ALERT SERVICE BULLETIN AS350 

Approved under EASA DOA No. 21J.056. 55.00.13 Page 1/16

 2008.02.28

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

 EUROCOPTER

DIRECTION TECHNIQUE SUPPORT

13725 MARIGNANE CEDEX FRANCE CIVIL VERSION(S): B3 

 

 ALERT SERVICE BULLETIN 

No. 55.00.13 

SUBJECT: STABILIZERS

Improvement and/or monitoring of upper and lower fin attachments

Corresponds to MOD 073288 

REVISION No. DATE OF APPROVAL DATE OF ISSUE 

 

Revision 0 On: January 17, 2006 2006.01.20 

Revision 1 On: June 21, 2006 2006.06.21 

Revision 2 On: February 28, 2008 2008.02.28 

 

 
 ALERT SERVICE BULLETIN AS350 

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1. PLANNING INFORMATION 

1.A. EFFECTIVITY 

1.A.1. Helicopters/Installed equipment 

- Helicopters equipped with upper and lower fins pre-MOD 073288 and equipped with an upper 

fin pre- or post-MOD 073148 (see NOTE 2) and pre-MOD 073330 (see NOTE 3). 

- Helicopters equipped with upper and lower fins post-MOD 073288 and equipped with an upper fin 

pre-MOD 073148 (see NOTE 2) and pre-MOD 073330 (see NOTE 3). 

NOTE 1

Refer to the aircraft individual inspection record (RIC) or the 

aircraft log book to identify the actual configuration of the 

aircraft. 

NOTE 2

An upper fin pre-MOD 073148, is a fin equipped with a long 

trailing edge angle (1,700 mm) riveted over the whole height of 

the fin. 

An upper fin post-MOD 073148, is a fin equipped with a short 

trailing edge angle (770 mm) riveted over the lower section the 

fin. 

NOTE 3

Helicopters equipped with upper and lower fins: 

- post-MOD 073288, are no longer concerned by the 

instructions in AS350 ALERT SERVICE BULLETIN 

No. 05.00.46. 

- post-MOD 073288, and equipped with an upper fin postMOD 073148, are not concerned by the instructions in this 

ALERT SERVICE BULLETIN. 

- post-MOD 073330, are not concerned by the instructions of 

this ALERT SERVICE BULLETIN. 

1.A.2. Non-installed equipment 

Not applicable. 

1.B. ASSOCIATED REQUIREMENTS 

Not applicable. 
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Approved under EASA DOA No. 21J.056. 55.00.13 Page 3/16

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1.C. REASON 

To improve the attachment of the upper and lower fins on the tail boom: 

For helicopters equipped with the attachment screws for upper and lower fins pre-MOD 073288 and 

equipped with an upper fin pre-MOD 073148 by: 

- The embodiment of MOD 073288, including, 

. the installation of longer screws, compatible with the various setting thicknesses between the tail boom 

and the fin mounting fitting, 

. safetying of the attachment screws, and 

. a periodic check, including, 

- a check of the tightening torque, replacement of the upper fin attachment screws and a check of the 

upper fin splice every 110 flying hours. 

For helicopters equipped with the attachment screws for upper and lower fins post-MOD 073288 and 

equipped with an upper fin pre-MOD 073148 by: 

- Performing a periodic check, including, 

. a check of the tightening torque, replacement of the upper fin attachment screws and a check of the 

upper fin splice every 110 flying hours. 

For helicopters equipped with the attachment screws for upper and lower fins pre-MOD 073288 and 

equipped with an upper fin post-MOD 073148 by: 

- The embodiment of MOD 073288, including, 

. the installation of longer screws, compatible with the various setting thicknesses between the tail boom 

and the fin mounting fitting, 

. safetying of the attachment screws. 

Revision 0 of this ALERT SERVICE BULLETIN formed the subject of an EASA Airworthiness Directive. 

Compliance with the measures in this ALERT SERVICE BULLETIN will cancel the requirements of 

AS350 ALERT SERVICE BULLETIN No. 05.00.46. 

Revision 1 of this ALERT SERVICE BULLETIN which will form the subject of Revision 1 of the EASA 

Airworthiness Directive completes the procedure for replacing the upper and lower fin mounting fitting 

attachment screws by applying a bead of sealing product around the screw heads in order to ensure a 

sealed assembly. 

Revision 1 of this ALERT SERVICE BULLETIN does not affect compliance with Revision 0, but 

completes the operational procedure. 

Revision 2 of this ALERT SERVICE BULLETIN informs users that compliance with MOD 073330 cancels 

compliance with the instructions of this ALERT SERVICE BULLETIN. 

This ALERT SERVICE BULLETIN will be covered by an EASA Airworthiness Directive. 
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1.D. DESCRIPTION 

ALERT TELEX No. 05.00.46 was issued following two cases of cracks found in the spar of the upper fin on 

AS355 N helicopters. This ALERT TELEX introduced periodic monitoring to ensure that there is no crack in 

the spars of the upper and lower fins. 

Since this ALERT TELEX was issued, EUROCOPTER has continued analyses which have revealed that, 

according to the required setting value, the length of the upper and lower fin mounting fitting attachment 

screws may not enable optimum safetying of the attachment. 

EUROCOPTER has therefore defined modification 073288 which consists in: 

- replacing the original attachment screws with longer screws, P/No. 22126BV060032L, in order to take into 

account the various setting thicknesses, 

- adding screw safetying with lock-wire. The double safetying is necessary because failure of the attachment 

can lead to the loss of the fin. 

These analyses have also shown that the introduction of these new screws (post-MOD 073288) on 

this helicopter version does not by itself ensure the security of the fin on helicopters equipped with 

fins pre-modification 073148 (upper fin fitted with a long trailing edge angle). In fact, the presence of 

a long trailing edge angle on the upper fin increases the aerodynamic loads and has a direct effect 

on the security of the fin mounting fitting attachment screws. For this reason, and in addition to this 

modification concerning helicopters pre-modification 073148, EUROCOPTER renders the periodic 

replacement of these screws and the checks defined in this ALERT SERVICE BULLETIN, 

mandatory. 

EUROCOPTER is continuing analyses in order to define a modification aimed at canceling these checking 

requirements, as soon as possible. 

ALERT TELEX No. 05.00.46 will be converted into an ALERT SERVICE BULLETIN, with the same 

reference number, in order to specify that compliance with this ALERT SERVICE BULLETIN cancels the 

periodic monitoring of the fin spars. 

Revision 2

EUROCOPTER has defined MOD 073330, which increases: 

- the hole diameter for the screws attaching the upper and lower fins in order to reduce the risk of forced 

fitting, 

- the fatigue strength of the fin attachments through the use of modified washers and special bolts with 

higher heads. 

Compliance with this modification cancels compliance with the instructions of this ALERT SERVICE 

BULLETIN. 

1.E. COMPLIANCE 

EUROCOPTER renders compliance with the measures in this ALERT SERVICE BULLETIN, mandatory. 

1.E.1. Compliance at the works 

1.E.1.a. On helicopters/installed equipment: - Embodiment of MOD 073288 as from July 01, 2004. 

- On the helicopter, before delivery, apply a bead of sealing product 

around the heads of the upper and lower fin mounting fitting 

attachment screws. 

NOTE 4

This date is given for reference purposes only. Refer to the 

aircraft individual inspection record (or RIC) to identify the 

actual modification status of the aircraft. 

1.E.1.b. Non-installed equipment 

Not applicable.
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1.E.2. Compliance in service: By the operator. 

1.E.2.a. On helicopters/installed equipment 

NOTE 5

A simplified description for compliance with this ALERT 

SERVICE BULLETIN is given by a block diagram in the 

APPENDIX. 

1) For helicopters with upper and lower fins which do not embody MOD 073288, and with an upper 

fin pre-MOD 073148: 

- Comply once with paragraph 2.B.2. (MOD 073288) within 110 flying hours as from receipt of revision 0 

of this ALERT SERVICE BULLETIN dated January 20, 2006, 

then, 

. comply with paragraph 2.B.3. every 110 flying hours. 

2) For helicopters with upper and lower fins which embody MOD 073288, and with an upper fin 

pre-MOD 073148: 

a) On helicopters modified in compliance with Revision 0 of this ALERT SERVICE BULLETIN 

dated January 20, 2006: 

- Apply a bead of sealing product (5) around the heads of the upper and lower fin mounting fitting 

attachment screws within 25 flying hours as from receipt of this ALERT SERVICE BULLETIN issued 

on the date indicated at the foot of the page, 

then, 

. comply with paragraph 2.B.3. at the scheduled 110-flying-hour limit, then every 110 flying hours. 

b) On helicopters not modified in compliance with Revision 0 of this ALERT SERVICE BULLETIN 

dated January 20, 2006: 

- Comply with paragraph 2.B.3. within 110 flying hours as from receipt of Revision 0 of this 

ALERT SERVICE BULLETIN dated January 20, 2006, 

then, 

. comply with paragraph 2.B.3. every 110 flying hours. 

3) For helicopters with upper and lower fins which do not embody MOD 073288, and with an 

upper fin post-MOD 073148: 

- Comply once with paragraph 2.B.2. (MOD 073288) at the next 500-flying-hour inspection following 

receipt of Revision 0 of this ALERT SERVICE BULLETIN dated January 20, 2006, or before 

March 31, 2006 (the first limit reached is applicable). 

4) For helicopters with upper and lower fins which embody MOD 073288, and with an upper fin 

post-MOD 073148: 

- Apply a bead of sealant (5) around the heads of the lower and upper fin mounting fitting attachment 

screws, within 25 flying hours following receipt of this ALERT SERVICE BULLETIN issued on the date 

indicated at the foot of the page. 

1.E.2.b. Non-installed equipment: Not applicable. 
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1.F. APPROVAL 

Approval is limited to civil version helicopters subject to an Airworthiness Certificate. 

1.F.1. Approval of the modifications 

The information or instructions relate to change: MOD 073288, which was approved on September 16, 

2005, through modification approval form FAM 073288 edition 2, under the authority of EASA Design 

Organisation Approval No. 21J.056. 

1.F.2. Approval of the ALERT SERVICE BULLETIN 

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

on January 17, 2006 under the authority of EASA Design Organisation Approval No. 21J.056. 

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

on June 21, 2006 under the authority of EASA Design Organisation Approval No. 21J.056. 

The technical information contained in Revision 2 of this ALERT SERVICE BULLETIN was approved 

on February 28, 2008 under the authority of EASA Design Organisation Approval No. 21J.056. 

1.G. MANPOWER 

- Qualification: Structural technician or mechanic. 

- Time for the operations: Approximately 2 hours. 

1.H. WEIGHT AND BALANCE 

Negligible. 

1.I. EFFECT ON ELECTRICAL LOADS 

Not applicable. 

1.J. SOFTWARE MODIFICATION EMBODIMENT STATE 

Not applicable.

1.K. REFERENCES 

Standard Practices Manual (MTC) Work Cards: 20.02.05.404, 20.02.06.402, 

20.02.09.601, 20.05.01.211, 

20.05.01.222. 

Maintenance Manual (MET) Work Cards: 24.00.00.301, 55.00.00.402. 

Repair Manual (MRR) Work Card: 55.20.10.777. 
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1.L. OTHER DOCUMENTS CONCERNED 

Maintenance Manual (MET). 

Maintenance Program (PRE). 

1.M. INTERCHANGEABILITY AND MIXABILITY OF PARTS 

1.M.1. Interchangeability 

Not affected. 

1.M.2. Mixability 

Mixing is prohibited. The attachment screws for the upper and lower fins must be post-MOD 073288. 
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2. ACCOMPLISHMENT INSTRUCTIONS 

2.A. GENERAL 

Not applicable. 

2.B. OPERATIONAL PROCEDURE 

2.B.1. Preliminary steps 

Install suitable access equipment. 

2.B.2. Embodiment of MOD 073288 

2.B.2.a. Replacement of the upper fin attachment screws 

As per Figure 1: 

- Remove the sealing product around the fin fitting (d). 

- Remove the 2 screws (a) and washers (b) attaching the fin. 

- Retain the washers (b) and discard the screws (a). 

- Check whether setting peel washers (c) are installed under the fitting (d): 

. if setting peel washers (c) are installed, 

- check that the fitting (d) is correctly seated on the existing peel washers; if this is not the case, 

. remove the peel washers (c) and follow the procedure below. 

. if there are no setting peel washers (c), 

- check the clearance between the fin and the skin of the tail boom as per MET Work Card 

55.00.00.402, and if fin setting is necessary: 

. define the thickness of the peel shims (2) to be installed according to the measured clearance, as 

per MET Work Card 55.00.00.402, 

. install and bond the peel shims (2) to the skin of the tail boom with adhesive (7). 

2.B.2.a.1. Procedure for installing the screws (1) 

- Coat the shanks of screws (1) with Mastinox (6) as per MTC Work Card 20.05.01.211. 

- Install the 2 screws (1) equipped with washers (b). 

- Tighten the screws (1) to a dry torque value of 0.85 to 1.05 daN.m. 

- Safety the screws (1) with lock-wire (3) as per MTC Work Card 20.02.06.402. 

- Protect the twist of wire (3) with a piece of sheath (4). 

- Run a bead of sealing product (5) around the fitting (d) of the fin and around the screw heads (1), as 

per MTC Work Card 20.05.01.222. 

2.B.2.b. Replacement of the lower fin attachment screws 

Replace the fin attachment screws (a) with screws (1) and set the fin where necessary in accordance with 

the procedure described in paragraph 2.B.2.a. 
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2.B.3. Check of the tightening torque, of the upper fin splice and replacement of the attachment screws 

As per Figures 1 and 2: 

- Remove the lock-wire from the two fin attachment screws (a). 

- Check the tightening torque of each screw (a) as per MTC Work Card MTC 20.02.05.404. 

- Make sure there is no crack or loosened rivet in the reinforcement splice (9). 

2.B.3.a. Interpretation of the results:

1) If a crack is detected in the reinforcement splice (9), 

- remove and replace the upper fin as per MET Work Card 55.00.00.402, 

- discard the two screws (a), 

- install 2 screws (1) equipped with washers (b) in accordance with the procedure described in 

paragraph 2.B.2.a.1., 

- inform the EUROCOPTER Customer Technical Support Operations Department (STXV) by: 

. Tel: +33 (0)4.42.85.97.03 

. Fax: +33 (0)4.42.85.99.66 

2) If the tightening torque of one of the two upper fin attachment screws (a) is less than 80% of the 

minimum torque value and/or if there is a loosened rivet in the reinforcement splice (9), 

- remove the tail cone and the tail light cut-off connector (refer to MET Work Card 24.00.00.301 before 

removing the tail light cut-off connector). 

- Make sure that there is no crack in the upper fin spar (8) in the tail boom (10) attachment area. If in doubt, 

perform a dye penetrant crack detection inspection as per MTC Work Card 20.02.09.601. 

. If there is a crack in the spar, 

- remove and replace the upper fin as per MET Work Card 55.00.00.402, 

- discard the two screws (a), 

- install 2 screws (1) equipped with washers (b) in accordance with the procedure described in 

paragraph 2.B.2.a.1., 

- inform the EUROCOPTER Customer Technical Support Operations Department (STXV) by: 

. Tel.: +33 (0)4.42.85.97.03 

. Fax: +33 (0)4.42.85.99.66 

. If there is a loosened rivet, 

- remove the upper fin as per MET Work Card 55.00.00.402, 

- replace the loosened rivet(s) as per MRR Work Card 55.20.10.777, 

- install the upper fin as per MET Work Card 55.00.00.402, 

- discard the two screws (a), 

- install 2 screws (1) equipped with washers (b) in accordance with the procedure described in 

paragraph 2.B.2.a.1., 

- inform the EUROCOPTER Customer Technical Support Operations Department (STXV) by: 

. Tel.: +33 (0)4.42.85.97.03 

. Fax: +33 (0)4.42.85.99.66 

. If there is no crack and no loosened rivet, 

- leave as is, 

- install the tail light cut-off connector and the tail cone, 

- remove the two screws (a) and washers (b), 

- discard the two screws (a), 

- install 2 screws (1) equipped with washers (b) in accordance with the procedure described in 

paragraph 2.B.2.a.1. 
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3) If the tightening torque of the two fin attachment screws (a) is equal to or more than 80% of the 

minimum torque value and if there is no crack and no loosened rivet in the reinforcement splice (9), 

- remove the 2 screws (a) and washers (b), 

- discard the two screws (a), 

- install 2 screws (1) equipped with washers (b) in accordance with the procedure described in 

paragraph 2.B.2.a.1. 

2.B.4. Final steps 

Return the aircraft to flight configuration. 

Remove the access equipment. 

2.C. IDENTIFICATION 

Record the following in the aircraft documents: 

- embodiment of MOD 073288, 

- initial compliance with paragraph 2.B.3. of this ALERT SERVICE BULLETIN. 

2.D. OPERATING AND MAINTENANCE INSTRUCTIONS 

Not applicable. 
 ALERT SERVICE BULLETIN AS350 

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Figure 1 
 ALERT SERVICE BULLETIN AS350 

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PAGE LEFT BLANK INTENTIONALLY 
 ALERT SERVICE BULLETIN AS350 

Approved under EASA DOA No. 21J.056. 55.00.13 Page 13/16

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Figure 2 
 ALERT SERVICE BULLETIN AS350 

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3. MATERIAL INFORMATION 

3.A. MATERIAL: COST - AVAILABILITY 

The 4 screws 22126BV060032L will be delivered free of charge on the customer's order. 

3.B. INFORMATION CONCERNING INDUSTRIAL SUPPORT 

Not applicable. 

3.C. MATERIAL REQUIRED FOR EACH AIRCRAFT, ENGINE/COMPONENTS 

3.C.1. Kit or component(s) to be ordered 

New Part Number Qty Item Key Word Former Part 

Number 

Instructions 

Disposition 

22126BV060032L 4 1 Hexagonal head screw 

3.C.2. Material to be ordered separately 

New Part Number Qty Item Key Word Former Part 

Number 

Instructions 

Disposition 

 

350A14003020 AR 2 Peel washer 

GAINE2,5X3,5 AR 4 Sheath 

3.C.3. Product(s) to be ordered separately 

The materials identified by an asterisk "*" or required for compliance with the tasks and/or work cards listed in 

paragraph 1.K., can be ordered from the INTERTURBINE company, 

Website: http://www.itlogistics.de

Phone: +49.41.91.809.300 

AOG: +49.41.91.809.444 

 Part Number Qty Item Key Word 

 

"*" EN3628-0,8 AR 3 Lock-wire 

"*" PR1771B2SEMK654 AR 5 Sealing product 

"*" MASTINOX 6856 K AR 6 Sealant 

"*" DHS172-171.20 AR 7 Adhesive AW106 
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3.D. MATERIAL REQUIRED FOR EACH SPARE PART 

Not applicable. 

3.E. RE-IDENTIFIED PARTS 

Not applicable. 

3.F. TOOLING: COST - AVAILABILITY 

For any information, contact the Sales and Customer Relations Department of the EUROCOPTER Network. 

3.G. PROCUREMENT CONDITIONS 

Order the required quantities (unless otherwise specified) 

from 

EUROCOPTER 

Etablissement de Marignane 

Direction Ventes et Relations Client 

ECR 

13725 MARIGNANE CEDEX 

FRANCE 

NOTE 1

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

the destination and the serial numbers of the aircraft to be 

modified. 

NOTE 2

For ALERT SERVICE BULLETINS, order by: 

Telex: HELICOP 410 969F 

Fax: +33 (0)4.42.85.99.96. 
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4. APPENDIX 

MOD 073148 

 embodied? 

MOD 073288 

 embodied? 

MOD 073288 

 embodied? 

no yes 

Comply with § 2.B.2. 

within 110 flying 

hours as from the 

date of issue of 

Revision 0 of this 

ASB, then comply 

with § 2.B.3 every 

110 flying hours 

Apply a bead of PR 

sealant (§ 2.B.2.a.1) 

within 25 flying hours as 

from receipt of Revision 

1 of this ASB 

Helicopters without PR 

sealant bead (§ 2.B.2.a.1): 

Apply a bead of PR 

 sealant within 25 flying 

hours as from receipt of 

Revision 1 of this ASB 

 no yes yes no, (improbable 

 on receipt of 

 Revision 1) 

Comply with § 

2.B.2. 

within 500 flying 

hours as from 

receipt of Revision 

0 of this ASB, and 

at the latest by 

March 31, 2006 

Comply with § 2.B.3 

every 110 flying hours 

Helicopters with PR 

sealant bead 

(§ 2.B.2.a.1): 

Not concerned by the 

instructions in this ASB 

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4. APPENDIX 

MOD 073148 

 embodied? 

MOD 073288 

 embodied? 

MOD 073288 

 embodied? 

no yes 

Comply with § 2.B.2. 

within 110 flying 

hours as from the 

date of issue of 

Revision 0 of this 

ASB, then comply 

with § 2.B.3 every 

110 flying hours 

Apply a bead of PR 

sealant (§ 2.B.2.a.1) 

within 25 flying hours as 

from receipt of Revision 

1 of this ASB 

Helicopters without PR 

sealant bead (§ 2.B.2.a.1): 

Apply a bead of PR 

 sealant within 25 flying 

hours as from receipt of 

Revision 1 of this ASB 

 no yes yes no, (improbable 

 on receipt of 

 Revision 1) 

Comply with § 

2.B.2. 

within 500 flying 

hours as from 

receipt of Revision 

0 of this ASB, and 

at the latest by 

March 31, 2006 

Comply with § 2.B.3 

every 110 flying hours 

Helicopters with PR 

sealant bead 

(§ 2.B.2.a.1): 

Not concerned by the 

instructions in this ASB