{"id":"F2006B06950","name":"AD/SF340/21 - Auto-Coarsening","slug":"ad-sf340-21-auto-coarsening","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114848,"registerId":"commonwealth-F2006B06950-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SF340/21 - Auto-Coarsening","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/SF340/21 Auto-Coarsening  2/91 DM\n\n \n\nApplicability: All SAAB SF340 Series aircraft S/No 004 through 159 inclusive.\n\n \n\nRequirement: Action in accordance with the technical requirements of FAA AD 90-21-16 Amdt 39- 6763.\n\n \n\nNote 1: This directive cancels AD/SF340/13.\n\n \n\nNote 2: Swedish AD No 1-037 refers and cancels Swedish AD No 1-028.\n\n \n\nCompliance: Prior to 30 April 1991\n\n \n\nBackground:  As previously incorporated Electrical Control Unit (ECU) modifications may affect single engine climb performance. The FAA, Swedish Airworthiness Authority and the Aircraft Manufacturer requires these modifications to be removed and a modified ECU to be installed.\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, time-bound safety directive addressing a specific technical defect in specific aircraft. It has not expanded beyond its original purpose of mandating ECU replacement to ensure safe single-engine climb performance."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 substantive operative provisions (Applicability and Requirement)","Single cross-reference to external FAA directive rather than detailed technical requirements in the text itself","No defined terms section — relies on common aviation terminology","Simple unconditional compliance requirement with fixed deadline","Background section provides context but creates no additional legal obligations"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**Who it affects:** Owners and operators of SAAB SF340 series aircraft with serial numbers 004 through 159. These are regional turboprop airliners commonly used by airlines like Regional Express (Rex) in Australia.\n\n**What it requires:** Operators must follow the technical instructions in an American Federal Aviation Administration (FAA) directive (AD 90-21-16). Specifically, they need to:\n- **Remove** certain previously installed Electrical Control Unit (ECU) modifications\n- **Install** a different, modified ECU instead\n\n**Why it matters:** The old ECU modifications could reduce the aircraft's ability to climb safely if one engine failed during takeoff or flight. This directive fixes a potential safety issue that could affect single-engine performance — critical for safe operation, especially during takeoff when the aircraft is heavy and close to the ground.\n\n**Key deadlines:** The work had to be completed before 30 April 1991.\n\n**Other notes:** This directive replaced an earlier Australian directive (AD/SF340/13) and aligns with similar safety orders from Sweden and the United States."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The directive changes the regulatory position in that it cancels the earlier domestic directive (AD/SF340/13) and mandates removal of previously incorporated ECU modifications and installation of a modified ECU for SAAB SF340 aircraft S/No 004–159 (Note 1) (Requirement). The scope therefore shifts from permitting or addressing earlier modifications under the prior AD to requiring their removal and replacement by the solution specified in FAA AD 90-21-16 Amdt 39-6763; the domestic text requires compliance by a set date (Compliance)."},"complexity_factors":["Cross-reference to external technical document (FAA AD 90-21-16 Amdt 39-6763) — requires obtaining and following another jurisdiction's AD for technical detail (Requirement).","Limited technical detail in the domestic text — the specific modifications to remove and the exact installation steps are not specified here (Requirement) (Background).","Fixed applicability to a serial-numbered subset of the fleet (S/No 004–159) — requires operators to check aircraft serial numbers for applicability (Applicability).","Clear compliance deadline (prior to 30 April 1991) — creates a time-bound operational constraint (Compliance).","Cancellation of a prior directive (AD/SF340/13) — requires operators to reconcile previous compliance with the new requirement (Note 1).","Safety-critical consequence referenced (single-engine climb performance) — raises implementation priority despite minimal procedural text (Background)."],"plain_english_summary":"This directive requires owners/operators of SAAB SF340 aeroplanes S/N 004–159 to remove certain previously installed ECU modifications and install a modified ECU per FAA AD 90-21-16 (Amdt 39‑6763), cancelling the earlier AD/SF340/13. Compliance is required by 30 April 1991.\n\nIt matters because the prior modifications may harm single‑engine climb performance; owners/operators bear retrofit costs, downtime and must follow the FAA technical instructions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sf340-21-auto-coarsening","history":"/api/acts/ad-sf340-21-auto-coarsening/history","analysis":"/api/acts/ad-sf340-21-auto-coarsening/analysis","conflicts":"/api/acts/ad-sf340-21-auto-coarsening/conflicts","importantCases":"/api/acts/ad-sf340-21-auto-coarsening/important-cases","documents":"/api/acts/ad-sf340-21-auto-coarsening/documents"}}