TM 1-1520-238-23
Change 4
6-549
6.132.
TAIL ROTOR GEARBOX INSPECTION – continued
f. Check retainers for serviceability.
(1) Check for fractures and/or cracks. None allowed. Use fluorescent inspection kit (TM 55-1500-335-23).
(2) Check clinch nuts for crossed, stripped, or flattened threads. None allowed.
(3) Check top of serrations, flush or below surface of housing, for looseness. None allowed.
(4) Maximum diameter of bolt holes 0.330 INCH. Use caliper.
(5) Check for nicks, gouges, burrs, and corrosion not deeper than 0.040 INCH before blending, except for
specific surfaces. Use depth gage.
(a) Check mounting surface for damage or corrosion not deeper than 0.020 INCH before blending, and
not over 25 percent of total area. Not more than 10 percent damage in one localized area. Use depth
gage.
(6) Minimum mounting diameter 4.6225 INCH. Use caliper.
(7) Check packing groove for damage. None allowed.
g. Check static support mast for serviceability.
NOTE
Discoloration on static support mast can be caused by teflon wear.
(1) Check static support mast for surface discoloration or corrosion.
(a) Remove surface discoloration and corrosion by polishing. Use mat (item 122, App F) and lubricated
with lubricating oil (item 119, App F).
(b) If surface discoloration cannot be removed by polishing, replace (paragraph 6.145).
(2) Inspect for surface scratches and nicks. Use magnifier, as required.
(a) Axial scratches shall not exceed 15 scratches per discolored band, 3.00 INCH in length or 0.030 INCH
wide.
(b) Radial scratches. None allowed.
h. Check gearbox cooling fins for serviceability.
(1) 10 degree maximum allowable bend in fins.
(2) Check for damage and corrosion to fins not deeper than 0.250 INCH before blending. Use depth gage.
(3) Check for broken or cracked fins. None allowed.
END OF TASK
