Figure 2-21.Combustion liner dome igniter tube.
INNER AND OUTER LINER ASSEMBLIES.
circumferential stiffeners and are not visible when
You can inspect all areas of the inner and outer liner
assemblies aft of the fuel nozzles by rotating and tilting
the probe, and by varying the immersion depth. Some
of the damage that you may find is described in the
Circumferential Cracks. Figure 2-22 shows an
example of circumferential cracking on a high-time
combustion liner. This type of cracking occurs over the
area of the inner liner stiffening bands. The bands are
viewed through the borescope inside the combustor
assembly. Before actual cracking, the thermal working
of the liner shows stress lines. These lines will be visible
in all panels. Take care to inspect for the presence of
cracks, not merely lines. A crack will be open and the
separation will show an edge. The distortion occurs so
that the inner liner lifts up into the flow path and the
outer liner bends down into the flow path. These
irregularities are usually obvious when the liners are
Figure 2-22.Inner/outer liner circumferential cracks.