BHT-412-MM-2
5-00-00
15 DEC 2015 Rev. 23 Page 157
Export Classification C, ECCN EAR99
5. Check mast bearing for smooth rolling and freedom from
binding.
6. Visually examine lower mast bearing inner race for
scratches, dents, corrosion, pitting, spalling, roller skidding, or
scoring.
7. Visually examine splines on mast for dents, wear, or
damage.
USE CARE IN REMOVING AND INSTALLING
TORQUEMETER TUBE ASSEMBLY IN MAST TO
PREVENT DAMAGE TO CADMIUM PLATING OF
MAST INSIDE DIAMETER AND TO AVOID
DAMAGE TO SPLINE TEETH AT THE LOWER
END OF THE TORQUE TUBE.
8. Remove torquemeter tube assembly and plug at upper
end of mast from the mast inside diameter.
9. Check torque on upper mast bearing nut 412-040-104-101
or 412-040-104-103 by applying torque in increasing torque
direction. Do not exceed 1400 foot-pounds (1898 Nm) for -101
nut or 900 foot-pounds (1220 Nm) for -103 nut.
It may be necessary to mark an index on torque
multiplier wrench to determine whether or not
rotation of nut occurs.
10. If rotation is evidenced at torque less than values above,
remove nut and mast bearing. Examine bearing inside
diameter and mast journal for evidence of rotation and/or
fretting. Record that the reason for disassembly was low nut
torque. Replace any discrepant parts.
11. Visually examine inside diameter and outside diameter of
mast for evidence of corrosion and/or mechanical damage.
5-30. EACH 2500 OR 3000 HOURS OF MAIN ROTOR MAST
(412-040-366-109 AND SUBSEQUENT) OPERATION (CONT)
DATA REFERENCE INSPECTION TASK DESCRIPTION
INITIAL
MECH OTHER
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