engine. The probable cause is failure of the af-
fected wing jet pump.
NOTE
The engine-driven pump is capable
of suction-feeding enough fuel to sus-
tain engine operation without either
the wing standby pump or jet pump.
However, 25,000 feet is the highest al-
titude at which continuous operation
should be attempted in this event; the
limiting factor is that possible dam-
age to the engine-driven pump may
occur due to reduced fuel flow.
PRESSURE-RELIEF VALVES
A 75-psi relief valve is installed in each main
fuel line on the engine side of the main shut-
off valve. The valves relieve pressure buildup
caused by thermal expansion of trapped fuel
when the engines are shut down by venting fuel
overboard.
Two one-way pressure-relief valves are lo-
cated at wing rib 0.0, which separates the left
and right wing fuel tanks. Each valve, reliev-
ing in the opposite direction, opens at 1 psi to
equalize fuel pressure between the wing tanks
during crossflow operation.
FUEL DRAIN VALVES
Drain valves are located at low points through-
out the fuel system for draining condensation
or sediment. A small amount of fuel should be
drained from each valve during the exterior
preflight inspection. The valves, spring-loaded
to the closed position, are located as follows:
one for each tip tank, one for the crossflow
valve, one for each wing, one for each line to
the engines, one for each fuel filter, and one, two,
or three for the fuselage tank (Figure 5-7).
5-10
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
FLUSH SUMP DRAIN
WING SUMP DRAIN
RIGHT WING
LEFT WING
LH ENGINE FUEL
LINE DRAIN
EPA CAN DRAIN
RH ENGINE FUEL
LINE DRAIN
EPA CAN DRAIN
FUEL VENT DRAIN
FUEL FILTER DRAIN
FUEL FILTER DRAIN
FUSELAGE
LINE
DRAIN
FLUSH SUMP DRAIN
CROSSFLOW DRAIN
WING SUMP DRAIN
FUSELAGE TANK DRAIN(S)
24 D, E, F
25 B, D
25 C
1 DRAIN
2 DRAINS
3 DRAINS
Figure 5-7. Fuel Drain Locations
