I'm sorry to read of another FAA enforcement case against a pilot who was not acting as a required crewmember but was found responsible following an incident. In the private flying arena there is often no "paper trail" to identify the PIC and in fact the person "designated as PIC" during a flight may be changed at any time by agreement of the individuals concerned. No record of this fact is usually present. So what test can the FAA rely upon to make a determination following an incident where identifying the PIC is necessary?
In air carrier ops a dispatch document is required listing all required crew and their duty position assignment will be specified on the dispatch document. The only way to nominate a new PIC is to issue a new document. If a part 135 or 121 flight is completed and a part 91 tail-end or other repositioning flight is conducted, are the duty position assignments still the same as before? Yes as far as the FAA sees it. If a pilot was switching from SIC to PIC or vice versa during a trip their best protection might be to request that the company issue a new flight release (dispatch document) with the modified duty assignments duly reflected. Otherwise it would be left to the FAA to determine by whatever standards they choose to determine who to enforce against following a flight rules violation or accident.
As an ATP and CFI myself, I realize that I might be found to be at least partially responsible if anything happens while I'm aboard a light aircraft being commanded by another pilot. The precedent has been established for all practical purposes. If seated at a control position and having agreed to be a safety pilot (required crew) as either SIC or as PIC, my acceptance of responsibility is self evident. If anything happens I expect to come under FAA scrutiny regardless of any agreement I and the other pilot might have made prior to the flight. My only protection in this situation is that I act accordingly by fulfilling my responsibility to see that the flight is conducted safely and in compliance with regulations. I'm just going to presume I'm held to that standard and I'll take my naps on the ground thank you!
westhawk