive requires owners, operators and maintenance engineers of Skyfox CA21/CA22A (including Calair-marketed) to inspect and maintain the wing strut mounting/tube after an in‑flight failure. It mandates checking for corrosion‑preventing fluid, visual inspection for cracks/corrosion, and, if dry, a dye‑penetrant crack test.\n\nInspections are initial (by 500 flight hours or within 50 hours after 1 Feb 1996) and repeated every 100 flight hours to prevent wing collapse from undetected tube failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ca21-5-wing-strut-carry-through-structure","history":"/api/acts/ad-ca21-5-wing-strut-carry-through-structure/history","analysis":"/api/acts/ad-ca21-5-wing-strut-carry-through-structure/analysis","conflicts":"/api/acts/ad-ca21-5-wing-strut-carry-through-structure/conflicts","importantCases":"/api/acts/ad-ca21-5-wing-strut-carry-through-structure/important-cases","documents":"/api/acts/ad-ca21-5-wing-strut-carry-through-structure/documents"}}