Look for a model with rotor blades that have good visibility, e.g. one of the nightflight-models like HELIX600Night. Can be found in <path>\resources\models\helicopter\HELIX600Night - where <path> is the path to your Heli-X installation.
Take the files Mainrotor.mtl and Mainrotor.obj and copy them into the directory of your preferred model.
Start Heli-X and load your preferred model - you're done.
But keep in mind: you will run into the same problem again when flying real models. So it might be a good idea to train what we call "Lageerkennung" (don't know the english word for that) without a look at the rotating blades.
Have fun
ThomasC