C. Make a record of all ultrasonic signals that are less than 40% full screen height in the monitored area
so you can refer to these records when you do this inspection again.
D. To make sure there are cracks when you get the ultrasonic indications with the fuse pin installed, do an
eddy current inspection. It will be necessary to first remove all cadmium and corrosion from the inner
diameter of the fuse pin. Refer to Part 6, 51-00-00, Procedure 13, to do an eddy current inspection. To
make sure there are cracks when you get the ultrasonic indications with the fuse pin removed from the
airplane, do a magnetic particle inspection as specified in service bulletin 747-54A2150.
Table 1: Crack Signal Locations
ENGINE
FUSE
PIN
*[1]
STRUT
*[2]
FUSE PIN
BACK SURFACE SIGNAL CRACK LOCATION
*[3]
STEP
*[5] *[6]
METAL DISTANCE
%FSW
*[4]
METAL DISTANCE
%FSW
*[4]
IN. MM IN. MM
JT9D-70 -1 I/B 4.07 103.4 82% 0.83 21 16% B G1
-15 O/B 4.51 114.6 90% 1.04 26.4 20% A G2
ALL
JT9D
BUT -70
-14 I/B 3.64 92.5 72% 0.60 15.2 12% C G1
-2 O/B 4.01 101.9 80% 0.80 20.3 16% B G2
CF6-50 -1 I/B 4.07 103.4 82% 0.83 21 16% B G1
-2 O/B 4.01 101.9 80% 0.80 20.3 16% B G2
CF6-80C2 -1 I/B 4.07 103.4 82% 0.83 21 16% B G1
-20 O/B 4.01 101.9 80% 0.80 20.3 16% B G2
RB211 -16 I/B 4.07 103.4 82% 0.83 21 16% B G3
-17 O/B 4.09 103.9 82% 0.80 20.3 16% B G2
PW4000 -1 I/B 4.07 103.4 82% 0.83 21 16% B G1
-20 O/B 4.01 101.9 80% 0.80 20.3 16% B G2
*[1]
BOEING PART NUMBER 69B90909
*[2]
I/B = INBOARD; O/B = OUTBOARD
*[3]
APPROXIMATE LOCATIONS WHERE WE THINK CRACKS WILL START. SEE Figure 1, FLAGNOTE 3.
*[4]
%FSW = POSITION OF THE SIGNAL AS A PERCENTAGE OF FULL SCREEN WIDTH.
*[5]
REFERENCE STANDARD NDT4106 STEP TO USE
*[6] TRANSDUCER GUIDE NUMBER NDT4106-() TO USE
747
NONDESTRUCTIVE TEST MANUAL
PART 4 54-30-05
Page 4
Nov 15/2015D6-7170
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
EFFECTIVITY
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