Refer to figure.
An alternative to increasing the angle of attack to increase lift is to lower trailing-edge flaps provided the speed is at or below the maximum speed for lowering flap (V_FO). This effectively increases the camber of the wing, the angle of attack and the coefficient of lift. However, the thrust may have to be increased to overcome the increased drag, even though when deployed they decrease the magnitude of the wing-tip vortices.
Not only does the extension of trailing-edge flaps decrease the critical angle of attack it also increases the C_LMAX, increases the total lift generated, increases the total drag, unfavorably affects the lift/drag ratio and decreases the stalling speed no matter what the altitude or mass of the airplane.
Unlike slats, trailing-edge flaps increase lift at all angles of attack up to the stall. Thus, if the angle of attack remains constant during flap extension the airplane will begin to climb. All trailing-edge flaps when lowered, increase the acceleration of the airflow over the upper surface of the wing, which reduces the pressure above the wing and increases the upwash over the leading edge. Together these influences generate an increased nose-down pitching moment because of the altered pressure distribution around the flaps and the aft movement of the wing CP.