EASA AD No.: 2010-0198 

EASA Form 110 Page 1/2

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2010-0198 

Date: 01 October 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 : 

Turboméca 

Type/Model designation(s) : 

ARRIEL 2 series turboshaft engines 

TCDS Number : EASA.E.001 

Foreign AD : Not applicable 

Supersedure : None 

ATA 72 Engine – Module M03 (Gas Generator) – Turbine Blade – 

Modification 

Manufacturer(s): Turboméca S.A. 

Applicability: Arriel 2B, 2B1, 2B1A turboshaft engines, if not modified by TU166 

modification. 

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

Eurocopter AS 350 B3, EC 130 B4 helicopters and Changhe Z11 

helicopters. 

Reason: Several cases of Gas Generator (GG) Turbine Blade rupture occurred in 

service on ARRIEL 2 twin engine applications and recently one on a single 

engine helicopter. For the case occurring in flight on a single engine 

helicopter (ARRIEL 2B1 engine), the pilot performed an emergency 

autorotation, landing the helicopter without further incident. 

The design of ARRIEL 2 engines (containment shield around the GG 

turbine) allows debris from a blade or the disc inter-blade area to be 

contained in the event of rupture. However, the rupture of a GG Turbine 

Blade may lead to an uncommanded In Flight Shut-Down which, on a 

single-engine helicopter, could ultimately lead to an emergency 

autorotation landing. 

The most probable root cause of the ruptures is an excitation of one of the 

vibration modes of the GG Turbine Blade in conjunction with several 

secondary contributing factors which are deemed sufficient to reduce the 

stress margin of the blade to a level consistent with the rate of occurrences 
EASA AD No.: 2010-0198 

EASA Form 110 Page 2/2

of ruptures encountered. 

Turboméca has released TU166 modification which consists in inserting 

Blade dampers between the GG Turbine Disc and the GG Turbine Blade 

platform. Introduction of these dampers minimizes the effects of HP blade 

vibratory excitation and increases the blade tolerance for this type of 

stress. 

For the reasons stated above, this AD requires the accomplishment of 

TU166 modification on ARRIEL 2 single engine applications. 

After the issuance of EASA PAD 10-094 related to this AD, Turboméca has 

issued Turboméca Mandatory Service Bulletin (MSB) A292 72 3166 

version B. 

Effective Date: 15 October 2010 

Required Action(s) 

and Compliance 

Time(s): 

Required as indicated, unless accomplished previously:

(1) Accomplish TU166 modification in accordance with the instructions 

specified within Turboméca Mandatory Service Bulletin (MSB) A292 72 

3166 version B: 

when the GG Turbine is replaced (at approved Operator or Service 

Center) 

or 

when the engine or Module M03 is going through overhaul or repair (at 

approved Maintenance or Repair Center), 

whichever occurs first, but no later than 25 months after the effective 

date of this AD. 

(2) Accomplishment, before the effective date of this AD, of TU166 

modification in accordance with the instructions of Turboméca MSB 

A292 72 3166 version A is acceptable for compliance with the 

requirement of paragraph (1) of this AD. 

Ref. Publications: Turboméca Mandatory Service Bulletin (MSB) A292 72 3166 version B 

dated 20 September 2010. 

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. This AD was posted on 31 August 2010 as PAD 10-094 for 

consultation until 28 September 2010. No comments were received 

during the consultation period. 

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 at www.turbomeca-support.com