{"id":"F2006B09319","name":"AD/EC 135/5 Amdt 3 - Main Rotor Drive Torque Struts","slug":"ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":53459,"registerId":"commonwealth-F2006B09319-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/EC 135/5 Amdt 3 - Main Rotor Drive Torque Struts","content":"![](image.001.png)\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/EC 135/5 Amdt 2 and issues the following 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\nEurocopter EC 135 Series Helicopters\n\nAD/EC 135/5\n\nAmdt 3\n\n  \n\nMain Rotor Drive Torque Struts 10/2003 DM\n\nApplicability: All Model EC135 helicopters.\n\nRequirement: Action in accordance with Eurocopter Deutschland Alert Service Bulletin ECD 135- 63A-002 Revision 4.\n\nNote 1: Installation of titanium torque struts constitutes terminating action for the Requirements of this Directive.\n\nNote 2: LBA AD 2001-107/3 refers.\n\nCompliance: 1. As of the effective date of this Directive, a life limit of 500 flight hours applies for aluminium torque struts.\n\n    2. Aluminium torque struts that have exceeded the 500 flight hour life limit at the effective date of this Directive, are to be replaced with new torque struts within 100 flight hours after 13 August 2003, unless already accomplished. If affected, during this 100 flight hour transition period aluminium torque struts are to be inspected daily before the first flight of the day.\n\n    3. Use of aluminium torque struts is permitted only until 31 December 2004.\n\nIf no externally mounted hoist is installed, and if the before the first flight of the day inspection is required to be performed by the pilot, this Directive shall be entered on the Maintenance Release as maintenance required. The required visual inspection may be performed and certified by the Pilot in Command who has been trained to do the inspection by an appropriately qualified person. In this case, a copy of the Requirement document and this Directive are to be carried in the aircraft.\n\nThis Amendment becomes effective on 13 August 2003.\n\nBackground: During flight a helicopter encountered a thump-like sound, which was later followed by unusual vibrations. After the subsequent precautionary landing, it was discovered that the attachment between the tensile stress-loaded torque strut located on the right hand side of the main transmission and the fuselage structure, had ruptured. This Directive requires a visual inspection for cracking and a change of installation side of the torque struts, and eventual strut replacement.\n\nEurocopter EC 135 Series Helicopters\n\nAD/EC 135/5 Amdt 3 (continued)\n\nAmendment 1 corrected a drafting error, which significantly reduced the impact of the Directive.\n\nAmendment 2 introduced new torque struts, which are not subject to a life limit. Installation of the new torque struts constitutes optional terminating action to the requirements of this Directive.\n\nAmendment 3 is issued in response to revision of the related LBA AD, which introduces Revision 4 of the Requirement document.\n\nAmendment 2 of this Airworthiness Directive became effective on 4 September 2002\\. Amendment 1 of this Airworthiness Directive became effective on 6 April 2001.\n\nThe original issue of this Airworthiness Directive became effective on 26 March 2001.\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 7 August 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 13 August 2003.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The Directive’s scope evolved from the original 2001 issue. Amendment 1 corrected a drafting error that reduced impact; Amendment 2 introduced new (titanium) torque struts that are not subject to the life limit and made their installation an optional terminating action; Amendment 3 updates the Requirement document to Revision 4 of the Eurocopter service bulletin and aligns the AD with the revised LBA AD. These changes altered compliance options, added a defined life limit for aluminium struts, and introduced specific transition and inspection obligations, while the applicability (all EC135 helicopters) remained unchanged."},"complexity_factors":["Multiple amendments and cross-references: revokes prior AD/EC 135/5 Amdt 2 and follows Amendment 3 which aligns with a revised LBA AD and Eurocopter Alert Service Bulletin ECD 135-63A-002 Revision 4 (Requirement document).","Technical life-limit and phased compliance: introduces a 500 flight‑hour life limit for aluminium torque struts, a 100 flight‑hour replacement window for already-exceeded parts, and a final prohibition date (31 Dec 2004), creating tracking and scheduling burdens.","Operational inspection burden: requires daily pre‑flight visual inspections during the transition period and permits pilots to perform and certify these inspections if trained and no externally mounted hoist is installed (affects training and maintenance release entries).","Optional terminating action: installation of titanium torque struts removes the AD’s ongoing requirements, creating a clear but potentially costly retrofit option for operators.","Record-keeping and delegation: the Directive must be entered on the Maintenance Release and allows non-maintenance personnel (Pilot in Command) to certify inspections if properly trained, introducing delegation and evidentiary considerations.","Interplay with foreign authority and service bulletin: mandatory compliance framed by Eurocopter service bulletin Revision 4 and referenced LBA AD, meaning technical compliance relies on an external manufacturer document and foreign regulator action.","Effective dates and transitional rules: staggered effective dates (directive effective 13 Aug 2003, transition allowances) increase administrative complexity for operators with differing asset states."],"plain_english_summary":"This Airworthiness Directive for all Eurocopter EC135 helicopters imposes a 500-flight‑hour life limit on aluminium main rotor drive torque struts, mandates inspections and a staged replacement timetable, and bans aluminium struts after 31 December 2004. Installing titanium torque struts removes the AD’s requirements. It affects owners/operators and pilots who must track hours, perform daily pre‑flight inspections during the transition period, record the AD on the Maintenance Release, and replace or retrofit torque struts to meet the directive."},"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":true,"description":"The original directive (March 2001) required visual inspections and changing the installation side of torque struts. Through Amendments 2 and 3, the scope expanded significantly: Amendment 2 introduced new titanium struts as optional terminating action, and Amendment 3 added hard life limits (500 hours), replacement deadlines, and an absolute use-by date (31 December 2004). The directive evolved from an inspection-and-repositioning order to a comprehensive component phase-out mandate with multiple compliance pathways."},"complexity_factors":["Multiple amendment history referenced (Amendments 1, 2, and 3) creating layered context","Conditional compliance deadlines (500-hour life limit, 100-hour transition period, 31 December 2004 absolute cutoff)","Nested exception for pilot-conducted inspections (no hoist + pilot inspection required + training requirement + documentation requirement)","Cross-reference to external German aviation authority document (LBA AD 2001-107/3 and Eurocopter Alert Service Bulletin ECD 135-63A-002 Revision 4)","Terminating action provision (titanium struts) that creates an optional compliance pathway"],"plain_english_summary":"This CASA safety order for Eurocopter EC135s replaces an earlier directive and requires operators to limit use of aluminium torque struts to a short certified life, inspect and replace or upgrade them within the transition window, and cease using aluminium struts by the end of 2004; fitting titanium struts is a permanent fix that removes the requirements.\n\nIssued after an in‑flight torque‑strut attachment rupture, the order prevents similar structural failures; if a pilot must perform daily inspections without a hoist, they may certify them when trained, note it on the Maintenance Release, and carry the directive."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts","history":"/api/acts/ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts/history","analysis":"/api/acts/ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts/analysis","conflicts":"/api/acts/ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts/conflicts","importantCases":"/api/acts/ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts/important-cases","documents":"/api/acts/ad-ec-135-5-amdt-3-main-rotor-drive-torque-struts/documents"}}