TM 1-1520-265-23
Change 2
2--42.1
2.18A Bifilar Weight Bushings (PT)
2.18A.1 Description (Figure 2-1, Index No. 18A). The bifilar weight bushings are installed within
the body of the bifilar weight.
2.18A.2 Defects. Inspect the inside diameter of the bushings for stress cracks along its edges.
No cracks are allowed.
2.18A.3 Primary Method. Fluorescent Penetrant.
2.18A.3.1
NDI Equipment and Materials. (Refer to Appendix B.) Inspection Equipment is listed
in Table 1-7. AMS 2644 level 3 penetrant materials shall be selected from the approved list in Table
1-8. Parts requiring flourescent penetrant inspection shall be cleaned prior to inspection with n--
Propyl Bromide (vapor degreasing only)(Table 1--8), DS--108 (Table 1--8), Electron (Table 1--8),
Positron (Table 1--8). DS--108, Electron, Positron must be followed by an acetone (Table 1--8) rinse
or wipe: or drying until there is no visible solvent residue left on parts.
2.18A.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground mainte-
nance. A 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. The bifilar
weight shall be removed in accordance with the applicable technical manuals listed in Table 1-1.
2.18A.3.3
Preparation of Part. Refer to Preparation of Part or Area for NDI, paragraph 1.4.4.
2.18A.3.4
Inspection Procedure. Perform fluorescent penetrant inspection. Refer to Fluores-
cent Penetrant Method, paragraph 1.4.7 and Table 1-5. Apply penetrant with a brush to prevent
overspray. Inspect area of concern.
2.18A.3.5
Marking and Recording of Inspection Results. Mark and record inspection results as
required by paragraph 1.3.
2.18A.3.6
Backup Method. None required.
2.18A.3.7
System Securing. Clean the bushings to remove inspection media. Refer to Post
Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.16. The bifilar weight requires
installation in accordance with the applicable technical manuals listed in Table 1-1.
Figure 2-18. Bifilar Weight (Sheet 2 of 3)
