EASA AD No.: 2010-0189 

EASA Form 110 Page 1/2 

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2010-0189 

Date: 23 September 2010 

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 34 Navigation – Modular Avionic Unit – Inspection / Replacement / 

Modification 

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

Applicability: AB139 and AW139 helicopters, from serial number (S/N) 31005 to S/N 

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

41001 to S/N 41023 included. 

Reason: The analysis of some in-flight emergency occurrences has led to identify salt 

water and external moisture as a contributory factor to the corrosion of 

Modular Avionic Units (MAU)2 module circuit card assemblies. In particular, 

Custom Input/Output modules have been verified to be susceptible to this 

type of corrosive agents. 

When exposed to high levels of moisture, MAU can cause the system to 

provide false indications or misleading data to be displayed to the flight crew. 

In addition, misleading data may cause disengagement of the flight director 

modes of the autopilot, or other alerting system anomalies. These failures 

and anomalies would significantly increase the workload of the flight crew 

and could ultimately lead to loss of control of the helicopter. 

The failure mode has been confirmed by an Air Accident Investigation Branch 

(AAIB) investigation on an incident where the triggering of false confusing 

warnings was reported onboard an Agusta AW139 engaged in off-shore 

operations. 

This AD requires the inspection of MAU1 and MAU2 modules and connectors 

to ensure there is no sign of corrosion, and the accomplishment of the 

applicable corrective actions, as necessary. Furthermore, this AD requires 

the modification of the MAU2 ventilation duct installation, in order to keep the 

MAU2 modules out of direct air flow coming from the ventilation duct outlet. 
EASA AD No.: 2010-0189 

EASA Form 110 Page 2/2 

Effective Date: 07 October 2010 

Required action(s) 

and Compliance 

Time(s): 

Required as indicated, unless already accomplished: 

(1) Within 150 flight hours (FH) or 3 months, whichever occurs first, after the 

effective date of this AD, inspect the MAU1 and MAU2 Power Supply 

(PS) modules, Custom Input/Output (CSIO) modules and Control 

Input/Output (CIO) modules for structural integrity and to ensure that 

there is no sign of corrosion, and inspect all related connectors for any 

sign of corrosion, in accordance with the instructions of Agusta Bollettino 

Tecnico (BT) 139-166. 

(2) If any sign of corrosion on the connectors is found, clean the connectors 

before further installation, in accordance with the instructions of Agusta 

BT 139-166. 

(3) If any sign of corrosion or structural damage is found on a module, before 

next flight replace the module in accordance with the instructions of 

Agusta BT 139-166. 

(4) Within 150 flight hours (FH) or 3 months, whichever occurs first, after the 

effective date of this AD, modify the MAU2 ventilation duct, in 

accordance with the instructions of Agusta BT 139-166. 

Ref. Publications: Agusta Alert Bollettino Tecnico 139-166 dated 06 April 2009. 

The use of later approved revisions 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 .