(a)
Remove cap on end of starter.
(b)
Insert a 1/4 inch hex socket, with attached 6 inch extension and ratchet wrench, onto the 1/4 inch hex shaft on the end of the starter.
(2)
Put the optic fiber borescope through the compressor inlet duct and perforated inlet housing to examine the engine compressor impeller.
NOTE : MAKE SURE THE APU INTERNAL TEMPERATURE IS NOT MORE THAN 176F
____ (80C) BEFORE THE BORESCOPE IS PUT INTO THE APU. HEAT CAN DAMAGE THE BORESCOPE.
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CES MAKE SURE THE BORESCOPE CLEARS THE COMPRESSOR IMPELLER BLADES BEFORE THE APU IS ROTATED. ROTATION OF THE APU ROTATING GROUP CAN DAMAGE THE BORESCOPE.
(3) Turn the rotating group as necessary and examine the engine compressor impeller leading edges. (Ref. Fig. 608/TASK 49-20-00-991-022)
NOTE : The trailing edge of the engine compressor impeller is not
____ accessible for borescope examination while APU is installed on the aircraft.
(4)
The following observations are acceptable:
(a)
Bent inducer main or splitter blade tips are permitted on one blade only (26).
(b)
Rough edges due to nicks or erosion without significantly displaced material is acceptable (27).
(c)
Discoloration of impeller blades is acceptable (29).
(d)
Indications of impeller to shroud incursions (rubs) are acceptable (28).
(5)
The following observations are not acceptable, the observations are criteria for APU removal:
(a) Remove the APU if there are visible cracks of the leading edge, fillets, hub (30) or visible pieces are missing (31).
Subtask 49-20-00-960-058
F. Examine the engine compressor diffuser for damage.
(1)
Push borescope past the leading edge of the engine compressor impeller and examine the Engine Compressor Diffuser vanes for damage (Ref. Fig. 609/TASK 49-20-00-991-023)
(2)
The following observations are acceptable:
(a)
Leading edge nicks and rough edges due to erosion are acceptable without significantly displaced material (32).
(b)
Discoloration of vanes are acceptable
(c)
Cracks found in the braze fillet area is acceptable (33).
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CES
Engine Compressor-Impeller Damage Criteria
Figure 608/TASK 49-20-00-991-022
CES
Compressor-Diffuser Damage Criteria
Figure 609/TASK 49-20-00-991-023
CES
(3)
The following observations are not acceptable, the observations are criteria for APU removal:
(a) Bucket shaped erosion is not acceptable (34).
(4)
Remove optic fiber borescope from the compressor inlet.
(5)
Install cap on end of starter. Subtask 49-20-00-960-059
G.
Examine the combustor for damage. (Ref. Fig. 610/TASK 49-20-00-991-024)
(1) Remove igniter plug from the engine assembly (Ref. TASK 49-41-41-000-005).
(a)
Put the optic fiber borescope through the igniter plug port.
(b)
The following observations are acceptable:
(c)
The following observations are not acceptable, the observations are criteria for APU removal:
1_ Discoloration of panels and plugged effusion holes are
acceptable (35).
2_ Missing or disbonding TBC (thermal barrier coat) on outer
transition liner is acceptable (37).
3_ Cracks between holes are permitted, if material breakaway is
not present or the pattern of cracks could cause a loss of
material to occur (36).
1 Hot spots with severe oxidation or erosion that causes a loss
_ of material is not acceptable (37).
2 Examine the fuel nozzle shrouds for cracks, distortion, or
_ burn-through. No cracks, distortion, or burn-through permitted. If damaged fuel nozzle shroud is discovered, remove and replace with serviceable fuel nozzle shroud (Ref. Fig. 611/TASK 49-20-00-991-025)
(d) Remove optic fiber borescope from the igniter plug port.
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CES
Combustor Damge Criteria
Figure 610/TASK 49-20-00-991-024
CES
Combustion Chamber
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