TM 1-1520-253-23
4.2.1 Description (Figure 4-1. Index No. 2). This inspection is applicable to parts or components made of
metallic/nonmetallic skins bonded to metallic/nonmetallic cores and laminations of facings of metal or fiberglass panels.
The structural assembly components identified for inspection are: fuselage honeycomb panels, decking honeycomb
panels, and pylons.
4.2.2 Defects. Perform the NDI method contained herein on the assembly components listed above for the primary
purpose of verification of void indications identified by visual inspection.
NOTE
A void is defined as an unbonded area that is supposed to be bonded. Many sub-definitions of
voids are given such as lack of adhesive, gas pocket, misfit, etc. However, this manual makes no
distinction among these, grouping them all under one general term ("void").
4.2.3
Primary Method. Bond Testing.
4.2.3.1
NDI Equipment and Materials. (Refer to Appendix B.)
a. Bond Test Unit
b. Probe, Mechanical Impedance Analysis
c.
Probe Holder
d. Cable Assembly
e. Test Block, metal honeycomb with skin thickness closest to that of the panel to be inspected
f.
Teflon Tape, refer to Table 1-8
g. Aircraft Marking Pencil, refer to Table 1-8
4.2.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance and in accordance
with applicable technical manuals listed in Table 1-1.
4.2.3.3
Access. Refer to paragraph 1.1.9, Figure 1-4, and Table 1-2 to locate applicable access panels and fairings.
WARNING
Maintenance Platforms/Workstands
Use only appropriate platforms, workstands, or other approved locally procured stands and
restraint equipment when working above 10 feet on helicopters in a nontactical environment.
Otherwise, personnel injury could result from accidental falls.
4.2.3.4
Preparation of Part. The components shall be thoroughly cleaned. Refer to Preparation of Part or Area for
NDI, paragraph 1.4.4.
4.2.3.5
NDI Equipment Settings. Refer to Bond Test Equipment, paragraph 1.4.6.1.
4-3
