ASB No. EC155-05A021 

Revision 0 2011-04-11 Page 1/11 

Revision 1 2011-07-20 This document is available on the Internet: www.eurocopter.com/techpub

 

 Civil version(s): B, B1 

ALERT SERVICE BULLETIN 

SUBJECT: TIME LIMITS - MAINTENANCE CHECKS - Tail Rotor Hub (TRH) 

Visual check of the 10-blade TRH hub 

ATA 64

Revision No. Date of issue 

Revision 0 2011-04-11 

Revision 1 2011-07-20 

Summary: 

The purpose of this Service Bulletin is to do a visual check of the 10-blade TRH hub with removal of the Tail 

Gearbox (TGB) cover. 

Purpose of the last revision: 

The purpose of revision 1 of this ALERT SERVICE BULLETIN is to render mandatory the visual inspection of the 

10-blade TRH hub every 55 flight hours. 

Compliance: 

EUROCOPTER renders compliance with revision 1 of this ALERT SERVICE BULLETIN mandatory 

For the attention of 
 

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1. PLANNING INFORMATION 

1.A. EFFECTIVITY 

1.A.1. Helicopters/installed equipment 

Helicopters equipped with a rotor hub P/N 365A33351100, 365A33351101 

or 365A33351102 installed on the 10-blade Tail Rotor Hub (TRH) of the quiet fenestron tail rotor. 

1.A.2. Non-installed equipment 

Not applicable. 

1.B. ASSOCIATED REQUIREMENTS 

Not applicable. 

1.C. REASON 

Revision 0: 

During a 2T inspection on an AS365 helicopter equipped with a 10-blade TRH, the technician found cracks 

on the TRH hub. 

Pending the results of additional investigations, EUROCOPTER recommends that you do a visual check of 

the 10-blade TRH hub, with removal of the Tail Gearbox (TGB) cover, every 110 flying hours. 

Revision 1: 

Subsequent to a second case similar to the first case of cracks being detected on the a 10-blade TRH hub, 

and pending further investigation to determine the origin of such cracks, EUROCOPTER renders mandatory 

the visual inspection of the 10-blade TRH hub, with removal of the TGB cover, every 55 flight hours. 

Revision 1 of this ALERT SERVICE BULLETIN will form the subject of an EASA Airworthiness Directive. 

1.D. DESCRIPTION 

Revision 0: 

Compliance with this Service Bulletin consists in performing a visual check, without removal of the 10-blade 

TRH hub, with removal of the TGB cover. 

Revision 1: 

Revision 1 of this ALERT SERVICE BULLETIN consists in rendering mandatory the visual inspection, 

without removal of the 10-blade TRH hub, with removal of the TGB cover, every 55 flight hours. 
 

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1.E. COMPLIANCE 

1.E.1. Compliance at the works 

Not applicable. 

1.E.2. Compliance in service 

Helicopters/installed equipment: 

Comply with paragraph 3. before reaching 55 flight hours following receipt of revision 1 of this ALERT 

SERVICE BULLETIN, issued on the date indicated at the foot of the page. 

Then, 

Comply with paragraph 3. at time intervals not exceeding 55 flight hours. 

Non-installed equipment: 

Not applicable 

1.F. APPROVAL 

Approval of modifications: 

Not applicable. 

 Approval of this document: 

The technical information contained in this Service Bulletin Revision 0 was approved 

on April 08, 2011 under the prerogatives of the recognition of design capability FRA21J-002-DGA for French 

Government helicopters. 

The technical information contained in this Service Bulletin Revision 0 was approved 

on April 08, 2011 by the EUROCOPTER Airworthiness Department for export military versions. 

The technical information contained in Revision 1 of this ALERT SERVICE BULLETIN was approved 

on July 20, 2011 under the authority of EASA Design Organisation Approval No. 21J.056 for civil version 

helicopters subject to an Airworthiness Certificate. 

The technical information contained in Revision 1 of this ALERT SERVICE BULLETIN was approved 

on July 20, 2011 by the EUROCOPTER Airworthiness department for export military version helicopters. 
 

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1.G. MANPOWER 

EUROCOPTER recommends that compliance with this ALERT SERVICE BULLETIN be ensured by 

personnel with the following qualification: 

Qualification: 1 Mechanical Engineering Technician. 

The time for the operations is given for information purposes, for a standard configuration. 

Time for the operations: Approx. 1 hour for one mechanical engineering technician for the check. 

1.H. WEIGHT AND BALANCE 

Not applicable. 

1.I. EFFECT ON ELECTRICAL LOADS 

Not applicable. 

1.J. SOFTWARE MODIFICATION EMBODIMENT RECORD 

Not applicable. 

1.K. REFERENCES 

The following document is necessary for compliance with this ALERT SERVICE BULLETIN: 

- AMM: 64-20-04-061 - Tail rotor hub - Removal - Installation. 

- AMM: 64-20-00-225 - TRH detailed inspection. 

- AMM: 64-20-00-991 - TRH inspection criteria. 

1.L. DOCUMENTS AFFECTED 

Not applicable. 

1.M. INTERCHANGEABILITY OR MIXABILITY OF PARTS 

Not applicable. 
 

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2. MATERIAL INFORMATION 

2.A. MATERIAL: PRICE - AVAILABILITY - PROCUREMENT 

Price

For any information concerning the kits and/or components, contact the EUROCOPTER Network Sales & 

Customer Relations Department.

Availability

The kits and/or components are delivered on the operator's order. 

Procurement conditions

Order the required quantity (unless otherwise specified) 

from 

EUROCOPTER 

Etablissement de Marignane 

Direction Ventes et Relations Client (ECR) 

13725 MARIGNANE CEDEX 

FRANCE 

NOTE 

On the purchase order, please specify the mode of transport, 

the destination and the serial numbers of the helicopters to be 

modified. 

2.B. INFORMATION CONCERNING INDUSTRIAL SUPPORT 

Not applicable. 

2.C. MATERIAL REQUIRED FOR EACH HELICOPTER/COMPONENT 

Kits or components to be ordered for one helicopter or one assembly:

 Old Designation Qty New Part Number Item Part Number → Instructions 

 

Rotor hub A/R 365A33-3511-00 1 365A33-3511-00 Replace if cracks are detected 

Rotor hub A/R 365A33-3511-01 2 365A33-3511-01 Replace if cracks are detected 

Rotor hub A/R 365A33-3511-02 3 365A33-3511-02 Replace if cracks are detected 

 

Products to be ordered separately: 

Refer to the Tasks and Work Cards specified in this Service Bulletin. 

The products can be ordered separately from the INTERTURBINE AVIATION LOGISTICS company. 

Website: http://www.interturbine.com

Phone: +49.41.91.809.300 

AOG: +49.41.91.809.444 

2.D. MATERIAL TO BE RETURNED 

Not applicable. 
 

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3. ACCOMPLISHMENT INSTRUCTIONS 

3.A. GENERAL 

Not applicable. 

3.B. OPERATIONAL PROCEDURE 

3.B.1. Preliminary steps

- Install the access equipment. 

- If necessary, release the rotor brake. 

- Remove the TGB cover (b). 

3.B.2. Check for cracks (Figures 1, 2 and 3)

- Using a light source, check for cracks the entire Area C of the TRH hub (a) on the TGB (c) side; pay 

particular attention around screws (e). 

NOTE 1 

The check must be done between the lower part of the TGB (c) 

and its fairing (d) (see details D and E, Figure 3). 

NOTE 2 

In order to check the entire Area C, turn the Tail Rotor (TR) by 

hand. 

Interpretation of the results: 

- If no cracks are found on the TRH hub (a): 

. Leave as is. 

. Comply with paragraph 3.B.3. 

- If cracks are found on the TRH hub (a): 

. Remove the TRH hub (a) and replace it with a TRH hub (1), (2) or (3) as per AMM task 64-20-04-061. 

. Perform a detailed check and a dimensional check of: (figure 4): 

- shouldered slide bushes (4) 

- clamping plate (5) 

- torsion bar bolts (6) 

- splined flange (7) 

as per AMM tasks 64-20-00-225 and 64-20-00-991 . 

. Inform immediately the Customer Service Technical Support Department by: 

Phone: + 33 (0)4.42.85.99.67 

Fax: + 33 (0)4.42.85.99.66 

E-mail: DynComp.Technical-Support@eurocopter.com

. Comply with paragraph 3.B.3. 

3.B.3. Final steps

Install the TGB cover (b). 

If necessary, apply the rotor brake. 

Remove the access equipment. 
 

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3.C. IDENTIFICATION 

Identification of this document: 

- Record initial compliance with revision 0 of this document in the helicopter documents. 

- Record initial compliance with revision 1 of this document in the helicopter documents. 

3.D. OPERATING AND MAINTENANCE INSTRUCTIONS 

Not applicable. 
 

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Figure 1: TRH hub 

TGB 

side 

Area C 

A

A - B

a

1

2

e 3 
 

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Figure 2: Location of the area to be checked (Area C) 

b 

c 

B

d 

D 
 

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Figure 3: Visual check of Area C 

E 

a 

1

2

3 

D 

E 

a 

1

2

3 

d 

d 

c 

c 

e 
 

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Figure 4 

DETAIL A 

A 

DETAIL A 

6 

7 

5 4