Learjet 60 - Breather System; Scavenge System

Pilot's
Manual
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Learjet 60
SCAVENGE
SYSTEM
The
scavenge system
incorporates
three gear-type scavenge
pumps
installed
in the accessory
gearbox .
Oil from the number 1 and 2 bear-
ing
compartments
drains by gravity into
the accessory gearbox sump
.
Oil from number 3
and 4 bearings is
pumped by scavenge
pumps into
the
accessory gearbox
sump . Scavenge
flow from all bearing
compart-
ments
is aided by
pressurizing airflow
through the labyrinth
air seals .
Bypass
valves are
incorporated
around the number 3
and 4 bearing
scavenge
pumps to prevent
pressure build-up in the
scavenge lines at
higher
bearing cavity
pressure conditions . Oil collected
in the accesso-
ry
gearbox sump is
pumped to the top of
the oil tank by a
separate
scavenge
pump .
BREATHER SYSTEM
Air
from the bearing
compartments,
accessory gearbox, and
oil tank
is
vented overboard
through an
impeller-type centrifugal
air/oil sep-
arator installed
in the accessory gearbox .
ENGINE
IGNITION SYSTEM
Each engine ignition
system consists
of
an
IGNITION switch, a green
annunciator,
two
ignition
exciter units,
two shielded cables, two ignit-
er plugs, and associated
aircraft wiring
. The ignition exciter unit is
a
solid-state,
high-voltage unit
which provides a spark rate of 1 to
4
sparks
per second at an output
of 24,000 to 35,000 volts . The
igniter
plugs are mounted at
four and five o'clock positions in the
combus-
tion chamber case .
The plugs are operated by separate
cables and
spark when pulsed by
the ignition exciter units . During
the start cy-
cle, the ignition system
is automatically energized by the
FADEC
when the thrust levers
are placed in the IDLE position and
N2 is
above approximately 6%
. The ignition system is automatically
de-
energized by the FADEC
at approximately 40% N2 . At pressure
alti-
tudes
below 20,000 feet and
TLA
at or
above IDLE, the FADEC will
sequence the
ignition system on should N2 speed
fall below 40% . This
feature provides for an
immediate relight when the aircraft is
below
20,000 feet . The
ignition system may be operated
continuously
through the corresponding
IGNITION switch . The ignition
system
light will be illuminated
whenever the associated ignition system
is
operating either continuously
(IGNITIONOn) or automatically (FA-
DEC control) . The ignition system is
powered by 28 VDC from the L
and
RIGN
CH
A and IGN CH B circuit breakers on the pilot's and
co-
pilot's circuit breaker panels . The ignition system is
operative during
EMER BUS mode .
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PM-123
Change 2