EASA AD No.: 2008-0175-E 

EASA Form 111 Page 1/2

EASA EMERGENCY AIRWORTHINESS DIRECTIVE 

AD No.: 2008-0175-E 

Date: 16 September 2008 

Note: This Emergency Airworthiness Directive (AD) is issued by EASA, acting in accordance with 

Regulation (EC) No 216/2008 on behalf of the European Community, its Member States and of 

the European third countries that participate in the activities of EASA under Article 66 of that 

Regulation 

This AD is issued in accordance with EC 1702/2003, Part 21A.3B. In accordance with EC 2042/2003 Annex I, Part M.A.301, the 

continuing airworthiness of an aircraft shall be ensured by accomplishing any applicable ADs. Consequently, no person may operate an 

aircraft to which an AD applies, except in accordance with the requirements of that AD unless otherwise specified by the Agency [EC 

2042/2003 Annex I, Part M.A.303] or agreed with the Authority of the State of Registry [EC 216/2008, Article 14(4) exemption]. 

Type Approval Holder’s Name : 

Eurocopter Deutschland GmbH 

Type/Model designation(s) : 

EC 135 and EC 635 helicopters 

TCDS Number : EASA.R.009 

Foreign AD : Not applicable 

Supersedure : None 

ATA 63 Main Rotor Drive – Main Transmission Mast Bearing Retainer Bolts 

– Inspection / Modification 

Manufacturer(s): Eurocopter Deutschland GmbH (ECD) 

Applicability: 

EC 135 P1(CDS), EC 135 P1(CPDS), EC 135 P2(CPDS), EC 135 P2+, 

EC 135 T1(CDS), EC 135 T1(CPDS), EC 135 T2(CPDS), EC 135 T2+, 

EC 635 T1(CPDS), EC 635 P2+ and EC 635 T2+ helicopters, all serial numbers. 

Reason: 

One operator has reported the occurrence of unusual vibrations during the start 

phase of the main rotor on one helicopter. These vibrations stopped after the 

application of torque. The troubleshooting accomplished by the maintenance 

personnel showed that six of the eight attachment screws of the lower hub-shaft 

bearing support had loosened. After inspection of the affected operator’s fleet, 

the attachments screws of the lower hub-shaft bearing support were found 

loosened on the main transmissions of two additional helicopters. The lower 

hub-shaft bearing consists of a ball bearing and a roller bearing. The outer race 

of the roller bearing is fixed to the housing with screws. Should all attachment 

screws become loose, the outer race of the roller bearing might separate, which 

would constitute an unsafe condition. In such case, however, the axial guidance 

of the rotor hub-shaft would still be ensured. 

For the reasons described above, this new EASA Emergency AD requires the 

inspection of the main transmission attachment hardware and installation of 

locking washers in accordance with the instructions of ECD Alert Service Bulletin 

(ASB) No. EC135-63A-013 Revision 02. 

Effective Date: 18 September 2008 
EASA AD No.: 2008-0175-E 

EASA Form 111 Page 2/2

Required Action(s) 

and Compliance 

Time(s): 

Required as indicated, unless already accomplished: 

(1) After the effective date of this AD, when unusual vibrations are detected 

during the start or the end phase of the main rotor’s running, within 3 flight 

cycles after detection, inspect the attachment hardware and install locking 

washers in accordance with Section 3.B of ECD ASB No. EC135-63A-013 

Revision 02. 

(2) Unless accomplished as required by paragraph (1) of this AD, within the 

next 50 flight hours (FH) after the effective date of this AD, but not later than 

31 March 2009, inspect the attachment hardware and install locking 

washers in accordance with Section 3.B of ECD ASB No. EC135-63A-013 

Revision 02. 

(3) For helicopters that have already been modified, prior to the effective date 

of this AD, in accordance with ECD ASB No. EC135-63A-013 at original 

issue or Revision 01, within 400 FH (+/- 10%) after the effective date of this 

AD, inspect the attachment hardware and install locking washers in 

accordance with Section 3.B of ECD ASB No. EC135-63A-013 Revision 02. 

(4) After the effective date of this AD, no person shall install a main 

transmission on a helicopter, unless it has been modified in accordance with 

Section 3.B of ECD ASB No. EC135-63A-013 Revision 02. 

Ref. Publications: 

Eurocopter Deutschland EC135 Alert Service Bulletin No. EC135-63A-013 

Revision 02 dated 12 September 2008. 

The use of later approved revisions of this document is acceptable for 

compliance with the requirements of this AD. 

Remarks :

1. If requested and appropriately substantiated, EASA can approve 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 Airworthiness 

Directives, Safety Management & Research Section, 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 Deutschland GmbH 

P.O. Box 80 11 40 

D-81663 München, Federal Republic of Germany 

Telephone: + 49 (0) 151 14 22 89 76, Fax: + 49 (0) 89 6000-4111 

E-mail maintransmission@eurocopter.com