GeorgeC1 said:
It's possible a curved approach using GPS could be constructed however I question if it can be done and meet the TERPS criteria if it has not already been done. It's not expensive since ground based equipment is not required.
TERPS criteria for a RNP approach would likely facilitate an approach into EIS.
I'd guess a RNP approach hasn't been implemented at this point because the existing fleet at EIS can't utilize RNP procedures. If you bring in A320/B737/B757 from mainland US there's a good chance those aircraft are equipped to fly RNP approaches.
