EASA AD No.: 2012-0071 

EASA Form 110 Page 1/4

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2012-0071

Date: 26 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 1 engines

TCDS Number: EASA.E.073 

Foreign AD: Not applicable 

Supersedure: This AD supersedes DGAC France AD 1990-064(A) R1 dated 21 March 2001. 

ATA 72 Engine – Axial Compressor, Gas Generator Hollow Shaft and Rear 

Bearing – Identification / Inspection / Cleaning / Replacement

Manufacturer(s): Turboméca S.A. 

Applicability: ARRIEL 1A, 1A1, 1A2, 1B, 1C, 1C1, 1C2, 1D, 1D1, 1E2, 1K, 1K1, 1S and 1S1 

turbo-shaft engines, all serial numbers, except those incorporating Turboméca 

TU360 modification. 

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

(formerly Eurocopter France, Aerospatiale) AS 350 B, BA, BB, B1and B2, and 

AS 365 N, Eurocopter Deutschland (formerly Messerschmidt-Bölkow-Blohm) 

MBB-BK117-C1 and -C2, AgustaWestland (formerly Agusta) A 109 K2, and 

Sikorsky S-76A helicopters. 

Reason: Several cases have been reported of uncommanded in-flight shut-down 

(IFSD) on ARRIEL 1 engines. Results of subsequent investigations showed 

that engine operation in a dust laden atmosphere may lead to dust ingestion 

inside the engine, the possible consequences of which are erosion of the air 

path components (mainly the axial compressor wheel), and/or laterite deposit 

inside the gas generator hollow shaft which, in case of uneven distribution or 

detachment, can lead to an unbalanced condition of the gas generator rotating 

assembly and, ultimately, gas generator rear bearing failure. 

This condition, if not detected and corrected, could lead to an uncommanded 

engine in-flight shut down and may lead to an emergency landing. 

To address this potential unsafe condition, DGAC France issued AD 1990-

064(A), later revised to R1, to require periodic vibration monitoring (Engine 

Maintenance Manual Chapter 05-10-03) and repetitive gas generator hollow 

shaft cleaning based on axial compressor erosion checks. 

Since that AD was issued, in-service experience has shown that laterite 
EASA AD No.: 2012-0071 

EASA Form 110 Page 2/4

deposits inside the gas generator hollow shaft may be found when the axial 

compressor wheel has less erosion than initially assessed. In addition, 

Turboméca have developed an improvement of the hollow shaft (modification 

TU360), which makes the engine less susceptible to laterite deposits.

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

engine history and operating conditions, and a one-time inspection of the axial 

compressor for erosion, in order to define the first cleaning of the Gas 

Generator hollow shaft. It also requires a repetitive cleaning of the shaft. 

Modification of an engine through Turboméca modification TU360 (which can 

be done during overhaul) constitutes terminating action for the requirements of 

this AD. 

Effective Date: 10 May 2012 

Required Action(s) 

and Compliance 

Time(s): 

Required as indicated, unless accomplished previously: 

(1) Within 50 engine hours (EH) after the effective date of this AD, determine 

the engine history and operating conditions. If the engine operates, or has 

been operated, in dust laden atmosphere, or the operating history of the 

engine or Module 03 cannot be established, or doubt exists about the 

current operating conditions of the engine, within 50 EH after the effective 

date of this AD, inspect the axial compressor for erosion in accordance 

with the instructions of paragraph 1.A.(1) and Figure 2 of Turboméca 

Mandatory Service Bulletin (MSB) A292 72 0230 Version C. 

Actions accomplished before the effective date of this AD in accordance 

with the instructions of Turboméca MSB A292 72 0230 Issue 1 are 

acceptable to comply with the requirements of this paragraph. 

(2) Depending on the results of the inspection as required by paragraph (1) 

of this AD, determine the compliance times and accomplish initial and 

repetitive cleanings of the gas generator hollow shaft as specified in 

Appendix 1 of this AD. 

(3) If, during any of the cleanings as required by paragraph (2) of this AD, the 

dust weight collected inside the gas generator hollow shaft is more than 8 

grams, before next flight, replace the gas generator rear bearing. 

Replacement of the gas generator rear bearing as required by this AD 

does not constitute terminating action for the repetitive cleaning. 

(4) After the effective date of this AD, if the helicopter configuration is 

modified, or the type of mission or geographical operating area changes, 

within 50 EH after such a change, accomplish the actions as specified in 

paragraph (1) of this AD. Depending on the results, accomplish all the 

actions as specified in paragraphs (2) and (3) of this AD. 

(5) From the effective date of this AD, do not install a Module 03 (gas 

generator) on an engine unless it is in compliance with the requirements 

of this AD. 

(6) Modification of an engine through Turboméca modification TU360 

constitutes terminating action for the requirements of this AD. 

Ref. Publications: Turboméca MSB A292 72 0230 Version C dated 29 February 2012. 

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 23 March 2012 as PAD 12-021 for consultation 

until 20 April 2012. The Comment Response Document can be found at 

http://ad.easa.europa.eu. 

3. Enquiries regarding this AD should be referred to the Safety Information 
EASA AD No.: 2012-0071 

EASA Form 110 Page 3/4

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 1 Customer Support, 

40220 Tarnos, France, Fax: +33 5 59 74 45 15, or 

contact your usual or nearest Turboméca technical representative at 

www.turbomeca-support.com. 

 
EASA AD No.: 2012-0071 

EASA Form 110 Page 4/4

Appendix 1 - Compliance Times 

for Initial and Repetitive Cleanings of the Gas Generator Hollow Shaft 

Erosion of the Axial 

Compressor 

(See Note 1)

Gas Generator 

(Module M03) and 

Axial Compressor 

(Module M02) are 

installed on the same 

Engine

Compliance Time for 

the Initial Cleaning of 

the Gas Generator 

Hollow Shaft

(see Note 2)

Intervals for the 

Repetitive Cleanings 

of the Gas Generator 

Hollow Shaft

(see Note 2)

Erosion rate is higher 

than 1 mm per 1 000 

EH 

or 

Total erosion is more 

than 3 mm 

Since equal or more 

than 200 EH 

Within 50 EH after the 

inspection of the 

erosion of the axial 

compressor 

Refer to Figure 6 of 

Turboméca MSB A292 

72 0230 Version C 

Since less than 200 

EH, or unknown To be determined in 

accordance with 

Figure 3 of Turboméca 

MSB A292 72 0230 

Version C 

(see Note 3)

Erosion rate is lower 

than 1 mm per 1 000 

EH 

and 

Total erosion is less 

than 3 mm 

Not relevant 

Note 1: For inspection of the erosion of the Axial Compressor, refer to tasks 72-32-00-280-801 and 72-

32-00-280-802 of applicable Arriel 1 Maintenance Manuals (these tasks define acceptance criteria and 

maintenance actions following findings of erosion check). 

Note 2: Refer to paragraph 2.B ‘Operating Instructions’ and 2.D ‘Identification’ (for recording of the

required periodicity) of Turboméca MSB A292 72 0230 Version C. 

Note 3: Two different methods may be used for determination of the compliance time: 

(1) “Lump” method: 

• If take-off and/or landing is carried out in « brown-out » (= no visibility) condition : 

 Within 50 EH after the inspection of the erosion of the axial compressor 

• If no take-off or landing is carried out in « brown-out » condition : 

 For single engine application: Within 150 EH after the inspection of the erosion of the 

axial compressor 

 For twin engine application: Within 300 EH after the inspection of the erosion of the 

axial compressor 

(2) “Counting” method: Time calculated in function of flight condition parameters.