eurocopter 

an EADS Company 

ALERT SERVICE BULLETIN AS355 

EUROCOPTER 

DIRECTION TECHNIQUE SUPPORT 

13725 MARIGNANE CEDEX FRANCE CIVIL VERSION(S): E,F,F1 ,F2,N 

ALERT SERVICE BULLETIN 

No. 05.00.51 

SUBJECT: TIME LIMITS - MAINTENANCE CHECKS 

Monitoring of the MGB oil pump 

ATA: 63 

REVISION No. DATE OF APPROVAL 

Revision 0 On: July 06, 2007 

Approved under EASA DOA No. 21J .056. 05.00.51 

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

DATE OF ISSUE 

2007.07.09 

Page 1/12 

2007.07.09 
ALERT SERVICE BULLETIN AS355 

lcAUTIONI 

THE INFORMATION AND INSTRUCTIONS CONTAINED IN 

THIS ALERT SERVICE BULLETIN ARE INTENDED FOR 

MAINTENANCE PERSONNEL AND FLIGHT CREWS. 

1. PLANNING INFORMATION 

1.A. EFFECTIVITY 

1.A.1. Helicopters/Installed Equipment 

Helicopters equipped with main gearbox (MGB) oil pumps P/N 355A32-0700-01 , 355A32-0700-02 and 

355A32-0701-00. 

1.A.2. Non-Installed Equipment 

Not applicable. 

1.B. ASSOCIATED REQUIREMENTS 

Not applicable. 

1.C. REASON 

To monitor the oil pump periodically for wear to prevent insufficient lubrication of the MGB. 

Compliance with this ALERT SERVICE BULLETIN supersedes the instructions of ALERT SERVICE 

BULLETIN AS355 No. 05.00.40 (mandatory check at each After Last Flight of day (ALF) check of the MGB 

magnetic plug and oil level sight). 

This ALERT SERVICE BULLETIN will be the subject of an EASA Airworthiness Directive. 

1.D. DESCRIPTION 

Following an incident in late 2006, EUROCOPTER issued Revision 2 of ALERT SERVICE BULLETIN 

No. 05.00.40 on December 20, 2006, to extend its effectivity to all the part numbers of the oil pumps. This 

ALERT SERVICE BULLETIN required monitoring of the magnetic plug and the color of the oil at each ALF 

check. 

Since then, EUROCOPTER has studied a procedure for detecting any oil pump wear as early as possible in 

order to reduce the risks of helicopter downtime. 

Oil pump wear is a slow-acting phenomenon that causes a progressive drop of pressure in the oil system 

over time. 

Approved under EASA DOA No. 21J .056. 05.00.51 Page 2/12 

2007.07.09 
eurocopter 

an EAOS Company 

ALERT SERVICE BULLETIN AS355 

During helicopter starts, the oil system pressure increases with the rotor RPM (NR). 

As the wear of the oil pump increases, its efficiency drops. In successive starts, the oil pressure indicator 

light therefore extinguishes later and later, occurring at higher and higher rotor RPM (NR). 

The pressure in the oil system also varies with the oil tem perature, which is itself variable and dependent on 

the Outside Air Temperature (OAT). To determine the pressure, temperature of the oil in the MGB must 

therefore be steady. 

The procedure given in this ALERT SERVICE BULLETIN is based on these phenomena. The following 

values are to be recorded periodically during starting phases after the MGB oil temperature has stabilized: 

the NR value at which the MGB oil pressure indicator light goes out, and the outside air temperature. Charts 

are included for determining the amount of wear on the oil pump and for defining the new measurement 

intervals and the removal criterion for the pump. 

EUROCOPTER renders compliance with this ALERT SERVICE BULLETIN mandatory. 

1.E. COMPLIANCE 

1.E.1 . Compliance at the works 

1.E.1 .a. On Helicopters: Comply with paragraph 1.E.2.a. 

1.E.1.b. On Non-Installed Equipment: Not applicable. 

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

1.E.2.a. On Helicopters/Installed Equipment 

Comply with paragraph 2.B. within 25 flying hours following receipt of this ALERT SERVICE BULLETIN, 

issued on the date specified in the footer, and immediately upon return from a flight lasting more than 

20 minutes, to ensure the MGB oil temperature has stabilized. 

-Then, depending on the value measured as per paragraph 2.B.2.: 

. Measured value in ZONE 1: Comply with paragraph 2.B. at intervals not exceeding 110 flying hours 

OR 

. Measured value in ZONE 2: Comply with paragraph 2.B. at intervals not exceeding 25 flying hours 

OR 

. Measured value in ZONE 3: Replace the oil pump before resuming flights. 

1.E.2.b. On Non-Installed Equipment 

Comply with paragraph 2.B. during the flight following installation of an MGB fitted with an oil pump whose 

P/N is defined in paragraph 1.A.1. or during the flight following installation on the MGB of an oil pump 

whose P/N is defined in paragraph 1.A.1. 

Approved under EASA DOA No. 21J.056. 05.00.51 Page 3/12 

2007.07.09 
ALERT SERVICE BULLETIN AS355 

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 July 06, 2007 under the authority of EASA Design Organisation Approval No. 21J .056. 

1.G. MANPOWER 

Qualification: Mechanic and/or flight crew. 

Time for the operation: Approximately 15 minutes. 

1.H. WEIGHT AND BALANCE 

Not applicable. 

1.1. EFFECT ON ELECTRICAL LOADS 

Not applicable. 

1.J. SOFTWARE MODIFICATION EMBODIMENT STATE 

Not applicable. 

1.K. REFERENCE DOCUMENTS 

Maintenance Manual (MET) Work Cards: 

- 63.00.00.402, 

- 63.00.00.403. 

1.L. OTHER DOCUMENTS CONCERNED 

Maintenance Program (PRE). 

Flight Manual (MV). 

Maintenance Manual (MET). 

1.M. TOOLING CONCERNED 

Not applicable. 

1.N. INTERCHANGEABILITY AND MIXABILITY OF PARTS 

Not applicable. 

Approved under EASA DOA No. 21J .056. 05.00.51 Page 4/12 

2007.07.09 
ALERT SERVICE BULLETIN AS355 

2. ACCOMPLISHMENT INSTRUCTIONS 

2.A. GENERAL 

Not applicable. 

2.8. OPERATIONAL PROCEDURE 

2.B.1. Preliminary steps 

Upon return from a flight lasting more than 20 minutes to ensure the MGB oil temperature has stabilized, 

comply immediately with the procedure in paragraph 2.B.2. 

2.B.2. Oil Pump Wear Inspection Procedure 

1. Shut down the engines. 

2. Record the OAT (°C or oF). 

3. Start at least one engine. 

4. Record the NR RPM at which the red MGBP oil pressure indicator light goes out. 

5. Shut down the engine(s). 

6. Transfer the OAT and NR values on to the chart (see Figure 1 (

0

C) or Figure 2 CF)). 

7. Perform the action required according to the position of the measurement on the charts: 

- ZONE 1 (Below curve A), comply with paragraph 2.B. at intervals not exceeding 110 flying hours 

-ZONE 2 (Between curves A and B), comply with paragraph 2.B. at intervals not exceeding 25 flying 

hours. 

- ZONE 3 (Above curve B), remove and replace the oil pump before resuming flights, as per MET Work 

Cards 63.00.00.402 and 403. 

When the measurement is in ZONE 2 (monitoring every 25 flying hours) and the following 

measurement is in ZONE 1 (monitoring every 110 flying hours), two successive monitoring 

operations must be carried out at intervals not exceeding 25 flying hours to confirm the 

measured value in ZONE 1 before going back to the monitoring at intervals not exceeding 

11 0 flying hours. 

When the measurement is in ZONE 2 (monitoring every 25 flying 

hours): 

a) The possible causes for oil pressure loss are explained in 

paragraph 4.A. (APPENDIX) 

Approved under EASA DOA No. 21J .056. 05.00.51 Page 5/12 

2007.07.09 
ALERT SERVICE BULLETIN AS355 

b) A table for you to record the OAT and NR values is included in 

paragraph 4.8. (APPENDIX) 

When the measurement is in ZONE 2 (monitoring every 

25 flying hours), please send this table (once only) to the 

address below: 

EUROCOPTER Marignane, 

Direction Technique Support (ESTVM) 

13725 Marignane CEDEX 

France 

Tel: +33 (0)4.42.85.99.51 

Fax: +33 (0)4.42.85.99.66 

Email : frederic.antoine@eurocopter.com 

We will use this table to study the behaviour of the MGB oil 

pump throughout the fleet and to forecast the need for oil 

pump spares more accurately. 

8. Also record the OAT (•c or •F) and NR (RPM) values each time in the table in paragraph 4.8. 

(APPENDIX) to monitor their variation. 

2.C. IDENTIFICATION 

Record the first compliance with this ALERT SERVICE BULLETIN on the oil pump logcard (FM). 

2.D. OPERATING AND MAINTENANCE INSTRUCTIONS 

Not applicable. 

Approved under EASA DOA No. 21J.056. 05.00.51 Page 6/12 

2007.07.09 
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CHART DEFINING OAT (°F) AND NR ZONES 

Equations of straight lines 

Curve A: NR(A) = 1.0494 x OAT(A) +174.98 

Curve 

B: NR(B) = 1.1481 x OAT(B) +190.93 

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ALERT SERVICE BULLETIN AS355 

3. MATERIAL INFORMATION 

3.A. MATERIAL: COST- AVAILABILITY 

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

Relations Department. 

3.8. INFORMATION CONCERNING INDUSTRIAL SUPPORT 

Not applicable. 

3.C. EQUIPMENT REQUIRED FOR EACH AIRCRAFT/ENGINE/COMPONENT 

Not applicable. 

3.D. PROCUREMENT CONDITIONS 

Order the required quantity, unless otherwise specified, 

to 

EUROCOPTER 

Marignane Plant 

Sales & Customer Relations Department 

ECR. 

13725 MARIGNANE CE DEX 

FRANCE 

NOTE1 

For ALERT SERVICE 8 ULLETINS, order by: 

Telex: HELl COP 410 969F. 

Fax: +33 (0)4.42.85.99.96. 

NOTE2 

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

destination, and the serial numbers of the helicopters to be 

modified. 

Approved under EASA DOA No. 21J.056. 05.00.51 Page 9/12 

2007.07.09 
ALERT SERVICE BULLETIN AS355 

4. APPENDIX 

4.A. POSSIBLE CAUSES FOR MGB OIL PRESSURE LOSS 

' ' ' ' P min ' ' ' ' I \ + 

' ' ' ' ' ' Oil filter 

I 

' ' 

Oil jets ' ' ' ' ' ' ' 

Coolers 

Oil pump 

~ Pressure relief valve 

----------------------

The loss of oil pressure may be due to: 

1. MGB oil pump wear 

2. A clogged filter or cooler, 

3. A pinched hose, 

4. An incorrectly set pressure switch. 

- Check points 2, 3 and 4 when the measurement is in ZONE 2 after replacement of an oil pump or for an 

oil pump which has logged a few flying hours. 

If the oil filter has clogged up, replace it with a new filter. 

If the oil cooler has clogged up, use White Spirit to clean the cooler oil circuit (refer to the CMM). 

If a hose is pinched , replace it with a new hose. 

If the operation of the oil pressure switch is in doubt, replace it with a new pressure switch. 

- After compliance with points 2 to 4, if the oil pressure is still low, please contact the EUROCOPTER 

Technical Support Directorate (ESTVM) at: 

Tel: +33 (0)4.42.85.99.51 

Fax: +33 (0)4.42.85.99.66 

Email : frederic.antoine@eurocopter.com 

Approved under EASA DOA No. 21J .056. 05.00.51 Page 10/12 

2007.07.09 
eurocopter 

an EADS Company 

ALERT SERVICE BULLETIN AS355 

4.8. TABLE FOR RECORDING OAT AND NR VALUES- OIL PUMPS 

CUSTOMER 

NAME: 

Address : 

Tel: ...... ... ... .... .. .. .... .. .... ...... .. .. 

Email: .. ............................ ...... ... .. ..... .. ... ...... .. ..... . 

HELICOPTER VERSION REGISTRATION 

AS 355 

I P/N: 

OIL PUMP TYPE OF OIL 

I S/N: 

DATE OF OIL PUMP 

MEASUREMENT **TSO 

*TSN : Time Since New. 

**TSO : Time Since Overhaul. 

Approved under EASA DOA No. 21J.056. 

TIME OF LAST OAT (

0

C) NR (RPM) FLIGHT OAT (°F) 

05.00.51 Page 11/12 

2007.07.09 
ALERT SERVICE BULLETIN AS355 

4.C. FOR INFORMATION: SEE ENCLOSED PAGE 

Draft of the modified page of the Flight Manual Supplement to be given to the Flight Crew 

Pending the revision of the Flight Manual, this page must be inserted for information in the Flight Manual. 

Upon receipt of the revision , this Flight Manual page will no longer be applicable. 

Subsequent changes made to this Flight Manual page will not give rise to a revision of this ALERT SERVICE 

BULLETIN. 

Approved under EASA DOA No. 21J.056. 05.00.51 Page 12/12 

2007.07.09 
SHEET 

No. 

3 

HELICOPTER 

AS355 

SUBJECT AND TEST 

REQUIREMENTS 

COMPLEMENTARY FLIGHT MANUAL 

CHECKS AFTER EXCHANGING THE MGB OR THE 

COMBINER MODULE 

MGB OIL PUMP CHECK 

Run-up- Hover Flight 

RESULTS TO BE ACHIEVED 

OR LIMITATIONS 

RESULTS ACHIEVED 

I 

Engine starting in compliance with Extinction of the MGB P Correct Incorrect 

the Normal Procedures of Flight indicator light at NR< 200 rpm. 

Manual SECTION 4.1. 

Hover flight for 5 to I 0 min. 

FROM 6 ft, at a weight close to the 

maximum takeoffweight. 

See Flight Manual 

SECTION 5. 

PROCEDURE FOR CHECKING 

THE MGB OIL PUMP 

Immediately on completion of a 

~ 20-minute flight. 

- Record the OAT 

Restart at least one engine. 

- Record the NR upon extinction of 

the MGB P indicator light 

Record the values on the crossreference chart by complying with 

the directives of ASB 05.00.51. 

See Limitations, 

Flight Manual SECTION 2.1 . 

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07-xx page xx