T.F.S. No. 00000449

Approved under EASA DOA No. 21J.056. Page 1/14

 2008.05.07

EUROCOPTER 

DIRECTION TECHNIQUE SUPPORT

13725 MARIGNANE CEDEX FRANCE

EMERGENCY

ALERT SERVICE BULLETIN 

DAUPHIN NUMBER VERSIONS 

Civil: N,N1,N2,N3. AS 365 63.00.17 Military: F,Fs,Fi,K. 

AS 565 63.00.12 Military: AA,MA,MB,SA,SB,UB

Civil: B,B1 EC 155 63A011 

Civil: G1 SA 366 65.03 Military: GA 

Civil: C,C1,C2,C3 SA 360/SA 365 65.47 

SUBJECT: MAIN ROTOR DRIVE 

Check of the Main Gearbox Casing (to make sure that there is no corrosion in 

the area of the servo-control attachment fittings) 

REVISION No. DATE OF APPROVAL DATE OF ISSUE 

 

Revision 0 On: May 06, 2008 2008.05.07 

This document is available on the internet : www.eurocopter.com/techpub 
 T.F.S. No. 00000449

Approved under EASA DOA No. 21J.056. Page 2/14

 2008.05.07

1. PLANNING INFORMATION 

1.A. EFFECTIVITY 

1.A.1. Helicopters / Installed equipment: 

Main Gearboxes (MGBs), all part numbers: 

- New MGBs delivered until December 5, 2007 (inclusive), or installed on new helicopters delivered until 

December 5, 2007 (inclusive) (refer to the conformity certificate of the helicopter), 

- MGBs newly overhauled or repaired before September 30, 2008. 

1.A.2. Non-installed equipment 

Main Gearboxes (MGBs), all part numbers: 

- New MGBs delivered until December 5, 2007 (inclusive), 

- MGBs newly overhauled or repaired before September 30, 2008. 

NOTE 1

This ALERT SERVICE BULLETN does not apply to: 

- New MGBs delivered after December 5, 2007 

 (date recorded on the equipment log card). 

- MGBs newly overhauled or repaired after 

September 30, 2008 (date recorded on the equipment 

log card). 

- MGBs installed on new helicopters (refer to the 

conformity certificate of the helicopter) delivered after 

December 5, 2007. 

1.B. ASSOCIATED REQUIREMENTS 

Not applicable. 

1.C. REASON 

To make sure that there is no corrosion in the lower area located between the two Main Gearbox casing 

servo-control attachment ribs if there is a bead of PR sealing compound on the lower part of the servocontrol attachment fittings. 

This ALERT SERVICE BULLETIN will form the subject of an DGAC Airworthiness Directive. 

 
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1.D. DESCRIPTION 

EUROCOPTER has received some reports of atmospheric corrosion on the Main Gearbox casing 

lower area, between the two servo-control anchoring fitting attachment ribs (see Figure 1). 

The examinations and analyses of this occurrence have revealed that this corrosion results from 

an area trapped under the anchoring fittings. This trapped area is associated with a bead of PR 

sealing compound on the lower part of the fitting/casing attachment. 

This occurrence of corrosion weakens this area of the casing and could, in time, lead to crack 

initiation and crack growth which could cause this area to fail and lead to the loss of control of the 

helicopter. 

Consequently, EUROCOPTER renders compliance with the measures defined in this ALERT 

SERVICE BULLETIN, mandatory. 

1.E. COMPLIANCE 

1.E.1. Compliance at the works 

1.E.1.a. On helicopters / installed equipment: Not applicable. 

1.E.1.b. Non-installed equipment: Not applicable. 

1.E.2. Compliance in operation: By the operator. 

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

Comply with paragraph 2.B.2. at the latest within 15 flying hours following receipt of this ALERT 

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

- If there is no PR sealing compound on any of the lower parts of the MGB servo-control anchoring 

fittings: 

. leave as is, 

. Return the helicopter to flight condition in compliance with paragraph 2.B.4. 

- If there is a bead of PR sealing compound on the lower part of at least one MGB 

servo-control anchoring fitting: 

. Contact the Customer Service Technical Support Operations Department (STVM) to inform it that 

you have discovered a bead of PR sealing compound on the lower part of the attachment fittings, 

by: 

 Tel: +33 (0)4.42.85.99.67 

 Fax: +33 (0)4.42.85.99.66. 

Email : Dyncomp.technical-support@eurocopter.com 

. Comply with paragraph 2.B.3. (See NOTE 3 of paragraph 1) 

Or 

. Leave as is and, 

. Return the helicopter to flight condition in compliance with paragraph 2.B.4. 

then: 

- Comply with paragraph 2.B.3. according to the conditions specified in paragraphs 1.E.2.a.1. 

or 1.E.2.a.2. 
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NOTE 2

For MGBs for which the history of the operating 

conditions cannot be traced back, comply with the 

instructions given in paragraph 1.E.2.a.1. 

1.E.2.a.1. For MGBs installed since new or last complete overhaul, on helicopters that have been operated in 

one of the following operating conditions, regardless of the time spent:

- Helicopters based onboard ship and operated offshore 

- Helicopters operated less than 1 kilometer off the coast 

- Helicopters operated at low attitude (less than 1000 feet) over the sea 

and 

a) which have logged less than 30 months since new or last complete overhaul: 

 

- comply with paragraph 2.B.3. at the latest when the MGB reaches 33 months since new or last 

 complete overhaul of the MGB: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

- comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. at the latest when the MGB reaches 33 months since new 

or last complete overhaul of the MGB. 

b) which have logged between 30 and 33 months since new or last complete overhaul: 

 

- comply with paragraph 2.B.3. at the latest when the MGB reaches 33 months since new or last 

 complete overhaul of the MGB: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

- comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. at the latest when the MGB reaches 33 months since new 

or last complete overhaul of the MGB. 

or 

- comply with paragraph 2.B.3. within 3 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 55 flying hours: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

 - comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. within 3 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 55 flying hours. 
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Approved under EASA DOA No. 21J.056. Page 5/14

 2008.05.07

c) which have logged more than 33 months since new or last complete overhaul: 

-comply with paragraph 2.B.3. within 3 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 55 flying hours: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

 - comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

-comply with paragraph 2.B.3.b. within 3 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 55 flying hours. 

1.E.2.a.2. For MGBs which have never been installed since new or last complete overhaul, on helicopters that 

have been operated in one of the following operating conditions:

- Helicopters based onboard ship and operated offshore 

- Helicopters operated less than 1 kilometer off the coast 

- Helicopters operated at low attitude (less than 1000 feet) over the sea 

and 

a) which have logged less than 54 months since new or last complete overhaul: 

 

- comply with paragraph 2.B.3. at the latest when the MGB reaches 60 months since new or last 

 complete overhaul of the MGB: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

 - comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. at the latest when the MGB reaches 60 months since new 

or last complete overhaul of the MGB. 
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b) which have logged between 54 and 60 months since new or last complete overhaul: 

 

- comply with paragraph 2.B.3. at the latest when the MGB reaches 60 months since new or last 

 complete overhaul of the MGB: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

 - comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. at the latest when the MGB reaches 60 months since new 

or last complete overhaul of the MGB. 

or 

- comply with paragraph 2.B.3. within 6 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 110 flying hours: 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

 - comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. within 6 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 110 flying hours. 

c) which have logged more than 60 months since new or last complete overhaul: 

- comply with paragraph 2.B.3. within 6 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 110 flying hours. 

. If there is no corrosion on the lower parts of the MGB servo-control anchoring fittings: 

 - comply with paragraph 2.B.3.a. 

. If there is corrosion on at least one of the lower parts of the MGB servo-control anchoring 

fittings: 

- comply with paragraph 2.B.3.b. within 6 months following receipt of this ALERT SERVICE 

BULLETIN without exceeding 110 flying hours. 
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Approved under EASA DOA No. 21J.056. Page 7/14

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1.E.2.b. Non-installed equipment: Before installing a MGB on a helicopter, comply with the instructions 

 given in paragraph 2.B.2., and if there is PR sealing compound, comply 

 with the instructions given in paragraph 2.B.3. 

NOTE 3

The time limits specified above are maximum time limits 

enabling operators to detect any corrosion before it 

affects the integrity of the fitting/casing attachment. 

However, we recommend that you remove the PR 

sealing compound in compliance with paragraph 2.B.3. 

as soon as possible, in order to limit the risk of corrosion 

occurring in this area and thus avoid replacing the MGB. 

1.F. APPROVAL 

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

The technical information contained in this ALERT SERVICE BULLETIN was approved 

on May 06, 2008 under the authority of EASA Design Organization Approval No. 21J.056. 

1.G. MANPOWER 

Qualification: Mechanic. 

Time for the operations: For compliance with paragraphs 2.B.1., 2.B.2. and 2.B.4.: Approximately 

 30 minutes. 

 For compliance with paragraphs 2.B.1., 2.B.3. and 2.B.4.: 1 to 17 hours, 

 depending on the results of the check for absence of corrosion on the lower 

 parts of the anchoring fittings. 

 

1.H. WEIGHT AND BALANCE 

 Not applicable. 
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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: 

- 20.04.04 

- 20.04.05 

- 20.05.01 

1.L. OTHER DOCUMENTS CONCERNED 

Not applicable. 

1.M. INTERCHANGEABILITY AND MIXABILITY OF PARTS 

Not applicable. 
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2. ACCOMPLISHMENT INSTRUCTIONS 

2.A. GENERAL 

Not applicable. 

2.B. OPERATIONAL PROCEDURE 

2.B.1. Preliminary steps 

- Install the equipment providing access to the MGB. 

- Remove the cowling providing access to the MGB. 

2.B.2. Check all the lower parts of the MGB servo-control anchoring fittings, in order to make sure that there is 

no PR sealing compound 

As per Figure 1: 

- Check all the lower parts of the MGB servo-control anchoring fittings 

 using a lamp or a dentist’s mirror, in order to make sure that there is no PR sealing compound. 

Interpretation of the results: 

a) If there is no PR sealing compound on any of the lower parts of the MGB servo-control 

anchoring fittings: 

- Leave as is. 

- Return the helicopter to flight condition in compliance with paragraph 2.B.4. 

b) If there is a bead of PR sealing compound on the lower part of at least one MGB servocontrol anchoring fitting: 

- Contact the Customer Service Technical Support Operations Department (STVM) to inform it 

that you have discovered a bead of PR sealing compound on the lower part of the attachment 

fittings, 

by: 

 Tel: +33 (0)4.42.85.99.67 

 Fax: +33 (0)4.42.85.99.66. 

Email : Dyncomp.technical-support@eurocopter.com 

- Comply with paragraph 2.B.3. 

Or 

- Leave as is and return the helicopter to flight configuration in compliance with paragraph 2.B.4., 

then: 

- Comply with paragraph 2.B.3. according to the conditions specified in paragraphs 1.E.2.a.1. 

 or 1.E.2.a.2. 
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2.B.3. Check to make sure that there is no corrosion on the lower parts of the MGB servo-control anchoring 

fittings 

As per Figure 1: 

- Remove the bead of PR sealing compound from the lower part of the servo-control anchoring fitting(s) 

concerned. 

NOTE 1

There are different procedures for removing the bead of PR sealing 

compound. The procedures applied by EUROCOPTER to facilitate 

removal are described below: 

Use of a bronze knife or a plexiglas spatula: 

- Carefully cut the bead of PR sealing compound from the two zones 

identified by (xxx) as shown on Figure 1 (zones located in the area 

of the hole for the lower bolt attaching the fitting). 

- Pull the bead of PR sealing compound gently from the cutting to 

prevent it from tearing. 

Use of plastic milling cutters: 

Designation: 50 mm diameter radial scoring disk – SR 

Part number: 30097 

Manufacturer: 

3M, St Paul, MN 55144-1000, USA 

3M, France Construction et Maintenance Aéronautique Bd de 

l'Oise 95006 Cergy Pontoise Cedex, France 

- Protect the adjacent areas from PR particle ejections. 

- Machine the bead of PR sealing compound with plastic milling 

cutters. You must stack several (at least 3) plastic milling cutters. 

- Remove the PR sealing compound residues using a plexiglas 

spatula or a bronze knife. 

Then: 

- Visually check using a lamp and a dentist’s mirror that there is no corrosion in the lower area of the 

Main Gearbox casing, between the two servo-control anchoring fitting attachment ribs. 

Interpretation of the results:

a) If there is no corrosion in the lower area of the Main Gearbox casing, between the two servo-control 

anchoring fitting attachment ribs: : 

- If necessary, touch up protective treatment as per MTC Work Cards 20.04.04 and 20.04.05. 

- If the bead of PR sealing compound in the areas referred to is damaged, renew it as per MTC 

Work Card 20.05.01 (see Figure 1 ). 
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THE BEAD OF PR SEALING COMPOUND MUST BE APPLIED TO THE 

LATERAL EDGES AND TO THE UPPER PART OF THE SERVOCONTROL ANCHORING FITTINGS. NEVER APPLY A BEAD OF PR 

SEALING COMPOUND TO THE LOWER PART OF THE SERVOCONTROL ANCHORING FITTINGS. 

- Return the helicopter to flight configuration as per paragraph 2.B.4. 

b) If there is corrosion on at least one MGB servo-control anchoring fitting lower part: 

- Suspend flights immediately or at the latest at the time limits specified in paragraph 1.E.2.a.1. 

or 1.E.2.a.2. 

- Comply with Repair Sheet FR 365-63-36-08 before resuming flights. 

- Return the helicopter to flight configuration in compliance with paragraph 2.B.4. 

NOTE 2

Repair Sheet (FR) 365-63-36 -08 is available from the 

Customer Service Technical Support Operations 

Department (STVM) on the operator’s request: 

Tel: +33 (0)4.42.85.99.67 

Fax: +33 (0)4.42.85.99.66 

Email : Dyncomp.technical-support@eurocopter.com 

2.B.4. Final steps 

Install the cowlings providing access to the MGB. 

Remove the equipment providing access to the MGB. 

2.C. IDENTIFICATION 

Record compliance with this ALERT SERVICE BULLETIN on the log card of the MGB after having 

complied with paragraph 2.B.2., and where applicable: 

Record compliance with this ALERT SERVICE BULLETIN on the log card of the MGB after having 

complied with paragraph 2.B.3. 

2.D. OPERATING AND MAINTENANCE INSTRUCTIONS 

Not applicable. 

CAUTION 
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Lower part of the MGB servo-control anchoring fittings 

No bead of PR sealing compound Bead of PR sealing compound 

applied 

Figure 1 – Location of the anchoring fittings and beads of PR sealing compound 

Servo-control anchoring 

fitting 

Location of the beads of 

PR sealing compound 

Lower attachment bolt

Lower attachment bolt

Locations of the 

servo-control 

anchoring fittings 

Zones(XXX) 
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3. MATERIAL INFORMATION

3.A. MATERIAL: COST – AVAILABILITY 

Not applicable. 

3.B. INFORMATION CONCERNING INDUSTRIAL SUPPORT 

Not applicable. 

3.C. MATERIAL REQUIRED FOR EACH HELICOPTER / ENGINE / COMPONENT 

The products 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

Telephone: +49.41.91.809.300 

AOG: +49.41.91.809.444 

3.D. MATERIAL REQUIRED FOR EACH SPARE PART 

Not applicable. 

3.E. RE-IDENTIFIED PARTS 

 Not applicable. 

3.F. TOOLING: COST – AVAILABILITY 

 Not applicable. 
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3.G. PROCUREMENT CONDITIONS

Order the required quantity (unless otherwise specified) 

from 

EUROCOPTER 

Etablissement de Marignane 

Direction Ventes et Relation Client 

ECR 

13725 MARIGNANE CEDEX 

FRANCE 

NOTE 1

For ALERT SERVICE BULLETINS, order by: 

Telex: HELICOP 410 969F 

Fax: +33 (0)4 42 85 99 96 

NOTE 2

On the purchase order, please specify the 

mode of transport, the destination and the 

serial numbers of the helicopters to be 

modified. 

4. APPENDIX 

 

Not applicable.