Embraer EMB145, Operation Manual

Page: 1857 / 2662

AUXILIARY
POWER UNIT
AIRPLANE
OPERATIONS
MANUAL
2-09-05
Page
4
Code
01 REVISION 37
AOM
-145/
111
4
CONTROL SYSTEM
The APU control systems include the electrical, fuel, ignition,
lubrication, and pneumatic systems.
On the Model T-62T-40C11 APU, the electrical control system
consists of the Electronic Sequence Unit (ESU) and electric
accessories. On the Model T-62T-40C14 APU, the electrical control
system consists of the Full-Authority Digital Electronic Control
(FADEC). Both control systems incorporate the APU starting system,
control logic, and failure indication. Electric accessories provide ESU
(or FADEC) inputs and execute output commands.
For airplanes Pre-Mod. SB 145-49-0025 the APU ESU/FADEC is fed
by CENTRAL DC BUS and by the ESS DC BUS 2. The APU shuts
down if both buses are lost, but it remains on if only one is lost.
For airplanes Post-Mod. SB 145-49-0025 or equipped with an
equivalent modification factory incorporated, the APU ESU/FADEC is
electrically fed by HOT BUS 1. The APU control system (relays logic)
is supplied by ESS DC BUS 2. The APU shuts down immediately if the
HOT BUS 1 is lost, or shuts down after 6 seconds if the ESS DC
BUS 2 is lost.
The fuel system is composed of the fuel pump, fuel solenoid valves
(Start, Main, and Maximum), acceleration control, purge valve, fuel
nozzles, fuel filter, and manifold. Acceleration control provides fuel in
accordance with a preprogrammed schedule. Fuel from the right wing
tank is normally used to supply the APU. Alternatively, fuel from the
left wing tank may be used by means of the crossfeed valve.
NOTE: The fuel system for the Model T-62T-40C14 APU does not
include a start and maximum fuel solenoid valves.
The ignition system provides the electrical power necessary during the
APU starting sequence. It consists of an exciter, igniter plugs, and
wiring.
The APU has a self-contained lubrication system totally integrated into
the accessory gearbox. In addition to lubrication functions, the system
provides the required oil cooling, with no need for an external heat
exchanger. A thermostat, installed in the oil tank, sends a signal to the
EICAS in case the oil temperature exceeds 166
q
C (331
q
F).