How do winglets affect an aircraft's performance?

Winglets are specialized aerodynamic surfaces mounted at the tips of an aircraft's wings. Their primary function is to reduce the induced drag that results from the formation of wingtip vortices. When an aircraft flies, the high-pressure air from below the wing moves around the wingtip to the lower-pressure area above the wing, creating these vortices. This phenomenon increases drag and can negatively impact fuel efficiency.

By adding winglets, the airflow around the wingtip is altered, which diminishes the strength of these vortices. This reduction in induced drag allows the aircraft to maintain lift with less energy expenditure, which in turn enhances fuel efficiency. Therefore, the presence of winglets directly contributes to smoother airflow and reduced drag, ultimately helping the aircraft perform better with less fuel consumption.

The other options do not accurately reflect the contributions and impacts of winglets on aircraft performance. Increased overall weight due to winglets is minimal and not a primary reason for their use. Furthermore, while an increase in drag is generally detrimental to performance, winglets help decrease induced drag rather than increase it. Lastly, enhancing an aircraft's speed is a secondary effect and not the main advantage of winglets; their primary purpose is the reduction of drag and improvement of fuel efficiency.