How does a decrease in speed generally affect drag on an aircraft?

When an aircraft decreases its speed, the drag it experiences generally reduces. This phenomenon occurs due to the relationship between airspeed and aerodynamic drag. Drag is composed of two main components: parasitic drag (which includes form drag and skin friction) and induced drag (which is related to lift).

As speed decreases, particularly at lower velocities, the dynamic pressure—the pressure exerted by the moving air—increases, which contributes to lower parasitic drag. Induced drag increases as speed decreases at lower airspeeds because a larger angle of attack is required to maintain lift. However, when considering the overall drag at a lower speed, the reduction in parasitic drag often outweighs the increased induced drag, leading to a general decrease in total drag at lower speeds until a point where stall characteristics begin to change.

This understanding of drag is crucial for pilots as it aids in selecting optimal flight profiles, speed management in approach and landing phases, and energy management during various phases of flight.

While other choices suggest that drag increases or remains unchanged, or even fluctuates depending on the aircraft, these do not accurately reflect the fundamental aerodynamic principles at play. The correct answer highlights the underlying physics regarding the effects of speed on drag.