Airworthiness Directives; Turbomeca S.A. Turboshaft Engines

We propose to adopt a new airworthiness directive (AD) for all Turbomeca S.A. Arriel 2E turboshaft engines. This proposed AD was prompted by reports of fuel flow non-conformities found during acceptance tests of Arriel 2E hydro-mechanical metering units (HMUs). This proposed AD would require removing the pre-TU 193 adjusted high- pressure/low-pressure (HP/LP) pump and metering valve assembly and replacing it with a part that is eligible for installation. This proposed AD would also require replacing the constant delta-pressure (delta-P) diaphragm of the fuel metering valve. We are proposing this AD to prevent failure of the delta-P diaphragm, which could result in an uncommanded in-flight shutdown and damage to the helicopter.