{"id":"F2006B06769","name":"AD/SA-TP/20 - Drive Blocks on Dunlop Main Wheel","slug":"ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114605,"registerId":"commonwealth-F2006B06769-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SA-TP/20 - Drive Blocks on Dunlop Main Wheel","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/20 Drive Blocks on Dunlop Main Wheel NK\n\nApplicability: All models fitted with main wheels P/N AH50742, Issue 1 to 5. Document:  Scottish Aviation TNS No. 31, Issue 3.\n\nCompliance: 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\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The text of the AD itself does not indicate any change to the scope from an earlier or original instrument. It plainly applies to all Twin Pioneer models fitted with Dunlop main wheels P/N AH50742, Issues 1–5 and directs compliance with Scottish Aviation TNS No. 31, Issue 3 forthwith; no modification of that applicability or scope is stated in the provided text (Applicability; Document; Compliance)."},"complexity_factors":["Narrow technical scope: applies only to aircraft fitted with main wheels P/N AH50742, Issue 1–5 (Applicability).","Reliance on external technical document: the AD mandates compliance with Scottish Aviation TNS No. 31, Issue 3 rather than listing remedial steps inside the AD (Document).","Immediate timing: compliance required 'Forthwith', creating urgent operational and scheduling effects (Compliance).","Lack of procedural detail in AD text: absence of explicit inspection/repair steps in the AD shifts complexity to interpreting and obtaining the referenced TNS (Document).","Regulatory provenance is clear and simple: an airworthiness directive under the schedule (header), so legal authority is straightforward."],"plain_english_summary":"What this directive does (mechanically):\n\n- The Civil Aviation Safety Authority (CASA) directive AD/SA-TP/20 requires immediate compliance with the maintenance/inspection instructions contained in \"Scottish Aviation TNS No. 31, Issue 3\" for aircraft that have a particular Dunlop main wheel. (See: \"AD/SA-TP/20\", \"Document\", \"Compliance\")\n\nWho it affects:\n\n- Owners, operators, and maintenance organisations responsible for British Aerospace (Scottish Aviation) Twin Pioneer series aeroplanes that are fitted with main wheels part number AH50742, Issues 1 through 5. (See: \"Applicability\")\n\nWhy it matters (stated and inferred):\n\n- The directive is titled \"Drive Blocks on Dunlop Main Wheel\", indicating it addresses a problem related to the drive blocks on that specific Dunlop main wheel. The AD requires operators to follow the referenced technical note forthwith, so operators must obtain and carry out whatever inspections, replacements, or corrective actions that TNS prescribes. (See: title and \"Document\")\n\nPractical mechanics and who decides/pays:\n\n- Who decides: CASA issued the directive under the airworthiness directive schedule. The AD identifies the required source of corrective action as Scottish Aviation TNS No. 31, Issue 3. (See: header and \"Document\")\n- Who pays: The directive assigns the compliance obligation to the operators/owners/maintenance organisations of the affected aircraft; they will bear direct costs such as parts, labour, and any out-of-service time required to follow the TNS instructions. (Inferred from the AD's Applicability and Compliance statements.)\n- What behaviour changes: Affected operators must obtain the referenced TNS and implement its instructions immediately (\"Forthwith\"); this will typically change maintenance scheduling and may require parts replacement or inspections specified in the TNS. (See: \"Compliance\", \"Document\")\n\nImplementation and compliance considerations (trade-offs and risks):\n\n- Compliance is triggered immediately by the AD wording \"Forthwith\", so operators must act without delay; that creates short-term scheduling and cost impacts. (See: \"Compliance\")\n- The AD does not specify the remedial steps in its text; it mandates adherence to an external technical note (Scottish Aviation TNS No. 31, Issue 3). That creates a dependency on that document for precise instructions and on whoever holds or controls that document for access. (See: \"Document\")\n- The AD is narrowly targeted by part number and issue range (P/N AH50742, Issue 1–5), so the direct regulatory burden is confined to aircraft fitted with those specific wheels. That narrow scope concentrates costs on a limited group of operators but also reduces the number of parties required to act. (See: \"Applicability\")\n- Because the AD does not contain the corrective steps itself, there is limited administrative discretion shown in the AD text — CASA prescribes the TNS as the mandatory source. Any flexibility in how to comply will depend on allowances (or lack thereof) within the referenced TNS or on future direction from CASA. (See: \"Document\")\n\nNet effect summary:\n\n- The AD places an immediate, document-specified maintenance obligation on operators of Twin Pioneer aeroplanes fitted with Dunlop main wheels P/N AH50742 Issues 1–5. Operators must obtain Scottish Aviation TNS No. 31, Issue 3 and carry out the actions it prescribes, bearing the costs and scheduling impacts that follow. (See: \"AD/SA-TP/20\", \"Applicability\", \"Document\", \"Compliance\")"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive targeting a specific mechanical component on a specific aircraft type. It remains tightly scoped to its original safety purpose with no evidence of scope creep."},"complexity_factors":["Extremely short document (under 200 words)","Only 1 defined applicability criterion (wheel part number)","Single compliance requirement with no conditional exceptions","No cross-references to other legislation or regulations beyond the parent CAR 1998 citation","Straightforward imperative language ('Forthwith') with no procedural alternatives"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA).\n\n**What it does:**\nOrders immediate inspection or replacement of **drive blocks** (components that transfer power from the brakes to the wheel) on specific **Dunlop main wheels** fitted to **British Aerospace (Scottish Aviation) Twin Pioneer aircraft**.\n\n**Who it affects:**\nOwners and operators of Twin Pioneer aeroplanes equipped with main wheels part number **AH50742, Issues 1 through 5**.\n\n**Why it matters:**\nDrive block failures can cause brake system malfunctions, potentially leading to loss of braking control during landing or ground operations. The directive requires compliance **\"forthwith\"** (immediately), indicating this addresses an urgent safety risk.\n\n**Key details:**\n- **Compliance deadline:** Immediate (no grace period)\n- **Technical reference:** Scottish Aviation Technical News Sheet (TNS) No. 31, Issue 3\n- **Classification:** \"NK\" — typically indicates the directive is new (N) and relates to known unsafe conditions (K)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel","history":"/api/acts/ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel/history","analysis":"/api/acts/ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel/analysis","conflicts":"/api/acts/ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel/conflicts","importantCases":"/api/acts/ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel/important-cases","documents":"/api/acts/ad-sa-tp-20-drive-blocks-on-dunlop-main-wheel/documents"}}