TM 1-1520-240-10
2-4-3
2-4-6. Manual Defueling Valve.
A manual defueling valve is in the aft cargo compartment
next to FUEL VALVE # 2 ENGINE. The valve should only
be used by maintenance personnel to defuel the helicop-
ter or adjust fuel load.
2-4-7. Fuel Quantity Indicator and Selector.
An indicator calibrated to measure fuel quantity in
pounds and seven position selector switch (fig. 2-4-4) is
on the center instrument panel. Power is supplied to the
indicator through the FUEL QUANTITY selector switch
by the No. 1 AC bus through the FUEL QTY circuit break-
er on the No. 1 PDP.
a.
FUEL QUANTITY Indicator. The indicator pro-
vides two types of display. One display is in the digital
form and the other is a pointer. The digital readout contin-
uously indicates the total amount of fuel remaining in all
the fuel tanks. The pointer remains hidden until one of the
tank positions on the FUEL QUANTITY selector switch
is selected. Then, the pointer will indicate fuel remaining
in that tank. The fuel quantity indicator is electrically con-
nected to 10 capacitance-type measuring units in the
tanks.
b.
Fuel Quantity Selector Switch. The fuel quantity
selector switch has seven positions labeled TOTAL, L
(left) and R (right) FWD, MAIN, and AFT. Selecting any
position other than TOTAL causes the indicator pointer
to display the fuel remaining in that tank. The digital read-
out is not affected during individual tank readings.
2-4-8. Fuel System Cautions.
Four caution capsules are dedicated to the fuel system.
a.
L and R FUEL LOW. Two fuel quantity caution
capsules, one for each main tank, are on the master
Figure 2-4-3. Fuel Valve Warning Light, Sta. 500
Figure 2-4-4. Fuel Quantity Indicator and Selector
Switch
caution panel (fig. 2-14-5) of the center instrument con-
sole. Each light is electrically connected to a thermistor
sensor on a measuring unit in the respective main tank.
These lights are labeled L FUEL LOW an R FUEL LOW.
When the is 20 percent of fuel remaining in the main tank,
the caution capsule for that main tank illuminates (20
percent of fuel is equal to 320 to 420 pounds.) Power for
these capsules is supplied by the DC essential bus
through the LIGHTING CAUTION PNL circuit breaker on
the No. 1 PDP.
b.
L and R FUEL PRESS. Two caution capsules
labeled L FUEL PRESS and R FUEL PRESS ar on the
master caution panel. Each caution capsule is electrical-
ly connected to a fuel pressure switch between the main
tank and the engine fuel valves. When one of these cap-
sules illuminates, it indicates that fuel pressure in the
respective fuel line is below 10 $ 1 psi. Fuel pressure is
measured after the fuel boost pumps and not at the en-
gine driven pump. When fuel pressure caution illumi-
nants, it does not represent a possible engine flameout,
unless flight is being conducted above 6,000 feet PA.
Power for these capsules is supplied by the DC essential
bus through the LIGHTING CAUTION PNL circuit break-
er on No. 1 PDP.
2-4-9. FUEL Flow Indicators.
A dual fuel-flow indicator (fig. 2-4-5), on the center instru-
ment panel, indicates fuel flow to each engine in pounds
per hours. The indicator dial is graduated from 0 to 3,000
