{"id":"F2006B06759","name":"AD/SA-TP/11 - Ice Guard on CSU Swivel Assembly","slug":"ad-sa-tp-11-ice-guard-on-csu-swivel-assembly","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114590,"registerId":"commonwealth-F2006B06759-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SA-TP/11 - Ice Guard on CSU Swivel Assembly","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)  British Aerospace (Scottish Aviation) Twin Pioneer Series Aeroplanes\n\n \n\nAD/SA-TP/11 Ice Guard on CSU Swivel Assembly NK\n\nApplicability: All Series 1 and 3.\n\n \n\nDocument: Scottish Aviation Mod. No. C680. Compliance: Forthwith.\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":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The source text contains only this AD and does not indicate any change in scope from an earlier instrument or differing original intent. The AD as written applies to all Series 1 and 3 Twin Pioneer aeroplanes and requires compliance with Scottish Aviation Mod. No. C680 forthwith; no indication in the text suggests the applicability or requirements have been widened or narrowed relative to an earlier statement."},"complexity_factors":["Short, single-action directive: mandates one modification (install ice guard) with immediate compliance.","References external technical document (Scottish Aviation Mod. No. C680) — implementers must obtain and interpret that document to perform the work.","No detail in the AD text about acceptable alternatives, exemptions, or verification procedures, increasing implementation uncertainty for operators.","Applies to a narrowly defined fleet (Series 1 and 3 Twin Pioneer), limiting scope but concentrating compliance requirements on a small group.","Immediate compliance timing (\"Forthwith\") can add logistical complexity (sourcing parts, scheduling certified maintenance) despite the AD’s brevity."],"plain_english_summary":"What this instrument does\n\n- The Civil Aviation Safety Authority (under the Civil Aviation Regulations 1998, Part 39) issues an Airworthiness Directive titled “AD/SA-TP/11 Ice Guard on CSU Swivel Assembly.” The directive requires installation of an \"ice guard\" on the CSU swivel assembly of affected aeroplanes (as identified in the AD header).\n\nWho it affects\n\n- The AD applies to all British Aerospace (Scottish Aviation) Twin Pioneer aeroplanes of Series 1 and Series 3 (\"Applicability: All Series 1 and 3\").\n\nWhat it requires and how it works mechanically\n\n- The AD mandates that the modification described in Scottish Aviation Mod. No. C680 be carried out. The AD sets the compliance timing as \"Forthwith,\" meaning operators must do the modification without delay.\n\nStated purpose and what the instrument actually establishes\n\n- The AD’s title and instruction (\"Ice Guard on CSU Swivel Assembly\"; \"Document: Scottish Aviation Mod. No. C680\") indicate the action is to fit an ice-protection/ice-prevention guard to the CSU swivel assembly. The AD itself prescribes the mandatory action (install the modification described in Mod. No. C680) but does not include technical data, cost estimates, or an explicit statement of measured safety benefits in the text provided.\n\nWho pays, who decides, and what changes in behaviour\n\n- Owners/operators of affected Twin Pioneer Series 1 and 3 aeroplanes must have the modification installed; they therefore bear the cost of parts, labour, downtime and any associated paperwork (inferred from the requirement to comply with the Mod. No. C680). The Civil Aviation Safety Authority issues the directive and sets the compliance requirement (as shown by the AD header referencing the Civil Aviation Regulations and the Schedule of Airworthiness Directives).\n\nCompliance, implementation risk and administrative discretion\n\n- Compliance is mandatory and immediate (\"Forthwith\"). The AD references an external technical document (Scottish Aviation Mod. No. C680) for the required work; operators must obtain and follow that modification document to meet the AD. The AD text provided does not specify acceptable alternative means of compliance, exemptions, or how CASA will verify compliance; those matters are left to the implementing processes or the referenced modification document. Practical implementation considerations that follow mechanically from the AD’s wording include obtaining parts and a qualified maintenance facility, scheduling aircraft downtime, and completing any record-keeping required by airworthiness regulations.\n\nTrade-offs, incentives and distribution of costs and benefits (source-linked)\n\n- The AD creates a concentrated compliance obligation on a small, identifiable group (owners/operators of Series 1 and 3 Twin Pioneers) because it applies to those specific airframes (\"Applicability: All Series 1 and 3\"). The immediate compliance timing (\"Forthwith\") raises operational and logistical costs for those operators. The AD does not, in the text supplied, quantify the safety benefit, cost, or possible alternatives; it simply requires the modification described in Mod. No. C680. Consequently, assessing net benefits, substitution effects, or the scope for alternative mitigations depends on the technical content of Scottish Aviation Mod. No. C680 and any supporting safety data not included in this AD text.\n\nSource citations\n\n- Issuing authority and legal basis: header (COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY, SCHEDULE OF AIRWORTHINESS DIRECTIVES).\n- Applicability: \"Applicability: All Series 1 and 3.\"\n- Required action / technical reference: \"Document: Scottish Aviation Mod. No. C680.\"\n- Timing: \"Compliance: Forthwith.\""},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive focused specifically on ice protection for a particular aircraft component. It has not expanded beyond its original technical scope."},"complexity_factors":["Extremely short document (under 150 words)","Only 2 defined applicability criteria (Series 1 and 3)","Single compliance requirement with no conditional exceptions","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","No nested definitions or interpretive provisions","Straightforward command structure: applicability + document reference + compliance deadline"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires immediate action on specific British aeroplanes.\n\n**What it does:**\n- Orders the installation of an \"ice guard\" (a protective shield) on the Constant Speed Unit (CSU) swivel assembly of certain British Aerospace (Scottish Aviation) Twin Pioneer aircraft\n- The CSU is a component that helps maintain consistent propeller speed; the swivel assembly allows movement. Ice buildup here could cause mechanical failure\n\n**Who it affects:**\n- Owners and operators of **all Series 1 and Series 3** British Aerospace (Scottish Aviation) Twin Pioneer aeroplanes\n- These are vintage twin-engine transport aircraft originally built in Scotland\n\n**Why it matters:**\n- **Safety critical:** Ice accumulation on flight control or propeller components can cause loss of control or engine failure\n- **Immediate compliance required:** The directive uses \"Forthwith\" — meaning operators must do this right away, not at the next scheduled maintenance\n- **Mandatory:** Unlike service bulletins (which are recommendations), Airworthiness Directives are legally enforceable. Non-compliance grounds the aircraft\n\n**The fix:**\n- Follow **Scottish Aviation Modification No. C680** — a manufacturer-approved engineering change that adds the ice guard"}},"importantCases":[],"_links":{"self":"/api/acts/ad-sa-tp-11-ice-guard-on-csu-swivel-assembly","history":"/api/acts/ad-sa-tp-11-ice-guard-on-csu-swivel-assembly/history","analysis":"/api/acts/ad-sa-tp-11-ice-guard-on-csu-swivel-assembly/analysis","conflicts":"/api/acts/ad-sa-tp-11-ice-guard-on-csu-swivel-assembly/conflicts","importantCases":"/api/acts/ad-sa-tp-11-ice-guard-on-csu-swivel-assembly/important-cases","documents":"/api/acts/ad-sa-tp-11-ice-guard-on-csu-swivel-assembly/documents"}}