What purpose do vortex generators serve on the horizontal stabilizer?

Vortex generators on the horizontal stabilizer are designed primarily to prevent flow separation over the elevator. These small aerodynamic devices create vortices that energize the airflow over the control surfaces. By maintaining attached airflow at higher angles of attack, vortex generators help to delay flow separation which can lead to a loss of control effectiveness. This is especially important during critical phases of flight, such as takeoff and landing, where maintaining elevator effectiveness is crucial for pitch control.

In contrast, while increasing overall lift, enabling faster ascent and descent, and enhancing fuel efficiency are important aerodynamic considerations, the specific role of vortex generators is focused on ensuring smooth airflow and preventing separation over control surfaces, thereby improving handling characteristics and stability.