{"id":"F2006B02831","name":"AD/B737/13 - Horizontal Stabilizer Centre Section","slug":"ad-b737-13-horizontal-stabilizer-centre-section","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42173,"registerId":"commonwealth-F2006B02831-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/13 - Horizontal Stabilizer Centre Section","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)  Boeing 737 Series Aeroplanes\n\n \n\nAD/B737/13 Horizontal Stabilizer Centre Section 2/88\n\nApplicability: All model 737 aircraft, Line Numbers 1 to 316, 323 and 324. Requirement:  Inspect in accordance with Boeing SB 737-55A1029 Revision 3.\n\nNote: FAA AD 84-23-05 refers.\n\n \n\nCompliance: As detailed in the Requirement Document.\n\n \n\nBackground: Fatigue cracking has been detected in a lug on an overseas aircraft. Failure to detect cracks in these lugs may result in the separation of the horizontal stabilizer from the aircraft. This AD has been raised because SB 737-55A1029 has been listed in Section 9.0 of the 737 Supplemental Structural Inspection Document as having flight safety implications.\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 focused on a specific mechanical defect in specific aircraft. It has not expanded beyond its original purpose of mandating inspections for fatigue cracking in horizontal stabilizer lugs."},"complexity_factors":["Very short document (under 200 words)","Only 2 defined applicability criteria (aircraft line numbers)","Single requirement with reference to external technical document (Boeing SB)","No nested conditions, exceptions, or cross-references to other legislation","Straightforward compliance timeline ('as detailed in Requirement Document')","Background explanation provided in plain language"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order for aircraft owners and operators. It applies to specific older Boeing 737 aircraft (serial numbers 1 through 316, plus 323 and 324).\n\n**What it requires:**\n- Owners must inspect a specific part of the aircraft called the **\"horizontal stabilizer centre section\"** — that's the central part of the tail wing that keeps the plane stable in flight.\n- The inspection must follow a technical document called **Boeing Service Bulletin 737-55A1029 Revision 3**.\n\n**Why it exists:**\n- Cracks from metal fatigue were found in a \"lug\" (a type of bracket or connector) on an aircraft overseas.\n- If these cracks aren't caught, the horizontal stabilizer could **separate from the aircraft entirely** — a catastrophic failure.\n- The US Federal Aviation Administration issued a similar directive (FAA AD 84-23-05), and Australia's Civil Aviation Safety Authority followed suit.\n\n**Who must comply:**\n- Anyone operating the affected Boeing 737 models must complete this inspection according to the timeline in the referenced Boeing document.\n\n**Bottom line:** This is a critical safety measure to prevent the tail from falling off certain older 737s."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The instrument, as published, sets a clear applicability group and mandates inspection according to Boeing SB 737-55A1029 Revision 3 (Applicability; Requirement). There is no text in the instrument indicating a change of scope from an earlier stated intent; it implements the inspection requirement identified in the 737 Supplemental Structural Inspection Document Section 9.0 for the listed aircraft (Background)."},"complexity_factors":["Narrow, specific technical focus (horizontal stabilizer centre section lug fatigue) reduces scope complexity (Background).","Applicability limited to specific line numbers (1–316, 323, 324), making affected population clearly defined (Applicability).","Substantial reliance on an external technical document (Boeing SB 737-55A1029 Revision 3) for procedures, intervals and technical detail increases operational complexity for implementers (Requirement; Compliance).","Reference to an external regulator action (FAA AD 84-23-05) requires cross-checking but does not expand technical requirements in the AD text (Note).","AD text provided here lacks explicit timing/intervals and repair criteria, so implementers must obtain and interpret the Service Bulletin, adding an administrative step and potential for variation (Requirement; Compliance)."],"plain_english_summary":"The directive mandates inspections for cracking in the horizontal stabilizer centre‑section lugs on specified early Boeing 737s, to be done exactly as Boeing Service Bulletin 737‑55A1029 Revision 3 prescribes. It affects owners, operators and the maintenance organisations that must perform and bill for the work. It matters because fatigue cracking was found overseas and undetected cracks risk stabilizer separation; operators bear inspection, repair and downtime costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-13-horizontal-stabilizer-centre-section","history":"/api/acts/ad-b737-13-horizontal-stabilizer-centre-section/history","analysis":"/api/acts/ad-b737-13-horizontal-stabilizer-centre-section/analysis","conflicts":"/api/acts/ad-b737-13-horizontal-stabilizer-centre-section/conflicts","importantCases":"/api/acts/ad-b737-13-horizontal-stabilizer-centre-section/important-cases","documents":"/api/acts/ad-b737-13-horizontal-stabilizer-centre-section/documents"}}