AD/Arriel/32 Engine Module M04 Power Turbine Blades (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Turbomeca Turbine Engines - Arriel Series

AD/ARRIEL/32 Engine - Module M04 Power Turbine Blades 5/2009 TX

Applicability:

Turboméca S.A. Arriel 1B, 1D and 1D1 turboshaft engines, fitted with Modules M04 (Power Turbine) as identified in figure 1 of Turboméca Mandatory Service Bulletin (MSB) A292 72 0827 version A, and Arriel 2B, 2B1 and 2B1A turboshaft engines, fitted with Modules M04 as identified in figure 1 of Turboméca MSB A292 72 2833 version A.

Note 1:  Arriel 1B, 1D and 1D1 turboshaft engines are known to be installed on, but not limited to, Eurocopter AS 350 B, AS 350 BA, AS 350 B1 and AS 350 B2 helicopters; Arriel 2B, 2B1 and 2B1A turboshaft engines are known to be installed on, but not limited to, Eurocopter AS 350 B3 and EC 130 B4 helicopters.

Note 2:  The variants above are installed on single-engine helicopters.

Requirement:

1.    For engines with a Module M04 (PT module) which has accumulated 1,000 Total Power Turbine (PT) Cycles or more at the effective date of this AD:

Replace the module M04, or PT wheel assembly, or PT blades, as instructed in paragraph 2.B.(1)(b) of Turboméca MSB A292 72 0827 version A for Arriel 1 engines and A292 72 2833 version A for Arriel 2 engines.

2.    For engines with a Module M04 which has accumulated less than 1,000 Total PT Cycles at the effective date of this AD:

a.     Update the module M04 log card and the engine log book to enter the 1,000 PT Cycle life-limit of the PT blades as instructed in paragraph 2.B.(1)(a) of Turboméca MSB A292 72 0827 version A for Arriel 1 engines and
A292 72 2833 version A for Arriel 2 engines.

b.    Replace the module M04, or PT wheel assembly, or PT blades as instructed in paragraph 2.B.(1)(b) of Turboméca MSB A292 72 0827 version A for Arriel 1 engines and A292 72 2833 version A for Arriel 2 engines.

The use of later approved revisions of these documents is acceptable for compliance with the requirements of this AD.

Note 3:  Serial numbers of Modules M04 (PT) as listed in Figure 1 of the referenced MSB is, when known, the confirmed location of the affected PT blades.  The engine serial numbers are also provided for information when available.  In the case the Module M04 is listed as “NC” (Unknown to this date), the affected PT blades location must be determined through the engine serial number.

Note 4:  EASA Emergency AD 2009-0068-E dated 25 March 2009 refers.

Compliance:

For Requirement 1 - Before further flight after the effective date of the AD, unless previously accomplished.

For Requirement 2a - Before accomplishment of Requirement 2b. of this AD.

For Requirement 2b - Before accumulation of 1,000 Total PT Cycles on a given Module M04.

This Airworthiness Directive becomes effective on 27 March 2009.

Background:

During production of Arriel 1 and Arriel 2 Power Turbine (PT) wheels, geometric non-conformities on blade fir-tree roots have been detected by Turboméca.  Potentially non-conforming PT blades have been traced as having been installed on Module M04 (PT) listed in Mandatory Service Bulletin (MSB) A292 72 0827 for Arriel 1 engines and A292 72 2833 for Arriel 2 engines.

The geometric non-conformities of the blades may potentially lead to a reduction in the fatigue resistance of PT blades to a lower level than their authorized in service use limit.  This reduction of fatigue resistance can potentially result in blade release, which could cause an uncommanded in-flight shut down.  On a single-engine helicopter, the result may be an emergency autorotation landing.

For the reasons stated above, this AD requires a restriction of the cyclic use limit of these PT blades to 1,000 flight cycles.  For PT blades having reached a number of flight cycles superior or equal to 1,000, removal of Module M04, or PT wheel assembly, or PT blades is required prior to next flight.

James Coyne
Delegate of the Civil Aviation Safety Authority

26 March 2009