The casement windows I've lived with over the years all had hinges with attachment screws visible on the top and bottom frame corners. This was years ago, so possibly newer casements are built differently. Maybe a visit to Weather Shield's website would get you the information you need.
Another approach would be to find a local window repair guy, reputable and experienced with casements. Pay him (at a pre-agreed-upon price) to do just one window while you watch and take notes. Then you should be able to do all of the remaining windows for just the cost of replacement materials, unless the magic factory tools required put the job out of reach.