Which of the following must not occur during refueling operations at a FARP?

The correct answer highlights that pilot changes, commonly referred to as "hot seating," should not occur during refueling operations at a Forward Arming and Refueling Point (FARP). This is because the primary focus during refueling is to ensure the safety of personnel, equipment, and the aircraft. Allowing pilot changes while refueling introduces unnecessary complexities and risks, such as increased personnel movement around the aircraft and potential distractions that could lead to accidents or mishandling of fuel operations.

In contrast, landing of aircraft, checking fuel levels, and using auxiliary power units are standard procedures that can contribute to the overall process during refueling operations. Aircraft must land to be refueled, fuel levels need to be assessed to ensure that the aircraft is receiving the correct amount of fuel, and auxiliary power units may be utilized to maintain power and functionality during refueling operations. Therefore, the prohibition of pilot changes is rooted in the need for a streamlined, safe, and focused environment while conducting these critical operations at a FARP.