EASA AD No.: 2012-0054 

EASA Form 110 Page 1/2

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2012-0054

Date: 02 April 2012

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 turboshaft engines

TCDS Number: EASA.E.001 

Foreign AD: Not applicable 

Supersedure: This AD supersedes EASA AD 2010-0198 dated 01 October 2010. 

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

Modification

Manufacturer(s): Turboméca S.A. 

Applicability: ARRIEL 2B, 2B1, 2B1A and 2S2 turboshaft engines, all serial numbers, except 

those incorporating Turboméca modification TU166. 

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

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

and Sikorsky S-76C++ helicopters. 

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

service on ARRIEL 2 twin engine and one on single engine helicopters. 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 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 (IFSD) 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 

vibratory stress margin of the blade to a level consistent with the rate of 

occurrences 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 the GG Turbine blade 
EASA AD No.: 2012-0054 

EASA Form 110 Page 2/2

vibratory excitation and increases the blade tolerance for this type of stress. 

For the reasons stated above, EASA issued AD 2010-0198 to require the 

accomplishment of TU166 modification on ARRIEL 2 single engine 

applications. 

After that AD was issued, an accident occurred with a Sikorsky S-76C++ twinengine helicopter following an uncommanded IFSD of one of its ARRIEL 2S2 

engines, resulting from a GG Turbine blade rupture. The affected ARRIEL 2S2 

engine did not have TU166 modification incorporated. 

For the reason described above, this AD, which supersedes EASA AD 2010-

0198, extends the applicability of the AD to the ARRIEL 2S2 engines and 

requires embodiment of modification TU166. 

Effective Date: 16 April 2012 

Required Action(s) 

and Compliance 

Time(s): 

Required as indicated, unless accomplished previously:

(1) Accomplish TU166 modification in accordance with the instructions of 

Turboméca Mandatory Service Bulletin (MSB) A292 72 3166 version B for 

the ARRIEL 2B, 2B1 and 2B1A, and Turboméca MSB A292 72 4166 

version A for the ARRIEL 2S2: 

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 15 October 2010 [the effective date of EASA AD 

2010-0198] for ARRIEL 2B, 2B1 and 2B1A engines 

 7 months after the effective date of this AD for ARRIEL 2S2 

engines. 

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

TU166, in accordance with the instructions of Turboméca MSB A292 72 

3166 version A for the ARRIEL 2B, 2B1 and 2B1A, or in accordance with 

the instructions of Turboméca SB 292 72 2166 versions A through F for 

the ARRIEL 2S2, is acceptable for compliance with the requirement of 

paragraph (1) of this AD. 

(3) From the effective date of this AD, do not install an ARRIEL 2B, 2B1, 2B1A 

or 2S2 engine on a helicopter, unless in compliance with the requirements 

of this AD. 

Ref. Publications: Turboméca MSB A292 72 3166 version B dated 20 September 2010. 

Turboméca MSB A292 72 4166 version A dated 23 March 2012. 

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 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 Safety Information 

Section, Executive 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