Which auxiliary control can also be used to improve stability at speed?

The auxiliary control that can be used to improve stability at speed is the spring tab. Spring tabs function by creating a differential force on control surfaces, allowing for enhanced responsiveness and stability during flight, particularly at higher speeds. When the aircraft experiences increased airflow over the control surfaces, such as ailerons or elevators, the spring tab assists in providing the necessary corrective force to maintain control and stability without requiring excessive pilot effort. This makes it beneficial for handling the aircraft more efficiently, allowing pilots to manage more challenging flight conditions with ease.

The balance tab, while also a type of tab on the control surface, is primarily designed to reduce control forces rather than enhance stability directly. It helps the pilot by making control surfaces easier to move but does not fundamentally change how the aircraft behaves at higher speeds.

Leading edge flaps are used to increase lift at lower speeds and may contribute to improved control and stability during slow flight but are not specifically designed or effective for improving stability at higher speeds.

Ailerons are essential for roll control but do not inherently improve stability at speed. Instead, they are more focused on maneuverability and lateral control.

Overall, the spring tab provides that critical adjustment to enhance stability specifically at speed, distinguishing it from the other options listed.