MD Helicopters 369D - Fault Isolation; Power Train Instruments Fault Isolation; Tachometer Generator Troubleshooting; TOT Indicating System Troubleshooting

CSP-HMI-3MD Helicopters, Inc.
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95-30-00
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POWER TRAIN INSTRUMENTS
FAULT ISOLATION
1. Power Train Instruments Fault Isolation
The following tables are to be used in trouble
shooting the power train instruments.
2. Tachometer Generator Troubleshooting
Table 101. Tachometer Indicating Systems
Symptom Probable Trouble Corrective Action
Excessive scale error (low reading) Weak magnets in tachometer Replace indicator.
Excessive scale error (high
reading)
Weak restraining spring in
tachometer indicator
Replace indicator.
Pointer off zero position with
engine inoperative
Pointer shifted Replace indicator.
No reading or intermittent reading
Loose wiring, disconnected
connector or defective ground
terminal connection
Check continuity through wiring and
connectors. Repair as necessary.
Defective tachometer indicator or
generator
Replace defective indicator or
generator.
Defective ground connection on
tachometer generator
Check for electrical bond between
tachometer generator mounting
flange and engine pad stud.
3. TOT Indicating System Troubleshooting
Table 102. TOT Indicating System
Symptom Probable Trouble Corrective Action
No reading on indicator
Loose connection Check and tighten all connections.
Defective airframe thermocouple
harness
Replace or repair thermocouple
harness.
Defective engine thermocouple
harness
Replace engine thermocouple
harness (Ref. applicable Allison
Engine Operation and Maintenance
Manual, Table 201, 01−00−00).
Defective indicator Replace indicator.
Open adjustable resistor R4 Replace resistor.
Erratic reading on indicator
Defective indicator Replace indicator.
Defective connections or resistor
R4 on TB9 at back of instrument
Repair connections or replace
resistor.
Incorrect reading on indicator TOT indicating system out of
calibration
Perform TOT Indicating System
Calibration.