Jan You are supposing correctly Wing flaps reduce stalling speed and this allows lift off and climb out at a lower speed and hence they reduce the takeoff distance During the ground roll and initial takeoff still in ground effect the contribution to drag from the wing flaps is small However wing flaps cause a significant contribution to drag during the climb out and this explains why there is a limit to the amount of flap used during takeoff and why pilots retract wing flaps as soon as they achieve the necessary airspeed t