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° 139-133

The technical content of this document is approved 

under the authority of DOA nr. EASA.21J.005 

DATE February 20, 2009

REV. A – March 17, 2009 

Compliance with 

this bulletin is: 

Page 1 of 4

SUBJECT: GENERATOR CONTROL UNIT (GCU) P/N 1152550-5 

REASON: to replace GCU P/N 1152550-3 with improved version P/N 1152550-5. 

HELICOPTERS AFFECTED: AB139/AW139 helicopters from S/N 31005 up to S/N 31143 

(except S/N 31007, S/N 31037, S/N 31038, S/N 31094 and S/N 31112), from S/N 

31146 up to S/N 31148, S/N 31155, from S/N 31201 up to S/N 31218 and from S/N 

41001 up to S/N 41022 (except S/N 41007). 

NOTE

Implementation of this revision is required also for 

helicopters that have complied with the first issue of 

this Bollettino. 

COMPLIANCE: within 6 months from receipt of this Bollettino. 

DESCRIPTION: the modification described in this Bollettino improves Electrical Power 

Generation and Distribution System functionalities, in particular the overvoltage 

protection and the ground fault protection device. 
B.T. 139-133 Rev.A 

Page 2 of 4 

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

(4) man-hours are necessary. 

WARRANTY: upon request, the parts required to apply this Bollettino Tecnico shall be 

supplied on a Free of Charge basis by Agusta. 

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, necessary to accomplish this bollettino, 

can be required to AgustaWestland: 

 P/N DESCRIPTION Q.TY

(1) (2) 1152550-5 GCU AR (2 minimum) 

Moreover, the following consumable materials are necessary to accomplish this 

bollettino: 

 SPEC./AW Code Number DESCRIPTION. Q.TY

 A556A-22 Wire 0.5 m 

Notes: (1) GCU P/N 1152550-3 replacement must be extended to all modules kept 

in storage. 

(2) GCU P/N 1152550-4 may be supplied (q.ty 2 minimum) as an alternative 

to P/N 1152550-5. GCU P/N 1152550-4 and P/N 1152550-5 are not 

intermixable. 

SPECIAL TOOLS: N.A. 

WEIGHT AND BALANCE CHANGES: N.A. 

REFERENCES: 

A. AW139 Aircraft Maintenance Publication (AMP) 
B.T. 139-133 Rev.A 

Page 3 of 4 

PUBLICATIONS AFFECTED:

9 AW139 Illustrated Parts Data (IPD) 

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 AMP, see data 

module n° 39-A-00-20-00-00A-120A-A. 

2. Remove the Number 1 generator control unit (refer to AMP, see data module n° 39-A24-31-03-00A-520A-A) and send it to AgustaWestland. 

3. Remove the Number 2 generator control unit (refer to AMP, see data module n° 39-A24-31-04-00A-520A-A) and send it to AgustaWestland. 

4. With reference to figure 1, perform modification as shown on the electrical connector 

A13P1 before connecting it to the generator control unit A13. 

5. Install the new Number 1 generator control unit P/N 1152550-5. Refer to AMP, see 

data module n° 39-A-24-31-03-00A-520A-A. 

6. With reference to figure 1, perform modification as shown on the electrical connector 

A14P1 before connecting it to the generator control unit A14. 

7. Install the new Number 2 generator control unit P/N 1152550-5. Refer to AMP, see 

data module n° 39-A-24-31-04-00A-520A-A. 

8. Check every spare GCU kept in stock. In case the P/N is 1152550-3, send the GCU to 

AgustaWestland. It must be replaced with a new spare part 1152550-5. 

9. Return helicopter to flight configuration and record for compliance of this Bollettino. 
B.T. 139-133 Rev.A 

Page 4 of 4 

Figure 1 

BT133A22-G

BT133B22-G

Applicable to helicopters S/N 31005 up to S/N 31143 (except S/N 31007,

S/N 31037, S/N 31038, S/N 31094 and S/N 31112), from S/N 31146 up to S/N 

31148, S/N 31155 and from S/N 41001 up to S/N 41022 (except S/N 41007) 

Applicable to helicopters from S/N 31201 up to S/N 31218 

BT133B22-G

BT133A22-G

A46C22-G

P90B22-G
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.