I found out that the reflection is in the base already prepared, is now totally suppressed.
When you first attempt to highlight, the result is not very good.
It is in the package under the name UH1_glass_refl.dds.
Edit:
If anyone has a problem with clean glass, I created a little mirror in the cockpit.
Beta version for jsgme: https://www.dropbox.com/s/jhhej11ttbgjwh8/UH-1H%20Glass%20mirror.zip
Not to forget to switch in the menu special of the cockpit : Glass mirror