Textron Bell 412, Maintenance Manual

Page: 204 / 288

BHT-412-MM-2
5-00-00
Page 156
Rev. 20 2 SEP 2014 Export Classification C, ECCN EAR99
Chapter 63
BHT-412-CR&O MAIN ROTOR MAST (412-040-366-109, AND
SUBSEQUENT)
CAUTION
R E M O V E M O N O P O L E S E N S O R B E F O R E
REMOVING MAST.
NOTE
Prior to removing mast assembly from transmission,
check chip detector located in top case for evidence
of debris. Presence of ferrous foreign material on
chip detector will require additional inspection to
determine origin.
The 412-040-366-109 (Pre TB 412-01-179) mast is
not field serviceable and must be returned to BHTI
for the following inspections. The mast assembly
must be returned with torquemeter tube, plug, and
lower torquemeter rotor in place. Also note the
number of the monopole sensor 412-375-004-105 or
-107 used with the mast.
1. Remove main rotor mast assembly from transmission.
CAUTION
DO NOT STAND OR LAY MAST HORIZONTALLY
W I T H M A S T B E A R I N G R E TA I N I N G P L AT E
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.
SPECIAL INSPECTIONS
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