WEACLRS

I'm assuming you want to do one of two things: either log pilot-in-command time or log time toward your flight time (note: there is no such thing as "total time"). Lets break this into two areas: First, the FAA regulations.

To log Pilot-in-Command time you must be in one of two situations. You must be the pilot designated as pilot-in-command as defined in 14 CFR part 1.1. You must hold the appropriate category, class, and if necessary, type ratings for the aircraft in question and be instrument rated if the flight operates under IFR. To be PIC usually requires that designation from the operator of the aircraft in some form of written documentation (dispatch release, rental agreement, job description, etc.), completion of the operator's FAA approved training program, and/or some other formal form of designation. You would know it if you had it.

The second situation falls under 14 CFR part 61.51. This section allows to you log PIC time for the sole purpose of applying "for a certificate or rating issued under this part..." (61.51(c)). 14 CFR 61.51.(e) says as long as you hold a sport, recreational, private, or commercial pilot certificate (not an ATP), you may log pilot-in-command time only for that flight time during which you are "...the sole manipulator of the controls of an aircraft for which the pilot is rated...". Rated means holding the appropriate catagory, class, and type if necessary. If you are an ATP, this provision no longer applies.

So from an FAA standpoint, if you hold a commercial pilot certificate or less, with category, class, and if necessary, type, and you are allowed to manipulate the controls (i.e. fly the aircraft), you can log the time as PIC and Flight Time (and instrument, night, etc.) because the FAA assumes you're still building time for the purpose of an ATP.

If you are designated by the company as the PIC for the return part 91 flight, and you're appropriately rated (which you would be), then you can log the flight as pilot-in-command, flight time, night, instrument, etc.

Logging second-in-command time falls under two areas. To fly under part 91 and log second-in-command time, 1) Part 61.51 (f)(1) and 61.55 requires the pilot be qualified as stated in 61.55 and occupy a crewmember station in an aircraft requiring more than one pilot by the aircraft's type certificate; or 2) 61.51(f)(2) requires the pilot hold the appropriate category, class, and type (if necessary) for the aircraft, and that more than one pilot is required under the type certification of the aircraft or the regulations under which the flight is being conducted. SIC qualifications under 61.55 are recent additions to 14 CFR (basically a copy from part 135) and are extensive. They basically require a formal training program approved by the FAA.

So if the aircraft requires two pilots by it's FAA type certificate or if the flight requires two pilots under the FAA regulations it is flying under, and you are rated (category, class, and type), and you find yourself in the right seat, and its a part 91 flight, you can log SIC, flight time, day/night, cross-country, but not instrument.

If the aircraft requires two pilots by it's type certificate and you meet 61.55, and its a part 91 flight, you may log SIC time.

If the aircraft is not a jet, or not over 12,500 lbs GTOW, it probably is single pilot certified and doesn't require a SIC - no logging SIC time. If it's a jet or over 12,500 lbs, you'd have to hold the appropriate type rating to log the time. Generally, unless the flight operates under part 121, 125, or 135, few other operations would allow for the logging of SIC flight time.

If the flight operates under part 135, you would have to meet the requirements of part 135 (training programs, recurrent training, check rides, etc. - you'd know it if you went through it) to log either PIC or SIC time.

Second - the insurance company. Even if the FAA allows it, the insurance company will probably force the operator of the aircraft to keep you out of the left seat, prohibit you from "manipulating the controls", or designating you as PIC until they have approved you. If it's your buddy's aircraft/company and he lets you go ahead, then it's his risk. But his insurance company probably wouldn't cover the cost of an incident or accident (which means you could be liable as well), unless there is a clause in the policy allowing him to designate other pilots at his digression to fly the aircraft.