{"id":"F2006B02696","name":"AD/B727/172 - MLG Forward Trunnion Bearing Support Fitting","slug":"ad-b727-172-mlg-forward-trunnion-bearing-support-fitting","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42012,"registerId":"commonwealth-F2006B02696-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)  For 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\n\n\nBoeing 727 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/B727/172 MLG Forward Trunnion Bearing","sectionType":"part","heading":"AD/B727/172 MLG Forward Trunnion Bearing Support Fitting 13/2001","content":"# AD/B727/172 MLG Forward Trunnion Bearing Support Fitting 13/2001\n\n\n\nApplicability: All Model 727 series aircraft.\n\n\n\nRequirement: Inspect in accordance with the technical requirements of FAA AD 2001-20-09 Amdt 39-12457.\n\n\n\nNote: Boeing Alert Service Bulletins 727-57A0179 Revisions 3, 4, and 5 refer.\n\n\n\nCompliance: As specified in the Requirement document with a revised effective date of 27 December 2001.\n\nThis Airworthiness Directive becomes effective on 27 December 2001. Background: The manufacturer received several reports of main landing gear collapse.\n\nInvestigation revealed failure of the forward trunnion bearing support fitting as the cause. Collapse of a main landing gear can occur during normal operations as a result of a cracked support fitting, with consequent damage to the aircraft structure and injury to personnel. The actions specified in this Directive are intended to address the identified unsafe condition.\n\n![Signature of David Villiers, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\n\n\n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 14 November 2001\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![](image.001.png)","sortOrder":1}],"analysis":{"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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD is narrowly focused on a single unsafe condition (failure of the MLG forward trunnion bearing support fitting) for one aircraft family. The instrument does not broaden regulatory reach beyond addressing that specific structural/airworthiness risk; it simply mandates inspections per the FAA AD and related Boeing service bulletin. The revised effective date is administrative and does not expand substantive scope."},"complexity_factors":["Single-airframe applicability: all Boeing Model 727 series (straightforward scope).","Direct references to external technical documents: FAA AD 2001-20-09 and Boeing Alert Service Bulletin 727-57A0179 Revisions 3–5 (requires readers to consult other documents for technical steps).","No detailed inspection procedure reproduced in the AD text (delegates technical content to referenced documents).","Simple conditional logic: inspect as required, comply by the stated effective date (27 December 2001).","One normative compliance date and one regulatory basis (issued under subregulation 39.1(1) of CAR 1998)."],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- This is an Airworthiness Directive (AD) that applies to all Boeing 727 series aeroplanes (Applicability).\n- It requires operators to carry out inspections exactly as set out in the referenced FAA Airworthiness Directive 2001-20-09 (Requirement). The Boeing Alert Service Bulletin 727-57A0179 (Revisions 3, 4 and 5) is noted as related technical material.\n- The compliance timing is the same as in the FAA AD, with a revised effective date of 27 December 2001 (Compliance). The AD became effective on that date.\n\n**Who it affects**\n\n- Aircraft owners and operators of Boeing 727 series airplanes, and the maintenance organisations that service those aircraft.\n- The regulator (Civil Aviation Safety Authority, represented by the named CASA delegate) issues and enforces the requirement.\n\n**Why it matters (safety and operational mechanics)**\n\n- The directive responds to reports of main landing gear (MLG) collapse caused by failure of the forward trunnion bearing support fitting (Background).\n- A cracked support fitting can lead to collapse during normal operations, causing structural damage and potential injury. The inspection requirement is intended to detect cracking or damage and ensure corrective action is taken before collapse occurs.\n\n**How it works in practice**\n\n- Operators must follow the inspection procedures and any corrective actions set out in FAA AD 2001-20-09. The AD text does not reproduce the inspection steps; it mandates compliance with that external FAA document (Requirement).\n- If the inspection finds cracking or defects, operators will need to repair or replace parts per the referenced FAA AD and/or Boeing service bulletin. That may require parts, labour and aircraft downtime.\n- CASA enforces compliance; the AD is issued under the aviation regulations cited and signed by the CASA delegate.\n\n**Costs, incentives and trade-offs**\n\n- Who pays: direct costs fall to aircraft owners/operators (inspection labour, parts, maintenance shop time, and any required repairs). Indirect costs include aircraft downtime and possible schedule disruptions.\n- Benefits are concentrated (reduced risk of landing gear collapse for affected aircraft, passengers, crew and ground personnel) while costs are borne by the aircraft operators/maintainers.\n- Trade-offs: the AD trades operator time and maintenance expense for reduced operational risk. Operators may schedule inspections into maintenance cycles to reduce disruption, or, if costs or parts availability are material, consider aircraft retirement or operational restrictions.\n- Compliance burden and implementation risk: the AD relies on an external FAA AD and a Boeing service bulletin for technical detail. That creates dependency on those documents for correct interpretation and on maintenance organisations for consistent execution. Misinterpretation or delays in obtaining parts/technical data can increase implementation risk.\n\n**Regulatory discretion and enforcement**\n\n- The CASA delegate issued the AD under the relevant aviation regulation; CASA retains enforcement authority. The AD prescribes an inspection obligation rather than prescribing a specific repair method in-line text (the repair methods are in the referenced FAA/Boeing documents).\n\n**Net effect on private choice and markets**\n\n- The directive restricts operators’ freedom to continue flying without the required inspection/repair: continued operation without complying would be non‑compliant and unsafe. It does not transfer ownership or alter commercial terms, but it imposes an operational cost and scheduling constraint. The measure does not directly affect competition between airlines beyond the uniform safety requirement; any competitive effects arise from variation in operators’ ability to absorb inspection and repair costs or schedule downtime.\n\n(References in the AD: Applicability; Requirement — FAA AD 2001-20-09; Note — Boeing Alert Service Bulletin 727-57A0179 Revisions 3,4,5; Compliance; Background; signature of CASA delegate.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-b727-172-mlg-forward-trunnion-bearing-support-fitting","history":"/api/acts/ad-b727-172-mlg-forward-trunnion-bearing-support-fitting/history","analysis":"/api/acts/ad-b727-172-mlg-forward-trunnion-bearing-support-fitting/analysis","conflicts":"/api/acts/ad-b727-172-mlg-forward-trunnion-bearing-support-fitting/conflicts","importantCases":"/api/acts/ad-b727-172-mlg-forward-trunnion-bearing-support-fitting/important-cases","documents":"/api/acts/ad-b727-172-mlg-forward-trunnion-bearing-support-fitting/documents"}}