Textron Cessna 172S Skyhawk SP, Information Manual

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CESSNA
MODEL 172S
FUEL INDICATING
SECTION.?
.AIRPLANE & SYSTEMS DESCRIPTION
Fuel quantity is measured by two float type fuel quantity
transmitters (one in each .tank) and indicated by an. electrically
operated fuel quantity indicator on the left side of the instrument
panel. The gauges are marked in gallons of fuel. An empty tank is
indicated by a red ,line and the number
O. When an'indicator shows
an empty tank, approximately 1.5 gallons remain in each tank as
unusable fuel. The indicators should not be relied upon for accurate
readings during skids, slips, or unusual attitudes.
Each fuel tank also incorporates warning. circuits which can
detect low fuel conditions and erroneous transmitter messages .
. Anytime fuel in the tank drops below approximately.5 gallons (and
remains below this level for more than 60 seconds), the amber LOW
FUEL message will flash on the annunciator panel for approximately
10 seconds and then remain steady amber:'The
annunciator cannot
be turned off by the .pilot. If the .left tank is low, the message will
read L LOW FUEL. If the right tank is low, the. message will read
. LOW FUEL R. If both tanks are low, the message will read L LOW
FUEL R.
In addition to low 'fuei . annunciation, the warning circuitry is
designed to report failures with each transmitter_ caused by shorts,
opens or transmitter
resistance which increases overtime. If the
circuitry detects anyone of these conditions, the fuel level indicator
needle will go. to the OFF position (below.-the 0 mark on the fuel
indicator),. and the amber annunciator will illuminate. If the left tan'"
transmitter has failed, the message will readL LOW FUEL. If the
right tank iransmitter has failed, the message.will read LOW FUEL
R. If both tanks transmitters have failed, the-message will read L
LOW FUEL R.
Fuel pressure is measured by use of a transducer mounted near
the fuel manifold. This transducer produces an electrical signal
which is translated for the cockpit-mounted indicator ingallons-per-
hour.
Revision 4
7-25