Airworthiness Directives; Safran Helicopter Engines, S.A., Turboshaft Engines

We are superseding Airworthiness Directive (AD) 2012-03-11 for all Safran Helicopter Engines, S.A., Arriel 2B and 2B1 turboshaft engines. AD 2012-03-11 required checking the transmissible torque between the low-pressure (LP) pump impeller and the high-pressure (HP) pump shaft on the HP/LP pump and metering valve assembly, hereafter referred to as the hydro-mechanical metering unit (HMU). Since we issued AD 2012-03-11, the manufacturer determined that incorporating Modification TU 178 is a more effective method to reduce the risk of uncoupling between the LP fuel pump impeller and the HP fuel pump shaft than the prior Modification TU 147. This AD requires inspection and possible replacement of the HMU. This AD was prompted by three cases of uncoupling of the HMU LP fuel pump impeller and the HP fuel pump shaft since AD 2012-03-11 was issued. We are issuing this AD to address the unsafe condition on these products.