Look at it this way. A Citation 1/SP (501) only requires single pilot, but
certification for the Citation 1 (500) requires 2. Rules here say multi-crew PIC must hold an ATPL. Does not say anything about weight. Nothing about ATPL does (common misconception).
If operators are
contractually requiring multi-crew (ie. not required by certification) then either the PIC must hold an ATPL and the operators and pilots are operating illegally, or the 2nd pilot shouldn't be logging co-pilot time. Can't have it both ways. As I said, would it seem right to log co-pilot with two people flying a C172? It's laughable! When there is a co-pilot rating for a PA-31 or B200, then the conditions change.
If the aircraft is only certified single pilot operation, you can't "create" your own hours. I've flown multi-crew in Caravans, but haven't logged a single hour as co-pilot. ICUS would be a legal way to do it, but the PIC would need to have been approved under the company ops manual as at least a supervisory or equivalent qualification. Both pilots could count full hours toward total aeronautical experience then, not just the half co-pilot time.
