What is the typical impact of gear and flap configuration on parasite drag?

• A. Extended gear and flaps decrease parasite drag.
• B. Gear and flap configuration do not affect parasite drag.
• C. Retracted gear and clean configuration minimize parasite drag.
• D. Retracted gear and clean configuration minimize parasite drag.

Answer: (C)

Parasite drag comes from all parts of the aircraft that do not generate lift, including the shape of the fuselage, antennas, and especially any protruding gear or trailing-edge devices. When the landing gear is retracted and the air is flowing over a smooth, uncluttered surface (clean configuration), there are no bulky elements disturbing the flow, so the air experiences less form and interference drag.

If the gear is extended, or flaps are deployed, those surfaces add frontal area and create more flow separation, vortices, and interference with the wing and fuselage. This raises parasite drag because the airflow has more obstacles to negotiate and more wetted area to shear over.

So the typical impact is that retracting the gear and keeping the configuration clean minimizes parasite drag, while extending gear or deploying flaps increases it. (Note: flaps increase lift at lower speeds but raise parasite drag, which is why they’re retracted for high-speed or cruise flight.)