EASB

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EMERGENCY 

ALERT SERVICE BULLETIN 

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

pitch horn 

 Check of the TRH pitch horn condition 

 ATA: 64 

 

AIRCRAFT 

CONCERNED NUMBER Version(s) 

Civil Military

350 05.00.74 B, B1, B2, B3, BA, BB, D L1 

550 05.00.49 A2, C2, C3, U2 

355 05.00.65 E, F, F1, F2, N, NP 

555 05.00.44 AF, AN, SN, UF, UN 

Revision No. Date of issue 

Revision 0 2013-05-27 

Revision 1 2013-06-25 

Summary: 

Check that there are no cracks on the inner yoke of the two TRH pitch horns. 

Reason for last Revision: 

The purpose of Revision 1 of this ALERT SERVICE BULLETIN is: 

- To authorize the pilot to carry out the first check for cracks on the inner yoke of the two TRH pitch horns if he has 

the appropriate training and certification in compliance with the local regulation in force. 

- To extend effectivity to part numbers 350A12-1368-XX in order to list all the P/Nos. for bare pitch horns and pitch 

horn assemblies. 

- And, if necessary, to modify the Log Card of the Tail Rotor Blade Assembly. 

Compliance: 

Compliance with this ALERT SERVICE BULLETIN is mandatory. 

For the attention of 
 

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1. PLANNING INFORMATION 

1.A. EFFECTIVITY 

1.A.1. Helicopters/installed equipment 

Helicopters equipped with TRH pitch horn assemblies P/Nos. 350A12-1368-01 / 02 / 03 / 04 equipped with 

pitch horn P/N 350A12-1368-XX. 

CAUTION 

ON SOME LOG CARDS FOR THE TAIL ROTOR 

BLADE ASSEMBLY, THE PART NUMBER OF 

THE PITCH HORN ASSEMBLY MAY BE 

INCORRECT. 

READ 350A121368.01 or 02 or 03 or 04 INSTEAD 

OF 355A121368.01 or 02 or 03 or 04. 

 

NOTE 

Refer to the aircraft individual inspection log book (MOD 

record) to identify the actual configuration of the helicopter. 

1.A.2. Non-installed equipment 

Not applicable. 

1.B. ASSOCIATED REQUIREMENTS 

Not applicable. 

1.C. REASON 

Revision 0: 

EUROCOPTER has been informed of a case of crack detection on the yoke of a TRH pitch horn. 

If this crack is not detected, it may eventually lead to the failure of the two horn yokes, resulting in the loss of 

the anti-torque function. 

Consequently, EUROCOPTER makes it mandatory to comply with this ALERT SERVICE BULLETIN, the 

purpose of which is to check that there are no cracks on the yokes of the two TRH pitch horns, and to 

replace them if any cracks are detected. 
 

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Revision 1: 

The purpose of Revision 1 of this ALERT SERVICE BULLETIN is: 

- To authorize the pilot to carry out the first check for cracks on the inner yoke of the two TRH pitch horns if 

he has the appropriate training and certification in compliance with the local regulation in force. 

- To extend effectivity to part numbers 350A12-1368-XX in order to list all the P/Nos. for bare pitch horns and 

pitch horn assemblies. 

- And, if necessary, to modify the Log Card of the Tail Rotor Blade Assembly. 

This is due to the fact that some of the pitch horn P/Nos. recorded on the Log Card are incorrect: 

The Part Number 355A121368.01 or 02 or 03 or 04 is recorded instead of 350A121368.01 or 02 or 03 or 

04. 

1.D. DESCRIPTION 

1) Check that there are no cracks on the inner yoke of the two TRH pitch horns: 

If no cracks are found: Leave as is and inspect every 165 flying hours. 

If any cracks are found: Replace the cracked TRH pitch horn before resuming flights. 

2) On the Log Card of the Tail Rotor Blade assembly, record Part Number 350A121368.01 or 02 or 03 or 04 

if necessary instead of 355A121368.01 or 02 or 03 or 04. 

1.E. COMPLIANCE 

1.E.1. Compliance at the works 

Not applicable. 

1.E.2. Compliance in service 

Helicopters/installed equipment: 

a) - With less than 155 flying hours logged since new: 

. comply with paragraph 3. (except paragraph 3.B.4.) of this ALERT SERVICE BULLETIN at the latest 

upon reaching 165 flying hours unless this was already ensured in compliance with previous revisions. 

Then, 

. comply with paragraph 3.B. (except paragraph 3.B.4.) at intervals not exceeding 165 flying hours. 

- With more than 155 flying hours logged since new: 

Comply with paragraph 3. (except paragraph 3.B.4.) of this ALERT SERVICE BULLETIN: 

. within 10 flying hours following receipt of Revision 1 of this ALERT SERVICE BULLETIN issued on the 

date indicated at the bottom of the page, unless this was already ensured in compliance with previous 

revisions. 

Then, 

. comply with paragraph 3.B. (except paragraph 3.B.4.) at intervals not exceeding 165 flying hours. 

b) If necessary, comply with paragraph 3.B.4. within 10 flying hours following receipt of Revision 1 of this 

ALERT SERVICE BULLETIN in order to modify the Log Card. 

 Non-installed equipment: 

Not applicable. 
 

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1.F. APPROVAL 

 Approval of modifications: 

Not applicable. 

 Approval of this document: 

The technical information contained in this ALERT SERVICE BULLETIN Revision 0 was approved 

on May 27, 2013 under the authority of EASA Design Organization Approval No. 21J.056 for helicopters of 

civil versions subject to an Airworthiness Certificate. 

The technical information contained in this ALERT SERVICE BULLETIN Revision 0 was approved 

on May 27, 2013 under the prerogatives of the recognition of design capability FRA21J-002-DGA for French 

Government helicopters. 

The technical information contained in this ALERT SERVICE BULLETIN Revision 0 was approved 

on May 27, 2013 by the EUROCOPTER Airworthiness Department for export military versions. 

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

on June 25, 2013 under the authority of EASA Design Organization Approval No. 21J.056 for helicopters of 

civil versions subject to an Airworthiness Certificate. 

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

on June 25, 2013 under the prerogatives of the recognition of design capability FRA21J-002-DGA for French 

Government helicopters. 

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

on June 25, 2013 by the EUROCOPTER Airworthiness Department for export military versions. 

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, 

- 1 Pilot with appropriate training and certification in compliance with the local regulation in 

force. 

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

Time for the operations: 

- Check: Approximately 5 minutes (1 hour if there is any doubt). 

- Check + replacement of the TRH pitch horn: Approximately 1 hour. 

Estimated helicopter grounding time: Approximately 1 hour. 

1.H. WEIGHT AND BALANCE 

Not applicable. 

1.I. EFFECT ON ELECTRICAL LOADS 

Not applicable. 
 

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1.J. SOFTWARE MODIFICATION EMBODIMENT RECORD 

Not applicable. 

1.K. REFERENCES 

Aircraft Maintenance Manual (AMM): 

- AMM: 60-00-00, 3,1: General safety instructions - Mechanical Assemblies 

- AMM: 64-10-00, 8-2: Replacing - Pitch horn assembly 

Maintenance Manual (MET): 

- MET: 60.00.00.301: General Instructions 

Mechanical Repair Manual (MRM): 

- MRM: 64.10.00.707: Replacing the pitch horn assembly 

Standard Practices Manual (MTC): 

- MTC: 20.02.09.101: Crack detection through dye-penetrant inspection: General 

- MTC: 20.02.09.601: Checking structural parts/components using the dye-penetrant procedure 

- MTC: 20.04.02.401: Chemical stripping of organic surface finishes 

1.L. DOCUMENTS AFFECTED 

Not applicable. 

1.M. INTERCHANGEABILITY OR MIXABILITY OF PARTS 

 Interchangeability: 

 Not applicable. 

 Mixability: 

 Not applicable. 
 

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2. MATERIAL INFORMATION 

2.A. MATERIAL: PRICE - AVAILABILITY - PROCUREMENT 

2.A.1. Price 

For any information concerning the price of kits and/or components, contact the EUROCOPTER Network 

Sales & Customer Relations Department. 

Order the required quantity 

from 

EUROCOPTER 

Etablissement de Marignane 

Direction Ventes et Relations Client (ECR) 

13725 MARIGNANE CEDEX 

FRANCE 

NOTE 

On the purchase order, please always specify the mode of 

transport, the destination and the serial numbers of the 

helicopters to be modified. 

2.A.2. Availability 

The parts will be delivered on the operator's order. 

2.B. INFORMATION CONCERNING INDUSTRIAL SUPPORT 

Not applicable. 

2.C. MATERIAL REQUIRED FOR EACH HELICOPTER/COMPONENT 

 Kits or components to be ordered for a helicopter or an assembly: 

Key Word Qty Item New P/N Former P/N→ Instruction

If cracks are detected: 

 

TRH pitch horn assembly 1 or 2 1 350A12136804 

Material to be ordered separately: 

Order attachment components (screws, washers, nuts, etc.) according to the Work Cards and Tasks given in 

this ALERT SERVICE BULLETIN. 

 Products to be ordered separately: 

As per Work Cards and Tasks given in this ALERT SERVICE BULLETIN. 

2.D. MATERIAL TO BE RETURNED 

 Not applicable. 
 

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3. ACCOMPLISHMENT INSTRUCTIONS 

3.A. GENERAL 

- Read and comply with the crack detection instructions as per MTC 20.02.09.101.

- Read and comply with the instructions for checking structural components and parts using the 

dye-penetrant procedure as per MTC 20.02.09.601. 

- Read and comply with the instructions for the chemical stripping of organic surface coatings as per 

MTC 20.04.02.401. 

3.B. OPERATIONAL PROCEDURE 

3.B.1. Preliminary steps 

- Set up the appropriate access equipment. 

3.B.2. Procedure 

CAUTION 

COMPLY WITH THE GENERAL MECHANICAL 

INSTRUCTIONS AS PER MET WORK CARD 

60.00.00.301 OR AMM TASK 60-00-00, 3-1. 

3.B.2.a. Check of the TRH pitch horn 

Visually check that there are no cracks on the inner yoke of the two TRH pitch horns (a) (Figure 1, 

DETAIL A and B). If in doubt, carry out a dye-penetrant test. 

- case 1: no cracks detected on the two TRH pitch horns: leave as is and proceed with the final steps as 

per paragraph 3.B.3. 

- case 2: at least one crack detected on the TRH pitch horn: remove and replace the incriminated horn as 

per paragraph 3.B.2.b. before resuming flights. 

3.B.2.b. Replacement of the TRH pitch horn 

- Remove the TRH pitch horn (a) as per MRM Work Card 64.10.00.707 or AMM Task 64-10-00,8-2. 

- Install the TRH pitch horn (1) as per MRM Work Card 64.10.00.707 or AMM Task 64-10-00,8-2. 

3.B.3. Final steps 

- Remove the access equipment. 

3.B.4. Update of the Log Card 

On the Log Card of the tail rotor blade assembly indicating pitch horn Part Number 355A121368.01 or 02 or 

03 or 04: 

- Cross out the incorrect Part Number 355A121368.01 or 02 or 03 or 04, and, 

- Record Part Number 350A121368.01 or 02 or 03 or 04. 
 

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3.C. IDENTIFICATION 

 Identification of this document: 

Record compliance with this ALERT SERVICE BULLETIN in the helicopter documents. 

3.D. OPERATING AND MAINTENANCE INSTRUCTIONS 

Not applicable. 

4. APPENDIX 

 Not applicable. 
 

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Areas to be checked 

Figure 1: Areas to be checked for cracks 

1

a

1

a

B

A

A B