# ALERT SERVICE BULLETIN **EC135**

**CHANGE INSTRUCTION NO. 2 FOR EC135-63A-013**

PAGE 1 of 1 2008-09-12 **Date:** First issue: 2008-09-10 Revision 01: 2008-09-12 Revision 02: 2008-09-12

Please replace Revision 01 of Alert Service Bulletin EC135-63A-013 with Revision 02.
With Revision 02 a printing error was corrected in Section 3.B.(7). The dimension given in this section was corrected from 0.5 mm to 0.05 mm.

# ALERT SERVICE BULLETIN **EC135**

**EC135-63A-013** PAGE 1 of 6 2008-09-10 REVISION 02, 2008-09-12 

## Main Rotor Drive – Main Transmission **– Check of screws at the lower hub–shaft bearing for correct attachment**  **1. Planning Information A. Effectivity**  (1) Helicopters affected: EC135/EC635, all models with main transmission S/N 0001 to 1420 and 1500 to 1749. (2) Components affected: P/N 4649 010 003, 4649 010 005, 4649 010 006, 4649 010 006X, 4649 010 008, 4649 010 008X, 4649 001 007 and 4649 010 010. (3) Spare parts affected: see 1.A.(2) **B. Concurrent Requirements** Not applicable. **C. Reason** Unusual vibrations occurred 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 the affected operator’s fleet had been inspected, two more main transmissions were found on which the screws of the lower hub–shaft bearing support had loosened. 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. If all attachment screws should become loose, the outer race of the roller bearing might drop down. However, the axial guidance of the rotor hub–shaft is still ensured. **D. Description** Remove interior panelling. Drain oil, secure attachment hardware by means of locking washers. **E. Compliance** (1) If unusual vibrations are detected during the start or the end phase of the main rotor’s running the attachment hardware must be secured with locking washers i.a.w. Section 3.B. of this Alert Service Bulletin no later than 3 flights after receipt of this Alert Service Bulletin. (2) The securing of attachment hardware i.a.w. Section 3.B of this Alert Service Bulletin must be accomplished within the next 50 fh after receipt of this Alert Service Bulletin, but by 31.03.2009 at the latest.

This document is available on the internet: www .eurocopter.com/techpub

# ALERT SERVICE BULLETIN **EC135**

**EC135-63A-013** PAGE 2 of 6 REVISION 02, 2008-09-12 2008-09-10 (3) If the first issue of the Alert Service Bulletin has already been accomplished, the attachment hardware must be secured i.a.w. Section 3.B of this Alert Service Bulletin after 400 fh (plus a tolerance of 40 fh) at the latest. (4) The main transmissions in stores are to be secured i.a.w. Section 3.B before their installation at the latest. **F. Approval** The technical content of this document is approved under the authority of DOA No. EASA.21J.034. **G. Manpower** – without EMS equipment: 4 h – with EMS equipment: 8 h **H. Weight and Balance** Not applicable. **I. Electrical Load Data** Not applicable. **J. Software Accomplishment Summary** Not applicable. **K. References** – AMM EC135 – AMM EC135/635 **L. Other publications affected** Not applicable. **M. Interchangeability of Parts** Not applicable.


### 2. Material Information **A. Material – Price and Availability** Not applicable. **B. Support Information** On receipt of the completed reply form sheet of page 6, retrofit kit EC135–63–011–2C3, which contains 12 liters of lubricating oil (CM 1001) will be provided free of cost. Should the main transmission still be filled with CM103 the retrofit kit EC135-63-011-2C2 (Retrofit modification for the use of CM1001) is available on special terms. Further information will be provided by ECD, Dept. Spares Order Administration on request.

# ALERT SERVICE BULLETIN **EC135**

**EC135-63A-013** PAGE 3 of 6 2008-09-10 REVISION 02, 2008-09-12 **C. Material Necessary for Each Helicopter** Material kit SB-135-63A-013-2C. No. New P/N Keyword Old P/N Qty Disposition

1 0634313686 O−ring 0634313686 1 A 2 0639021002, alternatively 0639021005 Locking washer LN9023B6 alternatively Locking washer LN9023A6

both in material 1.4544.9 − 8 A

Disposition: A = New, included in kit, the O–ring can be reused once. **D. Material Necessary for Each Spare** See Section 2.C. **E. Reidentified Parts** Not applicable. **F. Special Tooling** Not applicable.


### 3. Accomplishment Instructions A. Preliminary work steps: **NOTE** If the transmission oil is drained into a clean container, it can be reused. (1) Remove lower transmission cover i.a.w. AMM, 63-21-00, 4-13. B. Secure attachment screws (1, Figure 1) using locking washers (7): (1) Measure clearance , Figure 1 between bearing outer race (2) and transmission housing at four positions offset by 90 degrees using a feeler gauge: (a) If the measured maximum clearance is less than or equal to 0.1 mm, proceed i.a.w. Section 3.B.(3). (b) If the measured maximum clearance is more than 0.1 mm, the dif ference between the smallest and the biggest clearance must be determined: – If the difference is less than 0.4 mm, proceed i.a.w. Section 3.B.(2). – If the difference is equal to or more than 0.4 mm, the bearing must be replaced. To do so, send main transmission to the manufacturer for **repair**

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# ALERT SERVICE BULLETIN **EC135**

**EC135-63A-013** PAGE 4 of 6 REVISION 02, 2008-09-12 2008-09-10 **WARNING** IF SCREWS ARE MISSING, SEARCH AND FIND THEM. **NOTE** Not damaged screws can be reused. (2) Lift helicopter i.a.w. AMM, 07–00–00, 2–1 until landing gear is relieved. (3) Torque–tighten all screws to 9 Nm. (4) Successively put a locking washer (7) under all 8 screws i.a.w. Figure 1. (5) Crosswise torque–tighten all screws to 9 Nm. (6) Bend all locking washers i.a.w. Figure 1. (7) Measure clearance , Figure 1 between bearing outer race (2) and transmission housing using a feeler gauge. The clearance has to be less or equal to **0.05 mm**

. C. Conclusive work: **NOTE** If the O–ring on the lower transmission cover is not damaged, it can be reused once. (1) Install lower transmission cover i.a.w. AMM, 63-21-00, 4-13. (2) Replenish oil i.a.w. AMM, 63-21-00, 3-2. (3) Copy reply form sheet on page 6, fill out and send to ECD customer support Fax: **+49–906–71–4111** or E–Mail: **maintransmission@eurocopter.com** D. Confirm accomplishment of this Alert Service Bulletin by an entry in the log card of the main transmission. – ASB EC135-63A-013, **Rev.02** accomplished, all screws secured by means of locking washers. 

### 4. Appendix Not applicable.

# ALERT SERVICE BULLETIN **EC135**

**EC135-63A-013** PAGE 5 of 6 2008-09-10 REVISION 02, 2008-09-12 Lower Hub–Shaft Bearing Figure 1 1 Attachment screw 2 Bearing outer race 3 Roller bearing 4 Hub–shaft nut 5 Retainer ring 6 Ball bearing 7 Locking washer LN9023 B6 / A6 Measure clearance of bearing outer race to the housing at four positions using a feeler gauge

1 2 3 4 5 6

7

# ALERT SERVICE BULLETIN **EC135**

**EC135-63A-013** PAGE 6 of 6 REVISION 02, 2008-09-12 2008-09-10 **Reply form sheet for ASB EC135-63A-013 “Attachment of screws of the lower hub–shaft bearing”**  

### Completely fill out this form sheet and send by FAX to + 49 906 714111 or by email to maintransmission@eurocopter.com

.



## Please copy **page! Original remains in Alert Service Bulletin!**

Loose screws? No Yes 

### Number **Customer Contact**  **(Name) Telephone** 
**Telefax E–Mail**  **Operator**
**Helicopter S/N Helicopter Total Time TT**

**Main transmission S/N Important data regarding helicopter** 
**Important data regarding main transmission**

**Main transmission TT Main transmission TSO**  **Main transmission P/N**

**Printed name ASB EC135-63A-013 Revision 02 accomplished**  **Date Signature**  Dropped out screws?

Remarks: **Address for material kit EC135-63-011-2C3 (see Section 2.B. of the ASB)** 

3

5 8

7 2 1

4 6 **Mark position:** Secured with 8 locking washers?

LH RH No Yes Number 

### No YesFLIGHT DIRECTION