{"id":"F2006B06960","name":"AD/SF340/31 - Stabilizer De-Icing","slug":"ad-sf340-31-stabilizer-de-icing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114858,"registerId":"commonwealth-F2006B06960-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SF340/31 - Stabilizer De-Icing","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)  SAAB SF340 Series Aeroplanes\n\n \n\nAD/SF340/31 Stabilizer De-Icing 3/92\n\nApplicability: Model 340B Serial Number 240 through 299 inclusive.\n\n \n\nRequirement: Action in accordance with the Technical Requirements of LFV (Sweden) AD No 1- 051.\n\n \n\nNote: SAAB SB SAAB 340-30-039 refers.\n\n \n\nCompliance: Prior to issue of a Certificate of Airworthiness.\n\n \n\nBackground:  Freezing of the control valve and the pressure switch located in the dorsal fin may result in continuously inflated or deflated de-ice boots.\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 defect in a limited aircraft population. It has not expanded beyond its original purpose of mandating a pre-certification fix for a known freezing issue in the stabilizer de-icing system."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined applicability criterion (serial number range)","Single compliance requirement with external reference to Swedish directive","No nested conditions or exceptions","No internal cross-references within the document itself","Straightforward cause-and-effect explanation in background section"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order for aircraft. It applies to specific **SAAB 340B aeroplanes** (serial numbers 240–299).\n\n**What it does:**\n- Requires operators to fix a de-icing problem before the plane can get its **Certificate of Airworthiness** (the official document saying an aircraft is safe to fly).\n- The problem involves the **stabilizer de-icing system** — specifically, a control valve and pressure switch in the dorsal fin (the vertical fin on top of the aircraft) that can freeze up.\n- If these freeze, the rubber de-ice \"boots\" on the tail stabilizer can get stuck either inflated or deflated, which is dangerous because:\n  - **Stuck inflated:** Creates drag and handling problems\n  - **Stuck deflated:** Ice builds up unchecked, risking loss of control\n\n**Who must act:**\n- Owners and operators of the affected SAAB 340B aircraft\n- Must follow the technical requirements set out in a Swedish aviation authority directive (LFV AD No 1-051)\n\n**Why it matters:**\n- Ice on aircraft surfaces is a serious flight safety hazard. This AD prevents a specific mechanical failure that could lead to dangerous ice accumulation or flight control issues."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive, as presented, imposes a corrective requirement on a defined set of aircraft (Model 340B serial numbers 240–299) to follow LFV AD No 1-051 before a Certificate of Airworthiness will be issued (Applicability; Requirement; Compliance). There is no text in the instrument indicating an expansion, reduction or other alteration of that scope compared to the directive as written here, so the scope has not changed within the terms of this document."},"complexity_factors":["Narrow and explicit applicability limited to SAAB 340B serial numbers 240–299 (Applicability) — reduces scope complexity.","Delegation of technical detail to an external foreign AD (LFV AD No 1-051) increases procedural dependency and requires consultation of another document (Requirement).","Reference to a manufacturer service bulletin (SAAB 340-30-039) introduces an additional external source to interpret and follow (Note).","A single clear compliance point (before Certificate of Airworthiness issuance) simplifies timing but concentrates implementation effort and can create scheduling pressure (Compliance).","The directive does not itself detail acceptable corrective actions, alternate compliance paths or variance procedures, requiring reliance on the external documents and the certifying authority for specifics (Requirement; Note)."],"plain_english_summary":"# What this directive does\n\nThis airworthiness directive requires specific SAAB 340B aeroplanes (serial numbers 240 through 299 inclusive) to have a particular technical action carried out before they can be issued a Certificate of Airworthiness. The directive does not itself set out the technical steps; instead it requires operators to carry out the \"Technical Requirements of LFV (Sweden) AD No 1-051\" (Requirement). The directive also cross-references SAAB Service Bulletin SAAB 340-30-039 (Note).\n\n# Who it affects\n\n- Owners, operators, manufacturers and maintenance organisations responsible for SAAB Model 340B aircraft with serial numbers 240–299 (Applicability).\n- The Civil Aviation Safety Authority (CASA) or delegated authority that issues Certificates of Airworthiness, because compliance must be demonstrated prior to certificate issue (Compliance).\n\n# How it works, mechanically\n\n- The directive makes compliance with an external foreign airworthiness directive (LFV AD No 1-051) mandatory for the listed serial numbers (Requirement).\n- The required work must be completed and evidenced before a Certificate of Airworthiness will be issued for an affected aircraft (Compliance).\n- The SAAB service bulletin referenced (SAAB 340-30-039) provides related technical information and should be consulted when carrying out the required work (Note).\n\n# Reason stated in the text\n\nThe directive states the safety concern motivating the requirement: freezing of the control valve and the pressure switch in the dorsal fin can cause the stabilizer de-ice boots to stay continuously inflated or continuously deflated, which the directive treats as an unsafe condition requiring corrective action (Background).\n\n# Who pays, who decides, and what changes in behaviour\n\n- Who pays: the owner/operator or manufacturer who must perform the technical work and any inspections required to comply (Applicability; Requirement; Compliance). Those parties will bear labour, parts and administrative costs needed to implement the LFV technical requirements and to show compliance before a CoA is issued.\n- Who decides: CASA enforces this requirement at the point of Certificate of Airworthiness issuance; the specific technical content is determined by the LFV AD and the SAAB service bulletin that the directive makes mandatory (Requirement; Note; Compliance).\n- Behavioural change: operators/manufacturers must schedule and complete the mandated technical actions and document compliance prior to certification. This can delay issuance of a CoA until the work is done (Compliance).\n\n# Costs, incentives and implementation considerations\n\n- Compliance burden: the directive delegates the technical detail to an external AD and a manufacturer service bulletin, so affected parties must obtain and follow those documents and carry out the physical work and record-keeping before certification (Requirement; Note; Compliance).\n- Incentives and trade-offs: completing the required work avoids the operational hazard described (Background) but imposes time and monetary costs on the aircraft owner/operator or manufacturer prior to entry into service (Applicability; Compliance).\n- Discretion and coordination risk: because the directive makes a foreign airworthiness directive (LFV AD No 1-051) mandatory, affected parties must coordinate with the content of that external document and with CASA’s certification process. The instrument itself does not specify alternate compliance methods or a timetable beyond \"prior to issue of a Certificate of Airworthiness,\" which concentrates the compliance deadline at certification (Requirement; Compliance).\n\n# Practical note on implementation\n\nTo comply, an affected aircraft’s responsible organisation should obtain LFV AD No 1-051 and SAAB SB SAAB 340-30-039, plan the required work, retain records demonstrating the work was done, and present that evidence when applying for the Certificate of Airworthiness (Requirement; Note; Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sf340-31-stabilizer-de-icing","history":"/api/acts/ad-sf340-31-stabilizer-de-icing/history","analysis":"/api/acts/ad-sf340-31-stabilizer-de-icing/analysis","conflicts":"/api/acts/ad-sf340-31-stabilizer-de-icing/conflicts","importantCases":"/api/acts/ad-sf340-31-stabilizer-de-icing/important-cases","documents":"/api/acts/ad-sf340-31-stabilizer-de-icing/documents"}}