AUXILIARY POWER UNIT
Sep 13/2004 Flight Crew Operating Manual Volume 2
REV 1 CSP 100-6 05-01-01
REV 1
INTRODUCTION
The Honeywell 36-150BD constant-speed gas turbine auxiliary power unit (APU) is installed in a fire-proof compartment
in the tailcone of the airplane. The APU is a fully automated gas turbine powerplant with automatic fault detection, automatic
and remote shutdown, and in the event of an APU fire on the ground, automatic fire extinguishing.
The APU compartment is accessed by a single panel aft of the aft equipment bay door. The panel must be unscrewed from
the fuselage underside. The APU is a self-contained unit.
The primary purpose of the APU is to provide power for the gearbox-mounted 400-amp DC generator. Secondary functions
of the APU are bleed-air supply for the environmental control system (ECS) and main engine starting. Under high demand,
the APU electrical loads take priority over pneumatic loads.
For APU maximum operating altitudes for ground and flight, and also for continuous starter attempts, refer to the Approved
Airplane Flight Manual.
The APU should not be started above speed limits stated in the Approved Airplane Flight Manual, as the APU may reverse
windmill.
An engine control unit (ECU) controls and monitors all facets of APU operation, including the recording of operating hours
and start cycles. The DC-powered ECU sets up the appropriate fuel acceleration and EGT temperature schedules. It relays
appropriate operating data to the pilots through the EICAS displays.
APU start is initiated by one switch on the APU control panel in the flight compartment. Operational control of the APU
electric and bleed-air systems is performed at the ELECTRICAL and AIR COND/BLEED control panels.
COMPARTMENT
The APU is mounted in the airplane tailcone and is accessed via the access panel located on the fuselage underside. The
APU compartment has a NACA inlet for ventilation. The air is pulled through the NACA inlet and routed through the compartment
to cool the APU and its mounted components. This air is then exhausted overboard via the APU exhaust eductor.
The APU-driven air-cooled DC generator also has a NACA inlet for cooling air flow. The air is pulled through the generator
and dumped in the APU compartment. This air is then exhausted overboard via the APU exhaust eductor.
CFO0501002_002
APU
LOCATION
AUXILIARY POWER UNIT
Volume 2 Flight Crew Operating Manual Sep 13/2004
05-01-02 CSP 100-6 REV 1
APU ACCESS PANEL LOCATIONS
CFO0501002_007
SIDE ACCESS
PANEL
BOTTOM ACCESS
PANEL
AUXILIARY POWER UNIT
May 06/2005 Flight Crew Operating Manual Volume 2
REV 2 CSP 100-6 05-01-03
APU SCHEMATIC
SURGE
DUCT
BLEED AIR
DUCT
TO
AIRCRAFT
BLEED AIR
SYSTEM
AIRCRAFT
SKIN
AMBIENT SENSING
TEST PORT
TORQUE
MORTOR
CONTROL
PRESSURE
REGULATOR
OIL
PUMP
BLEED
DIFFUSER
CFO0501002_005
INLET AIR
BLEED AIR
ELECTRICAL CIRCUITS
ECU
FROM/TO
APU
SYSTEMS
FROM/TO
AIRCRAFT
SYSTEMS
AIR INLET
STARTER
MOTOR
LOW OIL-PRESSURE
SWITCH
FUEL CONTROL
UNIT
APU
GENERATOR
APU BLEED
VALVE SURGE VALVE
REV 2
AUXILIARY POWER UNIT
Volume 2 Flight Crew Operating Manual Sep 13/2004
05-01-04 CSP 100-6 REV 1
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