CIRCUMFERENTIAL CRACK IN THE CRACKS
INNER DIAMETER OR OUTER DIAMETER LEADING EDGE FILLET RADIUS
DECREASED TIME INSPECTION
(OUTER DIAMETER PLATFORM) FWD
CRACK IN THE INNER
E
DIAMETER FILLET RADIUS OR AXIALLY ON L-A1747CONCAVE AIR PLATFORM SURFACE THE FILLET RADIUS
FOIL SIDE CRACKS
DECREASED TIME INSPECTION(INNER DIAMETER PLATFORM)
D  L-A1747
1st-Stage HPT Vane Continue-In-Service Limits Figure 621 (Sheet 4)
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
No. 17 - HPT (1st- and 2nd-Stage) Blade and Duct Segments, and (1st-Stage)
__________________________________________________________________________ Vane Inspection
_______________
 S 296-158-N00
 WARNING:_______ DO NOT USE THE POWER CABLE OF THE BORESCOPE IF YOU FIND
 CIRCUMFERENTIAL CUT HOLES, 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.
 (5)  Put the borescope through each access port to examine the condition of the HPT 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).
 NOTE: It is possible that you will find local cracks and spalling
____ on the HPT duct segments during the borescope inspection. These local cracks and spalling are permitted, if the engine is in the EGT limits.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
No. 17 - HPT (1st- and 2nd-Stage) Blade and Duct Segments, and (1st-Stage)
__________________________________________________________________________ Vane Inspection_______________
 S 226-159-N00
 (6)  Compare the damage as identified in Figure 621, Figure 622, and Figure 624 with the continue-in-service limits shown in Tables 609, 610 and 611.
 NOTE: The frequency of the regular time inspection that is referred
____ to in the tables is from our Maintenance Planning Document. The frequency of the decreased time inspection is two times the frequency of the regular time inspection. In other words, the interval between decreased time inspections is half the interval of regular time inspections.
 NOTE: The maximum limits for the regular time and decreased time
____ inspections were calculated to have the qualities that follow:
 During usual conditions of operation, permitted damage will not become unsatisfactory before the time for the subsequent applicable inspection.
 Usually, higher damage limits are permitted for the decreased time inspection because that inspection is done more frequently.
 Damage and deterioration in some areas change the performance of the engine very quickly, which makes a higher limit (for the decreased time inspection) not possible. For damage in these areas, the limits for the decreased and regular time inspections are the same.
 (a)  Use these limits when you examine the 1st-stage HPT vanes (Table 609): 1) If damage is more than the decreased time inspection
 limits, remove the engine before the 6th cycle.
 2)  If these conditions will quickly occur, immediately remove the engine: part failure, or areas where material will break off.
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