Boeing 747 - Page 22

3. Prepare for the Inspection
A. Identify the inspection locations. The inspection locations are the ends of the fuse pins. See Figure 1.
B. Remove the parts specified in Service Bulletin 747-54A2150 to get the necessary access to the
inspection surfaces of the fuse pins.
C. Remove all paint and sealant from the ends of the fuse pin and clean fully. Use a non-abrasive scraper
to remove the paint. The part number is etched on the end of the fuse pin and can cause the surface to
be rough. If necessary, lightly sand this area by approved methods to permit the transducer to fully
touch the part.
NOTE: Make sure that the part number is not removed when you sand the part.
4. Instrument Calibration
NOTE: (1) The reference standard has three calibration steps identified as "A", "B", and "C". Table 1
identifies what calibration step to use for each fuse pin part number.
NOTE: (2) Because of the small transducer size a transducer guide is used during the inspection. Only one
guide is necessary to do an inspection of a fuse pin. Refer to Table 1.
A. Connect the transducer to the instrument with a coaxial cable and do the initial adjustments of the
instrument.
NOTE: Do not use reject unless the instrument has certified linear reject. Do not use more than 10%
reject.
B. Set the instrument frequency to 10 MHz. Refer to Paragraph 2.A.(1).
C. Find the part number on the fuse pin to be examined.
D. Find the part number of the fuse pin to be examined in Table 1 and use Table 1 to see what transducer
guide is necessary to use.
E. Put the transducer into the transducer guide so that the bottom of the transducer is equal with the
bottom of the hole. Tighten the setscrew lightly. See Figure 4.
F. Put couplant on reference standard NDT4106 at position 1 and then put the transducer at this position.
See Figure 4.
G. Adjust the instrument controls to get the first two back surface signals at 40% and 80% of full screen
width. The instrument is now calibrated for a 5.0 inch (127 mm) instrument screen range. See Figure 4.
H. With the part number of the fuse pin to be examined, look in Table 1 to find out what step of the
reference standard must be used. Put couplant on the step identified in Table 1 and then put the
transducer on this step at a location above the reference notch. See Figure 5.
I. Move the guide above the reference notch to get a maximum signal from the reference notch. The
approximate screen location for the reference notch signals are as follows:
(1) Step "A" = 20% full screen width.
(2) Step "B" = 16% full screen width.
(3) Step "C" = 12% full screen width.
J. Adjust the instrument gain controls to get the notch signal at 80% full screen height. Turn the
transducer in the guide hole to make sure the notch signal is at a maximum amplitude and adjust the
setscrew so that it is tight. Move the transducer guide above the reference notch one more time to
make sure the signal is at a maximum height of 80%. See Figure 5.
K. Increase the gain 6 dB.
747
NONDESTRUCTIVE TEST MANUAL
PART 4 54-30-05
Page 2
Nov 15/2015D6-7170
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
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