4.8 FUSELAGE SUPPORT HOLES (ET).
Description (Figure 4-1. Index No. 8). The fuselage support holes to be checked are located inside the
helicopter in the wing mounting area. The holes are used to mount the wing barrel nuts.
Defects. Defects can occur anywhere on the surface of the fuselage support holes. No cracks are allowed.
Primary Method. Eddy Current.
220.127.116.11 NDI Equipment and Materials. (Refer to Appendix B.)
Eddy Current Inspection Unit
Probe, straight, shielded surface, 100 KHz-500 KHz
Probe, right angle, shielded surface, 100 KHz-500 KHz, 90
1/2 inch drop
Reference Block, three-notched aluminum (0.008, 0.020, and 0.040 EDM notches)
Teflon Tape, refer to Table 1-8
Aircraft Marking Pencil, refer to Table 1-8
18.104.22.168 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance and the wings,
ammunition storage magazine, and the barrel nuts removed in accordance with the applicable technical manuals listed in
Access. Not applicable.
22.214.171.124 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
126.96.36.199 NDI Equipment Settings.
Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-1 9e
- 200 KHz
Probe drive - mid
Refer to Eddy Current Method, paragraph 1.4.11. Set up on test block as follows:
(1) Null probe on test block.
(2) Adjust phase as required to obtain horizontal lift-off.
(3) Move probe over all three notches in test block. Adjust gain to obtain a three block vertical si
gnal when probe
is passed over 0.040-inch notch in test block. (See the standard instrument display shown in Figure 1-7.)