Flaps have two main purposes, to increase lift and to increase drag. Jet transport aircraft have high speed wings (since this is the enviroment they spend most of their time in) and in order for them to fly slowly enough to land/takeoff on a reasonably short runway they have to produce more lift. Thus if you extend flap you produce more lift and thus baloon. You compensate by reducing the AoA, if you anticipate this you can compensate and after a while you will do it automaticaly and by the correct amount. On the B737 Stages 1-25 compartively produce more lift than they produce drag. Flap 30 and 40 produce more drag than they increase lift.
Last edited by ifleeplanes; 29th May 2005 at 14:58.