TM 1-1520-253-23
4.9.3.8
Demagnetization. With the switch remaining in the AC position, place the probe/yoke legs in the same
position used for magnetizing. Press the test switch and withdraw the probe/yoke from the part for a distance of two feet
before releasing the switch.
4.9.4
Backup Method. None required.
4.9.5 System Securing. Clean the identified component(s) thoroughly to remove all residual magnetic particle media.
Refer to Post Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.16. The rescue hatch lower door
gearbox requires assembly and installation in accordance with the applicable technical manuals listed in Table 1-1.
4.10.1 Description (Figure4-1, Index No. 10). This inspection is applicable to the rescue hatch lower door gearbox
assembly housing and cover.
4.10.2 Defects. Defects may occur anywhere on the surface of the housing and cover. Particular attention shall be
given to the areas of the four mounting holes. No cracks are allowed.
4.10.3 Primary Method. Eddy Current.
NDI Equipment and Materials. (Refer to Appendix B.)
a. Eddy Current Inspection Unit
b. Probe, straight, shielded surface, 100 KHz-500 KHz
Probe, right angle, shielded surface, 100 KHz-500 KHz, 901/2 inch drop
c.
d. Cable Assembly
e. Reference Block, three-notched aluminum (0.008, 0.020, and 0.040 EDM notches)
f.
Teflon Tape, refer to Table 1-8
g. Aircraft Marking Pencil, refer to Table 1-8
4.10.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. Partial inspection
for cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposed surfaces of
the installed part using this procedure. If required, the rescue hatch lower door gearbox shall be removed and
disassembled in accordance with the applicable technical manuals listed in Table 1-1.
4.10.3.3
Access. Not applicable.
4.10.3.4
Preparation of Part. The housing and cover shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1.4.4.
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