Which factor is affected negatively by adding an overweight payload to an aircraft?

Adding an overweight payload to an aircraft significantly impacts its performance, particularly by increasing the stall speed. Stall speed is the minimum speed at which an aircraft can maintain level flight, and this speed is directly related to the weight of the aircraft. When weight is increased, lift must also be increased to maintain flight, which generally requires flying at a higher speed. This shift means that the stall speed also rises, increasing the risk of a stall during takeoff, landing, or any maneuvering in-flight, particularly if the operator does not account for this change in their flight planning.

In contrast, an increase in payload does not lead to faster responses to control inputs. In fact, it may make the aircraft less responsive due to the extra weight, which could dampen the effectiveness of control surfaces and increase inertia. Similarly, adding weight decreases fuel efficiency, as the engines must work harder to maintain flight, and it also adversely affects the ascent rate; a heavier aircraft will climb more slowly, if at all, compared to one with an optimal load.