{"id":"F2006B06985","name":"AD/SF340/57 Amdt 1 - Horizontal Stabiliser Front Spar Fastener Holes","slug":"ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114909,"registerId":"commonwealth-F2006B06985-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SF340/57 Amdt 1 - Horizontal Stabiliser Front Spar Fastener Holes","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/SF340/57\n\nAmdt 1\n\n  \nHorizontal Stabiliser Front Spar Fastener Holes 1/99\n\nApplicability: Model SF-340A, serial numbers SF-340A-004 through SF-340A-159, and model SAAB 340B, serial numbers 340B-160 through 340B-439.\n\nRequirement: Action in accordance with SAAB Aircraft Service Bulletin 340-55-34.\n\nNote: LFV AD 1-133 refers.\n\nCompliance: As specified in the Requirement Document with a revised effective date of 28 January 1999.\n\nThis Amendment becomes effective on 28 January 1999.\n\nBackground: During simulated flight testing in the “Full Scale Fatigue Test Rig”, fatigue cracks were found in the forward spar of the horizontal stabiliser. The cracks were located at the intersection between the rear fuselage and the forward spar upper spar cap. The starting point for the initial crack is considered to be in the upper part of the web at one of the fastener holes.\n\nAmendment 1 is issued in response to a new Requirement document which introduces a Cold Working Expansion Procedure for four of the holes in the upper cap and the web. This procedure will extend the fatigue life and minimise future need for repairs.\n\nThe original issue of this Airworthiness Directive became effective on 14 August 1997.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment stays tightly within the original purpose of addressing fatigue cracks in the horizontal stabiliser front spar. It simply updates the repair methodology based on improved technical understanding. The scope has not expanded beyond the specific aircraft models and structural issue originally targeted."},"complexity_factors":["Very short document (under 300 words)","Only 2 defined applicability criteria (model and serial number ranges)","Single cross-reference to SAAB Service Bulletin and one Swedish aviation authority directive (LFV AD 1-133)","No nested conditions or exceptions — straightforward command structure: identify aircraft → apply specified procedure → meet deadline","Technical content is externalised to the Service Bulletin, keeping the legislative instrument minimal"],"plain_english_summary":"Owners and operators of specified SAAB SF340A/B aircraft (listed serial ranges) are ordered to carry out a mandatory Cold Working Expansion repair on four horizontal‑stabiliser bolt holes per SAAB Service Bulletin 340‑55‑34 by 28 January 1999. The amendment replaces the 1997 fix with a more durable method after fatigue cracks were found where the rear fuselage meets the tail—flying without this repair would breach civil aviation law."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Amendment 1 adds a specific Cold Working Expansion Procedure for four holes in the upper cap and web of the horizontal stabiliser forward spar, changing the AD from its original form by prescribing a preventive structural modification (Amendment 1; Requirement; Background)."},"complexity_factors":["Technical structural action: requires cold‑working expansion of specific fastener holes (Background; Amendment 1).","Dependency on an external document: mandatory compliance with SAAB Service Bulletin 340‑55‑34 (Requirement).","Serial‑number‑limited applicability: affects only listed SF‑340A and 340B serial ranges (Applicability).","Operational impact: maintenance downtime, specialised tooling/skills and scheduling burden for operators (Compliance).","Regulatory timing: revised effective/compliance date imposes a fixed deadline for action (Compliance)."],"plain_english_summary":"Mandates that operators of SAAB SF‑340A (S/N SF‑340A‑004–159) and SAAB 340B (S/N 340B‑160–439) carry out a cold‑working expansion procedure on four fastener holes in the horizontal stabiliser forward spar, per SAAB Service Bulletin 340‑55‑34 (Requirement). The change follows discovery of fatigue cracks during full‑scale testing and intends to extend fatigue life and reduce future repairs (Background). Aircraft owners/operators pay for the work, need qualified maintenance, and must schedule downtime to meet the compliance date (Compliance)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes","history":"/api/acts/ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes/history","analysis":"/api/acts/ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes/analysis","conflicts":"/api/acts/ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes/conflicts","importantCases":"/api/acts/ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes/important-cases","documents":"/api/acts/ad-sf340-57-amdt-1-horizontal-stabiliser-front-spar-fastener-holes/documents"}}