Cessna 172P - Page 43

CESSNA
MODEL
172P
SECTION
3
EMER,GENCY
PROCEDUR,ES
EMERGENCY OPERATION
IN
CLOUDS
(Vacuum
System
Failure)
In the event of a va,cuum system failure
during
fligbt, the directional
indicator
and attitude indicator
will be disabled, and the
pilot
will have to
rely on the
turn
coordinator if he inadvertently flies into clouds. The
following
instructions
&ssume that
only
the
electrically-powered
turn
coordinator
is operativo,
and
that the
pilot
is not
completely
proficient
in
instrument flying.
EXECUTING
A 180'TURN ¡N
CLOUDS
Upon inadvertently entering the clouds, an immediate
plan
should be
made
to turn back as follows:
1.
Note the
compass
heading.
2.
Note
the time of the minute hand and observe the
position
of
the
sweep
second
hand on the
clock.
3. \f,then the sweep second hand indiaates the nearest
half-minute,
initiate a standard rate left turn,
holding the
turn coordinator
symbolic airplane wing opposite
the
lower left index mark for 60
seconds.
Then
roll
back to
level flight
by leveling
the miniature
airplane.
4.
Check
a,ccuracy
of
the
turn by observing the compass heading
whioh should
be
the reciprocal
of the original heading.
5.
If necessary,
adjust heading
primarily
with
skidding
motions
rather than rolling motions
so that the compass will read more
accurately.
6. Maintain
altitude and airspeed by cautious
applioation
of
elevator
control. Avoid
overcontrolling by
keeping
the hands off the control
wheel as much as
possible
and
steering
only
with ruddèr.
EMERGENCY DESCENT THROUGH
CLOUDS
If conditions
preclude
reestablishment
of VFR flight
by
a
180" turn, a
descent through a
cloud
deck to
VFR conditions may be appropriate.
If
possible,
obtain
radio
clearance for
an emergency
descent
through
clouds.
To
guard
against a spiral dive, choose
an easterly
or
westerly heading to
minimize compass
card swings due to
changing
bank
angles. In addition,
keep hands off the
control
wheel and steer
a straight course
with rudder
control by monitoring
the turn
coordinator.
Occasionally
check the
compass
heading
and make rninor
corrections to hold
an approximate
course. Before desconding
into
the clouds,
set up a stabilized
let-down
condition as follows:
30
May
1980
3-13