Systems Guide

Aerosoft
Twin Otter E
XTENDED
Systems
Vol
2
2-1-9
19 November 2013
Fuel heaters are installed on each engine to prevent ice crystals being formed. The heat exchangers use
engine oil to heat the fuel. It is operated automatically by a temperature control valve.
ELECTRICAL SYSTEM
The 28-volt direct current uses two engine driven starter-generators and a 40-amp-hour battery to feed the
system. Two static inverters provide 115-volt and 26-volt alternating current. Multiple busses to power diverse
equipment:
• Left (left generator): pilot’s directional gyro, pilot’s attitude indicator
• Right (right generator): copilot’s directional gyro, copilot’s attitude indicator
• Main Battery
• Battery / External
• Auxiliary battery dc bus
• Two ac busses
STARTER-GENERATORS
The engine driven generators (that serve as starter motors) provide 200 amperes at 28.5 volt. They come
online when the driving engine reaches idle + 15% rpm after the generator switch is moved through RESET and
set to ON.
DC MASTER SWITCH
The two position dc master switch is located on the overhead panel.
• OFF: no power to any bus except the main battery bus
• DC MASTER: connects the generators, battery or external power to the left and right bus
EXTERNAL / BATTERY SWITCH
This three position is located on the overhead panel.
• EXTERNAL: isolates the battery and connects external power to the left and right bus.
• OFF: no connection
• BATTERY: battery will power the electrical system if the generators are not running or if the generator
provided voltage is lower than the battery voltage.
BUS TIE SWITCH
The two position bus tie switch is located on the overhead panel.
• NORMAL: with generators offline external power or battery to both busses, with generator running
generators output is paralleled and both busses connected. When one generator fails, both busses
are powered from the other generator
• OPEN: left generator powers left bus and battery, right generator powers the right bus.
GENERATOR SWITCHES
The two (left/right) three position generator switches are located on the overhead panel.
• OFF: disconnects the generator.
• ON: connects the generator the bus via voltage regulator.