Inspect the edges of the swirl vanes. Inspect the downstream  edge of the guide vanes very closely, because cracks are  generally more prevalent in this area. Cracks that branch or  fork out so that a piece of metal could break free and fall into  the compressor are cause for vane rejection. Because of the thin-sheet construction of hollow vanes,  blending on-the concave and convex surfaces, including the  leading edge, is limited. Small, shallow dents are acceptable  if the damage is of a rounded or gradual contour type and  not a sharp or V-type, and if no cracking or tearing of vane  material is evident in the damaged area. Trailing edge damage may be blended, if one-third of the  weld seam remains after repair.  [Figure 10-62]  Concave  surfaces of rubber-filled vanes may have allowable cracks  extending inward from the outer airfoil, provided there is  no suggestion of pieces breaking away. Using a light and  mirror, inspect each guide vane trailing edge and vane body  for cracks or damage caused by foreign objects. Any inspection and repair of turbine compressor section  components require that the technician always use the  specific manufacturer’s current information for evaluation  and limits of repairs.  One of the controlling factors in the service life of the turbine  engine is the inspection and cleaning of the hot section.  Emphasis must be placed on the importance of careful  inspection and repair of this section. The following are general procedures for performing a hot  section (turbine and combustion section) inspection. It is not  intended to imply that these procedures are to be followed  when performing repairs or inspections on turbine engines.  However, the various practices are typical of those used on  many turbine engines. Where a clearance or tolerance is  shown, it is for illustrative purposes only. Always follow  the instructions contained in the applicable manufacturer's  maintenance and overhaul manuals. The entire external combustion case should be inspected for  evidence of hotspots, exhaust leaks, and distortions before the  case is opened. After the combustion case has been opened,  the combustion chambers can be inspected for localized  overheating, cracks, or excessive wear.  [Figure 10-63] Inspect the first stage turbine blades and nozzle guide vanes  for cracks, warping, or FOD. Also inspect the combustion  chamber outlet ducts and turbine nozzle for cracks and for  evidence of FOD. One of the most frequent discrepancies that are detected while  inspecting the hot section of a turbine engine is cracking.  These cracks may occur in many forms, and the only way  to determine that they are within acceptable limits or if  they are allowed at all, is to refer to the applicable engine  manufacturer’s service and overhaul manuals. Blending and Replacement Combustion Section Inspection Before blending After blending Figure 10-62.  Guide vane trailing edge damage.  10-49