G. Apply 0.5-inch (13 mm) squares of foam tape to the calibration standard as specified in Figure 2.
4. Instrument Calibration
A. Position the TTU device on the bonded area of the calibration standard. See Figure 2, Detail 1 for the
calibration positions for each inspection zone.
B. Align the transducers.
C. Adjust the screen range to position the highest part of the TTU signal between 10 and 20 percent of full
screen width. See Figure 3, sheet 1.
D. Adjust the gain to set the highest part of the TTU signal at 80 percent of full screen height. See
Figure 3, sheet 1.
E. Energize the gate and set the threshold at 20 percent of full screen height.
F. Position the gate across the main part of the TTU signal. See Figure 3, sheet 1.
G. Energize the alarm.
H. Set the alarm to sound when the signal falls below 20 percent of full screen height.
I. Move the TTU device above the disbond or foam tape area of the calibration standard. See Figure 2,
Detail I for the correct positions.
J. The TTU signal will become small and the alarm will sound. See Figure 3, sheet 2.
K. If the alarm does not sound or if there is too much noise, use a preamplifier (see Paragraph 2.F.)
between the receive transducer and the receive input of the ultrasonic instrument.
5. Inspection Procedure
A. Make scans of each inspection zone as specified below. Make the distance between each scan 0.40
inches (10.2 mm).
B. Inspection zone 1 (core bays and core bay ramps)
(1) Calibrate the equipment as specified in Paragraph 4.. Use Position A for the bonded areas and
Positions B and C for the disbond areas. See Figure 2.
(2) Make scans of inspection zone 1. Do not make scans on the solid laminate areas.
(3) For WTTU inspection, make scans of the honeycomb ramp areas in an up and down direction. If
you make scans along the ramp it is possible the wheels will not correctly touch the ramp.
C. Inspection zone 2 (solid laminate areas)
(1) Calibrate the equipment as specified in Paragraph 4. Use Position D for the bonded area and
Position E for the disbond area. See Figure 2.
(2) Make scans of inspection zone 2. Do the scans in lines that are parallel to the edge of the
laminate area. Do not make scans on the core bays or core bay ramps.
6. Inspection Results
A. Make a record of all areas where the TTU signal falls below 20 percent of full screen height. See
Figure 3, sheet 2.
B. Some structural conditions can cause indications. If you find indications that could be caused by
structure, examine them with secondary inspection procedures as specified in Part 4, 51-00-02,
paragraph 6.
747
NONDESTRUCTIVE TEST MANUAL
PART 4 57-50-01
Page 3
Nov 15/2015D6-7170
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
EFFECTIVITY
ALL; 747 AIRPLANES WITH COMPOSITE KRUEGER
FLAPS
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