Does "multi-pilot aircraft" not refer to mandatory multi-crew aircraft?
By certification or legislation, I would say yes. If a 172 had a second pilot you would legitimatly (read as credibly) class that as co-pilot time?
IMO you're scraping the bottom of the barrel for hours if you do.
The law is clear however that for CHTR and RPT (not that you would do the latter in a 172) if you did, the PIC would have to hold an ATPL.
Again I ask how many of those logging co-pilot time for their PA-31 types are sure their PIC had an ATPL?
