mutt:
But more and more operators are starting to see that value. Skky's reading of FAR91 might be correct, but the interpretation is not. Why is it that the Honeywell FMS has WAT climb limits under FAR91, surely if it wasn't required, Honeywell wouldn't have invested the money into validating the data?
When Honeywell designs a system, say for a Falcon 900EX or G550, they do not know whether the operator will be Part 91, 121, or 135.
There is no FAR 121.189 equivalent in Part 91. If the AFM made the flight path necessary for all Part 25 airplanes operated by U.S. operators then there would be no need or reason for 121.189 (or its Part 135 equivalent).