The performance of a propeller is influenced by the effects of the airplane components including the nacelle, fuselage and wing. These bodies induce flow velocity changes in the propeller plane which changes the blade load distribution from that in free air and thus effects the propeller performance. The flow field in the wake of the propeller influences the drag of the propeller nacelle and the lift of the wing. In addition, the mutual interference of the pressure fields induced by the propeller and bodies influence the performance. This includes a drag increase due to interference between the blade inboard section and the spinner. The effects of these mutual interactions between the propeller and its supporting bodies on performance is discussed along with methods for determining the performance changes. Illustrations are given to show the magnitude of the changes in performance due to the interactions and how the losses can be eliminated or reduced. With proper attention to the design of the propeller installation, the potential for improving the overall performance is large.