What is the purpose of boundary layer fences on swept-wing aircraft?

Boundary layer fences are specifically designed features on swept-wing aircraft that serve to improve low-speed characteristics. They are utilized to control airflow over the wings, particularly in the critical regions where airflow can separate from the wing surface. This separation can lead to increased drag and reduced lift, especially at lower speeds, which can be dangerous during takeoff and landing phases of flight.

By directing the flow of air and preventing it from detaching prematurely, boundary layer fences help maintain smooth airflow over the wing, thus enhancing lift and allowing for better control at lower speeds. This is crucial for maintaining flight stability and reducing the likelihood of stalling.

The other choices do not accurately represent the primary purpose of boundary layer fences. While stabilization during high-speed flight and fuel efficiency are important considerations in aircraft design, these features are not their main functions. Increasing drag during landing contradicts the goal of improving performance, and while high-speed stability may be a benefit of better low-speed flight characteristics, it is not the direct purpose of boundary layer fences.