{"id":"F2006B02881","name":"AD/B737/178 - MLG Support Beam Primary Support Pin","slug":"ad-b737-178-mlg-support-beam-primary-support-pin","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42223,"registerId":"commonwealth-F2006B02881-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\n![](image.001.png)  \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 CAR 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\nBoeing 737 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/B737/178 MLG Support Beam Primary Sup","sectionType":"part","heading":"AD/B737/178 MLG Support Beam Primary Support Pin 5/2002","content":"# AD/B737/178 MLG Support Beam Primary Support Pin 5/2002\n\nApplicability: Model 737-200, \\-200C, \\-300, and –500 series aircraft, as identified in Boeing Service Bulletin 737-57A1260 Revision 2, dated 18 October 2001.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 2002-02-08 Amdt 39-12636.\n\nNote: Boeing Service Bulletin 737-57A1260 Revision 2 refers.\n\nCompliance: As specified in the Requirement document, with a revised effective date of 16 May 2002.\n\nThis Airworthiness Directive becomes effective on 16 May 2002.\n\nBackground: The manufacturer received information that a batch of self-locking nuts did not meet required minimum locking torque levels. These nuts may be installed on the primary support pin retaining bolt. This Directive improves bolt retention by replacing the bolt and nut with a new bolt, castellated nut, washer, and cotter pin.\n\n![Signature of David Villiers, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 22 March 2002\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"Scope does not change from the instrument's stated purpose in the text: it addresses an identified unsafe condition (defective self‑locking nuts) by requiring replacement on the aircraft models listed in the Boeing service bulletin and by adopting the FAA AD's technical requirements (Background; Applicability; Requirement). The AD confines action to the identified models and corrective parts and sets the effective date (Compliance), rather than expanding applicability or measures beyond that remedial scope."},"complexity_factors":["Cross-references to external instruments (FAA AD 2002-02-08 and Boeing Service Bulletin 737-57A1260 Rev 2) create dependency on other documents for technical details (Requirement; Note).","Narrow technical scope — mechanical replacement of bolt/nut assembly (Background: replacement with bolt, castellated nut, washer and cotter pin) reduces legal complexity but raises technical/maintenance workload for operators.","Applicability limited to specific models identified in the Boeing service bulletin, so identification of affected airframes requires reference to that bulletin (Applicability).","Compliance timing and legal effect fixed by the AD effective date (effective 16 May 2002; Compliance), imposing a clear deadline for operators.","Who pays: cost of parts, inspections and labour will fall to aircraft operators or their maintenance organisations (Requirement; Background).","Operational burden: airlines must schedule inspections/replacements and source specified parts, which may cause downtime and logistics coordination (Requirement; Compliance).","Regulatory clarity: the AD delegates the technical corrective action to the FAA AD and Boeing SB rather than prescribing step‑by‑step methods in the text, shifting implementation detail to those documents (Requirement; Note)."],"plain_english_summary":"Requires operators of specified Boeing 737-200/-200C/-300/-500 aircraft to replace the main landing gear (MLG) primary support pin bolt and nut assembly with a new bolt, castellated nut, washer and cotter pin, per FAA AD 2002-02-08 and Boeing Service Bulletin 737-57A1260 Rev 2. It is effective 16 May 2002 and matters because a batch of self‑locking nuts may not meet required locking torque, risking bolt retention."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive addressing a specific manufacturing defect in a specific aircraft component. The scope remains tightly focused on the original safety issue (defective self-locking nuts on main landing gear support pins) and has not expanded beyond this original purpose."},"complexity_factors":["Short, single-purpose directive (approximately 250 words)","Only 4 defined aircraft models in applicability section","Single technical requirement that references external FAA document rather than reproducing full instructions","No nested exceptions or conditional logic — applies to all listed aircraft models","Minimal cross-referencing: only references one Boeing Service Bulletin and one FAA AD","Clear, linear structure: Applicability → Requirement → Compliance → Background"],"plain_english_summary":"This CASA Airworthiness Directive mandates replacement of a specific bolt and self‑locking nut on the main landing‑gear support beam of certain Boeing 737‑200/200C/300/500 aircraft with a bolt, castellated nut, washer and cotter pin. It affects operators and maintenance crews and addresses defective nuts that could allow bolt loosening and landing‑gear failure. Effective 16 May 2002; follow FAA AD 2002‑02‑08/Boeing SB 737‑57A1260 Rev 2."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-178-mlg-support-beam-primary-support-pin","history":"/api/acts/ad-b737-178-mlg-support-beam-primary-support-pin/history","analysis":"/api/acts/ad-b737-178-mlg-support-beam-primary-support-pin/analysis","conflicts":"/api/acts/ad-b737-178-mlg-support-beam-primary-support-pin/conflicts","importantCases":"/api/acts/ad-b737-178-mlg-support-beam-primary-support-pin/important-cases","documents":"/api/acts/ad-b737-178-mlg-support-beam-primary-support-pin/documents"}}