Which type of drag is caused by the collision of airstreams creating eddy currents and turbulence?

• A. Induced drag
• B. Parasitic drag
• C. Interference drag
• D. Skin friction

Answer: (C)

Interference drag is caused by the interaction of adjacent airstreams as they flow past connected surfaces, which disturbs the airflow and creates eddy currents and turbulence. This happens where wing surfaces meet the fuselage, nacelles, struts, or other joints, causing the airflow to collide and mix in ways that add extra drag beyond what each surface would produce alone.

Induced drag comes from the wing generating lift and the associated wingtip vortices, while skin friction drag results from viscous shear along a surface. Parasitic drag is the broader category for drag not associated with lift, including form drag and skin friction; interference drag is the specific effect due to the interaction of different airflows.