ROCKWELL
COMMANDER
112/B/TC
/TCA
MAINTENANCE
MANUAL
SECTION
IV
POWER PLANT
AND
PROPELLER
When
installing
the engine on the
rubber
shock
mounts
and engine mount, the
shock
mount
bolts
should
be
torqued
to
a value of 450-500 inch-pounds.
Do
not
over
tighten the
bolts
or
the
rubber
shock
mount will
be
compressed
and
rendered
ineffective.
Inspect
the
mount
for
cracks
and
deteriorated
shock
mounts
at
intervals
prescribed
in Section II.
ENGINE
SHOCK MOUNTS.
The
bonded
rubber
and
metal
shock
mounts
are
designed to
reduce
the
trans-
mission
of engine
vibrations
to
the
airframe.
Oil
causes
deterioration
of the
rubber
shock
mount pads;
therefore,
pads should
be
frequently wiped
clean
with
a
dry
cloth.
.0'.
Do
not
clean
the
rubber
pads
with any
type of cleaning solvent.
Inspect
the
rubber
pads
for
evidence of
separation
be-
tween the pad and
metal
baCking, swelling, craCking,
or
a pronounced
set
of the pad. Replace worn
or
damaged
shock
mounts.
ENGINE COWLING
The
engine cowling
(Figure
4-11)
consists
of two
fiberglass
segments
that
are
easily
removed
for
quick
access
to
all
parts
of the engine.
The
lower
segment
is
attached
to
the
forward
fuselage
with
machine
screws
and
is
removed
only when
removing
the
engine
or
performing
maintenance
on the
lower
portion
of
the
engine.
The
lower
segment
contains
the
cowl flap
doors,
nose
gear
doors
and
air
scoops.
The
upper
segment
containing
the
oil
access
door
is
held
in
place
to
the
lower
segment
by
four
Camloc
latches
and
two
studs.
Inspect
the cowling
for
evi-
denc e of
holes
or
cracks
and
chafing of
seals
and
repair
as
required
per
Section
II.
REMOVAL
a.
Unlatch two
Camloc
stud
fasteners
and four
latches
and
remove
upper
half
of
cowl.
b.
Disconnect cowl flap
control
rods.
c.
Disconnect
nose
gear
door
control
rods.
d.
Disconnect induction
air
box
from
inlet
scoop.
e.
Remove
rubber
boot
attaching
cowl
to
oil
cooler
ducting.
f.
Disconnect landing
light
wire
at
plastic
con-
nector.
g.
Disconnect flex
hose
from
exhaust
shroud
to
cowl landing light housing.
h.
Remove
screws
attaching
lower
half
of cowl to
forward
fuselage.
INST ALLATION
To
install
the cowling,
reverse
the
removal
proce-
dures.
ENGINE CONDITIONING HINTS
IGNI'rION
Proper
operation
of the engine ignition
system
is
necessary
for
efficient engine
performance
and long
life.
Although the ignition
system
will
not
require
frequent
attention,
it
is
important
to
recognize
and
know how
to
correct
ignition
problems
to
eliminate
the
adverse
effect on
operating
economy and flight
safety.
Spark
plugs
cause
the
majority
of ignition
problems.
Normal
erosion
of the plug
electrodes,
caused
by continuous
firing
of the plugs
requires
periodiC plug
replacement;
however,
spark
plug life
can
be
reduced
drastically
by extended ground
opera-
tion of the engine
or
operating
the engine on an
ex-
cessively
rich
idle
mixture.
Proper
adjustment
of
the
idle
mixture
will
assure
longer
spark
plug life.
Improper
magneto timing
or
fouled
spark
plugs may
be
the
cause
of an engine
rpm
drop when switching
from
both
to
Single magneto.
It
is
easy
to
determine
if
an
ignition
problem
is
caused
by
the
plugs
or
mag-
neto by
close
observation
of the engine
rpm
variations
during
the magneto check. As the
speed
of
the engine
increases
the
cylinder
compression
increases
and
makes
it
more
difficult
for
the
spark
plug to
fire;
therefore,
an
rpm
drop
caused
by defective
spark
plugs
should
decrease
as
the engine
speed
is
reduced.
An
engine
rpm
drop
caused
by magneto malfunction
or
timing
will not follow a
change
in
engine
speed
with
the
same
consistency
as
faulty
spark
plugs.
If
the
magneto
drop
is
excessive
in
either
the L
or
R
posi-
tion, manually lean and
operate
the engine approx-
imately
30
seconds.
This
technique will
increase
combustion
temperature
and may
clear
excess
oil
and fuel
from
spark
plug
electrodes.
Return
mixture
to
full
RICH pOSition, and
recheck
magneto
drop
in
L and R positions. Repetitious fouling of the
spark
plugs
in
a
particular
cylinder
is
indicative of the
ignition
cable
break-down
or
low
compression.
The
difference
between
the
two
causes,
and consequently
a
clue
to what
is
causing
the
trouble,
can
usually
be
obtained by
comparing
engine manifold
pressure
and
rate
of
rpm
drop
when
operating
on a single magneto.
Low
compression
is
characterized
by a
variation
in
manifold
pressure,
slower
rpm
drop
during 'magneto
check, and rough idling.
FUEL
MIXTURE
MODELS
112/B.
The
servo
regulator
fuel
mixture
should
be
maintained
in
proper
adjustment
to
assure
optimum engine
performance
and
prolong
spark
plug
life.
Instructions
for
adjusting
the
servo
regulator
idle
speed
and
mixture
control
are
provided
elsewhere
in
this
section.
MODELS
112TC/TCA.
The
carburetor
fuel
mixture
should
be
maintained
in
proper
adjustment
to
assure
optimum engine
performance
and prolong
spark
plug
life.
Instructions
for
adjusing
the
carburetor
idle
speed
are
provided
elsewhere
in
this
section.
4-27
Copyright Commander Owners Group 2013 All Rights Reserved
**unofficial copy**
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