{"id":"F2006B06954","name":"AD/SF340/25 Amdt 1 - Vertical Stabilizer Top Closure Rib","slug":"ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114852,"registerId":"commonwealth-F2006B06954-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SF340/25 Amdt 1 - Vertical Stabilizer Top Closure Rib","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nSAAB SF340 Series Aeroplanes\n\nAD/SF340/25\n\nAmdt 1\n\n  \nVertical Stabilizer Top Closure Rib 12/91\n\nApplicability: All model SF340 with Serial Nos SF340A-031 through 159 and Serial Nos SF340B- 160 through 194.\n\nRequirement: Inspect and modify the vertical stabilizer top closure rib in accordance with the Technical Requirements of SAAB Scania AB Service Bulletins, SAAB 340-55-022 Revision 1 dated 27 February 1990, and SAAB 340-55-023 dated 1 October 1990.\n\nNote: Swedish Airworthiness Directive No 1-036, Revision A. refers.\n\nCompliance: Inspect upon achieving 500 hours in service after 16 May 1991, as required by the previous issue of this Directive; and then at intervals not exceeding those in SAAB Service Bulletins 340-55-022 Revision 1.\n\nModify in accordance with SAAB Service Bulletin 340-55-023 before 1 August 1992.\n\nBackground: Fatigue cracks in the vertical stabilizer top closure rib could lead to friction and ultimate jamming between the fin and rudder. This amendment calls up Revision A of the Requirement Document, which makes terminating action mandatory.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original purpose: addressing fatigue cracks in the vertical stabilizer top closure rib of specific SAAB SF340 aircraft. The amendment strengthens the original directive by making terminating action (permanent modification) mandatory rather than optional, but this is a refinement within the original safety scope rather than scope creep."},"complexity_factors":["Short, single-purpose directive (approximately 200 words)","Only 4 defined elements: specific aircraft models, serial number ranges, two referenced SAAB Service Bulletins, and one Swedish Airworthiness Directive","Clear, unconditional compliance requirements with specific deadlines","No nested exceptions or conditional logic — straightforward 'inspect and modify' mandate","Single cross-reference to predecessor directive and foreign (Swedish) regulatory document","Technical content relies on external manufacturer documents rather than inline specification"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of specified SAAB SF340 aircraft (serials SF340A‑031–159 and SF340B‑160–194) to inspect and repair the vertical stabilizer top closure rib because fatigue cracks have been found. Cracks could lead to rudder jamming and loss of control, so initial inspections and recurring checks are required and—crucially—this amendment makes the permanent structural modification mandatory rather than optional."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The amendment incorporates SAAB Revision A, converting the previous requirement into one that mandates a terminating modification (see Background and Compliance: modify in accordance with SAAB Service Bulletin 340-55-023 before 1 August 1992). The change shifts scope from inspection-only recurrence toward a mandatory corrective action."},"complexity_factors":["Targeted applicability by serial number (Applicability: SF340A-031 through 159; SF340B-160 through 194) — narrows affected fleet but requires operators to check serials.","Reliance on external manufacturer documents (Requirement: inspect/modify in accordance with SAAB Service Bulletins 340-55-022 Revision 1 and 340-55-023) — compliance depends on those technical documents.","Fixed compliance timetable (Compliance: inspect at 500 hours after 16 May 1991; modify before 1 August 1992) — creates hard deadlines and scheduling/operational impacts for operators.","Mandatory terminating action (Background: amendment calls up Revision A making terminating action mandatory) — changes nature of compliance from recurring mitigation to a required corrective modification.","Operational and cost impact (Requirement/Compliance): inspections and structural modification impose maintenance labour, parts, and potential downtime costs on operators/owners.","Technical nature of work (Background): addresses fatigue cracking and risk of fin–rudder jamming — work likely requires structural inspection skills and certified maintenance approval.","Cross-reference to foreign directive (Note: Swedish Airworthiness Directive No 1-036, Revision A) — may require coordination with foreign ADs or imported technical data."],"plain_english_summary":"This airworthiness directive requires operators of SAAB SF340 aeroplanes with serial numbers SF340A‑031–159 and SF340B‑160–194 to inspect and then modify the vertical stabilizer top closure rib following SAAB service bulletins (SAAB 340‑55‑022 Rev 1 and 340‑55‑023). Inspections start at 500 flight hours after 16 May 1991 and recur per the bulletin; the modification (terminating action) must be completed by 1 August 1992.\n\nThe directive is intended to prevent fatigue cracks that could cause fin–rudder jamming; aircraft operators and maintenance organisations bear the inspection, modification and scheduling costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib","history":"/api/acts/ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib/history","analysis":"/api/acts/ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib/analysis","conflicts":"/api/acts/ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib/conflicts","importantCases":"/api/acts/ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib/important-cases","documents":"/api/acts/ad-sf340-25-amdt-1-vertical-stabilizer-top-closure-rib/documents"}}