CSP−900RMM−2 MD Helicopters, Inc.
Rotorcraft Maintenance Manual
Page 2
Revision 34
28-00-00
trapped between the cell and the helicopter
structure. The liner ribs route leaking fuel for
drainage through fuselage drain holes.
B. Fuel Vents
Two forward and two aft vent/rollover valves
are located on the top side of the fuel cell and
vent fuel to the atmosphere. The single
vent/rollover valves are located at the forward
right corner and the aft left corner of the fuel
cell. The dual vent/rollover valves are located
at the forward left corner and rear right corner
of the fuel cell. The dual vent/rollover valves
are attached to standpipes, which prevent any
fuel from draining overboard. Each single
vent/rollover valve is connected by hoses and
tubes to a dual vent/rollover valve.
Each vent/rollover valve is a normally open
poppet type float valve. The valve automatical
ly closes to prevent fuel loss through the vent
system. It's primary purpose is to allow the
fuel cell to vent to the atmosphere. It's
secondary function is to close when the
helicopter is outside of an 855 pitch or roll
angle. The valve also closes when fuel levels in
the fuel cell reach the float.
Flame arrestors are located in the outlet of
each standpipe to prevent any potential flames
from reaching the vent/rollover valves and fuel
cell.
C. Gravity Filler Port Fueling/Defueling
Refueling and defueling is through a gravity
filler port located on the right side of the
fuselage at the forward section of the fuel cell.
A check valve attaches to the filler neck
fitting. The filler neck fitting is secured to the
fuselage. The check valve is located within the
fuel cell. The valve opens when the fuel cap is
removed by pulling a lanyard for refueling and
defueling operations. The valve closes when
the fuel cap is secured to the filler neck fitting
preventing fuel leakage.
An optional “range extender” filler port
increases fuel capacity by 12 US gallons (45.4
liters) by allowing the fuel cell to fill complete
ly.
(902 CONFIG) The lanyard attached to the
fuel cap also opens a flapper valve in the
longitudinal baffle to decrease refueling time.
D. Fuel Sump Drain Valves
Two fuel sump drain valves are located on the
fuel cell sump plate. The sump plate is
centered on the bottom forward portion of the
fuel cell. The drain valves are spring loaded,
normally closed, poppet drain valves. The
valves are actuated by push cables to evacuate
fuel from the fuel cell. Fuel exits the fuselage
through drain hoses.
E. Fuel Quantity Probes
The fuel quantity probes are powered by
24-28 vdc current and consist of two capaci
tance type sensor probes bolted to the fuel cell
sump plate. The forward and aft gauging
probes output signals are processed by the
Integrated Instrument Display System (IIDS)
to illuminate the fuel quantity bar graph and
digital readout on the IIDS display.
The aft gauging probe has an independently
powered 24 to 28 Vdc fuel low level detector
(thermistor). The fuel low warning indicator on
the IIDS illuminates when the low level
warning detector is activated (900 CONFIG -
97 to 117 lb (44.0 to 53.1 kg) of fuel remain
ing) (902 CONFIG - 97 to 127 lb (44.0 to
57.6 kg) of fuel remaining).
(900 CONFIG - PW207E) The left FUEL
low level warning tic mark on the IIDS does
not operate for aircraft upgraded from
PW206A to PW207E engines.
The fuel quantity bar graph on the IIDS
displays the fuel quantity status, fuel low
caution bars, and fuel low warning bar. The
fuel quantity bars (green) indicate fuel in 50
pound increments. The fuel low caution bars
(yellow) indicate fuel in 150 lb (68.0 kg)
increments and illuminate when fuel quantity
is 151 to 300 lb (68.5 to 136.1 kg). The fuel
low warning bar (red) illuminates when fuel
quantity is 150 lb (68.0 kg). The digital
readout displays pounds of available fuel in a
numeric value.
902 CONFIG - The forward fuel probe also
has a low level sensor. The forward fuel probe
low fuel warning indicates low fuel in the left
fuel cell cavity. The aft fuel probe low fuel
indicator is for the right cavity. The IIDS
display will identify the warning as left or
right low fuel.
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