3.  Blade, spinner, and hubs for nicks, scratches, or other  flaws. Use a magnifying glass if necessary. 4.  Spinner or dome shell attaching screws for tightness. 5.  The lubricating requirements and oil levels, when  applicable. If a propeller is involved in an accident, and a possibility  exists that internal damage may have occurred, or if a  propeller has had a ground strike or sudden stoppage, the  recommendations of the engine and propeller need to be  adhered to. The propeller should be disassembled and  inspected. Whenever a propeller is removed from a shaft,  the hub cone seats, cones, and other contact parts should be  examined to detect undue wear, galling, or corrosion. It is also vitally important to keep up-to-date airworthiness  directives (ADs) or service bulletins (SBs) for a propeller.  Compliance with ADs is required to make the airplane  legally airworthy, but it is also important to follow the SBs.  All work performed on the propeller, including AD and SB  compliance, should be noted in the propeller logbook. The propeller inspection requirements and maintenance  procedures discussed in this section are representative of  those in widespread use on most of the propellers described  in this chapter. No attempt has been made to include detailed  maintenance procedures for a particular propeller, and  all pressures, figures, and sizes are solely for the purpose  of illustration and do not have specific application. For  maintenance information on a specific propeller, always refer  to applicable manufacturer instructions. Wood propellers should be inspected frequently to ensure  airworthiness. Inspect for defects, such as cracks, dents,  warpage, glue failure, delamination defects in the finish, and  charring of the wood between the propeller and the flange  due to loose propeller mounting bolts. Examine the wood  close to the metal sleeve of wood blades for cracks extending  outward on the blade. These cracks sometimes occur at the  threaded ends of the lag screws and may be an indication of  internal cracking of the wood. Check the tightness of the lag  screws, which attach the metal sleeve to the wood blade, in  accordance with the manufacturer’s instructions. In-flight tip  failures may be avoided by frequent inspections of the metal  cap, leading edge strip, and surrounding areas. Inspect for  such defects as looseness or slipping, separation of soldered  joints, loose screws, loose rivets, breaks, cracks, eroded  sections, and corrosion. Inspect for separation between the  metal leading edge and the cap, which would indicate the cap  is moving outward in the direction of centrifugal force. This  condition is often accompanied by discoloration and loose  rivets. Inspect the tip for cracks by grasping it with the hand  and slightly twisting about the longitudinal blade centerline  and by slightly bending the tip backward and forward. If the  leading edge and the cap have separated, carefully inspect  for cracks at this point. Cracks usually start at the leading  edge of the blade. Inspect moisture holes are open. A fine  line appearing in the fabric or plastic may indicate a crack  in the wood. Check the trailing edge of the propeller blades  for bonding, separation, or damage. Metal propellers and blades are generally susceptible to  fatigue failure resulting from the concentration of stresses at  the bottoms of sharp nicks, cuts, and scratches. It is necessary,  therefore, to frequently and carefully inspect them for such  defects. The inspection of steel blades may be accomplished  by either visual, fluorescent penetrant (see chapter 5), or  magnetic particle inspection. The visual inspection is easier if  the steel blades are covered with engine oil or rust-preventive  compound. The full length of the leading edge (especially  near the tip), the full length of the trailing edge, the grooves  and shoulders on the shank, and all dents and scars should be  examined with a magnifying glass to decide whether defects  are scratches or cracks. Tachometer inspection is a very important part of the overall  propeller inspection. Operation with an inaccurate tachometer  may result in restricted rpm operation and damaging high  stresses. This could shorten blade life and could result in  catastrophic failure. If the tachometer is inaccurate, then  the propeller could be turning much faster than it is rated  to turn, providing extra stress. Accuracy of the engine  tachometer should be verified at 100-hour intervals or at  annual inspection, whichever occurs first. Hartzell Propeller  recommends using a tachometer that is accurate within ± 10  rpm and has an appropriate calibration schedule. Carefully inspect aluminum propellers and blades for cracks  and other flaws. A transverse crack or flaw of any size is  cause for rejection. Multiple deep nicks and gouges on the  leading edge and face of the blade is cause for rejection.  Use dye penetrant or fluorescent dye penetrant to confirm  suspected cracks found in the propeller. Refer any unusual  condition or appearance revealed by these inspections to  the manufacturer.  Composite blades need to be visually inspected for nicks,  gouges, loose material, erosion, cracks and debonds, and  lightning strike.  [Figure 7-32]  Composite blades are  inspected for delaminations and debonds by tapping the  blade or cuff (if applicable) with a metal coin. If an audible  change is apparent, sounding hollow or dead, a debond or  Wood Propeller Inspection Aluminum Propeller Inspection Composite Propeller Inspection Metal Propeller Inspection 7-21