PART 4 - ULTRASONIC
NACELLE FORWARD AND AFT END DIAGONAL BRACE FUSE PIN
1. Purpose
A. To detect cracks in the steel fuse pin in the forward and aft ends of the diagonal brace. See Figure 1.
B. To detect cracks originating from the inner surface of the shear-out plane and extending
circumferentially and outwardly parallel to the pin end.
C. Service Bulletin Reference: 747-54-2066, 747-54-2101
2. Equipment
A. Any ultrasonic test instrument capable of operating at 5 MHz that satisfies the requirements of this
procedure may be used. The following was used to develop this procedure:
(1) Nortec Model 131 ultrasonic instrument.
B. Transducer - 5.0 MHz, 0.375-inch (0.95 cm) or less case diameter.
NOTE: Scanning guide is designed for use with transducer with 0.375-inch case diameter.
NOTE: If a high level of interfering ultrasonic signal is encountered, an improved signal presentation
may be obtained using a higher frequency transducer. Refer to Paragraph 2.C.
(1) A KB-Aerotech Alpha transducer, P/N 124-340, 1.25-inch (3.2 cm) long case, 5.0 MHz/0.25-inch
(0.63 cm) diameter element.
C. Alternate High Frequency Transducer - 10 MHz, 0.375-inch (0.95 cm) or less case diameter, 0.25-inch
(0.63 cm) or less element diameter.
NOTE: Scanning guide is designed for use with transducer with 0.375-inch case diameter.
(1) A KB-Aerotech Alpha transducer, P/N 226-590, 0.43-inch (1.10 cm) long case, 10 MHz/0.25-inch
(0.63 cm) diameter element.
D. Manufacture Reference Block per Figure 2, or procure P/N 6411-71, 6411-72 or 6411-73 from Ideal
Specialty Co.
NOTE: Refer to Part 1, 51-01-00, for information on equipment manufacturers.
E. A Transducer Scanning Guide is recommended to simplify the inspection but is not required.
Manufacture transducer scanning guide per Figure 3.
NOTE: Scanning guide is designed for use with transducer with 0.375-inch case diameter.
F. Couplant may be a heavy oil or light grease.
3. Prepare for the Inspection
A. Remove fairing per Figure 1.
B. If required to permit scanning, remove cutout in edge of panel at the fuse pin face (forward end fuse
pin only).
C. Remove retaining bolt and end caps from fuse pin.
D. Part numbering on the end of the fuse pin may cause surface roughness which can prevent adequate
contact. Surface roughness can be removed by sanding, or, the inspection may be performed from the
opposite end (normally only one end of pin would be numbered).
E. Wipe end of fuse pin and apply couplant.
747
NONDESTRUCTIVE TEST MANUAL
PART 4 54-30-02
Page 1
Nov 15/2015D6-7170
ECCN 9E991 BOEING PROPRIETARY - Copyright © Unpublished Work - See title page for details
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