This doesn't make sense to me. Looking up FAR-23 at
http://www.access.gpo.gov/nara/cfr/c...4cfr23_00.html which claims to be up to date for this month.
para 785 gives a 215lb mass (or 170lb in utility), para 561 gives a 9g forward load for seats and their occupants.
The only thing I can think is a player is para 562 which has a whole stack of requirements for maximum shock loads in various collisions using a 170lb dummy - but these are rather more to do with energy absorption than static retention, which is what 561 and 785 are about.
G