Trim
Thanks for the good and informative contributions.
I'm sure most of us have had rotation 'surprises' and, while the forward cg case obviously just requires a stronger pull and is usually just a minor inconvenience (unless grossly mistrimmed)
The aft cg case however can cause premature rotation and/or an unexpectedly rapid upward pitch at VR with all of the problems associated.
We take it on a certain amount of faith that the %mac and trim provided are accurate but 'surprises' still occur.
If one were to experience an aft CG surprise in addition to adding
a few units to 'make it easier to rotate' I think things could turn pear shaped quite rapidly.
I would welcome other input.