Transcript No Slide Title - Mauna Loa Helicopters

ELECTRICAL SYSTEM
The helicopter is equipped with a 28 VDC
electrical system. Power for this system is
obtained from a nickelcadmium 24 volt, 17
ampere-hour battery and a 30 volt, 200
ampere starter-generator.
Major components of the DC power system
include the battery, starter-generator,
voltage regulator, relays, 28 VDC bus, and
circuit breakers. All circuits in the
electrical system are single wire with
fuselage common ground return.
The negative terminals of the starter-generator
and the battery are grounded to the helicopter
structure. Controls for the electrical system are
located on the overhead console and instrument
panel.
The generator is provided with over voltage
protection set at 31 + 1 volts. Upon exceeding this
limit, the voltage regulator will disconnect the
starter-generator from the system. The failure of
the generator can be determined by the GEN
FAIL caution light and a zero loadmeter reading.
The battery can supply emergency DC load for
approximately 1 hour with a 17 ampere drain.
The BATTERY switch may be placed in the ON
position after external power is applied. In the ON
position, battery charging is supplied by external
power and must be monitored. In the event the
BATTERY HOT warning light illuminates, the
BATTERY switch shall be turned OFF.
If the Battery switch is turned OFF, and the
BATTERY RLY caution light illuminates, this
indicates that the battery relay has failed to open. If
the battery relay fails to open, the battery will
continue to receive a charge from the generator. To
prevent this, the pilot should turn GEN switch OFF.
The battery will continue to run all electrical
systems through the closed battery relay. To
reduce the load on the overheated battery,
the pilot should pull the circuit breakers on
all nonessential systems. The LEFT BOOST
circuit breaker should be left in to ensure
that fuel transfer from front tanks to main
tank continues.
External power may be supplied to the
helicopter by means of a receptacle located
on the lower front section of the helicopter.
An auxiliary power unit capable of delivering
28 VDC with a 500 ampere rating is required.
AUDIO WARNING SYSTEM
The ROTOR LOW RPM and ENG OUT audio
warnings are emitted from cabin horns
located aft and to the left of the overhead
console. The muting button for the system is
located on upper right side of instrument
panel, and mutes warning system audio.
The rotor RPM audio warning activates
(simultaneously with ROTOR LOW RPM
caution light illumination) whenever the
ROTOR decays below 90% RPM. The rotor
RPM audio will produce a steady sound until
the Rotor increases above 90% RPM.
Helicopters equipped with a WRN HORN
MUTE system will produce a steady sound
when the ROTOR decays below 90% RPM,
regardless of collective position.
The engine out audio warning (if
functional) is activated (simultaneously
with
ENG
OUT
warning
light
illumination) when the GAS PRODUCER
drops below 55 + 3% RPM. The engine out
audio will produce an intermittent sound
until the GAS PRODUCER increases above
55% RPM.
BATTERY
RELAY
BATTERY
BATTERY
SWITCH
28 VDC
BUS
STARTER
GENERATOR
STARTER
SWITCH
EXT. POWER
RELAY
LINE CONTROL
RELAY
STARTER
RELAY
GENERATOR
RESET SWITCH
VOLTAGE
REGULATOR
LOAD
METER
EXTERNAL
POWER
RECEPTACLE
ELECTRICAL
QUESTIONS?