MANDATORY

An appropriate entry should be made in the aircraft log book upon accomplishment.

If ownership of aircraft has changed, please, forward to new owner.

An Company

Via GiovanniAgusta, 520

21017 Cascina Costa di Samarate (VA) Italy

Tel.: +39 0331-229111 - Fax: +39 0331-229605/222595

BOLLETTINO TECNICO N° 139-166 

The technical content of this document is approved 

under the authority of DOA nr. EASA.21J.005 DATE April 6, 2009

REV. /

Compliance with

this bulletin is: 

 page 1 of 26

SUBJECT: MODULAR AVIONIC UNITS

REASON: inspect MAU#1 and MAU#2. Improve MAU#2 installation for corrosion 

prevention.

HELICOPTERS AFFECTED: AB139/AW139 short nose configuration helicopters: from 

S/N 31005 to S/N 31157 (except S/N 31007, S/N 31094 and S/N 31149) and from 

S/N 41001 to S/N 41023. 

COMPLIANCE: within 300 flight hours or six (6) months from receipt of this Bollettino, 

whichever comes first. 

DESCRIPTION: corrosion of MAU#2 cards due to salt water and external moisture has 

been identified as a contributory factor in some in-flight emergency occurrences. In 

particular Custom I/O #2 cards have been verified to be susceptible to this type of 

corrosive agents. 

This Bollettino provides the necessary instructions to inspect the MAU#2 cards in 

order to ensure that they are corrosion free. Moreover an improvement of the 

MAU#2 ventilation duct installation is implemented in order to move the MAU#2 

cards away from the direct flow of air coming from the ventilation duct outlet. 
B.T. 139-166 

page 2 of 26 

Even though no event of corrosion has been verified on MAU#1 cards, as a precautionary measure, also the MAU#1 cards are inspected. 

REQUIRED MANPOWER: it is estimated that in order to accomplish this Bollettino eight 

(8) man-hours (MMH) are necessary. 

Man-hours are based on hands-on time and may vary with personnel and facilities 

available. 

WARRANTY:

• Upon request, the parts required to apply this Bollettino shall be supplied on a 

free of charge basis by Agusta, except for the consumable materials. 

• Upon application of this Bollettino Tecnico, Customers are requested to submit to 

Agusta Warranty Administration a Maintenance Malfunction Information report 

duly completed in all its parts. 

REQUIRED MATERIALS: the following materials are necessary to accomplish this 

bollettino and can be required to AgustaWestland: 

P/N DESCRIPTION Q.TY

3P5340A40251 (1) Connector 1 

3G5306P25451 Plate 1 

CONSUMABLE MATERIALS: moreover the following consumable materials are 

necessary to comply with this bollettino: 

SPEC./AW Code Number DESCRIPTION Q.TY NOTE

199-05-002, Type I, Class 2 – 

Code no. 900000581 Adhesive AR local supply 

199-05-002, Type II, Class 2 – 

Code no. 900004603 Adhesive, EA934NA AR local supply 

AMS-C-9084 Ty. VIIIB Cl. 1 

Code no. 900005846 Glass Fiber AR local supply 
 B.T. 139-166 

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SPEC./AW Code Number DESCRIPTION Q.TY NOTE

199-50-002, Type I – 

Code no. 900001557 Resin AR local supply 

199-50-002, Type II – 

Code no. 900001558 Hardener AR local supply 

 / Sticker 6 local supply 

Notes

(1) alternative P/N 3A5340A40251 might be supplied. 

SPECIAL TOOLS: the following special tools are necessary to accomplish this 

bollettino: 

P/N DESCRIPTION Q.TY

Local supply Light source 1

WEIGHT AND BALANCE CHANGES: N.A. 

REFERENCES:

9 AW139 Aircraft Maintenance Publication (AMP) 

PUBLICATIONS AFFECTED: N.A. 

COMPLIANCE INSTRUCTIONS:

1. Prepare the helicopter for a safe ground maintenance. 

Disconnect the battery and all the electrical power sources and/or the external power 

supply. Refer to Aircraft Maintenance Publication (AMP), see DM n° 39-A-00-20-00-

00A-120A-A. 

2. Remove the Number 2 modular avionics unit (MAU2) cabinet. Refer to AMP, see DM 

n° 39-A-31-42-01-00A-720A-A. 
B.T. 139-166 

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NOTE

To perform MAU2 removal at step 2 it is necessary to 

remove (among the others) from the MAU2 cabinet 

the following MAU modules to be inspected at step 3: 

- Number 2 power supply (PS2) module,

- Number 2 custom input/output (CSIO2) module, 

- Number 2 control input/output (CIO2) module. 

CAUTION

Only personnel trained by AgustaWestland or 

Honeywell is permitted to do the inspection 

described at following step 3. 

3. Do a general visual inspection of the MAU modules and related connectors 

according to the following instructions: 

NOTE

Modules to be inspected are the following: 

- Power Supply (PS) module P/N 7024440-1901, 

- Custom I/O (CSIO) module P/N 7025410-1901, 

- Control I/O (CIO) module P/N 7026534-1902. 

3.1 Visually examine the connectors of the MAU modules for signs of corrosion 

(refer to attachment 1 of this Bollettino for detailed instructions). 

3.2 If you find any sign of corrosion, clean the connector before further installation 

(refer to attachment 1 of this Bollettino for detailed instructions). 

3.3 Visually examine the MAU modules for structural integrity and for evidence of 

corrosion (refer to attachment 1 of this Bollettino for detailed instructions). 

3.4 If you find sign of corrosion, get a new module for installation at step 12 

(MAU2) or step 13 (MAU1). Contact AW to coordinate the shipment of the 

removed module for reconditioning 

3.5 If you don’t find any sign of corrosion continue the inspection on all the modules 

listed in NOTE. 
 B.T. 139-166 

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3.6 Apply a sticker on every inspected module and mark “BT 139-166 applied”. 

4 Remove from Number 1 modular avionics unit (MAU1) cabinet the modules listed 

beyond. Refer to AMP, see DM listed in the following table: 

39-A-31-41-02-00A-520A-A Number 1 power supply (PS1) module – Remove 

procedures 

39-A-31-41-03-00A-520A-A Number 1 custom input/output (CSIO1) module – 

Remove procedures 

39-A-31-41-04-00A-520A-A Number 1 control input/output (CIO1) module – 

Remove procedures 

5 Repeat the inspection described at step 3 for MAU#1 modules removed at step 4. 

6 Disconnect the RH ventilation pipe as follows: 

6.1 Remove the AFT right float assembly, if installed. Refer to AMP, see DM n° 39-

A-95-61-04-00A-520A-K. 

6.2 If the AFT right float assembly is not installed, remove lower panel P/N 

3P5340A01631 (184BR). Refer to figure 1 for panel position. 

6.3 With reference to figure 2, get access to the air duct hose (2) and remove the 

clamp (1) that holds the hose on the connector (3). 

6.4 Disconnect the hose (2) from the connector (3). 

7 Remove the external skin P/N 3P5340A38651 (180ER) as follows: 

7.1 With reference to figures 1 and 4, remove access panel 182AR (6). 

7.2 With reference to figure 4, remove the screws (13) and the washers (14) that 

hold the support (12) on the floor. Retain the hardware for re-use. 

7.3 Remove the support (12). 

7.4 Remove the screws (17) and the washers (18) that hold the AFT RH vertical 

angle assy (19) on the angle assy (20). Retain the hardware for re-use. 

7.5 With reference to figure 3, remove the screws (2) and the washers (3) that hold 

the AFT RH vertical angle assy (4) on the joint assy (5). Retain the hardware 

for re-use. 

7.6 Remove the AFT RH vertical angle assy (4). 
B.T. 139-166 

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7.7 With reference to figure 4, remove the screws (16) and the washers (15) that 

hold the angle assy (20) on the floor. Retain the hardware for re-use. 

7.8 Remove the angle assy (20). 

7.9 Remove screws and washers that hold the FWD floor P/N 3P5340A03631 

(panel 180ER) on the helicopter. 

7.10 Remove the FWD floor P/N 3P5340A03631 (180ER) from the helicopter. 

8 With reference to figures 5 thru 8, rework FWD floor P/N 3P5340A03631 as follows: 

8.1 Trim connector P/N 3P5340A40251 from FWD floor P/N 3P5340A03631 as 

shown in figure 8 section B-B. Make sure to avoid damage to the panel. 

8.2 Close the existing hole using plate P/N 3G5306P25451 as shown in figure 6 

view A. Install the plate on the upper side of the panel using adhesive 199-05-

002 Type I Class 2. 

8.3 Perform a 69 mm φ hole on the FWD floor P/N 3P5340A03631 in the new 

position as shown in figure 6 view A. 

8.4 Install connector P/N 3P5340A40251 in the hole using adhesive 199-05-002 

Type I Class 2 as shown in figure 6 section C-C. 

8.5 Rename FWD floor with P/N 3G5306P25411. 

9 Install FWD floor P/N 3G5306P25411 on the helicopter using hardware removed at 

step 7.10. 

10 With reference to figure 2, connect the air duct hose (2) to the connector (3) installed 

at step 6.3 using the clamp (1). Refer to figure 7 for the new air duct hose 

positioning. 

11 With reference to figures 3 and 4, install support, angles and panels removed at step 

7, using previously retained hardware. 

12 Install the MAU2 cabinet. Refer to AMP, see DM n° 39-A-31-42-01-00A-720A-A. 

NOTE

Instructions to install MAU2 modules and to perform 

the related operational checks are provided in AMP 
 B.T. 139-166 

page 7 of 26 

Data Modules referenced in DM n° 39-A-31-42-01-

00A-720A-A referred to in step 10. 

13 Install in the MAU1 cabinet the modules listed beyond. Refer to AMP, see DM listed 

in the following table: 

39-A-31-41-02-00A-720A-A Number 1 power supply (PS1) module – Install 

procedures 

39-A-31-41-03-00A-720A-A Number 1 custom input/output (CSIO1) module – 

Install procedures 

39-A-31-41-04-00A-720A-A Number 1 control input/output (CIO1) module – 

Install procedures 

NOTE

Instructions to perform the related operational checks 

are provided in AMP Data Modules referenced in DM 

referred to in step 13. 

14 Install the AFT right float assembly (refer to AMP, see DM n° 39-A-95-61-04-00A520A-K) or the lower panel P/N 3P5340A01631 (184BR), whichever has been 

removed at step 6. 

15 Report the results of the inspection performed at steps 3 and 5 to AW139 Product 

Support Engineering (aw139.mbx@agustawestland.com). 

16 Return the helicopter to flight configuration and record for compliance of this 

bollettino. 
B.T. 139-166 

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Figure 1
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Figure 2 
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Figure 3 

STRUCTURE AND SYSTEMS 

ARE PARTIALLY OMITTED 

FOR CLARITY PURPOSES 
 B.T. 139-166 

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Figure 4 

STRUCTURE AND SYSTEMS 

ARE PARTIALLY OMITTED 

FOR CLARITY PURPOSES 
B.T. 139-166 

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Figure 5 
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Figure 6 
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Figure 7 
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Figure 8 
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A T T A C H M E N T 1 
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Note: 

Remarks:

Informazioni: 

Information:

Al fine di gestire le varianti alla configurazione base, in relazione all’emissione del Bollettino Tecnico, preghiamo di voler compilare il presente modulo in tutte le sue parti e spedirlo all’indirizzo sopra indicato. Si ringrazia per la gentile collaborazione data. 

We request your cooperation in filling this form, in order to keep out statistical data relevant to aircraft configuration up-to-date. The form should be filled in all 

its parts and sent to the above address. We thank you beforehand for the information given.

MODULO APPLICAZIONE BOLLETTINO TECNICO

TECHNICAL BULLETIN COMPLIANCE FORM

Data: 

Date:

Numero: 

Number:

Revisione: 

Revision:

Prego spedire a questo indirizzo: 

Please send to the following address: 

AGUSTA S.p.A. 

PRODUCT SUPPORT ITALY 

Via per Tornavento, 15 

21019 Somma Lombardo (VA) - ITALY 

Tel.: +39 0331 711100 

Fax: +39 0331 711180

Telefono: 

Telephone:

Fax:

Data Applicazione B.T.: 

B.T. Compliance Date:

Denominazione Cliente ed Indirizzo: 

Customer Name and Address:

Modello Elicottero 

Helicopter Model S/N Matricola Tail Number

Ore Totali 

Total Hours

Ore D.U.R. 

T.S.O.