Learjet 60 - Page 106

Pilot's Manual
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Learjet 60
Overload sensors are installed
between the DC BUS 1 buses
and the
associated generator bus .
The overload sensors are
installed to protect
the DC BUS
1 feeder circuits
from an overload . Basically, each
over-
load sensor
is a 70-amp circuit breaker
mechanically connected to
a
switch . Should
an overload
condition occur, the circuit breaker
will
reposition
the switch to de-energize
a power relay,
thereby discon-
necting the
DC BUS 1 bus .
Additionally, the
switch will apply a
ground to
trip the affected L or R
DC BUS 1 circuit
breaker . When the
overload
sensor circuit breaker
cools, the switch
will
reset ;
however,
the
power relay will not
re-energize due to the open
L or RDC BUS 1
circuit
breaker . When
the malfunction has been
corrected and the af-
fected L or RDC BUS
1 circuit breaker reset,
the power relay will re-
energize and power
to the DC BUS 1
bus will be restored . An
over-
load sensor is
installed between
the CABIN PWR bus and the battery
charging
bus . The overload sensor
is installed to protect the
CABIN
PWR BUS
feeder circuit from an
overload . Operation of the
CABIN
PWR BUS
overload sensor is
the same as that
described for the DC
BUS
1 overload sensors
.
The generators will
not come on-line if an operating
ground power
unit is connected to the
aircraft .
A cross start relay box
is installed which
enables an operating genera-
tor to assist in
providing power to
start the opposite engine . If one
generator is
on-line and a start of
the opposite engine is initiated, the
cross start
relay circuits will cause both
left and right starter relays to
close . In effect,
this will bypass
both battery charging bus 275-amp
current limiters and the output
of the operating generator will supple-
ment the aircraft batteries
in providing power for the starter
.
An airstart relay box is
installed which prevents the primary flight
displays from blanking
and ensures certain equipment, necessary
for
a successful start,
has adequate voltage during airstarts .
During an
airstart, the
#2 battery is isolated from the battery
charging bus and
its
power is dedicated
to the following loads :
" L & R STBY-SLAV PUMP
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" L & R JET PUMP-XFR VALVE
" L & R ENGCHA (FADEC)
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"
L &
R
IGN
CH
A
" L & R ENG CH B (FADEC)
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" L & RIGN CH
B
" L & RSTART
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" AHS
1
&
2
" ADC-ARP 1 & 2
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" PFD 1 &
2
When the aircraft is on the ground, operation of the airstart
circuits is
inhibited and both batteries will be available to power the starter .
4-2
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PM-123
Original