After major repairs have been made to an aircraft, it's important to reestablish the weight and balance of the airplane. Knowing the aircraft's empty weight, as well as resestablishing its center of gravity (CG), is critical to its safe operation whether hauling people, cargo, or both. When loading an airplane there are specific guidelines to follow regarding personnel and cargo placement based on the starting CG. Too much weight forward of the CG and the airplane will be nose heavy. Too much weight aft and the aircraft will be tail heavy. Being able to perform a "weight and balance" is an important part of every missionary airplane mechanic's skill set.