TM 1-1520-238-23
Change 9
6-547
6.132.
TAIL ROTOR GEARBOX INSPECTION – continued
(12) Check tail rotor head attachment studs for looseness, crossed, stripped, or flattened threads. None
allowed.
(a) Maximum allowable side play 0.022 INCH when measured 1.00 INCH above base. Use gap setting
gage.
(b) Lockring is flush or below base.
(13) If tail rotor gearbox collar was removed, ensure torque on nuts is 220 INCH-POUNDS. Use torque wrench.
b. Check tail rotor gearbox shouldered shaft for serviceability.
(1) Check for nicks, burrs, gouges, and corrosion. Except for surfaces identified below, depths not deeper than
0.020 INCH before blending are acceptable. Use depth gage. If crack in tail rotor gearbox shouldered shaft
is suspected, refer to TM 1-1520-264-23 non-destructive inspection procedure for AH-64A helicopter.
(2) Check for fractures and cracks. None allowed.
(3) Check identification marking. Must be readable.
(4) Check coupling mounting diameter. Minimum diameter 2.1221 INCH. Use caliper set.
(5) Check diameter of pilot between shaft and gear. Minimum diameter 2.4995 INCH. Use caliper set.
(6) Check diameter of pilot between gear and plug. Minimum diameter 2.0940 INCH. Use caliper set.
(7) Check spline teeth.
(a) No scuffing, scoring, or spalling allowed.
(b) Maximum pitting depth before blending 0.008 INCH. Use depth gage.
(c) Maximum wear step 0.008 INCH. Use depth gage.
(d) Measure “Over Balls” diameter with two 0.2500 INCH diameter gage balls placed in tooth spaces
approximately 180 degrees apart. Take three “Over Balls” measurements at locations approximately
120 degrees apart. Minimum “Over Balls” diameter 2.737 INCH. Use caliper set.
(8) Check five 0.2500 INCH hole diameters. Maximum diameter 0.2585 INCH. Use caliper set.
(9) Check plug for looseness and insertion depth. Minimum insertion depth from end of shaft 0.060 INCH. Use
depth gage.
(10) Check cadmium plating. Damaged or missing cadmium plating is acceptable.
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