BHT-412-MM-2
5-00-00
Page 170 Rev. 16 26 FEB 2013
Export Classification C, ECCN EAR99
DO NOT STAND OR LAY MAST HORIZONTALLY
WITH MAST BEARING RETAINING PLATE
SUPPORTING WEIGHT OF MAST.
2. Place main rotor mast assembly in horizontal position on
padded support, such as V blocks.
3. Remove lock ring, mast bearing retaining plate, and shim.
4. Visually inspect seal for signs of overheating, cracking,
wear, or damage.
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.
8. Check torque on upper mast bearing nut 412-040-104-101
or 412-040-101-103 by applying torque in increasing torque
direction. Do not exceed 1400 foot-pounds (1898 Nm) for nut
412-040-104-101 or 900 foot-pounds (1220 Nm) for nut
412-040-101-103.
It may be necessary to mark an index on torque
multiplier wrench to determine whether or not
rotation of nut occurs.
9. 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.
5-32. EACH 3000 HOURS OF MAIN ROTOR MAST (412-040-366-103 AND -105)
OPERATION (CONT)
DATA REFERENCE INSPECTION TASK DESCRIPTION
INITIAL
MECH OTHER
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