EASA AD No.: 2009-0264 

EASA Form 110 Page 1/2 

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2009-0264 

Date: 15 December 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) : 

A109S helicopters 

TCDS Number : EASA.R.005 

Foreign AD : Not applicable 

Supersedure : None 

ATA 24 Electrical Power – Battery Bus (BATT BUS) Circuit Breaker – 

Modification 

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

Applicability: A109S helicopters, all serial numbers (S/N) up to S/N 22151 included. 

Reason: Following a report of an electrical failure on one A109E helicopter, the 

investigations done by the Type Certificate holder Agusta have identified the 

inadequate functioning of the 35 Amperes (Amps) BATT BUS circuit breaker 

as the reason for the electrical failure. 

To prevent this unsafe condition, Agusta has developed a BATT BUS circuit 

breaker modification kit, for the replacement of the 35 Amps circuit breaker 

with a 50 Amps circuit breaker and the replacement of the wires with 

oversized ones. 

EASA AD 2009-0137 required such modification on the affected helicopters. 

This AD, due to the design commonality between the electrical power 

generation system of A109E and A109S models, requires installing this 

modification also on A109S models, in accordance with Agusta Bollettino 

Tecnico (BT) 109S-35. 

Effective Date: 29 December 2009 

Required action(s) and 

Compliance Time(s): 

Required as indicated, unless accomplished previously: 

Within 50 flight hours after the effective date of this AD but no later than 30 

June 2010, whichever occurs first, modify the fuselage electrical installation 

P/N 109-0742-52 and the overhead panel electrical installation P/N 
EASA AD No.: 2009-0264 

EASA Form 110 Page 2/2 

109-0742-55, installing the BATT BUS circuit breaker modification kit P/N 

109-0824-73-107, in accordance with the instructions of Agusta BT 109S-35. 

Ref. Publications: Agusta Bollettino Tecnico 109S-35 dated 11 December 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. Customer Support – 

Via per Tornavento, 15 21019 Somma Lombardo (VA) – Italy; 

Phone + 39 0331 940396; Fax: + 39 0331 711180; 

E-mail: custserv@agustawestland.com .