Fellow pilots!

The 727 did not have GPS or INS!

This stuff came later, much later.

As I have said before, putting all this fancy nav stuff in the 727 is like putting the brain of a 16 year old in the body of an 80 year old.

Navigate by VOR to VOR - it works great! If you want to simulate the way it was, get out the old chart and plot it via the VOR's.

At 35,000 feet you can use the high level VOR's a long way.

All that automatic stuff is for sissy pilots!  ;D