{"id":"F2006B02506","name":"AD/AS 355/52 Amdt 1 - TR Head Pitch Change Plate Bearing Spacer","slug":"ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41762,"registerId":"commonwealth-F2006B02506-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/52 Amdt 1 - TR Head Pitch Change Plate Bearing Spacer","content":"![](image.001.png)\n\n![](image.001.png)  \nAIRWORTHINESS DIRECTIVE\n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AS 355/52 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 AS 355 (Twin Ecureuil) Series Helicopters\n\nAD/AS 355/52\n\nAmdt 1\n\n  \nTR Head Pitch Change Plate Bearing Spacer 13/2004\n\nApplicability: AS 355 helicopters, versions E, F, F1, F2 and N, fitted with the tail rotor pitch change rotating plates, all part numbers, on which Eurocopter modification (Mod) 07 6554 has not been embodied.\n\nThis Airworthiness Directive (AD) does not apply to post-mod 076550 pitch change plate assembly part number 350A33-2030-00.\n\nRequirement: 1. Identify the position of the spacer and the tail rotor pitch change rotating plate as per provisions of paragraph 2.B.1 of Eurocopter AS355 Alert Service Bulletin (ASB) 05.00.33 R1 dated 15 March 2004 or later revision approved by DGAC / EASA.\n\n2. a. Monitor position of the spacer and the tail rotor pitch change rotating plate for alignment as per provisions of paragraph 2.B.2 of ASB 05.00.33 R1 or later revision approved by DGAC / EASA.\n\nThe inspection detailed in requirement 2 may be performed by the pilot-in- command, in which case, a certification is to be made by entering AD/AS 355/52 Amdt 1 against the daily inspection certification on the maintenance release. A copy of this directive and of the requirement document must be carried in the helicopter.\n\n2. b. If the paint index marks are aligned, embody Mod 076550 as per the provisions of paragraph 2.B.3 of ASB 05.00.33 R1 or later revision approved by DGAC / EASA.\n\n    2. c. If the paint index marks are mis-aligned, embody Mod 076550 as per the provisions of paragraph 2.B.4 of ASB 05.00.33 R1 or later revision approved by DGAC / EASA.\n\nNote 1: DGAC Airworthiness Directive F-2000-223-059 R1 as approved by EASA reference number 2004-9370 dated 7 September 2004 refers.\n\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\nAD/AS 355/52 Amdt 1 (continued)\n\nCompliance: 1. Unless previously accomplished, at the latest within 10 flying hours after the effective date of this AD.\n\n    2.a. Daily, after the last flight of the day.\n\n    2.b. Not later than the next “T” basic inspection.\n\n    2.c. With-in 25 flying hours from detection of the misalignment.\n\nNote 2: Compliance to the original issue of AD/AS 355/52 is an acceptable alternate to this amendment and no further action is required.\n\nThis Amendment becomes effective on 23 December 2004.\n\nBackground: This amendment of the Airworthiness Directive reflects changes in the document referred to, in the original issue of the AD, namely revision 1 of Eurocopter AS 355 ASB 05.00.33 and revision 1 of DGAC AD F-2000-223-059. The changes are in the effectivity list and there is no difference in the technical contents.\n\nThere have been reports of rotation of the bearing spacers in AS355 tail rotor. Such rotation indicates that the inner bearing race may be rotating on its shaft. Rotation may cause excessive wear and cut the rotating plate, which will cause deterioration and loss of pitch control of the tail rotor.\n\nThe original issue of the directive addressed unsafe condition caused by the loss of pitch control of the tail rotor.\n\nThe original issue of this airworthiness directive became effective on 14 June 2000.\n\n![](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 8 November 2004\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 1 December 2004.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The amendment altered the effectivity list but did not change the technical requirements. Background states: 'changes are in the effectivity list and there is no difference in the technical contents.' The directive therefore adjusts which serials/assemblies are covered while keeping the same inspections, monitoring and mod embodiment requirements (Background)."},"complexity_factors":["Applicability limits scope to AS355 versions E, F, F1, F2 and N lacking Mod 076550, determining which operators are affected (Applicability).","Express exclusion for post‑Mod 076550 pitch change plate assembly part number 350A33-2030-00 (Applicability).","Three-step operational requirement: identify spacer position, monitor alignment, and embody Mod 076550 conditionally (Requirement 1; 2.a; 2.b; 2.c).","Dependency on external technical documents and approvals: Eurocopter AS355 Alert Service Bulletin ASB 05.00.33 R1 (or later revision) and DGAC/EASA approval are required for procedures (Requirement; Note 1).","Pilot-in-command inspection option shifts hands-on inspection and creates an administrative recording obligation: pilot may perform daily check but must enter the AD against the daily inspection certification and carry copies of the directive and requirement document (Requirement 2.a).","Multiple, short and differing compliance deadlines increase scheduling complexity: initial check within 10 flying hours; daily after last flight; modification by next 'T' basic inspection or within 25 flying hours of misalignment detection (Compliance 1; 2.a; 2.b; 2.c).","Alternative compliance path preserved: compliance with the original issue of AD/AS 355/52 is accepted as an alternative, giving operators a choice of which action path to follow (Note 2).","Regulatory issuance and amendment via CASA delegate under subregulation 39.1(1) and revocation of the prior AD introduces administrative/regulatory discretion in how the directive was promulgated (introductory paragraph).","Clear safety linkage: background explains spacer rotation can allow inner race rotation, causing wear that may cut the rotating plate and result in loss of tail-rotor pitch control — the technical risk driving the mandated actions (Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of certain Eurocopter AS355 helicopters (versions E, F, F1, F2 and N) that have not had Mod 076550 fitted to inspect and monitor the tail-rotor pitch change plate bearing spacer alignment and, if needed, install Mod 076550. The measures aim to stop spacer rotation that can wear or cut the rotating plate and lead to loss of tail-rotor pitch control. It shifts inspection and some certification duties to operators and pilots and sets short compliance timeframes."},"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 is an amendment to an existing Airworthiness Directive (AD/AS 355/52). The Background section explicitly states that the changes are limited to updated document references (revision numbers of the Alert Service Bulletin and DGAC AD) and effectivity list updates, with 'no difference in the technical contents.' The scope remains identical to the original 2000 directive — addressing the same unsafe condition in the same helicopter models with the same required actions."},"complexity_factors":["Multiple cross-references to external technical documents (Eurocopter ASB 05.00.33 R1, DGAC/EASA directives)","Conditional logic with three distinct compliance paths based on inspection findings (aligned vs misaligned vs previously accomplished)","Specific part number exclusions and applicability criteria (post-mod 076550 assemblies excluded)","Dual compliance timelines (10 flying hours for initial inspection, daily thereafter, 25 flying hours for corrective action if misaligned)","Delegation chain and regulatory references (subregulation 39.1(1) of CASR 1998)"],"plain_english_summary":"This AD for Eurocopter AS355 helicopters addresses a fault in the tail-rotor pitch-change mechanism where a bearing spacer can rotate and cut the rotating plate, risking loss of tail-rotor control. It requires a one-time spacer/plate check, daily pilot visual alignment checks (with log entry and AD copy aboard), and installation of a modification either at the next inspection if aligned or within 25 flight hours if misaligned. It updates references to newer technical documents without changing required actions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer","history":"/api/acts/ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer/history","analysis":"/api/acts/ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer/analysis","conflicts":"/api/acts/ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer/conflicts","importantCases":"/api/acts/ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer/important-cases","documents":"/api/acts/ad-as-355-52-amdt-1-tr-head-pitch-change-plate-bearing-spacer/documents"}}