I suspect that we can survive without this poster's erudition - JT
I suspect JT is correct.
But I appreciated the opportunity presented to review AC 120-91 again aterpster.
This is probably the single most misunderstood and misapplied operational requirement I've encountered in my experience as a part 135 pilot. The very few pilots who do seem to grasp the concept are grossly outnumbered!
Anyway, it's been a treat!