Textron Cessna 172R, Pilot Operating Handbook

Page: 242 / 500

SECTION 7
AIRPLANE
&
SYSTEMS
DESCRIPTION
CESSNA
MODEL 172R
FUEL
VENTING
Fuel
system venting is essential to
system
operation. Blockage
of
the
system
will result in decreasing fuel flow and eventual engine'-'
stoppage.
Venting is accomplished by an
interconnecting line from
the
right fuel tank to the
left tank. The left fuel tank is vented
overboard
through a
vent
line, equipped with a check valve, which
protrudes from
the
bottom surface of the left wing near
the
strut.
Both
fuel filler
caps are
also vented.
REDUCED TANK CAPACITY
The airplane may be serviced
to
a
reduced capacity
to
permit
heavier cabin loadings. This is accomplished by
filling each tank
to
I
the bottom edge of the fuel filler tab, thus giving a reduced
fuel
of 17.5 gallons usable in each tank.
FUEL SELECTOR VALVE
The
fuel selector valve should be in the
BOTH
position
for
takeoff,
climb, landing, and maneuvers
that involve prolonged slips
or skids
of
more than
30 seconds.
Operation
from either
LEFT or
RIGHT tank is
reserved
for cruising flight.
_
in cruising flight, unequal fuel flow
from
each tank may
occur
if the wings
are
not
maintained exactly level.
Resulting
wing heaviness can
be alleviated
gradually by
turning the selector valve handle
to
the tank in the "heavy"
wing. It is
not
practical
to
measure
the time required
to
consume all of the fuel in one
tank, and, after
switching
to
the opposite
tank, expect
an
equal duration
from the
remaining fuel. The
airspace
in both fuel tanks is
interconnected by
a
vent
line
and,
therefore,
some sloshing
of fuel between tanks can be expected when the tanks are
nearly full and the wings are
not
level.
Feb
28/97
NOTE
When
the fuel
selector
valve
handle
is in the BOTH
position
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