Following aircraft system power-up, the fuel
quantity computer BITE sequence is initiated.
A n i nva l i d a n d / o r a t e s t d i s p l a y o n t h e
EICAS/MFD will be indicated by amber dashes
appearing in the fuel quantity display areas.
Should multiple quantity probes within a wing
tank system be at fault, a fuel quantity value
of zero for that fuel tank will be used by the
computer, and an invalid signal is displayed.
Seven capacitance fuel probes in each wing
plus a fuel density probe, which adjusts fuel
quantity readings for varying temperature con-
ditions, and a single probe in the fuselage tank
feed fuel level information to both channels
of the fuel quantity computer (Figure 5-3).
Both channels of the fuel quantity computer,
accounting for fuel tank geometry, aircraft
pitch (from AHRS #1) and fuel density, then
provide identical output signals to the No.1 and
No.2 DAUs (data acquisition units). The DAUs
reformat the electronic information and send
it to the left and right symbol generators in the
IC-600 integrated computers. The symbol gen-
erators then output the fuel information to the
EICAS and MFD displays. The DAUs also
send the fuel information to the left and right
radio management units (RMUs) for display
of fuel information on the RMU.
If a malfunction occurs in either channel of the
fuel quantity computer, in AHRS #1, or in the
capacitance probes, two different advisory
messages could be sent through the CAS. The
message will announce (1) “L or R FUEL
QTY FAULT” if the left or right channel has
detected a fault or a loss of compensation, or
(2) “FUEL QTY FAULT” (no L or R) if the at-
titude input from the AHRS is inoperative and
the quantity may not be as accurate as normal
or that a fuselage probe is inoperative or in-
valid. A fault detected in the capacitance
probes will result in dashes in place of the
digital display for the affected tank. A probe
failure may result in a “FUEL IMBALANCE”
amber CAS due to calculation in the fuel quan-
tity computer.
FUEL QUANTITY DISPLAY
The primary indication of fuel quantity is pro-
vided on the EICAS display format just below
the engine instruments (Figure 5-4). The
EICAS (Engine Instruments and Crew Alerting
System) is normally displayed on the pilot’s
inboard display unit (DU 2), but can also be
selected for display on the copilot’s inboard
display unit (DU 3). In some cases, the EICAS
will automatically be displayed on the co-
pilot’s inboard display unit.
As can be seen in Figure 5-4, the usable fuel
in each tank and the total fuel on board is a dig-
ital display located immediately below the
engine instruments on the EICAS. The first line
of the fuel display shows total usable fuel and
the second line shows left wing (L), fuselage
tank (F), and right wing (R) usable fuel. This
display of fuel quantities stays in view at all
times on the EICAS display.
The displays read in 10 pound increments. If
one fuel tank quantity is invalid (indicated by
amber dashes), the total fuel display assumes
zero fuel for that tank, and the total quantity
display will be in error.
The digital display of fuel quantity normally
shows in white digits; however, if wing fuel
imbalance exceeds 200 pounds when the flaps
are down, the digits for the wing quantity that
is lowest will turn amber and an amber box will
appear around that quantity. If the flaps are up,
an imbalance of 500 pounds will cause the
same indications. If the fuel out of balance con-
dition exceeds the above limits, an amber
“FUEL IMBALANCE” CAS message is dis-
played.
The wing quantities will also be boxed and turn
amber if an individual wing’s fuel decreases
to approximately 350 pounds. If the fuel quan-
tity is low an amber “L or R FUEL QTY LOW”
CAS message is posted (Table 5-1).
NOTE: The “L R FUEL QTY LOW” caution
CAS message and indication is only func-
tional on aircraft 45-195 and subsequent and
prior aircraft modufied by SB 45-28-5.
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
5-6
FOR TRAINING PURPOSES ONLY
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