What remains constant regardless of the aircraft's gross weight?

The stalling angle of attack is a fundamental characteristic of an aircraft's design that remains constant regardless of the aircraft's gross weight. This angle of attack is defined as the angle between the chord line of the wing and the oncoming airflow. It represents a specific aerodynamic condition at which the airflow begins to separate from the wing's upper surface, leading to a stall.

As an aircraft's weight changes, the stall speed does vary because it is linked to the lift required to counteract the weight at a given angle of attack. Therefore, while the stalling angle of attack remains unchanged for a given aircraft configuration, the corresponding stall speed will increase as the aircraft's weight increases, necessitating a higher speed to achieve the same lift.

The lift-to-drag ratio can also change with variations in weight and configuration, as it is influenced by how efficiently the aircraft transforms lift into drag. Maximum velocity is dependent on factors like thrust and drag, both of which can be affected by the weight of the aircraft.

In summary, the stalling angle of attack remains a constant factor in determining the aerodynamic characteristics of an aircraft, independent of its load.