Learjet 60 - Cabin Power Control Switch; EMER BUS Switch; Emergency Bus System; Emergency Bus System (Figure 4-4)

Learjet 60

Pilot's Manual
EMERGENCY BUS SYSTEM
An emergency bus system is installed to provide 28 VDC to selected
systems
in
the event of a dual generator system
failure
or to quickly de-
energize
and isolate
all
nonessential equipment
in
the event of electri-
cal smoke or
fire
.
The
system uses the aircraft's batteries to supply DC
power to the DC equipment on the emergency bus .
All
emergency bus
circuit breakers are denoted by a red
ring
on the panel overlay .
The
EMER
BUS
TIE
is located on the copilot's circuit breaker
panel . The
emergency bus system control circuits operate on 28 VDC supplied by
the batteries through the
EMER
BUS CONT circuit breakers
in
the
pi-
lot's and copilot's circuit breaker
panel .
CABIN POWER CONTROL SWITCH
The
cabin power control switch system adds a
CABIN PWR OFF
switch
inline
with the
CABIN PWR
BUS circuit breaker
. This
allows the pilot
to quickly and
efficiently
load shed
all
cabin power systems by select-
ing
the
CABIN PWR
switch to the
OFF
position
.
When the switch is se-
lected
CABIN PWR - OFF,
it
will
also disable the NO SMOKING/
FASTEN SEATBELT sign .
Also, selecting
CABIN PWR- OFF
is one
means of reducing generator loads when required by abnormal proce-
dures
in
the
FAA
Approved
Flight
Manual
. During
single-generator
operation, the aircraft load shed
will
automatically cause the
CABIN
PWR
to go to the
OFF
mode .
EMER BUS SWITCH
The EMER
BUS switch on the pilot's switch
panel
is used to select the
power source
for
the emergency buses .
The
switch has two positions-
EMER
BUS and NORMAL
.
When the
EMER
BUS switch is
in
the NORMAL
position,
the
emergen-
cy bus system relays
will
be de-energized and equipment on the
emer-
gency buses
will
be powered
from
the
normal
electrical system
.
DC
equipment on the emergency buses
will
be powered through the asso-
ciated DC BUS
1, 2,
or 3 . When the switch is
in
the
EMER
BUS position,
the battery relays
will
be de-energized, the emergency bus system re-
lays
will
be energized, and equipment on the emergency buses
will
be
powered through the emergency bus system
.
When the battery relays
are de-energized, the aircraft batteries are completely isolated
from
the
battery
charging
bus and the
normal
DC power distribution system
.
When
EMER
BUS is selected, electrical power
will
be distributed as
fol-
lows :
PM-123

4-15
Change 5