Pump grease in here Remove grease fitting Lubricating bearing in this area Figure 7-42.  Lubricating propeller bearings.  Propeller overhaul should be accomplished at the maximum  hours or calendar time limit  whichever occurs first. Upon  receipt for overhaul  prepare a document that tracks the  propeller components throughout the overhaul process.  Research all applicable ADs  current specifications  and  manufacturers’ SBs for incorporation during the overhaul  process. Double check the serial number and make notes on  the work order regarding the general condition in which the  propeller was received. As you disassemble and clean the  unit  perform a preliminary inspection on all related parts.  Record those revealing discrepancies requiring rework or  replacement in the overhaul record by part number  along  with the reason for the required action. Discard all threaded  fasteners during disassembly and  with a few exceptions  permitted by the manufacturer  replace with new components.  Many specialized tools and fixtures are required in the  disassembly and proper reassembly of propellers. These  tools are generally model specific and range from massive  15-foot torque adapter bars and 100-ton presses down to  tiny dowel pin alignment devices. Dimensionally inspect  components that are subject to wear to the manufacturer’s  specifications. After passing inspection  anodize aluminum  parts and cadmium plate steel parts for maximum protection  against corrosion.  Strip nonferrous hubs and components of paint and anodize  and inspect for cracks using a liquid penetrant inspection  (LPI) procedure. Etch  rinse  dry  and then immerse the  parts in a fluorescent penetrant solution. After soaking in  the penetrant  rinse them again and blow dry. Then  apply  developer  which draws any penetrant caught in cracks or  defects to the surface. Under an ultraviolet inspection lamp   the penetrant clearly identifies the flaw. Certain models of  hubs are also eddy-current inspected around critical  high- stress areas. Eddy-current testing passes an electrical current  through a conductive material that  when disturbed by a  crack or other flaw  causes a fluctuation on a meter or CRT  display. This method of inspection can detect flaws that are  below the surface of the material and not exposed to the eye.  Magnetic particle inspection (MPI) is used to locate flaws in  steel parts. The steel parts of the propeller are magnetized by  passing a strong electrical current through them. A suspension  of fluorescent iron oxide powder and solvent is spread over  the parts. While magnetized  the particles within the fluid  on the parts surface immediately align themselves with the  discontinuity. When examined under black light  the crack  or fault shows as a bright fluorescent line. The first step in blade overhaul is the precise measurement  of blade width  thickness  face alignment  blade angles   and length. Then  record the measurements on each blade’s  inspection record and check against the minimum acceptable  overhaul specifications established by the manufacturer.  Blade overhaul involves surface grinding and repitching   if necessary. Occasionally  blade straightening is also  required. The manufacturer’s specification dictates certain  allowable limits within which a damaged blade may be cold  straightened and returned to airworthy condition. Specialized  tooling and precision measuring equipment permit pitch  changes or corrections of less than one-tenth of one degree.  To ensure accuracy  take frequent face alignment and angle  measurements during the repair process. Precision hand grind  the blade airfoil to remove all corrosion  scratches  and surface  flaws. After completely removing all stress risers and faults   The Hub Propeller Overhaul 7-29