GEOMETRIC ORIENTATION OF THE ENGINE

To communicate information about an engine inspection, you must establish a geometric frame of reference for the engine assembly. A language for describing the physical damage is also necessary. An xample of this information is provided in geometric orientation of the LM2500 GTE. figure 2-1, Figure 2-2 shows an example of radial and axial cracking on a compressor blade; figure 2-3 shows an example of circumferential and axial cracking in the combustion section. Table 2-1, a foldout at the end of this chapter, provides a list of condition codes and definitions of terms that you need to know when inspecting the LM2500 GTE.

When the probe is in the inspection hole, it is not unusual for you to lose your sense of direction. On the Wolf borescope, the large plastic disk just beneath the eyepiece has an index mark that shows the direction the probe object window is facing. You can feel and see this mark. Another reference you can use to detect the direction the object window is facing is

Figure 2-3.- Examp1es of circumferential and axial cracking.

the light cable attachment. On the Wolf and Eder probes, the viewing window is 90 degrees clockwise from the light cable, as shown in figure 2-4. In the future, borescoping equipment may have changes incorporated that significantly improve the inspection equipment. Newer models may incorporate a swiveling light cable that allows the cable to hang down regardless of the viewing direction. You must read the manufacturer's instruction manual before you can successfully use the equipment. Figure 2-5 is an example of how the engine and borescope geometry work together. It shows you how the borescope appears when looking forward and aft from the right side of the engine or from the left side of the engine.

BORESCOPE PORTS Table 2-2 is a description of the ports and the areas that you can see from each borescope port. Figure 2-6 shows you the component materials

Figure 2-4.- Light cable azimuth for borescope probes. and the temperatures at which the various omponents normally operate. The locations

Figure 2-5.- Geometric orientation of the borescope

Table 2-2.- Area Visible From Borescope Inspection Ports

of the borescope inspection ports are shown in figure 2-7.

Compressor Fifteen borescope inspection ports are in the compressor near the 3 o'clock split line. A port is located at every compressor stator stage. These vane ports start at the IGVs and work aft in the same direction as the airflow (except for stage 8, which is internally blocked). Stator stages 9 and 13 borescope ports require you to remove piping interferences.