In article ,
"Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net wrote:

Neil Gould wrote:
Yes, but that usage renders 61.113 (c) meaningless without some
additional parameters. One can calculate many things precisely, even
without the use of a calculator. ;-) That might not guarantee
compliance with the FARs.


Pro Rata means a specific thing. It is well defined in law and common usage.
In 61.113 (c)the regulation is quite clear. A pilot may not pay less that
his pro rata share of the allowable expenses.

There's still an ambiguity here. The obvious way to compute the
pro-rata share is to divide the total cost by the number of passengers.
But that is not the only reasonable way to do it. One could, for
example, assign a pro-rata share according to weight, so that heavier
passengers (or passengers with more bags) pay more than lighter ones.
One could likewise use height, on the theory that taller passengers use
more room inside the plane, or some combination of weight and height.
If all the passengers are owners of the company for which business is
being conducted they might choose to assign their pro-rata shares
according to their percentage ownership in the company. None of these
are unreasonable on their face, and none of them are specifically
excluded by the regs. But I wouldn't want to be the one defending any
of these theories against an FAA enforcement action.

rg