How can one reduce friction drag on an aircraft?

To reduce friction drag on an aircraft, smoothing the exposed surfaces is an effective approach. Friction drag, a component of parasitic drag, arises from the interaction between the airflow and the surfaces of the aircraft. When the surfaces are uneven or rough, they create turbulence and lead to increased drag, as the boundary layer of air is disrupted and energy is lost.

By smoothing the surfaces, such as the wings, fuselage, and control surfaces, the airflow can remain attached longer, minimizing the turbulent wake and allowing for a more streamlined flow. This results in a significant reduction in friction drag, which can enhance the aerodynamic efficiency of the aircraft, improve fuel economy, and potentially increase speed.

In contrast, other methods mentioned may not effectively address friction drag. Lowering the angle of attack and installing wing devices could influence lift and overall drag but do not specifically target friction drag reduction. Asserting that friction cannot be reduced is incorrect; it can be significantly minimized through effective design and surface treatment. Increasing surface roughness would exacerbate friction drag rather than reduce it. Thus, smoothing the exposed surfaces is a key strategy for optimizing an aircraft's aerodynamic performance.