AD/ARRIUS/11 Amdt 1 - Fuel Control Unit "Delta P" Diaphragm (Cth)

AIRWORTHINESS DIRECTIVE On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/ARRIUS/11 and issues the following 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 - Arrius Series AD/ARRIUS/11 Amdt 1 Fuel Control Unit "Delta P" Diaphragm 9/2007

Applicability: TURBOMECA ARRIUS 2F turboshaft engines. Requirement: Incorporate modification Tf55 in accordance with paragraph 2 of Turbomeca Mandatory Service Bulletin No. 319 73 4055 or later NAA approved revisions.

Note: EASA AD 2006-0237 dated 9 August 2006 refers. Compliance: Before 30 September 2007, unless previously accomplished. This Amendment becomes effective on 30 August 2007. Background: This Directive is issued following the case of an increase in fuel flow resulting from deterioration of the constant delta pressure diaphragm.

The increase in fuel flow led to an increase in gas generator rating which resulted in an increase in power turbine and helicopter rotor rating. This then led to an uncommanded in-flight engine shut-down following power turbine blade-shedding (blades contained) due to overspeed.

This increase in fuel flow is attributed to the deterioration of the constant delta pressure diaphragm installed the wrong way round.