i didnt have a problem with it...did you follow the readme that came with the file ? basic install instructions read as follows;
1. Unzip the entire aircraft into your CFS3/AIRCRAFT folder.
2. Copy the contents of the weapons folder into your CFS3/WEAPONS folder
3. Copy the contents of the guns folder into your CFS3/GUNS folder
Please leave the Texture & Model folders in the B-17G's folder untouched
Hopefully that should do it...another problem you will encounter is because of the aircrafts size it will explode on certain airfields as it collides with the hangar buildings, but there is an 'Airbase' fix for that available at the netwings site, heres a link to the page;
http://www.netwings.org/library/CFS3_Scenery/Hope that sorts things for you.