Propeller blades are designed with a twist with higher angle at the hub than at the tip. This is to equalize the lift distribution along the blade to the extent possible. During the rotation the tips of the blades move at a faster pace than those areas near the hub. If the blade did not have twist all along from hub to the tip, there would be dissymmetrical rotation speed and consequently lift. Hence, the necessity for blade twist.
. The undesirable variation in pitch from root to tip caused by aerodynamic loading.ii
. The twist built into a propeller or rotor blade. In the case of a propeller, it is to ensure that the pitch
angle at the root is greater than the tip. In the case of rotors, it is to compensate for unequal lift between inside and outside the rotor as well as to maintain RPM during autorotation.