The airline industry long ago figured out that one of the most dangerous things in aviation is two pilots trying to fly the same airplane at the same time. One inevitable result of such an arrangement is that there are times when no one is flying, and one of the ways we know this is from the accident record. Airlines evolved the pilot-flying/pilot-not-flying concept to acknowledge this characteristic of crewed cockpits and established clear responsibilities for each pilot.
In single-pilot general aviation cockpits, however, we rarely have the discipline to carve out specific roles or tasks for a pilot-rated passenger, who probably is eager to help and/or demonstrate his/her skills to the pilot in command. This often means delegating tasks like untying the airplane or looking up a CTAF and getting the destination’s automated weather. When there’s a clear delineation of responsibilities, the pilot-rated passenger can be a huge asset to ensuring the flight’s safety and efficiency.
