6.2 FLIGHT CONTROL BELLCRANKS (ET).
6.2.1 Description (Figure 6-1. Index No. 2).
This inspection is applicable to all non-ferromagnetic bellcranks contained
within the flight control system.
6.2.2 Defects. The primary purpose of this inspection is for: (1) confirmation of crack indications identified by visual
inspections; (2) verification that scratches and gouges do not conceal cracks; and (3) ensure no cracks are present after
blend out procedures.
6.2.3 Primary Method. Eddy Current.
188.8.131.52 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
184.108.40.206 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. A partial inspection
for cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposed surfaces of
the installed bellcranks using this procedure. If required, the bellcrank(s) shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
220.127.116.11 Access. Accessibility of the bellcranks varies considerably. Refer to Figure 1-4 and Table 1-2 to locate
applicable access provisions.
18.104.22.168 Preparation of Part. The part(s) shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
22.214.171.124 NDI Equipment Settings.
Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19e
- 200 KHz
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 signal when probe
is passed over 0.040-inch notch in test block. (See the standard instrument display shown in Figure 1-7.)