PBR Traslucent ground polygons don't work

[redouane_bpw]

Hello all
I'm updating an OLD ground poly to P3D v4.5.12 PBR
I'm using MipMapped DXT 5 DDS textures and render mode set to translucent
decal orders are all set but I can't get my textures to be transparent

here is a result :

using translucent mode :


Using masked with alpha to coverage true and threshold to 0.5



I need the textures to be transparent as they used to be in the FSX version

thnx in advance