EASA AD No.: 2009-0042 

EASA Form 110 Page 1/2 

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2009-0042 

Date: 25 February 2009 

Note: This Airworthiness Directive (AD) is issued by EASA, acting in accordance with 

Regulation (EC) No 216/2008 on behalf of the European Community, its Member States and 

of the European third countries that participate in the activities of EASA under Article 66 of 

that Regulation.

This AD is issued in accordance with EC 1702/2003, Part 21A.3B. In accordance with EC 2042/2003 Annex I, Part M.A.301, the 

continuing airworthiness of an aircraft shall be ensured by accomplishing any applicable ADs. Consequently, no person may operate 

an aircraft to which an AD applies, except in accordance with the requirements of that AD unless otherwise specified by the Agency 

[EC 2042/2003 Annex I, Part M.A.303] or agreed with the Authority of the State of Registry [EC 216/2008, Article 14(4) exemption]. 

Type Approval Holder’s Name : 

Agusta S.p.A. 

Type/Model designation(s) : 

AB139 and AW139 helicopters 

TCDS Number : EASA.R.006 

Foreign AD : Not applicable 

Supersedure : None 

ATA 24 Electrical Power – Generator Control Unit (GCU) - Replacement 

Manufacturer(s): Agusta S.p.A. 

Applicability: All AB139 and AW139 helicopters, all serial numbers except from S/N 31002 

to S/N 31004 and S/N 31007. 

Reason: Laboratory tests performed on a new GCU model under development have 

shown a potential fault in the overvoltage protection of the currently installed 

generator control units P/N 1152550-3. This condition, if not corrected, could 

adversely affect the electrical power generation and distribution system 

functionalities. 

Therefore, this AD requires the replacement of the affected units with 

improved GCU to prevent the in service occurrence of the above described 

unsafe condition. 

Effective Date: 11 March 2009 

Required action(s) 

and Compliance 

Time(s): 

Required as indicated, unless accomplished previously: 

(1) Within 6 months after the effective date of this AD remove the number 1 

and 2 GCU P/N 1152550-3 and replace with number 1 and 2 GCU 

P/N 1152550-5 or, as an alternative, with two generator control units 

P/N 1152550-4, in accordance with the instructions of Agusta Bollettino 

Tecnico 139-133. 

(2) The two installed generator control units must have the same P/N 

(1152550-4 or 1152550-5). 
EASA AD No.: 2009-0042 

EASA Form 110 Page 2/2 

(3) After the effective date of this AD, no person shall install a GCU

P/N 1152550-3 on an helicopter. 

Ref. Publications: Agusta Bollettino Tecnico 139-133 original issue dated 20 February 2009. 

The use of later approved revision of this document is acceptable for 

compliance with the requirements of this AD. 

Remarks: 1. If requested and appropriately substantiated, EASA can approve 

Alternative Methods of Compliance for this AD. 

2. The required actions and the risk allowance have granted the issuance of 

a Final AD with Request for Comments, postponing the public 

consultation process after publication. 

3. Enquiries regarding this AD should be referred to the Airworthiness 

Directives, Safety Management & Research Section, Certification 

Directorate, EASA. E-mail: ADs@easa.europa.eu .

4. For any question concerning the technical content of the requirements in 

this AD, please contact Agusta S.p.A. 

E-mail: aw139.mbx@agustawestland.com .