I would like to install a french double opening glass patio door to my patio. Right now I have a window in its place. The house is a split level with half 30 inches of the foundation above ground with a 50h x 66w inch window atop. I want to remove this window and install a patio door and need to cut out 30 inches height by 72 inches width of foundation. Presently 30 inches of foundation is above grade and 50 inches of foundation is in the basement. Is it possble to make this cut without damage to foundation?

You won't Damage the foundation cutting it out and putting a new jamb in.

The Major thing here is temporally supporting the floor above so you can put in a new Header to span the added width of the opening.