EASA AD No : 2009-0090 

EASA Form 110 Page 1/2 

 

EASA AIRWORTHINESS DIRECTIVE 

AD No.: 2009-0090 

Date: 28 April 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) : 

MAKILA 1 turbo-shaft engines 

TCDS Number : DGAC (France) M10 

Foreign AD : Not applicable 

Supersedure : None 

ATA 73 Engine Fuel & Control - Engine Control Unit (ECU) – Hardware 

– Replacement 

Manufacturer(s): Turboméca 

Applicability: MAKILA 1A and MAKILA 1A1 turboshaft engines, all serial numbers, 

having ECUs equipped with TU250 Comparator / Selector (CS) boards 

with serial numbers in the range 241 EL to 1192 EL. 

These engines are installed in, but not limited to, Eurocopter AS 332 C, 

C1, L and L1 helicopters. 

Reason: MAKILA 1A and 1A1 ECUs incorporate a backup control law that fixes N1 

(gas generator speed) at 65% when at least two of the three N2 (power 

turbine speed) signals are lost. The intent is to limit the maximum speed 

attainable by the power turbine in the event of a failure of the shaft 

between the engine and the main gearbox that could result in collateral 

damage to the N2 speed probes. 

Several occurrences of 65% N1 backup activation remain unexplained 

despite detailed investigation. It is postulated that the events may have 

been due to corruption of the engine N2 speed signals by short 

perturbations, for example by electromagnetic interference. The potential 

therefore existed for a hazardous condition in which both engines on the 

same helicopter were simultaneously affected. 

To address this risk, Turboméca introduced modification TU250, which 

affects the CS board in the ECU and allows recovery from the 65% 

backup mode if the loss of N2 speed signals is determined to be 

temporary. Incorporation of modification TU250 is mandated by EASA AD 

2007-0144. 
EASA AD No : 2009-0090 

EASA Form 110 Page 2/2 

 

The installation of TU250 CS boards, however, has resulted in a few 

occurrences of erratic engine behaviour, in the form of unexpected N1 

variations and/or illumination of the “GOV” warning light. The conclusions 

from an investigation by Turboméca are that these malfunctions are due to 

a lapse of quality control in the varnishing process applied to the boards, 

and that only boards in a specific serial number range, as defined under 

“Applicability” and referred to below as the “suspect batch”, are affected. 

Turboméca has addressed this latest concern in two steps which provide 

first a near-term and then a long-term solution. The two steps are 

described in the referenced mandatory service bulletins (MSB). 

The first step, described in MSB 298 73 0809, recommends that no 

helicopter has CS boards from the suspect batch in both engines. Boards 

with more than 200 hours of trouble-free operation are exempt because 

service experience has shown that the malfunctions potentially induced by 

this manufacturing discrepancy are most likely to occur early in the lives of 

the boards. 

The second step, described in MSB 298 73 0810, recommends that 

ultimately all TU250 CS boards in the suspect batch, regardless of time in 

operation, be replaced with TU250 boards not from the suspect batch. 

This Airworthiness Directive makes the replacement of TU250 CS boards 

in the suspect batch mandatory. 

Effective Date: 12 May 2009 

Required Action(s) 

and Compliance 

Time(s): 

Required as indicated unless accomplished previously. 

1. Within 50 operating hours from the effective date of this AD, if both 

TU250 CS boards on the same helicopter are from the suspect batch 

and if both have an operating time since new of less than 200 hours, 

replace at least one of the boards with a board not from the suspect 

batch in accordance with the instructions of Turboméca MSB 298 73 

0809 Version A. 

2. During the next 500-hour routine inspection, or before 30 November 

2009, whichever comes first, replace all TU250 CS boards from the 

suspect batch with boards not from the suspect batch in accordance with 

the instructions of Turboméca MSB 298 73 0810 Version B. 

Ref. Publications: TURBOMECA Mandatory Service Bulletins 298 73 0809 Version A and 

298 73 0810 Version B. 

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. This AD was posted on 20 February 2009 as PAD 09-044 for 

consultation until 20 March 2009. No comments were received during 

the consultation period. 

3. Enquiries regarding this PAD 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., MAKILA 1 Customer Support, 40220 TARNOS, 

FRANCE. Fax: +33 5 59 74 45 15; or contact your nearest technical 

representative at www.turbomeca-support.com