Cessna 152 - Page 165

PILOT'S
OPERATING
HANDBOOK
SUPPLEMENT
O-235-N2C
ENGINE
MODEL
152
To
achieve
the
recommended
lean
mixture
fuel
consumption
figures
shown
'in
Section
5,
the
mixture
should
be
leaned
until
engine
RPM
peaks
and
drops
10-25
RPM.
At
lower
powers
it
may
be
necessary
to
enrichen
the
mixture
slightly
to
obtain
smooth
operation.
An
alternate
method
for
ob-
taining
the
above
cruise
mixture
setting
in
rough
air
is
to
lean
until
en-
gine
roughness
or
a
sharp
drop
off
in
power
is
experienced
and
then
im-
mediately
enrichen
the
mixture
by
rotating
the
mixture
control
vernier
a9-
proximately
3/4
of
El-
turn
clockwise.
Use
of
recommended
lean
mixture
rather
than
that
for
maximum
RPM
can
provide
fuel
savings
of
up
to
10%
and
an
increase
in
flight
endurance
of
approximately
20
minutes
based
on
standard
fuel
tanks
and
75%
power.
Use
of
recommended
lean
~ure
rather
than
full
rich
mixture
can
pro-
vide
fuel
savings
as
high
as
34%
and
an
increase
in
flight
endurance
of
ap-
proximately
one
hour
when
operating
at
an
altitude
of
7500
feet
with
75%
power
and
standard
fuel
tanks.
Carburetor
ice,
as
evidenced
by
an
unexplained
drop
in
RPM,
can
be
removed
by
application
of
full
carburetor
heat.
Upon
regaining
the
origi-
nal
RPM
(with
heat
off),
use
the
minimum
amount
of
heat
(by
trial
and
error)
to
prevent
ice
from
forming.
Since
the
heated
air
causes
a
richer
mixture,
readjust
the
mixture
setting
when
carburetor
heat
is
to
be
used
continuously
in
cruise
flight.
The
use
of
full
carburetor
heat
is
recommended
during
flight
in
very
heavy
rain
to
avoid
the
possibility
of
engine
stoppage
due
to
excessive
water
ingestion.
The
mixture
setting
should
be
readjusted
for
smoothest
operation.
FUEL
SAVINGS
PROCEDURES
FOR
FLIGHT
TRAINING
OPERATIONS
For
best
fuel
economy
during
flight
training
operations,
the
following
procedures
are
recommended.
1.
Lean
the
mixture
for
maximum
RPM
during
climbs
above
3000
feet
(after
50
hours
has
accumulated).
The
mixture
may
be
left
leaned
for
practicing
such
maneuvers
as
stalls.
2.
Lean
the
mixture
for
maximum
RPM
during
all
operations
at
any
altitude,
including
those
below
3000
feet,
when
using
75%
or
less
power.
NOTE
When
cruising
at
75%
or
less
power,
the
mixture
may
be
further
leaned
until
the
RPM
peaks
and
drops
10-25
RPM.
This
is
especially
applicable
to
cross-country
training
flights,
but
may
also
be
practicerl
during
transition
flights
1
July
1978
Revision
1 -
31
March
1983
11