4. Instrument Calibration
A. Select the appropriate back reflection reference block from Figure 2.
B. Connect transducer to instrument and perform preliminary adjustments.
C. Ensure reject and suppression controls are off.
D. Apply couplant and place transducer on end of the block.
E. Obtain a back reflection signal and position this signal at 80 percent of full screen width.
F. Adjust signal amplitude to 90 percent of screen height.
5. Inspection Procedure
A. Apply couplant to the end of selected fuse pin.
B. Insert transducer guide in the end of selected fuse pin.
NOTE: The scanning guide is recommended to simplify the inspection, but the inspection may be
performed without it.
C. Place transducer on fuse pin and obtain a back reflection signal. The back reflection signal should
occur at the same location as the signal from the reference standard. Refer to Figure 1, flagnote 1.
NOTE: An internal sound reflection indication around the entire fuse pin circumference may occur. The
reflection indication will occur at approximately 35 percent of screen width for the 2.937-inch
fuse pin and may vary for different length pins. Refer to Figure 1, flagnote 2.
D. The back reflection signal can be verified by placing couplant on a finger and touching the end of fuse
pin opposite to the transducer. The back reflection signal will diminish slightly as the area is touched
verifying the back reflection.
NOTE: A transducer that does not provide a clearly distinguishable back reflection signal from the fuse
pin is not acceptable for this inspection.
E. Adjust instrument gain to obtain approximately a full scale signal from the end of selected fuse pin.
F. Spot or slide transducer around end of fuse pin while observing the back reflection. If scanning guide is
not used, position transducer to obtain a maximum back reflection signal as it is moved around the end
of the fuse pin. Note losses of signal amplitude to below 50 percent of full screen height.
6. Inspection Results
A. Loss of back reflection is an indication of a crack. Back reflection loss is usually accompanied by one
or more signals appearing between the front surface and back reflection signals.
747
NONDESTRUCTIVE TEST MANUAL
PART 4 54-30-02
Page 2
Nov 15/2015D6-7170
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
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