{"id":"F2006B02505","name":"AD/AS 355/50 Amdt 4 - Tail Rotor Hub Pitch Change Bearings","slug":"ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41761,"registerId":"commonwealth-F2006B02505-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/AS 355/50 Amdt 4 - Tail Rotor Hub Pitch Change Bearings","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 355/50 Amdt 3 and issues the following 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![](image.001.png)\n\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\nAD/AS 355/50\n\nAmdt 4\n\n  \nTail Rotor Hub Pitch Change Bearings 13/2002\n\nApplicability: AS 355 helicopters versions E, F, F1, F2, and N fitted with tail rotor hub pitch change plate, P/N’s 350A33-2004-00/-01/-02/-03/-05 and not incorporating Mod 076551 as detailed in Eurocopter AS 355 Service Bulletin No. 65.00.15R1.\n\nRequirement: 1. Check the rotational torque of the tail rotor pitch change plate bearing in accordance with paragraph 2.B (1) of Eurocopter Alert Service Bulletin (ASB) No. 05.00.30 Revision 3.\n\n    2. Carry out the axial play, friction point and brinelling check in accordance with paragraph 2.B (2) of Eurocopter Alert Service Bulletin (ASB) No. 05.00.30 Revision 3.\n    3. Before installation of a spare pitch change plate assembly carry out the requirements of paragraphs 2.B 1 and 2.B 2 of Eurocopter Alert Service Bulletin (ASB) No. 05.00.30 Revision 3.\n    4. Disposition of components subject to the inspections as required by Items 1 \\- 3 of this Directive shall be in accordance with paragraph 2.B 3 of Eurocopter Alert Service Bulletin (ASB) No. 05.00.30 Revision 3.\n\nNote 1: DGAC AD 1999-085-076(A) R3 refers.\n\nNote 2: Incorporation of Eurocopter Service Bulletin AS 350 65.00.38.P5 constitutes terminating action for this Directive.\n\nCompliance: 1. Unless previously accomplished; within 10 flying hours after 31 October 2002.\n\n    2. At intervals not to exceed 50 flying hours from the previous check (without exceeding 6 months between two checks).\n\n    3. Prior to installation of a tail rotor pitch change plate assembly or a tail rotor gearbox assembly.\n\n    4. During compliance with Requirements 1, 2, or 3, as applicable.\n\nThe compliance times of Amendment 3 of this Directive remain unchanged by this issue.\n\nEurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\nAS/AS 355/50 Amdt 4 (continued)\n\nThis Amendment becomes effective on 26 December 2002.\n\nBackground: In service reports have revealed deterioration of the tail rotor hub pitch change plate bearing may result in the seizure of the bearing and loss of control of the aircraft.\n\nThis Directive introduces measures to check for correct rotational torque, and regular maintenance checks to ensure the integrity of the assembly.\n\nAmendment 1 was issued to correct Compliance Statement 2 to reflect the DGAC repetitive inspection requirements and to include the more stringent compliance requirements of DGAC 1999-084-057(A) R1 dated 14 May 1999.\n\nAmendment 2 provides terminating action for this Directive and adds reference to disposition of components subject to the required inspections.\n\nAmendment 2 of this Airworthiness Directive became effective on 15 June 2000. Amendment 3 was issued to reflect replacement of Eurocopter Service Bulletin No.\n\n05.00.30 R2 with Eurocopter Alert Service Bulletin No. 05.00.30 Revision 3. The\n\nService Bulletin was upgraded to Alert status with no change to the technical content of the Service Bulletin.\n\nAmendment 4 of this Airworthiness Directive has been issued to correct a typographical error in Amendment 3.\n\nAmendment 3 of this Airworthiness Directive became effective on 31 October 2002\\. The original issue of this Airworthiness Directive became effective on 20 May 1999.\n\n![](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 18 November 2002\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 4 December 2002.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"Amendment 4 corrects a typographical error in Amendment 3 and does not change the substantive requirements or compliance times. The Directive continues to require the same inspections per ASB No. 05.00.30 Rev 3, retains the same applicability, and preserves the terminating action (Eurocopter Service Bulletin AS 350 65.00.38.P5)."},"complexity_factors":["Cross-reference to an external technical document (Eurocopter ASB No. 05.00.30 Rev 3) for detailed procedures, creating dependency on that ASB for compliance.","Narrow applicability tied to specific part numbers (350A33-2004-00/-01/-02/-03/-05) and exclusion of assemblies incorporating Mod 076551, requiring detailed fleet configuration checks.","Multiple distinct inspection tasks (rotational torque, axial play, friction point, brinelling) that require technical tools/skills and interpretation.","Fixed short initial compliance window (within 10 flying hours after 31 Oct 2002) and recurring interval (every 50 flying hours or six months) imposing operational scheduling and maintenance burden.","Disposition and pre-installation requirements for spare assemblies introduce logistics and parts‑handling steps.","Terminology and amendment history (several amendments, revocation of the prior AD) increase administrative tracking complexity for operators and maintainers."],"plain_english_summary":"This Airworthiness Directive requires operators of Eurocopter AS 355 (E, F, F1, F2, N) helicopters fitted with specified tail rotor pitch change plates to inspect and test the pitch‑change plate bearings (rotational torque, axial play, friction point and brinelling) using Eurocopter ASB No. 05.00.30 Rev 3. Initial and repetitive inspections are mandated (first within 10 flying hours after 31 Oct 2002; then every 50 flying hours or six months); Service Bulletin AS 350 65.00.38.P5 is listed as terminating action. The stated aim is to prevent bearing seizure and potential loss of control."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This legislation maintains its original scope. Amendment 4 is explicitly described as correcting only a typographical error from Amendment 3. The directive remains focused on the specific safety issue of tail rotor hub pitch change bearing integrity for AS 355 helicopters. Previous amendments added terminating actions and updated manufacturer bulletin references, but these were natural evolutions of the original safety purpose rather than scope creep."},"complexity_factors":["Multiple amendment history (4 versions) with cross-references to previous amendments and their effective dates","Specific part number ranges (P/N's 350A33-2004-00/-01/-02/-03/-05) requiring careful identification","Conditional applicability based on modification status (Mod 076551) and Service Bulletin incorporation","Four distinct compliance timeframes with different triggers (flying hours, calendar dates, installation events)","External document dependencies: references to Eurocopter Alert Service Bulletin No. 05.00.30 Revision 3 and DGAC AD 1999-085-076(A) R3","Terminating action condition (incorporation of Eurocopter Service Bulletin AS 350 65.00.38.P5) creates an alternative compliance pathway"],"plain_english_summary":"This Airworthiness Directive mandates recurring inspections and maintenance of the tail-rotor hub pitch-change bearings on Eurocopter AS355 (E, F, F1, F2, N) helicopters that have not had Mod 076551. It requires checks of rotational torque, axial play, friction/brinelling, and inspection of spares, with initial and repeat intervals to prevent bearing seizure and potential loss of control.\n\nCompliance by owners/operators is mandatory; installing the specified Eurocopter service bulletin modification terminates the repetitive inspections."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings","history":"/api/acts/ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings/history","analysis":"/api/acts/ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings/analysis","conflicts":"/api/acts/ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings/conflicts","importantCases":"/api/acts/ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings/important-cases","documents":"/api/acts/ad-as-355-50-amdt-4-tail-rotor-hub-pitch-change-bearings/documents"}}