Summary
We propose to supersede airworthiness directive (AD) 2007-10- 07, which applies to all Turbomeca S.A. Arriel 2B, 2B1, and 2B1A turboshaft engines. AD 2007-10-07 currently requires an inspection of the splines of the coupling assembly and the hydro-mechanical metering unit (HMU) drive gear shaft for wear. This proposed AD would require the same inspection and expand the affected population. This proposed AD would also remove Arriel 2B1A engines from the applicability. We are proposing this AD to prevent failure of the HMU drive gear shaft, which could lead to damage to the engine and damage to the airplane.