EASA AD No.: 2011-0128-E 

EASA Form 111 Page 1/3

EASA EMERGENCY AIRWORTHINESS DIRECTIVE 

AD No.: 2011-0128-E 

Date: 06 July 2011 

Note: This Emergency 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 : 

Turboméca 

Type/Model designation(s) : 

ARRIEL 2 series engines 

TCDS Number : EASA.E.001 

Foreign AD : Not applicable 

Supersedure : None 

ATA 73 Engine Fuel & Control – Hydro-Mechanical Metering Unit 

(HMU) – Inspections / Replacement 

Manufacturer(s): Turboméca S.A. 

Applicability: Arriel 2B engines, all serial numbers. 

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

AS 350 B3 helicopters. 

Reason: Non-conformities on adjustment of some HMUs have been reported by a 

Turboméca repair centre. The technical investigations carried out by 

Turboméca are showing that only a limited number of HMUs are 

potentially affected by this non-conformity to HMU adjustment. 

This condition, if not corrected, could lead to an uncommanded In-Flight 

Shut-Down (IFSD) during fast decelerations in automatic or manual 

modes, ultimately leading to an emergency autorotation landing for a 

single-engine helicopter. 

To address this unsafe condition, Turboméca have issued Turboméca 

Mandatory Service Bulletin (MSB) A292 73 2841. 

For the reasons described above, this AD requires replacement of the 

affected HMU with a serviceable HMU or, alternatively, accomplishing an 

engine functional test in order to allow further flights and replacement of 

the HMU at a later stage. 

Turboméca have as well developed a modification (TU143) of the 

Electronic Engine Control Unit (EECU) software to improve the logic 
EASA AD No.: 2011-0128-E 

EASA Form 111 Page 2/3

concerning loss of steps tolerance. Introducing the TU143 software on the 

EECU of engines incorporating an affected HMU will limit the loss of 

automatic control function rate. Therefore, this AD requires as well 

embodiment of TU143 modification on each engine incorporating an 

affected HMU. 

Effective Date: 08 July 2011 

Required Action(s) 

and Compliance 

Time(s): 

Required as indicated, unless accomplished previously: 

(1) For the engines on which an HMU is installed, identified by Part 

Number and serial number in the Figure of Turboméca MSB A292 73 

2841 version A, except those which have already passed the 

inspection, in accordance with Turboméca Service Bulletin (SB) 292 73 

2840 version A, accomplish one of the actions specified in paragraph 

(2) or (3) of this AD. 

(2) Before next flight, replace the affected HMU with a serviceable HMU. 

Replacement of an HMU with a serviceable HMU constitutes 

terminating action for the requirements of this AD. 

Note: For the purpose of this AD, a serviceable HMU is a unit which is 

not identified in the Figure of Turboméca MSB A292 73 2841 

version A, unless that unit has passed the inspection in 

accordance with Turboméca SB 292 73 2840 version A. 

(3) Alternatively to the requirement of paragraph (2) of this AD, before next 

flight, accomplish a one-time engine functional test in accordance with 

the instructions of paragraph 2.B.(1)(a) of Turboméca MSB A292 73 

2841 version A. 

(3.1) If the engine fails the functional test as required by paragraph (3) 

of this AD, before next flight, replace the HMU with a serviceable 

HMU. 

(3.2) If the engine passes the functional test as required by paragraph 

(3) of this AD, accomplish the following actions: 

(3.2.1) Within 4 months after the effective date of this AD, install 

software modification TU143 on the Engine Electronic 

Control Unit (EECU) of the engine, in accordance with 

Turboméca SB 292 73 2143. 

(3.2.2) Within 12 months after the effective date of this AD, 

replace the affected HMU with a serviceable HMU. 

(4) From the effective of this AD, do not install an HMU on an engine or an 

engine on a helicopter unless the HMU or the engine is in compliance 

with the requirements of this AD. 

Ref. Publications: Turboméca Mandatory Service Bulletin A292 73 2841 version A dated 04 

July 2011. 

Turboméca Service Bulletin 292 73 2840 version A dated 28 June 2011. 

Turboméca Service Bulletin 292 73 2143 Initial Issue dated 24 July 2007. 

The use of later approved revisions of these documents 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 safety assessment has requested not to implement the full 

consultation process and an immediate publication and notification. 

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

Directives, Safety Management & Research Section, Certification 
EASA AD No.: 2011-0128-E 

EASA Form 111 Page 3/3

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 at www.turbomeca-support.com