Oil drain Governor to accumulator connection Propeller control oil Engine oil Propeller Change valve Accumulator Air or nitragen Piston Oil ENGINE Governor Rheostat Fluid pump Vent line Fluid tank Slinger ring Fluid feed shoe Figure 7-26.  Unfeathering system.  Figure 7-27.  Typical propeller fluid anti-icing system.  leading edge. These feed shoes are a narrow strip of rubber  extending from the blade shank to a blade station that is  approximately 75 percent of the propeller radius. The feed  shoes are molded with several parallel open channels in  which fluid flows from the blade shank toward the blade  An electric propeller-icing control system consists of an  electrical energy source, a resistance heating element, system  controls, and necessary wiring.  [Figure 7-28]  The heating  elements are mounted internally or externally on the propeller  spinner and blades. Electrical power from the aircraft system  is transferred to the propeller hub through electrical leads, Isopropyl alcohol is used in some anti-icing systems because  of its availability and low cost. Phosphate compounds are  comparable to isopropyl alcohol in anti-icing performance  and have the advantage of reduced flammability. However,  phosphate compounds are comparatively expensive  and, consequently, are not widely used. This system has  disadvantages in that it requires several components that add  weight to the aircraft, and the time of anti-ice available is  limited to the amount of fluid on board. This system is not used  on modern aircraft, giving way to the electric deicing systems. tip by centrifugal force. The fluid flows laterally from the  channels over the leading edge of the blade. Deicing Systems 7-18