D. Inspection Yoke
(1) Use a yoke that can extend at least 15 inches (380 mm) in from the edge of a part. Examples of
satisfactory yokes are as follows:
(a) Part number JTW-24/6; made by NDT Engineering Corp. (for MTTU).
(b) Part number RPTW-242A with part number GA-581 gimbals; made by NDT Engineering
Corp. (for WTTU).
E. Water Pump
(1) If you use a MTTU yoke, it will also be necessary to have a water pump. An example of an
acceptable water pump is as follows:
(a) Part number 3E-12N; made by NDT Engineering Corp.
F. Preamplifier
(1) Some ultrasonic instruments need a preamplifier to do a satisfactory inspection. Examples of
satisfactory preamplifiers are as follows:
(a) Part number 5662 wideband preamplifier; made by Panametrics Corp.
(b) Model number ULP-90; made by Sparta Technology (available from the NDT Engineering
Corp.)
G. Calibration Standard
(1) Use honeycomb calibration guide ST8870-1. Refer to Part 1, 51-04-00, Figure 7 for details about
this calibration standard.
(2) If you do not have the ST8870-1 calibration guide, you can use an alternate reference standard.
The reference standard must have:
(a) 3.0 pound nomex core (BMS 8-124, Type V, Class 4, Grade 3.0) with a 1-inch (25 mm) core
depth.
(b) Graphite fabric skins. The number of plies (total of front and back facesheets) must be
twelve, thirteen, or fourteen.
(c) A core ramp from a core bay to a solid laminate area.
H. Foam Tape - Use foam tape that will cause the received signal to decrease at least 18 dB. The foam
tape specified below was used when this procedure was prepared.
(1) Vinyl Foam Tape, part number 4416; made by the 3M Company, St. Paul, MN, 55144, USA.
3. Prepare for the Inspection
A. Remove the Krueger flap from the airplane and remove the fittings as specified in the applicable
Service Bulletin.
B. Do a visual inspection of the flap surfaces for cracks. Cracks can occur at the fastener holes at the
outboard end of the panel.
C. Do a visual inspection of the inside of the fastener holes for disbonds or separations. Make a record of
all holes where you find disbonds.
D. Put the flap on supports or on a bench with the flat side down.
E. Identify the inspection area. The inspection area is divided into two different inspection zones. It is
necessary to do a calibration for each inspection zone. See Figure 1, sheet 2.
F. If you use MTTU, seal the open holes in the inspection area with small pieces of tape. Use mylar tape,
teflon tape, flash tape or other tape that is transparent to ultrasound.
747
NONDESTRUCTIVE TEST MANUAL
PART 4 57-50-01
Page 2
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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