Cessna 172N - Page 53

CESSNA
MODEL 172N
SECTION
4
NORMAL
PROCEDURES
prlled
out to
the heat
position,
air entering
the
engine is
not filtered.
Tzu<iing
over
loose
gravel
or cinders should
be
done
at
low
engine
speed to
avoid abrasion and
stone
damage
to the
propeller
tips.
BEFORE
TAKEOFF
WARfrl-UP
If
the engine
accelerates
smoothly,
the
airplane
is ready
for
takeoff.
Since
the
engine
is closely cowled
for
efficient
in-flight
engine
cooling,
precautions
should
be taken to avoid
overheating
during
prolonged
engine
operation on the
ground.
Also, long
periods
of idling
may
cause fouled
spark
plugs.
frlAGNETO
CHECK
The magneto
check
should
be made
at 1700
RPM as
follows.
Move
ignition
switch
first to
R
position
and note RPM.
Next move switch
back
to BOTH to
clear
the
other
set
of
plugs.
Then
move
switch
to
the L
posi-
tion,
note
RPM
and
refurn the
switch
to the BOTH
position.
RPM drop
should
not exceed
125
RPM on either
magneto or
show
greater
than
50
RPM differential
between
magnetos.
If
there
is a
doubt concerning opera-
tion
of the ignition
system,
RPM checks
at
higher engine
speeds will usu-
ally
confirm whether
a
deficiency exists.
An absence
of RPM
drop
may be an
indication
of
faulty
grounding
of
one
side
of
the ignition
system or
should
be
cause
for
suspicion that
the
magneto timing is
set
in advance of the
setting
specified.
ATTERNATOR CHECK
Prior to flights
where
verification
of
proper
alternator and voltage
regulator
operation
is essential
(such
as night
or
instrument
flights), a
positive
verification can
be
made
by
loading the
electrical system mo-
mentarily
(3
to 5 seconds) with the optional
landing
light
(if
so
equipped),
or
by operating
the wing
flaps during the
engine
runup
(1700
RPM). The ammeter
will
remain
within
a needle
width
of its
initial
reading if the
alternator
and
voltage
regulator are
operating
properly.
TAKEOFF
POWER
CHECK
It is important
to
check full-throttle engine
operation
early in
the
4-t3