Which factor does NOT directly affect the aircraft's center of gravity?

The center of gravity (CG) of an aircraft is a critical aspect of its stability and performance, and it is influenced by several factors. Among the choices provided, fuel type does not have a direct impact on the aircraft's center of gravity.

The payload distribution refers to how cargo or passengers are arranged within the aircraft, which can shift the CG significantly depending on where weight is added or removed. Structural integrity, while essential for flight safety, affects how the aircraft itself can handle loads but does not directly adjust the CG. Aircraft configuration, which can include changes such as flap positions or loading variations, also directly influences the distribution of weight and thus the CG.

Fuel type, on the other hand, is primarily a consideration of the characteristics of the fuel itself (such as energy content or weight per gallon) rather than where the fuel is placed in the aircraft. It does not alter the CG unless there is a significant change in fuel placement that affects weight distribution. Consequently, while fuel can contribute indirectly—if it changes the total weight of the aircraft—the type of fuel itself does not inherently change the position of the CG.