What is the Servo Flap and How Does it Work? The servo flap is a small airfoil located at about 75 percent span of the rotor blade, situated on the trailing edge of each rotor blade. These flaps are controlled by the pilot through push-pull control rods and their function is similar to that of an elevator on fixed wing airplanes. Moving the trailing edge of the flap upward moves the leading edge of the main rotor blade up. This increases the rotor pitch or the lift in very much the same manner as the elevator, on a fixed wing aircraft, changes the angle of attack on the wing. Thus the helicopter pilot can cause the angle of attack of the flap to increase or decrease in pitch, causing the helicopter to alternately dive or climb.
So with that said why isn't it used more?