Nemeth Designs/MILVIZ AgustaWestland AW109 for F X Operations Manual
5. Ele tri al system
The electrical system is powered by single wire circuit with common
ground return through the helicopter structure.
The helicopter power supplies are:
− 28 V dc
− 115 V ac 00 hz single phase
− 26 V ac 00 Hz single phase
Two generators, a battery and, for ground handling, an external
power receptacle, are the dc power main sources. Two static
inverters, powered by dc voltage, are the ac sources. Both dc and
ac powers are distributed through a bus bar system and operated by
control switches located on the overhead console. The electrical
system is interfaced with the IDS for voltage, current, advisory,
caution and warning indications.
DC System
The dc electrical system is a 28 V direct current single conductor
system, using the helicopter structure as a negative ground. The
main components of the systems are two starter generators, two dc
control boxes, battery, external power receptacle and one dc relay
box.
The helicopter is equipped with a 2 V, 27 or 22 Ah or with a 25.2
V, 28 Ah nickel-cadmium battery located in the nose compartment.
A temperature switch, inside of the battery and connected to the
IDS, detects the internal temperature of the battery, giving a BATT
HOT warning message on the EDU 1 in case of battery
overtemperature.
The helicopter is provided with an external power receptacle on the
rear right side of the fuselage. A microswitch, activated by the
receptacle door, gives the EXT PWR ON advisory message on the
EDU 1 when the door is in the open condition.
Two starter-generators, installed each on the proper engine
reduction gear-box, provide engine start when operated as an
electric starter motor; after the engine start, the started generator,
driven by the engine, reverts into a dc generator providing the
necessary 28 V dc power.
