Cessna 172R, Operating Handbook

Page: 93 / 500

CESSNA
MODEL 172R
SECTION
3
EMERGENCY PROCEDURES
EXCESSIVE FUEL VAPOR INDICATIONS
Excessive
fuel
vapor is
most likely to
be generated during
ground operations when operating
at
higher altitudes, in unusually
warm
temperatures
or
with more volatile fuel blends. Operation
at
or near idle RPM
(low fuel flow) for extended periods will increase
the chances of fuel vapor
generation. (See "Leaning For Ground
Operations", Section 4.)
Indicated
fuel flow that is
not
stable (sudden changes
greater
than 1 gal/hr) is a sign that fuel vapor may be
present
in the
system.
Fuel flow indications that become less stable
(increasing
changes) may lead
to
power surges and power loss
if
not
corrected.
If in-flight vapor
is
suspected, smoother engine operation may
result from making the following changes (singly or
together): set
the auxiliary fuel pump
switch to the ON position, lean the mixture
|
for
smooth engine operation and select another fuel tank.
Increasing the airspeed
to
provide more air
flow through the
cowling will aid in cooling the engine
and fuel
system components.
LOW OIL PRESSURE
If
the low oil pressure annunciator
(OIL PRESS) illuminates
and
oil
temperature
remains
normal, the oil pressure sending unit or
relief valve may be malfunctioning. Land
at
the
nearest
airport to
inspect the source of trouble.
If a total loss of oil pressure is accompanied by a rise
in oil
temperature,
there is good reason
to suspect an engine failure is
imminent. Reduce
engine
power
immediately and select a
suitable
forced
landing
field.
Use only the minimum
power
required
to
reach
the desired touchdown
spot.
Revision
8
3-21