TM 1-1520-238-23
6-546
Change 4
6.132.
TAIL ROTOR GEARBOX INSPECTION – continued
6.132.3. Inspection
a. Check tail rotor gearbox for serviceability.
(1) Check for fractures and/or cracks. None allowed. Use fluorescent inspection kit (TM 55-1500-335-23).
(2) Check mounting feet for nicks, gouges, burrs, and corrosion not deeper than 0.020 INCH before blending,
and not over 30 percent of area. Maximum hole diameter 0.530 INCH. Criteria are for both sides of
mounting feet. Use depth gage and caliper.
(3) Check cover studs for crossed, stripped, or flattened threads. None allowed. Maximum total side play
0.022 INCH when measured 1.0 INCH above base.
(a) Lockring serrations flush or below surface of housing. Use gap setting gage.
(4) Check cover inserts for looseness, crossed, stripped, or flattened threads. None allowed.
(a) Top insert flush or below surface of housing.
(b) Keys not to protrude above insert.
(5) Check pins on cover for looseness. None allowed.
(6) Check holes on face of cover for maximum diameter of 0.287 INCH. Use caliper.
(7) Check mounting flanges for nicks, gouges, burrs, and corrosion not deeper than 0.020 INCH before
blending. Use depth gage.
(8) Check cover for nicks, gouges, burrs, and corrosion not deeper than 0.040 INCH before blending. Use
depth gage.
(9) Check housing for nicks, gouges, and burrs not deeper than 0.020 INCH before blending. Use depth gage.
(a) Corrosion not deeper than 0.020 INCH over 30 percent of area. Use depth gage.
(b) Scratches not deeper than 0.015 INCH over 20 percent of area. Use depth gage.
(10) Check housing studs for stripped or flattened threads. None allowed.
(a) Maximum total side play 0.010 INCH when measured 0.750 INCH above base. Use gap setting gage.
(b) Lockring serrations flush to below surface of housing.
(11) Check housing inserts for looseness, crossed, stripped, or flattened threads. None allowed. Top of insert
flush or below surface of housing.
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