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## EASA EMERGENCY AIRWORTHINESS DIRECTIVE

AD No : 2007-0288-E

Date: 15 November 2007

No person may operate an aircraft to which an Airworth iness Directive applies, except in accordance with the requirements of that Airworthiness Di rective unless otherwise agreed with the Authority of the State of Registry.



### Type Approval Holder’s Name :

EUROCOPTER Type/Model designation(s) :

AS 365, EC 155, SA 360, SA 365 and SA 366 helicopters

TCDS Number: France No. 153, 159 [TC No. 80 and 86, respectively]

Foreign AD: Not applicable.

Supersedure: DGAC France Airworthiness Directive (AD) F-2005-181, EASA approval No. 2005-6390; and DGAC France AD F-2005-182, EASA approval No. 2005-6391.



### ATA 05, 63 Main Rotor Drive – Main Gearbox (MGB) Planet Gear Carrier – Inspection/Replacement

Manufacturer(s): EUROCOPTER; EUROCOPTER FRANCE; AEROSPATIALE (SNIAS)

Applicability: AS 365 N2, AS 365 N3, EC 155 B, EC 155 B1, SA 360 C, SA 365 C, SA 365 C1, SA 365 C2, SA 365 C3, SA 365 N, SA 365 N1 and SA 366 G1 helicopters, all serial numbers.

Reason: In 2004, cracks were discovered in the web of the MGB planet gear carrier. The two affected MGB units had been removed for overhaul/repair, subsequent to the detection of metal chips at the magnetic plugs. This phenomenon can be detected by metal chips at the magnetic plug. Investigation of the first case, detected by a subsidiary, showed a failure of the head of a screw that secures the sun gear bearing. The screw head was caught by the planet gear / fixed ring gear / sun gear drive train. The second case was discovered at the EUROCOPTER Marignane works and did not seem to be associated with any other failure. To address the unsafe condition, EUROCOPTER published ALERT TELEX documents for the types affected, containing instructions to check the magnetic plug of the MGB after the last flight of each day, without exceeding 10 flying hours, and a check of the MGB planet gear carrier as soon as one or more chips are found. DGAC France classified these instructions MANDATORY by the issuance of Emergency ADs UF-2004-181 for SA 360, AS/SA 365 and SA 366 helicopters (EASA Approval Number 2004-11051), UF-2004-182 for EC 155 helicopters (EASA Approval Number 2004-11052) and UF-2004-194 for all2/2 affected helicopters (EASA Approval Number 2004-12387). When the ALERT TELEX documents were re-published in 2005 as ALERT SERVICE BULLETINS, these ADs were superseded by DGAC France AD F-2005-181 for EC 155 helicopters (EASA Approval Number 2005-6390) and F-2005-182 for all affected helicopters (EASA Approval Number 2005-6391) with no change to the technical requirements. Since the issue of those ADs on 09 November 2005, a further case of crack in a planet gear carrier of a MGB installed on an EC155 helicopter has been reported. Examination of the crack revealed a progressive fatigue failure of the planet gear carrier initially caused by a machining non- conformity (scoring) in the blend radius between a pin and the web. An additional analysis showed, however, that the time limit of 265 hours that was assigned to the first inspection of the planet gear carrier, can no longer guarantee safe flight. The established interval of the inspection is not invalidated as the analysis also showed that the non-conformity does not affect the crack growth rate. For the reasons described above, the present EASA Emergency AD supersedes DGAC France ADs F-2005-181 and F-2005-182, retaining the technical requirements thereof but requiring the initial inspection/check of the MGB planet gear carrier, irrespective of the accumulated operating hours.

Effective Date: 19 November 2007

Compliance: Required as indicated, unless accomplished previously: (1) From the effective date of this AD, accomplish the checks, inspections and replacements, as necessary, at the threshold and intervals as indicated in and in accordance with the instructions of EUROCOPTER AS365N Alert Service Bulletin (ASB) No. 05.00.48 Revision 1, SA366 ASB No. 05.33 Revision 1, SA360/365C ASB No. 05.26 Revision 1 or EC155 ASB No. 05A007 Revision 1, as applicable to type/model helicopter; (2) After the effective date of this AD, no person shall install a spare MGB on a helicopter as a replacement part unless the MGB has been inspected in accordance with instructions of EUROCOPTER AS365N Alert Service Bulletin (ASB) No. 05.00.48 Revision 1, SA366 ASB No. 05.33 Revision 1, SA360/365C ASB No. 05.26 Revision 1 or EC155 ASB No. 05A007 Revision 1, as applicable to type/model helicopter.

Ref. Publications: EUROCOPTER AS365N Alert Service Bulletin (ASB) No. 05.00.48 Revision 1, SA366 ASB No. 05.33 Revision 1, SA360/365C ASB No. 05.26 Revision 1 and EC155 ASB No. 05A007 Revision 1, all dated 13 November 2007. The use of later approved revisions of these documents is acceptable for compliance with the requirements of this AD.

Remarks : 1. If requested and appropriately substantiated, EASA can accept Alternative Methods of Compliance for this AD. 2. The safety assessment has requested not to implement the full consultation process and an immediate publication and notification. 3. Enquiries regarding this AD should be referred to the AD Focal Point - Certification Directorate, EASA. E-mail: ADs@easa.europa.eu

. 4. For any question concerning the technical content of the requirements in this AD, please contact: EUROCOPTER Aéroport de Marseille Provence 13725 Marignane Cedex – France; Tel: 33 (0) 4 42 85 97 97, Fax: 33 (0) 4 42 85 99 66; E-mail: Directive.technical-support@eurocopter.com

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