{"id":"F2006B03623","name":"AD/BEECH 18/4 Amdt 1 - Horizontal Stabiliser Spar - Inspection","slug":"ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":43214,"registerId":"commonwealth-F2006B03623-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BEECH 18/4 Amdt 1 - Horizontal Stabiliser Spar - Inspection","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)  \nBeechcraft 18 Series Aeroplanes\n\nAD/BEECH 18/4\n\nAmdt 1\n\n  \nHorizontal Stabiliser Spar \\- Inspection NK\n\nApplicability: Model C-18S, D-18S and AT-11, not modified to Beech SB D-18-48.\n\nRequirement: 1. Inspect the horizontal stabiliser front spar and sub-spar for cracks at the points of attachment to the fuselage.\n\n    2. Remove the stabiliser and stabiliser lower skin panel and inspect for cracks in the front spar and sub-spar.\n\n    3. If cracking has occurred modify the stabiliser attachment in accordance with Beechcraft Service Bulletin No. D-18-48 or to the satisfaction of the Secretary before further flight.\n\nCompliance: For Para. 1 \\- At intervals not exceeding 10 hours time in service.\n\nFor Para. 2 \\- At intervals not exceeding 500 hours time in service from the last inspection.\n\nFederal Register of Legislative Instruments F2006B03623","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive focused on a specific safety-critical inspection for a specific aircraft type. It has not expanded beyond its original purpose of ensuring structural integrity of the horizontal stabiliser."},"complexity_factors":["Very short document — only 3 operative paragraphs plus applicability and compliance sections","Only 1 defined term implicitly used ('time in service' — flight hours)","No cross-references to other legislation beyond the enabling Civil Aviation Regulations 1998","Simple conditional logic: if cracks found → modify before flight","Clear, unambiguous compliance deadlines (10 hours / 500 hours intervals)","Single, narrow applicability criterion (specific aircraft models not modified to specific service bulletin)"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nOrders owners and operators of certain **Beechcraft 18 series aeroplanes** (models C-18S, D-18S and AT-11) to inspect the horizontal stabiliser — the small wing at the tail of the plane that keeps it level — for dangerous cracks.\n\n**Who it affects:**\n- Owners and operators of these specific Beechcraft models\n- Only applies if the aircraft has **not** already been modified according to Beechcraft Service Bulletin D-18-48\n\n**What must be done:**\n1. **Quick check:** Inspect the front spar and sub-spar (the main structural beams) where they attach to the fuselage — **every 10 hours of flight time**\n2. **Deep inspection:** Remove the stabiliser and lower skin panel to check for cracks — **every 500 hours of flight time**\n3. **If cracks are found:** The aircraft cannot fly again until the stabiliser is modified according to the manufacturer's service bulletin or approved by the Secretary (a senior CASA official)\n\n**Why it matters:**\nCracks in the horizontal stabiliser spar could cause the tail structure to fail in flight, potentially leading to loss of control and crash. This directive prevents that by forcing regular inspections and grounding aircraft until repairs are made."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument, as provided, sets inspection and modification requirements for the named Beechcraft 18 models and excludes aircraft already modified to Beech SB D-18-48 (Applicability; Requirement Paras. 1–3; Compliance). The text does not indicate any change from an earlier scope or from its original intent; it imposes the stated inspections and a mandatory remedy if cracking is found."},"complexity_factors":["Narrow applicability: specific to Model C-18S, D-18S and AT-11 not modified to SB D-18-48 (Applicability)","Limited number of clear, sequential requirements (three listed actions) (Requirement Paras. 1–3)","Two distinct inspection regimes with different frequencies (10 hours and 500 hours) (Compliance)","One intrusive action requiring removal of stabiliser and skin panel for the 500-hour inspection (Requirement Para. 2)","Mandatory modification if cracking found, with option to comply via SB D-18-48 or an alternative acceptable to the Secretary (Requirement Para. 3) introducing regulatory discretion","Operational consequences (grounding until modification is complete) creating coordination and scheduling complexity for operators"],"plain_english_summary":"This directive requires operators of certain Beechcraft 18 models (unless already modified by SB D-18-48) to perform frequent inspections of the horizontal stabiliser front spar and sub‑spar and, if cracks are found, to have the attachment modified per SB D-18-48 or an alternative approved by the Secretary before further flight. It affects owners/operators by imposing recurring inspection, repair costs, downtime and increased demand for specialised maintenance."}},"importantCases":[],"_links":{"self":"/api/acts/ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection","history":"/api/acts/ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection/history","analysis":"/api/acts/ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection/analysis","conflicts":"/api/acts/ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection/conflicts","importantCases":"/api/acts/ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection/important-cases","documents":"/api/acts/ad-beech-18-4-amdt-1-horizontal-stabiliser-spar-inspection/documents"}}