Question id 56 - Aircraft General Knowledge - Airframe, Systems, Powerplant - ATPL - Airline Transport Pilot license

To increase lift without any drag penalty at low speed.
To reduce take-off and approach speeds only.
To reduce take-off, approach and landing speeds to an acceptable level.
To increase drag at low speed to assist landing only.

Training tests and timed exam simulations ATPL - Airline Transport Pilot license