The wing tanks are baffled with ribs and spars
to minimize fuel shift. Flapper-type check
valves, located in the wing ribs, allow unre-
stricted inboard flow of fuel and inhibit out-
board flow. There are no pressure relief valves
between the wing tanks on the Learjet 45. The
vent/expansion lines are open-ended from
each wing tank to the fuselage tank and relieve
any pressure into the fuselage tank.
The wing tanks have no external filler ports and
can only be filled with fuel transferred from
the fuselage tank. Whenever fuel is added to
the fuselage tank using the single-point refu-
eling system (SPPR) or by gravity filling, the
fuel automatically flows through two fuse-
lage transfer lines to fill the wing tanks.
Each wing tank contains seven fuel probes, a
fuel density compensator probe, and a float
switch which provide information to the fuel
quantity indicating system and low fuel sig-
nals to the Crew Alerting System (CAS).
A wing tank low fuel state will be indicated
by an amber “L or R FUEL QTY LOW” mes-
sage on the CAS, whenever the remaining fuel
i n t h e w i n g d r o p s t o a p p r o x i m a t e l y 3 5 0
pounds.
NOTE: The “L R FUEL QTY LOW” caution
CAS message is only functional on aircraft
45-195 and subsequent and prior aircraft mod-
ified by SB 45-28-5.
FUSELAGE TANK
The fuselage tank is a single bladder-type fuel
cell located immediately aft of the rear pres-
sure bulkhead. Located within the fuel cell is
plumbing for the fuel tank vent system and the
single-point refueling system. The fuselage
tank also contains a gravity fuel filler port lo-
cated at the top of the fuselage tank (Figure
5-2).
The usable fuel capacity of the fuselage tank
is approximately 404 gallons (1,529 liters), or
approximately 2,700 pounds (1,225 kg.). The
usable fuel is placarded as 2,708 in the fuse-
lage tank. The aircraft fuel system (including
wing tanks) is serviced through the fuselage
tank using the single-point pressure refueling
system or by gravity filling through the fuse-
lage filler port.
A single fuselage tank fuel probe is located in
the fuselage tank to provide information to
the fuel quantity indicating system.
The total fuel capacity of the Learjet 45 is ap-
proximately 904 gallons (3,422 liters) or ap-
proximately 6,062 pounds (2,748 kg.) when a
fuel density of 6.7 pounds per gallon factor is
applied. Total fuel quantity will vary with fuel
temperature.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
5-4
FOR TRAINING PURPOSES ONLY
FlightSafety
international
Figure 5-2. Fuselage Fuel Gravity Fill Port