APU STOPPING. - TM-55-4920-424-13-P0031

TM 55-4920-424-13&P

CAUTION

To preclude damage to electrical components, always monitor check stand

controls during ac generator operation to avoid operation at low frequency, high

frequency, or low voltage. Avoid contact with high-voltage components in the

control console during operation of the ac generator.

3-16. Before connecting power cable to aircraft, start APU. With APU at operating speed, move AC GEN switch to the

TEST position. Check voltages on all three phases using the ac selector switch.

3-17. Connect power cable to aircraft receptacle, and move AC GEN switch to ON. LOAD CONTACTOR CLOSED light

will illuminate. An AC FREQUENCY meter is provided on the instrument panel. AC volts and amperes may be read on

the AC VOLTS and AC AMPERES meters provided on the instrument panel by selecting the phase desired with the AC,

selector switch.

3-18. The ac overvoltage relay will operate to remove the ac generator from the line if an overvoltage condition exists.

The AC GEN FAILED light will illuminate. An engine malfunction shutdown will also cause the ac generator to go off the

line.

3-19. Move AC GEN switch to OFF before stopping A U after an ac power utilization tun.

The CLOSED light will

extinguish.

3-20. APU STOPPING.

a. Move AC GEN switch to OFF.

b. Pull DC GEN CONTROLS circuit breaker.

c. Move START-ON-OFF switch to OFF.

d. Pull TURBINE CONTROLS circuit breaker.

3-21. APU REMOVAL.

3-22. Removal of the APU from the mobile check stand is the reverse of the installation procedures given in

paragraph 3-4. Perform the following steps after removal of the APU from the check stand.

a. Disconnect battery.

b. Install metal cover on pad of speed increaser. Secure cover to prevent loss of spline drive adapter.

c. Remove tachometer generator from APU speed switch, and stow in receiver inside control console door. Place

nuts, washers, and drive coupling adapter in a cloth bag and stow with tachometer generator for future use.

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