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(2)
Remove the plugs from the HPC access ports AP-2, AP-3, AP-4, AP-5, AP-6, and AP-7 (Refer to Fig. 608 and 610 for the borescope data and the access port (AP) locations).
NOTE:____The access ports AP-5 and AP-7 have two plugs each. A PWA 75250 wrench and PWA 86580 driver are necessary to remove the inner plugs.
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(3) If it is necessary, do the steps that follow to turn the synchronizing ring which moves the synchronizing ring arms and the variable vanes.
NOTE: These steps are possibly necessary to get access to the AP-2
____ or AP-3 access port plugs. These steps will also help you to get a better view of the blades and vanes during the inspection.
(a)
Install a standard crowsfoot wrench of the SVA Bellcrank (flats), adjacent to the 5th-stage adjustor.
(b)
Push on the wrench in the applicable (up or down) direction to turn the synchronizing ring arm.
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(4)
While you do the HPC borescope inspection, you can do an optional check of the outer airseal rubstrip areas.
(a)
For the 6th- and 7th-stage areas, all quantities of feltmetal can be broken off, not bonded, or missing , if the conditions that follow occur: 1) All airfoil damage is not worse than the
continue-in-service limits. 2) The engine shows no signs that it operated unsatisfactorily or that it was not stable.
(b)
For the 8th- thru 15-stage areas, the limits for feltmetal that is broken off, not bonded, or is missing is as follows: 1) No more than four areas of material can be missing from
each stage.
2) No more than a total of 3.00 square inches (1935 square mm) of feltmetal can be broken off, not bonded, or missing from each stage.
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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
No. 15 - HPC Vane and Blade (5th- through 15th-Stage) Inspection
________________________________________________________________
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(5)
While you do the HPC borescope inspection, examine the 9th- thru 15th-stage of the HPC for blade seals that are loose or missing.
(a)
If those blade seals are loose or missing, the engine can stay in operation until the next regularly scheduled HPC disassembly.
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WARNING: DO NOT USE THE POWER CABLE OF THE BORESCOPE IF YOU FIND
_______ CIRCUMFERENTIAL CUT AREAS, FRAYING, OR BROKEN HOLES IN THE EXTERNAL RUBBER COVERING ON THE CABLE. POWER CABLES WITH THOSE CONDITIONS CAN CAUSE INJURY TO PERSONS.
CAUTION: MAKE SURE THE TEMPERATURE OF THE INSPECTION AREAS ARE BELOW
_______ 150°F (65.6°C) BEFORE YOU USE THE BORESCOPE. IF THE CASES ADJACENT TO THE INSPECTION AREAS ARE TOO HOT TO KEEP YOUR HAND ON, YOU CAN CAUSE DAMAGE TO THE BORESCOPE.
(6) Put a borescope through the applicable access port to examine the condition of the HPC blades and vanes.
NOTE: You can do a full 360° borescope inspection of the high
____ pressure rotor if you use the rotor crank provision (pad) on the main gearbox (AMM 72-00-00/201).
(a)
Refer to Table 601 for the number of blades in each of the gaspath stages.
(b)
If you find damage that is more than the limits, examine it to find if the area is a defect or a blend repair.
NOTE: Repaired areas have a 4 to 1 length to depth ratio and
____ have smooth round corners. This is important because a repaired area can possibly be more than the continue-in-service limits that follow. The limits apply only to defects and not to repaired areas.
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