Cessna 152 - Page 120

SECTION
7
AIRPLANE
&
SYSTEMS
DESCRIPTIONS
CESSNA
MODEL
152
Ignition
and
starter
operation
is
controlled
by
a
rotary
type
switch
located
on
the
left
switch
and
control
panel.
The
switch
is
labeled
clock-
wise,
OFF,
R,
L,
BOTH,
and
START.
The
engine
should
be
operated
on
both
magnetos
(BOTH
position)
except
for
magneto
checks.
The
R
and
L
positions
are
for
checking
purposes
and
emergency
use
only.
When
the
switch
is
rotated
to
the
spring-loaded
START
position,
(with
the
master
switch
in
the
ON
position),
the
starter
contactor
is
energized
and
the
starter
will
crank
the
engine.
When
the
switch
is
released,
it
will
automati-
cally
return
to
the
BOTH
position.
AIR
INDUCTION
SYSTEM
The
engine
air
induction
system
receives
ram
air
through
an
intake
in
the
lower
portion
of
the
engine
cowling.
The
intake
is
covered
by
an
air
filter
which
removes
dust
and
other
foreign
matter
from
the
induction
air.
Airflow
passing
through
the
filter
enters
an
airbox.
After
passing
through
the
airbox,
induction
air
enters
the
inlet
in
the
carburetor
which
is
under
the
engine,
and
is
then
ducted
to
the
engine
cylinders
through
intake
manifold
tubes.
In
the
event
carburetor
ice
is
encountered
or
the
intake
filter
becomes
blocked,
alternate
heated
air
can
be
obtained
from
the
muffler
shroud
through
a
duct
to
a
valve,
in
the
airbox,
operated
by
the
carburetor
heat
control
on
the
instrument
panel.
Heated
air
from
the
muffler
shroud
is
obtained
from
an
unfiltered
outside
source.
Use
of
full
carburetor
heat
at
full
throttle
will
result
in
a
loss
of
approximately
150
to
200RPM.
EXHAUST
SYSTEM
Exhaust
gas
from
each
cylinder
passes
through
riser
assemblies
to
a
muffler
and
tailpipe
on
the
underside
of
the
engine.
The
muffler
is
constructed
with
a
shroud
around
the
outside
which
forms
a
heating
chamber
for
carburetor
heat
and
cabin
heater
air
.
. CARBURETOR
AND
PRIMING
SYSTEM
The
engine
is
equipped
with
an
up-draft,
float-type,
fixed
jet
carburetor
~mounted
on
the
bottom
of
the
engine.
The
carburetor
has
an
idle
cut-off
·mechanism
and
a
manual
mixture
control.
Fuel
is
delivered
to
the
carburetor
by
gravity
flow
from
the
fuel
system.
In
the
carburetor,
fuel
is
atomized,
proportionally
mixed
with
intake
air,
and
delivered
to
the
cylinders
through
intake
manifold
tubes.
The
proportion
of
atomized
fuel
to
air
is
controlled,
within
limits,
by
the
mixture
control
on
the
instrument
panel.
For
starting,
the
engine
is
equipped
with
a
manual
priming
system.
The
primer
is
actually
a
small
pump
which
draws
fuel
from
the
fuel
strainer
when
the
plunger
is
pulled
out,
and
injects
it
into
the
cylinder
7-18
1
July
1978