{"id":"F2006B06135","name":"AD/PC-6/31 - Wing Strut Internal Corrosion - Inspection","slug":"ad-pc-6-31-wing-strut-internal-corrosion-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":46917,"registerId":"commonwealth-F2006B06135-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PC-6/31 - Wing Strut Internal Corrosion - Inspection","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)  Pilatus Porter PC-6 Series Aeroplanes\n\n \n\n \n\n| AD/PC-6/31 | Wing Strut Internal Corrosion - Inspection | 7/71 |\n| --- | --- | --- |\n| Applicability: | All models except Fairchild Hiller production. |  |\n| Document: | Pilatus SB No. 105. |  |\n\n\n \n\nCompliance: Within 100 hours time in service after 31 August 1971 and thereafter at intervals not exceeding 100 hours time in service.\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","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a vintage 1971 airworthiness directive that has remained unchanged in scope. It addresses exactly what it was designed to address: a specific corrosion risk in a specific aircraft type. No scope creep is evident — the document is a precise, targeted safety instrument typical of the era's aviation regulation."},"complexity_factors":["Extremely short document — only 4 substantive lines of regulatory text","Single defined term: 'time in service' (standard aviation term for flight hours)","No cross-references to other legislation beyond the parent Civil Aviation Regulations 1998","Simple binary applicability test (all models except Fairchild Hiller production)","Straightforward compliance timeline with no conditional exceptions or alternative methods of compliance","Refers to external technical document (Pilatus SB No. 105) for actual inspection procedures, keeping the legal instrument minimal"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of **Pilatus Porter PC-6 series aeroplanes** (except those made by Fairchild Hiller) to inspect the **wing struts for internal corrosion**.\n\n**What must be done:**\n- **First inspection:** Within 100 hours of flying time after 31 August 1971\n- **Repeat inspections:** Every 100 hours of flying time thereafter\n\n**Why it matters:**\nWing struts are critical structural components that hold the wings to the fuselage. Internal corrosion can weaken these parts without visible warning, potentially leading to structural failure in flight. This AD was issued after Pilatus (the manufacturer) identified this risk in their Service Bulletin No. 105.\n\n**Who it affects:**\nAnyone operating these Swiss-made utility aircraft in Australia — commonly used for skydiving, cargo, bush flying, and aerial work."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument's scope is stated explicitly in the text: it applies to all Pilatus PC-6 models except Fairchild Hiller production and mandates inspections at specified intervals. There is no language in the provided text indicating an alteration of scope from the directive's original stated applicability or inspection schedule."},"complexity_factors":["Short, narrowly targeted directive with a single technical requirement (inspection for internal corrosion). (Title/Applicability/Compliance)","Clear recurring timing requirement (every 100 hours) — simple numerically but operationally recurring. (Compliance)","Dependence on an external technical document (Pilatus SB No. 105) for inspection method and criteria — creates a dependency and potential ambiguity about procedural detail. (Document)","Narrow applicability with a specific exclusion (Fairchild Hiller production), requiring verification of production provenance. (Applicability)","No procedural or remedial detail included in the AD text itself, so compliance relies on the referenced service bulletin rather than being self-contained. (Document)"],"plain_english_summary":"What this instrument does (mechanical change)\n\n- The document is an Airworthiness Directive titled \"AD/PC-6/31 — Wing Strut Internal Corrosion - Inspection.\" It requires inspections for internal corrosion of the wing struts on Pilatus Porter PC-6 series aeroplanes. (See heading and title.)\n\nWho it applies to\n\n- It applies to all Pilatus PC-6 models except those built in the Fairchild Hiller production run. (Applicability)\n\nWhat operators must do and when\n\n- Operators must carry out the required inspection in accordance with Pilatus Service Bulletin No. 105. (Document)\n- The first inspection must be completed within 100 hours time in service after 31 August 1971, and then repeated at intervals not exceeding 100 hours time in service. (Compliance)\n\nStated purpose and how that shapes the rule\n\n- The directive is titled to address \"wing strut internal corrosion,\" which indicates its stated purpose is to detect and manage corrosion inside the wing struts. The instrument implements that purpose by mandating periodic inspection intervals and by referring operators to Pilatus SB No. 105 for the inspection procedure. (Title; Document; Compliance)\n\nCosts, incentives and compliance mechanics\n\n- Who pays: aircraft owners/operators must bear the direct costs of performing the inspections and any subsequent remedial work. (Compliance; Applicability)\n- Who decides how to comply: the directive requires compliance \"in accordance with\" Pilatus SB No. 105, so operators must follow the service bulletin for the inspection method and criteria. The AD itself does not set out a step‑by‑step procedure, but delegates the inspection technique and standards to the referenced service bulletin. (Document)\n- Behaviour changed: affected operators must schedule and perform recurring inspections every 100 hours time in service and record compliance aligned with the dates given. (Compliance)\n\nTrade‑offs, burdens and implementation points to note\n\n- Compliance burden: a recurring inspection every 100 hours imposes an ongoing maintenance obligation; frequency creates recurrent labour, downtime and parts/repair risk for operators. (Compliance)\n- Dependence on an external document: the AD references Pilatus SB No. 105 for the inspection procedure. The AD does not itself describe the inspection steps, acceptance criteria, or remedial actions, so operators must obtain and follow that service bulletin to know how to comply. (Document)\n- Scope precision: the applicability clause narrowly excludes Fairchild Hiller production aircraft, so owners/operators need to confirm their aircraft's production provenance to determine applicability. (Applicability)\n- Timing specificity: the AD fixes a firm initial deadline (within 100 hours after 31 August 1971) and identical repeat intervals, creating a clear recurring compliance window but also a potential administrative burden to track hours in service. (Compliance)\n\nImplementation risk and enforcement indicators\n\n- The directive is published within the Civil Aviation Regulations Part 39 airworthiness directive schedule, and sets clear mandatory timing for inspections; enforcement and verification will hinge on whether operators perform and document inspections per the directive and the referenced service bulletin. (Header; Compliance; Document)\n\nKey citations from the instrument\n\n- Applicability: \"All models except Fairchild Hiller production.\" (Applicability)\n- Procedure reference: \"Pilatus SB No. 105.\" (Document)\n- Timing: \"Within 100 hours time in service after 31 August 1971 and thereafter at intervals not exceeding 100 hours time in service.\" (Compliance)"},"summary":{"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This airworthiness directive has not been amended and remains in force as originally issued in 1971."},"complexity_factors":["Single, clearly defined repetitive inspection requirement","No immediate corrective action mandated by this AD (relies on the service bulletin for follow-up)","No complex compliance calculations or alternative methods of compliance"],"plain_english_summary":"This airworthiness directive (AD) applies to Pilatus Porter PC-6 series aeroplanes on the Australian civil register, except those manufactured by Fairchild Hiller. It requires routine internal inspections of the wing struts to check for corrosion. Owners and operators must carry out the inspection within 100 hours' time in service after 31 August 1971, and after that at intervals not exceeding 100 hours' time in service. The inspections must follow Pilatus Service Bulletin No. 105. There is no mention of a terminating action in this AD, so the 100-hour inspection cycle remains ongoing for the life of the affected aircraft. This is a longstanding corrosion prevention measure intended to help maintain structural integrity."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pc-6-31-wing-strut-internal-corrosion-inspection","history":"/api/acts/ad-pc-6-31-wing-strut-internal-corrosion-inspection/history","analysis":"/api/acts/ad-pc-6-31-wing-strut-internal-corrosion-inspection/analysis","conflicts":"/api/acts/ad-pc-6-31-wing-strut-internal-corrosion-inspection/conflicts","importantCases":"/api/acts/ad-pc-6-31-wing-strut-internal-corrosion-inspection/important-cases","documents":"/api/acts/ad-pc-6-31-wing-strut-internal-corrosion-inspection/documents"}}