{"id":"F2006B02928","name":"AD/B737/232 - Horizontal Stabiliser Pivot Hinge Pins","slug":"ad-b737-232-horizontal-stabiliser-pivot-hinge-pins","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42270,"registerId":"commonwealth-F2006B02928-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nBoeing 737 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/B737/232 Horizontal Stabiliser Pivot ","sectionType":"part","heading":"AD/B737/232 Horizontal Stabiliser Pivot Hinge Pins 12/2004","content":"# AD/B737/232 Horizontal Stabiliser Pivot Hinge Pins 12/2004\n\nApplicability: Model 737-100, \\-200, \\-200C, \\-300, \\-400, and \\-500 series aircraft, line numbers 1\n\nthrough 3132.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 2004-19-10 Amdt 39-13804.\n\nNote: Boeing Alert Service Bulletin 737-55A1077 original issue, or later FAA approved revision, refers.\n\nCompliance: As specified in the Requirement document, with a revised effective date of 25 November 2004.\n\nThis Airworthiness Directive becomes effective on 25 November 2004.\n\nBackground: Reports have been received of corrosion in the pivot hinge pins that attach the horizontal stabiliser centre section to the Body Station 1156 support bulkhead. The degree of corrosion found on outer primary pins, and inner fail-safe pins made from both 4330steel and 15-5 PH corrosion resistant steel, could increase the likelihood of stress corrosion cracking. An undetected failure of the outer primary pin and the inner fail-safe pin could enable the pins to migrate out of the stabiliser hinge joint and result in intermittent movement of the horizontal stabiliser structure, and consequent loss of controllability of the aircraft.\n\n![Signature of David Villiers, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 14 October 2004\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original narrow scope: addressing a specific corrosion defect in horizontal stabiliser hinge pins on specific Boeing 737 models. There is no evidence of scope creep — the instrument targets exactly the safety issue identified in the background (corrosion in pivot hinge pins) and applies only to the aircraft models and line numbers specified. The reference to FAA AD 2004-19-10 is standard practice for adopting foreign technical standards, not an expansion of scope."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined structural sections (Applicability, Requirement, Compliance, Background)","Single cross-reference to external technical document (FAA AD 2004-19-10) — the actual detailed instructions are not reproduced here","No nested conditional logic or exceptions within the document itself","Simple effective date and compliance structure","Technical complexity is outsourced to referenced Boeing/FAA documents rather than contained in the legislative instrument itself"],"plain_english_summary":"This safety order requires owners/operators of Boeing 737-100/-200/-200C/-300/-400/-500 aircraft (line numbers 1–3132) to inspect and repair corrosion-related stress cracking in the horizontal stabiliser pivot hinge pins. Compliance follows FAA AD 2004-19-10 using Boeing Alert Service Bulletin 737-55A1077, effective 25 November 2004. It’s a mandatory airworthiness directive: undetected pin failure could lead to loss of control, and non-compliance grounds the aircraft."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD adopts the technical requirements of FAA AD 2004‑19‑10 for the specified Boeing 737 models and line numbers and sets an effective date of 25 November 2004. It does not expand or narrow the described set of affected aircraft within the source text; scope is limited to the models and line numbers stated (Applicability; Requirement; Compliance)."},"complexity_factors":["Cross-reference dependence: Mandates compliance with FAA AD 2004‑19‑10 rather than specifying procedures directly (Requirement).","Service bulletin linkage: Notes Boeing Alert Service Bulletin 737‑55A1077 as the technical source, with potential for later FAA‑approved revisions (Note).","Defined applicability: Limited to specific Boeing 737 models and line numbers 1–3132, which narrows who must comply but requires operators to confirm line number applicability (Applicability).","Compliance timing: Specifies a revised effective date (25 November 2004), creating a fixed deadline for action (Compliance).","Safety‑critical technical work: Addresses corrosion and stress‑corrosion cracking of primary and inner fail‑safe hinge pins, including pins made from 4330 steel and 15‑5 PH stainless (Background).","Regulatory instruction framing: The CASA delegate issues the AD under CASR subregulation 39.1(1) and directs action ‘in the circumstances… in accordance with the instructions… at the time mentioned’, which delegates technical detail to the referenced documents and requires operator interpretation (opening paragraph).","Operational and cost impact: Requires inspections and likely maintenance or replacement work on a structural control‑surface joint, imposing direct repair and downtime costs on operators (Background; Requirement)."],"plain_english_summary":"This AD requires operators of Boeing 737‑100/200/200C/300/400/500 aircraft (line numbers 1–3132) to carry out the inspections and corrective actions set out in FAA AD 2004‑19‑10 and the referenced Boeing service bulletin to address corrosion in the horizontal stabiliser pivot hinge pins. It matters because corrosion and stress‑corrosion cracking of primary and fail‑safe pins can allow pins to migrate, cause intermittent stabiliser movement and risk loss of control; operators must pay for and complete the work by the effective date (25 November 2004)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-232-horizontal-stabiliser-pivot-hinge-pins","history":"/api/acts/ad-b737-232-horizontal-stabiliser-pivot-hinge-pins/history","analysis":"/api/acts/ad-b737-232-horizontal-stabiliser-pivot-hinge-pins/analysis","conflicts":"/api/acts/ad-b737-232-horizontal-stabiliser-pivot-hinge-pins/conflicts","importantCases":"/api/acts/ad-b737-232-horizontal-stabiliser-pivot-hinge-pins/important-cases","documents":"/api/acts/ad-b737-232-horizontal-stabiliser-pivot-hinge-pins/documents"}}