TM 1-1520-265-23
4.3
HONEYCOMB AND COMPOSITE STRUCTURES (BT).
4.3.1 Description (Figure 4-1. Index No. 3). 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: honeycomb panels, cabin floors, drive shaft covers,
access doors and covers, cowlings, and work platforms.
4.3.2 Defects. Perform the NDI method contained herein on the components listed above for the purpose of verification
of void damage identified by visual inspection. Void damage may occur anywhere on either side of bonded panels as a
result of mechanical damage (dents, punctures, scratches, etc.) or fluid intrusion/corrosion.
NOTE
A void is defined as an unbonded area that is suppose to be bonded. Many sub-definitions are
given such as bond separation, delamination, lack of adhesive, gas pocket, misfit, etc. This
procedure makes no distinction among these instead grouping under the general term "void."
4.3.3 Primary Method. Bond Testing.
4.3.3.1
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 (refer to Appendix
C)
f.
Test Block, Composite Defect Standard #1
g.
Test Block, Composite Defect Standard #3
h.
Teflon Tape, consumable material, refer to Table 1-8
i.
Aircraft Marking Pencil, refer to Table 1-8
4.3.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance in accordance with
applicable technical manuals listed in Table 1-1.
4.3.3.3
Access. Not applicable.
4.3.3.4
Preparation of Part. The components shall be thoroughly cleaned. Refer to Preparation of Part or Area for
NDI, paragraph 1.4.4.
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