{"id":"F2006B06823","name":"AD/SD3-30/21 - Rudder Lower Bearing","slug":"ad-sd3-30-21-rudder-lower-bearing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114687,"registerId":"commonwealth-F2006B06823-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SD3-30/21 - Rudder Lower Bearing","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)  Short SD3-30 Series Aeroplanes\n\n \n\nAD/SD3-30/21 Rudder Lower Bearing 5/87\n\nApplicability: All models.\n\n \n\nRequirement: Action in accordance with Shorts SB SD3-55-05 R2 Part A.\n\n \n\nCompliance: At next scheduled inspection for Maintenance Release issue after 7 May 1987 and thereafter at intervals not exceeding 600 hours time in service or 6 months, whichever occurs first.\n\n \n\nBackground:  This requirement will reduce possible ice formation due to water ingress in the rudder lower bearing.\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 discrete, targeted safety directive addressing a specific mechanical issue on a specific aircraft type. It has not expanded beyond its original purpose of ensuring rudder bearing integrity through periodic maintenance."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 1 defined applicability (\"All models\")","Single cross-reference to external technical document (Shorts SB SD3-55-05 R2 Part A)","Simple compliance structure: one-time initial action plus recurring interval","No nested conditions, exceptions, or conditional logic","Straightforward temporal trigger (date + flight hours/time alternative)"],"plain_english_summary":"This is an **Airworthiness Directive** (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nIt requires owners and operators of **Short SD3-30 series aeroplanes** (a type of regional turboprop aircraft, also known as the Short 330) to perform specific maintenance on the **rudder lower bearing** — a critical component that helps the aircraft's tail rudder move smoothly.\n\n**The specific requirement:**\nOperators must follow the instructions in **Shorts Service Bulletin SD3-55-05 R2 Part A** (a technical notice from the aircraft manufacturer). This maintenance addresses a problem where water can get into the rudder bearing, freeze, and potentially cause control issues.\n\n**Who must comply:**\n- All operators of Short SD3-30 aircraft registered in Australia\n- Maintenance organisations servicing these aircraft\n\n**When:**\n- First time: At the next scheduled inspection after 7 May 1987\n- Ongoing: Every 600 flight hours **or** every 6 months, whichever comes first\n\n**Why it matters:**\nWater freezing in flight controls is a serious safety hazard. Ice formation in the rudder bearing could restrict or jam the rudder, making the aircraft difficult or impossible to steer, especially during takeoff, landing, or in poor weather. This directive prevents that by ensuring regular inspection and maintenance."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive applies to all SD3-30 series aeroplanes and requires actions set out in the named Shorts service bulletin, with a repeating inspection interval defined. The AD text does not indicate any change in scope from an earlier or original requirement; it sets a clear, fleet‑wide obligation and a recurring compliance schedule (Applicability; Requirement; Compliance)."},"complexity_factors":["Reference to an external technical document (Shorts SB SD3-55-05 R2 Part A) creates dependency on that bulletin for detailed steps.","Recurring compliance schedule (600 hours TIS or 6 months) requires ongoing integration into maintenance planning.","Applicability to \"All models\" means the directive has broad coverage across the fleet.","Fixed compliance-start tied to inspections after a specific date (after 7 May 1987) requires calendar/record checks to establish initial applicability."],"plain_english_summary":"This AD requires all SD3‑30 aircraft to have the rudder lower bearing inspected and treated per Shorts SB SD3‑55‑05 R2 Part A at the next Maintenance Release after 7 May 1987 and then every 600 flight hours or 6 months. Its purpose is to reduce ice formation from water ingress. Operators/owners must ensure and pay for the recurring work and follow the referenced service bulletin for the technical details, affecting maintenance scheduling and costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sd3-30-21-rudder-lower-bearing","history":"/api/acts/ad-sd3-30-21-rudder-lower-bearing/history","analysis":"/api/acts/ad-sd3-30-21-rudder-lower-bearing/analysis","conflicts":"/api/acts/ad-sd3-30-21-rudder-lower-bearing/conflicts","importantCases":"/api/acts/ad-sd3-30-21-rudder-lower-bearing/important-cases","documents":"/api/acts/ad-sd3-30-21-rudder-lower-bearing/documents"}}