EASA AD No.: 2009-0246 

EASA Form 110 Page 1/2 

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2009-0246 

Date: 10 November 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 Airworthiness Directive applies, except in accordance with the requirements of that Airworthiness Directive 

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 : 

TURBOMECA 

Type/Model designation(s) : 

ARRIEL 2B turboshaft engines 

TCDS Number : EASA.E.001 

Foreign AD : Not applicable 

Supersedure : This AD supersedes EASA AD 2007-0026 dated 1 February 2007 which 

superseded DGAC AD (CN) F-2004-139 (EASA Approval number 2004-8594) 

dated 18 August 2004. 

ATA 73 Engine Fuel & Control – Hydro HMU Acceleration Control Axle – 

Inspection and Lubrication 

Manufacturer(s): Turboméca S.A 

Applicability: all ARRIEL 2B turboshaft engines, which do not incorporate modification 

TU149. 

These engines are known to be installed on, but not limited to, Eurocopter 

AS 350 B3 helicopters. 

Reason: Cases have been reported where the Hydro-Mechanical Unit (HMU) 

acceleration controller axle was sticking in its bearing, resulting in difficulty or 

in impossibility to control the fuel flow rate in manual or mixed mode. 

This condition, if not corrected, can lead to an unpredictable engine 

operation in manual or mixed mode which can cause gas generator or power 

turbine overspeed, resulting in uncommanded or commanded in-flight engine 

shutdown. On a single-engine helicopter, the result may be an emergency 

autorotation landing. 

EASA AD 2007-0026 which superseded DGAC France AD (CN) F-2004-139 

(EASA Approval number 2004-8594) was issued to account for Turboméca 

modification TU132 (SB 292 73 2132) which was designed to prevent the 

acceleration controller axle from sticking in its bearing located in the cover. 

For engines with TU132-modified HMU installed, repetitive inspection and 

lubrication of the HMU acceleration controller axle were no longer required. 

Since issuance of AD 2007-0026, some cases of sticking of the acceleration 
EASA AD No.: 2009-0246 

EASA Form 110 Page 2/2 

controller axle in the metering valve body have been encountered on 

engines which incorporated modification TU132. It has then been 

determined that additional design improvement was required. Turboméca 

has now released modification TU149 (SB 292 73 2149) to prevent the 

sticking of the acceleration controller axle. This modification enhances 

TU132 by improving both the cover side and the metering valve body side 

designs. 

This AD therefore supersedes AD 2007-0026 by retaining the same 

requirements except that its applicability is changed and now limited to Arriel 

2B engines which do not incorporate modification TU149. 

Effective Date: 24 November 2009 

Required Action(s) 

and Compliance 

Time(s): 

The following measures are made mandatory from the effective date of this 

AD, unless accomplished previously: 

1. Before receipt of the parts required for the application of Turboméca 

Mandatory Service Bulletin (MSB) A292 73 2814 version D (Paragraph 

3), perform before the first flight of the day, a ground check in mixed 

mode operation (refer to the AS350 B3 Flight Manual section 8 task 3C, 

dealing with the control system mixed mode). 

2. Within 20 operating hours of receiving parts provided by Turboméca, 

check the fuel metering system and perform maintenance procedures in 

accordance with Paragraph 2 of Turboméca MSB A292 73 2814 version 

D. 

3. Repeat the maintenance procedures of Paragraph 2 every 200 hours 

(+/- 10 hours). 

NOTE: If the HMU already incorporates modification TU149, or after the 

HMU has been modified with TU149, no action is required.

Ref. Publications: Turboméca Mandatory Service Bulletin n° A292 73 2814 version D dated 16 

October 2009. 

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

compliance with the requirement of this AD. 

Eurocopter AS 350 B3 Flight Manual: section 8, chapter “Check after engine 

or module replacement – Manual Emergency” – Sheet n° 3C. 

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: 

TURBOMÉCA S.A. 

ARRIEL 2 Customer Support 

40220 Tarnos, France 

Fax: +33 5 59 74 45 15, or your usual or nearest TURBOMÉCA 

technical representative (refer to http://www.turbomeca-support.com)