Damaged blade Damaged blade after blending Damaged blade Damaged blade after blending Figure 10-58.  Examples of repairs to damaged blades.  Figure 10-59.  Fan blade damage.  from the outside edge), if the depth of such nicks or dents  does not exceed that specified in the engine manufacturer’s  service or overhaul instruction manuals. Repair nicks by  stoning out material beyond the depth of damage to remove  the resulting cold-worked metal. A generous radius must be  applied at the edges of the blend. After blending the nick, it  should be smoothed over with a crocus cloth. Pitting nicks or  corrosion found on the sides of the inducer vanes are similarly  removed by blending. Loose objects often enter an engine either accidentally or  through carelessness. Foreign object damage (FOD), such as  pencils, tools, and flashlights, are often drawn into the engine  and can cause damage to the fan blades.  [Figure 10-59] Do not carry any objects in pockets when working around  operational turbine engines. A compressor rotor can be damaged beyond repair by tools  that are left in the air intake, where they are drawn into the  engine on subsequent starts. A simple solution to the problem  is to check the tools against a tool checklist. Prior to starting  a turbine engine, make a minute inspection of engine inlet  ducts to assure that items, such as nuts, bolts, lock wire, or  tools, were not left there after work had been performed. Figure 10-60  shows some examples of blade damage to an  axial-flow engine. The descriptions and possible causes of  blade damage are given in  Figure 10-61 . Corrosion pitting  is not considered serious on the compressor stator vanes  of axial-flow engines if the pitting is within the allowed  tolerance. Do not attempt to repair any vane by straightening,  brazing, welding, or soldering. Crocus cloth, fine files, and  stones are used to blend out damage by removing a minimum  of material and leaving a surface finish comparable to that  of a new part. The purpose of this blending is to minimize  stresses that concentrate at dents, scratches, or cracks. The inspection and repair of air intake guide vanes, swirl  vanes, and screens on centrifugal-flow engines necessitates  the use of a strong light. Inspect screen assemblies for breaks,  rips, or holes. Screens may be tin-dipped to tighten the wire  mesh, provided the wires are not worn too thin. If the frame  strip or lugs have separated from the screen frames, re-brazing  may be necessary. Inspect the guide and swirl vanes for looseness. Inspect the  outer edges of the guide vanes, paying particular attention to  the point of contact between the guides and swirl vanes for  cracks and dents due to the impingement of foreign particles.  Causes of Blade Damage 10-47