Originally Posted by
Swedish Blender
Not exactly sure what you mean to "sign" to be PIC in cruise. Do you sign the logbook in cruise? Get a re-release/dispatch in cruise naming you PIC? If you mean you sign into the trip as a relief officer, sole manipulator does not count for UPS, nor does it count for most airlines.
Unless your name is on the flight release as PIC, time spent occupying the left seat in cruise does not count.
When the PIC takes a break he designates one of the other two to act as PIC in his/her absence . You are supposed to sign by your name and write down the time that you took over as PIC for that portion of the flight. I know it's a technicality but you are signing and agreeing to be the PIC at that point