Cessna 172P Pilot's Operating Handbook And Flight Manual page 231

PILOT'S OPER,ATING HANDBOOK
SUPPLEMENT
2
AIR.
CONDITIONING SYSTEM
MODEL
172P
ds
a
is uot
corl or
at
less
used'
and without the
condenser
be
conducted
without
flaPs
e.
With
the
condenserfairing
s,
the
speeds
on
the Takeoff
Distance chart in
Section
5
of the
basio handbook and
a
10o
flap setting may
be
used.
AII
other
speeds
remain
unchanged
from
those
listed in
Section
4
of
the basic
handbook.
OPER,ATION
IN
FT,IGHT
on of the
air conditioning
system is basically
the
ration.
If
fast cool down is
desired, check
that
all
the
AIR
TEMP control
in
the MAX position,
and
place
the
FAN control
in the HI
position.
When
cabin
temperature
ha,s
been
reduced
to the desired level, rotate the
AIR
TEMP control knob counter-
clockwise as required to maintain that temperature and reposition
the
FAN control knob
as dosired.
During
extended
flight in extremely high temperature
and
humidity'
the
evaporator coils may frost over.
The
evaporator unit
is equipped
with
an
automatic defrost
system
which
will
normally prevent this. However'
when
the
AIR
TEMP
control is placed in
the
MA'X
position,
the
automatic
defrost system
will
not
operate.
This problem can be recognized
by
a
continual rise in
the
temperature
of
the
airflow from
the
outlets.
To
correct
the
problem,
move the
AIR
TEMP
control
knob
approximately one-third of
the
way toward
ühe
OFF
position
and
check that
the
FAN control knob
is
in
the
HI position. This
action should allow
the
automatic defrost system to
remove the frost,
NOTE
If
the
temperature
of
the
air coming from
the
outlets
does
not
start
to
cool
within a
reasonable
length
of
time
(depending on the
a,mount
of frost), the
system
may
be
malfunctioning
and
should
be
turned off.
The
blower portion
of the
system may
be
used any
time air
circulation
(heated
or
fresh)
is desired.
This
is
accomplished
by
leaving
the
AIR TEMP
control knob in
the
OFF
position,
and
placing
the
FAN control knob in
the
LOW,
MED, or HI position
as desired.
BEFOR,E
LANDING
1.
AIR TEMP Control Knob --
OFF
5
30
May
1980