{"id":"F2009L00676","name":"AD/AS 355/98 Amdt 1 - Stabiliser Upper and Lower Fin Attachment Fitting - Modification","slug":"ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":77601,"registerId":"commonwealth-F2009L00676-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Eurocopter AS 355 (Twin Ecureuil) Series","sectionType":"division","heading":"Eurocopter AS 355 (Twin Ecureuil) Series Helicopters","content":"### Eurocopter AS 355 (Twin Ecureuil) Series Helicopters\n\n| AD/AS 355/98 Amdt 1 | Stabiliser Upper and Lower Fin Attachment Fitting - Modification | 4/2009 DM |\n| ------------------- | ---------------------------------------------------------------- | --------- |\n\n| Applicability: | Model AS 355 E, F, F1, F2 and N helicopters, all serial numbers, fitted with the following upper and lower fins to which Modification (MOD) 073330 has not been incorporated:Upper fin assembly part number 355A14-0522-00XX, -01XX, -02XX, -03XX, -13XX, -14XX and -15XX.Lower fin assembly part number 355A14-0521-00XX, -01XX, -02XX and -03XX. |\n| -------------- | 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|\n| Requirement: | Required as indicated, unless already accomplished.1. For helicopters with upper and lower fins pre MOD 073288:a. For helicopters which have accumulated less than 110 flight hours after 31 August 2006:Within 110 flight hours after 31 August 2006, replace the upper and lower fin attachment screws in accordance with the instructions specified in paragraph 2.B.2 of EUROCOPTER AS 355 Alert Service Bulletin (ASB) No.55.00.11 Revision 2 (MOD 073288), or later EASA approved revision.b. For helicopters which have accumulated more than 110 flight hours after 31 August 2006:Within 15 flight hours after 26 February 2009, replace the upper and lower fin attachment screws in accordance with the instructions specified in paragraph 2.B.2 of ASB No. 55.00.11 Revision 2 (MOD 073288), or later EASA approved revision.c. At intervals not to exceed 110 flight hours, check the tightening torque of the upper fin attachment screws and check the upper fin reinforcement splice for cracks and loosened rivets in accordance with the instructions specified in paragraph 2.B.3 of ASB No. 55.00.11 Revision 2, or later EASA approved revision.d. In the case of cracks, loosened rivets in the reinforcement splice or if the tightening torque of one or both of the attachment screws is less than 80% of the minimum torque value, before further flight, apply the associated corrective actions in accordance with the instructions of paragraph 2.B.3.a.1, 2.B.3.a.2 or 2.B.3.a.3 (as applicable), of ASB No. 55.00.11 Revision 2, or later EASA approved revision.2. For helicopters with upper and lower fins post MOD 073288:a. For helicopters which have accumulated less than 110 flight hours since the latest check performed in accordance with paragraph 2.B.3 of ASB No. 55.00.11 Revision 0, or later EASA approved revision:Within 110 flight hours after the latest check performed in accordance with paragraph 2.B.3 of ASB No. 55.00.11 Revision 0, or later EASA approved revision, check the tightening torque of the upper fin attachment screws and check the upper fin reinforcement splice for cracks and loosened rivets in accordance with the instructions specified in paragraph 2.B.3 of ASB No. 55.00.11 Revision 2, or later EASA approved revision. Repeat thereafter at intervals not to exceed 110 flight hours.b. For helicopters which have accumulated more than 110 flight hours since the latest check performed in accordance with paragraph 2.B.3 of ASB No. 55.00.11 Revision 0, or later EASA approved revision:Within 15 flight hours after 26 February 2009, check the tightening torque of the upper fin attachment screws and check the upper fin reinforcement splice for cracks and loosened rivets in accordance with the instructions specified in paragraph 2.B.3 of ASB No. 55.00.11 Revision 2, or later EASA approved revision. Repeat thereafter at intervals not to exceed 110 flight hours.c. In the case of cracks, loosened rivets in the reinforcement splice or if the tightening torque of one or both of the attachment screws is less than 80% of the minimum torque value, before further flight, apply the associated corrective actions in accordance with instructions of paragraph 2.B.3.a.1, 2.B.3.a.2 or 2.B.3.a.3 (as applicable), of ASB No. 55.00.11 Revision 2, or later EASA approved revision.3. For helicopters with upper and lower fins pre MOD 073330:Unless already accomplished, no later than 31 March 2009, remove the fins, modify the upper and lower fittings on the tail boom by increasing the diameter of the bolt holes, and replace bolts part number 22126BV060032L and washers part number 23112AG060LE with special bolts part number 350A23-4016-20 and special washers part number 350A23-4017-22; in accordance with EUROCOPTER AS 355 Alert Service Bulletin No. 55.00.12 Revision 1 (MOD 073330), or later EASA approved revision.Compliance with Requirement 3 of this Directive is considered as acceptable compliance with Requirements 1.a. and 1.b, and terminating action for the repetitive checks of Requirements 1.c, 2.a. and 2.b of this Directive.4. After 31 March 2009, upper and lower fins with part numbers listed in the applicability section of this Directive, and held as spares, shall not be installed on any helicopter unless MOD 073330 has been incorporated.Note: EASA AD 2009-0029 refers. |\n| Compliance: | As specified in Requirement 1, Requirement 2, Requirement 3 and Requirement 4. |\n| | This Amendment becomes effective on 26 February 2009. |\n| Background: | The EASA received several reports of cracking in the stabiliser upper fin of Model AS 355 N helicopters. The growth of a crack in a fin attachment spar, unless detected and corrected, could lead to failure of the spar and loss of the fin.The EASA AD related to this Directive, AD 2008-0120, supersedes EASA ADs 2006-0096 (AD/AS 355/84 Amdt 1) and 2006-0097R1 (AD/AS 355/91 Amdt 1), and thereby constitutes terminating action to the requirements of these CASA ADs.Amendment 1 is issued in response to a new EASA AD, which adds new upper and lower fin assembly part numbers to applicability, and includes the repetitive checks of previous Directives; until accomplishment of MOD 073330. |\n\n![](image.001.png) \nDavid Villiers \nDelegate of the Civil Aviation Safety Authority\n\n18 February 2009","sortOrder":0},{"sectionNumber":"AD/AS 355/98 Amdt 1","sectionType":"part","heading":"AD/AS 355/98 Amdt 1","content":"## AD/AS 355/98 Amdt 1","sortOrder":1},{"sectionNumber":"Stabiliser Upper and Lower Fin Attachmen","sectionType":"part","heading":"Stabiliser Upper and Lower Fin Attachment Fitting - Modification","content":"## Stabiliser Upper and Lower Fin Attachment Fitting - Modification","sortOrder":2},{"sectionNumber":"4/2009 DM","sectionType":"part","heading":"4/2009 DM","content":"## 4/2009 DM","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":7,"scope_assessment":{"changed":true,"description":"Amendment 1 expands the Directive's scope by adding additional upper and lower fin assembly part numbers to the applicability and by reintroducing repetitive inspections (every 110 flight hours) for affected fins until MOD 073330 is incorporated. It also confirms MOD 073330 as terminating action for the repetitive checks and bans installation of listed unmodified spare fins after 31 March 2009 (Requirements 3 and 4; Background)."},"complexity_factors":["Multiple compliance branches depending on modification status: separate rules for fins pre/post MOD 073288 and pre/post MOD 073330 (Requirements 1, 2 and 3).","Flight‑hour thresholds create tiered deadlines: distinctions at 110 flight hours and shorter 15‑flight‑hour windows after 26 Feb 2009 (Reqs 1.a/b, 2.a/b).","Repetitive inspection requirement at intervals not to exceed 110 flight hours, with terminating action upon MOD 073330 (Reqs 1.c, 2.a/b, 3).","Mandatory immediate corrective actions before further flight when cracks, loosened rivets, or torque below 80% are found (Reqs 1.d, 2.c).","Modification work specified with particular part numbers to be removed/installed and bolt‑hole reaming (MOD 073330) — technical maintenance and parts sourcing obligations (Req 3).","Prohibition on installing listed spare fins after 31 March 2009 unless MOD 073330 is incorporated — inventory and compliance impact for spares holders (Req 4).","Dependence on external manufacturer documents and regulatory approvals: EUROCOPTER ASB No.55.00.11 Rev 2 and ASB No.55.00.12 Rev 1, or later EASA‑approved revisions, adds variability and document‑control needs.","Wide applicability across all serial numbers for multiple fin part numbers increases fleet coverage and potential aggregate cost/operational impact (Applicability, Background).","Regulatory linkage to EASA ADs (EASA AD 2009‑0029, and earlier EASA ADs), creating chained compliance obligations and supersessions (Background)."],"plain_english_summary":"This directive requires operators of Eurocopter AS 355 E/F/F1/F2/N helicopters fitted with specified upper and lower tail fins to inspect, replace and/or modify fin attachment fittings and fasteners on set timelines, and to perform recurring torque and reinforcement‑splice checks until a structural modification (MOD 073330) is incorporated. It affects aircraft operators, maintenance organisations and spare‑parts holders by imposing flight‑hour inspection deadlines, before‑flight corrective actions for detected cracks or low torque, and a prohibition on installing listed unmodified spare fins after 31 March 2009."},"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":6,"scope_assessment":{"changed":true,"description":"Originally issued as AD/AS 355/98, this Amendment 1 significantly expanded scope beyond the original directive. It added new upper and lower fin assembly part numbers to applicability, incorporated repetitive inspection requirements from previous superseded directives (AD/AS 355/84 and AD/AS 355/91), and introduced a permanent terminating modification (MOD 073330) that wasn't in the original. The directive evolved from a simple inspection/replacement order into a comprehensive multi-path compliance framework with interim and permanent solutions."},"complexity_factors":["Multiple parallel compliance paths depending on modification status (pre-MOD 073288, post-MOD 073288, pre-MOD 073330)","Time-based triggers using two different reference dates (31 August 2006 and 26 February 2009) combined with flight hour accumulation thresholds","Nested conditional logic: 'if less than X hours, do Y; if more than X hours, do Z; if cracks found, do A, B, or C depending on circumstances'","Cross-references to external documents (EUROCOPTER ASB 55.00.11 Revision 2, EASA AD 2009-0029) without reproducing their content","Terminating action provisions that cancel previous requirements when permanent modification is completed","Specific part number ranges with wildcard digits (XX placeholders) in applicability section","Dual regulatory layering: implements EASA AD 2009-0029 while superseding previous CASA ADs (AD/AS 355/84 Amdt 1 and AD/AS 355/91 Amdt 1)"],"plain_english_summary":"This CASA Airworthiness Directive mandates owners/operators of Eurocopter AS 355 (E/F/F1/F2/N) helicopters with specified upper/lower fin part numbers to address cracking in tail fin attachment fittings. It requires immediate screw replacement and recurring inspections until a permanent modification (MOD 073330) is installed by the compliance date, and bars installing unmodified spare fins thereafter. The AD prevents fin detachment in flight, which could cause loss of control and a fatal accident."}},"importantCases":[],"_links":{"self":"/api/acts/ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification","history":"/api/acts/ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification/history","analysis":"/api/acts/ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification/analysis","conflicts":"/api/acts/ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification/conflicts","importantCases":"/api/acts/ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification/important-cases","documents":"/api/acts/ad-as-355-98-amdt-1-stabiliser-upper-and-lower-fin-attachment-fitting-modification/documents"}}