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icing
encounter
should be
handled
as follows:
(1)
Turn
pitot
heat switch
ON (if installed).
(2)
Turn
back or change
altitude
to
obtain
an
outside
air
tempera-
ture that
is
less
conducive
to
icing.
(3)
Pull cabin
heat
control
full out
and
rotate
defroster
control
clockwise
to
obtain
maximum
defroster
airflow..
(4)
Increase
engine
speed
to
minimize
ice
build-up
on propeller
blades.
(5)
Watch
for
signs
of carburetor
air filter
ice and
apply
carburetor
heat
as
required.
An
unexplained
loss
in manifold
pressure
could
be caused
by carburetor
ice or air intake
filter
ice.
Lean
the
mix-
ture
if carburetor
heat is used
continuously.
(6)
Plan
a
landing
at
the
nearest
airport.
With
an
extremely
rapid
ice
build-up,
select
a suitable
"off airport"
landing
site.
(7)
With
an
ice
accumulation
of 1/4 inch or more
on
the
wing
leading
edges,
be prepared
for significantly
higher
stall
speed.
(8)
Leave
wing flaps
retracted.
With a
severe
ice build-up
on
the
.
horizontal
tail, the
change
in wing
wake airflow
direction
caused
by
wing
flap extension
could
result
in a loss
of elevator
effectiveness.
(9)
Perform
a
landing
approach
using
a forward
slip,
if necessary,
for improved
visibility.
(10)
Approach
at
90
to
100
MPH,
depending
upon
the
amount
of ice
accumulation.
(11)
Perform
a landing
in level
attitude.
ROUGH
ENGINE OPERATION
OR LOSS OF POWER.
CARBURETOR ICING.
An unexplained
drop
in manifold
pressure
and
eventual
engine
rough-
ness
may result
from
the
formation
of carburetor
ice.
To clear
the
ice,
apply full
throttle
and
pull
the
carburetor
heat knob full out until
the
en-
gine runs
smoothly;
then
remove
carburetor
heat
and
readjust
the throttle.
If conditions
require
the
continued
use of
carburetor
heat in cruise
flight,
use
the
minimum
amount
of heat necessary
to
prevent
ice from
forming
and
lean
the
mixture
slightly
for smoothest
engine
operation.
SPARK PLUG FOULING.
A
slight
engine
roughness
in flight
may be caused
by one or more
spark
plugs
becoming
fouled
by carbon
or
lead
deposits.
This
may be
verified
by
turning the
ignition
switch
momentarily
from
BOTH
to
either
3-7
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