Learjet 60 - Page 69

Learjet 60

Pilot's Manual
RAM AIR FUEL VENTSYSTEM
The fuel vent system
provides ram
air pressure to all interconnected
components
of
the
fuel system to ensure
positive pressure during all
flight conditions . Flush mounted underwing
scoops (inboard) admit
pressure to the fuselage vent system, and a
separate set of underwing
scoops (outboard) admit pressure for the wing
vent systems . The fu-
selage vent line is connected to a sump that
has a moisture drain
valve . Each wing tank vent system has a sump
witha moisture drain
valve located next to the wing vent underwing scoops
. Overpressuri-
zation due to thermal expansion in the wing tanks is
relieved through
the left and right expansion lines to the fuselage
tank . Overpressuriza-
tion of the fuselage tank, should the vent
and expansion lines be
clogged, is relieved
overboard through a pair of pressure relief
valves
and a separate vent
line .
SINGLE-POINT
PRESSURE REFUEL (SPPR) SYSTEM
The
single-point pressure refueling (SPPR) system
allows the entire
fuel system to be serviced through a fuel
servicing adapter located on
the right side of the aircraft below the engine
pylon . An SPPR control
panel is located immediately forward of
the refuel adapter . The
SPPR
incorporates
a precheck system which allows
the operator to check
the operation of the system vent and
shutoff valves before commenc-
ing refuel operations . The major
system components are the
refuel
adapter, the control panel, a vent
valve, a shutoff valve and
pilot
valve for each tank (both wings and
fuselage), solenoid valve for
the
fuselage tank, two precheck valves,
and associated plumbing and
wir-
ing . The control panel is located on the
right fuselage below the en-
gine pylon . Electrical power to operate
the system indicator lights
and
solenoid valve is 28 VDC supplied
from the #2 battery through the
BATT ON-OFF switch on the refuel
control panel .
The vent valve
is installed to prevent system
overpressurization in
the
event
of
a shutoff valve failure . Operation of
the valve is checked
during the
precheck sequence . The valve automatically opens
when-
ever fuel pressure
is
applied to the system . When the
valve reaches
the
full open position, a switch in the valve completes
a circuit to illu-
minate the VENT OPEN light on the SPPR control
panel .
PM-123

2-37
Original