Learjet 60 - Ground Idle System; Pressure System

Pilot's Manual
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Learjet 60
ENG
SYNC LIGHT
The amber
ENG SYNC light on the glareshield
annunciator panel will
be illuminated
when the nose gear is not up and
the SYNC-OFF
switch is in the
SYNC position .
GROUND IDLE
SYSTEM
The
ground idle system provides
reduced engine idle speeds for
ground
operations . When the
thrust lever is in the IDLE detent and
the squat
switch is in the ground
mode, idle speed is reduced from
approximately 65% N2 (flight
idle) to approximately 52% N2 (ground
idle) .
In flight, the idle speed
setting is selected to ensure adequate
transient response to
full takeoff power . The system
incorporates a
10-second delay after
touchdown before ground idle is
activated .
ENGINE
OIL SYSTEM
The engine oil
system provides lubrication
and cooling for the main-
shaft
bearings, all accessory drive
gears and all accessory bearings .
The
system consists of a pressure system, a
scavenge system, and a
breather system
.
PRESSURE
SYSTEM
The oil
tank is an integral part of the engine
intermediate case . Oil is
drawn from
the tank by a gear-type pressure
pump . Pump output is
directed
through a pressure adjusting
valve which bleeds excess pres-
sure back
to the pump inlet . From there, oil passes
through an oil fil-
ter
and fuel/oil heat exchanger before being routed
to the mainshaft
bearings,
accessory drive gears, and
accessory bearings . A cold-start
valve
diverts oil from the pump outlet
into the accessory gearbox
sump if
pressure exceeds 200 psi during cold
weather operation .
The oil filter incorporates a bypass
valve allowing oil to bypass the fil-
ter
should it become clogged .
An impending bypass indicator pro-
vides both a pop-up type visual
indicator and an electrical signal to
activate the ENG FILTERS light in the
cockpit . To avoid false indica-
tions at engine start-up with cold oil, a thermal lockout inhibits
the
impending bypass indication if oil temperature is below 38° C
(100°
F) .
An anti-siphon device is
incorporated to prevent oil from being si-
phoned out of the oil tank
following engine shutdown . The device
contains a small hole drilled through to the expansion
space at the top
of the oil tank . This breaks the siphon action caused by the oil tank
level
being higher than the main bearing oil jets .
2- 8
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PM-123
Change 2