Summary
We propose to supersede an existing airworthiness directive (AD) that applies to all Turbomeca S.A. Arriel 1A, 1A1, 1A2, 1B, 1C, 1C1, 1C2, 1D, 1D1, 1E, 1E2, 1K, 1K1, 1S, and 1S1 turboshaft engines. The existing AD currently requires initial and repetitive visual inspections for erosion caused by dust ingestion and, if necessary, cleaning of the gas generator (module M03). Since we issued that AD, in-service experience has shown that dust inside the gas generator hollow shaft may be found when the axial compressor wheel has less erosion than initially assessed. This proposed AD would require determining the engine history, a one-time visual inspection of the axial compressor for erosion, initial and repetitive cleaning of the gas generator hollow shaft, and replacement of the rear bearing if the amount of dust collected during cleaning exceeds 8 grams. This proposed AD also includes an optional terminating action. We are proposing this AD to prevent an unbalance of the gas generator rotating assembly, which may lead to gas generator rear bearing failure, and uncommanded engine shutdown.