What are the principal effects of lowering the flaps during flight?

Lowering the flaps during flight primarily serves to increase lift and also to increase drag, which plays a crucial role in flight performance during takeoff and landing phases. When flaps are extended, the camber of the wing is modified, allowing the wing to generate more lift at lower airspeeds. This effect is especially important during approaches to landing when aircraft require higher lift to maintain a slower and safer speed.

Along with the increase in lift, drag also increases due to the larger wing area and the increased airflow disruption around the extended flaps. The additional drag is beneficial as it helps to slow the aircraft down, allowing for safer approaches and landings.

As for stall speed, it decreases when flaps are lowered. This is because the increased lift enables the aircraft to fly safely at lower airspeeds without reaching the stall point. The combination of increased lift and drag while lowering stall speed allows pilots to operate aircraft more safely during critical flight phases.

Therefore, the selection indicating that lowering the flaps increases lift, increases drag, and decreases stall speed accurately captures the fundamental aerodynamic effects of this adjustment during flight.