Cessna T188C - Maintenance

MODEL
188 & T188
SERIES SERVICE
MANUAL
In all cases, It must
be definitely determined
that the fire at
the same time.
number one cylinder is at the correct firing position, i. Remove timing devices from magneto and engine.
on the compression stroke, when the crankshaft is j. Connect spark plug leads to their correct mag-
turned in its normal direction of rotation. After the neto outlets.
engine
has been placed
in the correct
firing position,
install and time the magneto to the engine in the fol- NOTE
lowing manner.
The No. 1 magneto outlet is the one closest
NOTE to the ventilation plug on the side of the
magneto having the manufacturer's insignia.
Install the magneto drive coupling retainer The magneto fires at each successive outlet
and rubber bushings into
the magneto drive
in clockwise direction.
Connect No. 1
gear hub slot. Insert the two rubber bush- magneto outlet to No. 1 cylinder spark plug
ings into the retainer with the chamfered lead, No. 2 outlet to the next cylinder to fire,
edges facing toward the front of the engine, etc. Engine firing order is listed in paragraph
11-8.
a. Turn the magneto shaft until the timing marks
visible through
the ventilation plug holes are aligned
k. Connect toggle
switch (primary) lead to the
ca-
(red-to-red
or black-to-black)
and insert a
timing
pacitor terminal
on the
magneto.
pin (or 0.093
inch 6-penny
nail) through
the timing
1. Inspect
magneto installation
and install
engine
hole in the bottom of
the magneto next to the flange
cowling in accordance
with paragraph 11-3.
and into the mating hole in the rotor shaft. This
locks
the magneto approximately
in the firing posi- 11-61.
MAINTENANCE. At the first
25-hour in-
tion while
installing on the engine.
spection and
at each 100-hour inspection thereafter,
the breaker compartment should be inspected. Mag-
NOTE neto-to-engine timing should be checked at the first
2
5-hour inspection, first 50-hour inspection, first
If the magneto drive gear was
disengaged 100-hour
inspection and thereafter
at each 100-hour
during magneto removal,
hold the magneto
inspection. If timing is
22
°
(plus zero, minus 2°),
in the horizontal position it will occupy when internal timing need not be checked. If timing is out
installed, make certain
that the drive gear
of tolerance, remove magneto
and set internal timing,
coupling slot is aligned with the magneto then install and time to the engine. In the event the
coupling lugs. If it is not aligned, pull the magneto internal timing marks are off more than plus
magneto
drive gear out
of mesh with its
or minus five
degrees when
the breaker points
open
drive
gear, and rotate
it to the aligned
angle,
to fire number
one cylinder,
remove the
magneto and
then push
it back into
mesh. DO NOT
WITH-
check the
magneto internal
timing. Whenever
the
DRAW
THE MAGNETO
DRIVE
GEAR
FROM
magneto
halves
are separated
the
breaker
point as-
ITS OIL
SEAL.
sembly should
always be checked.
As long
as inter-
nal timing and magneto-to-engine timing are within
b. After magneto gasket is
in place, position the the
preceding tolerances, it is recommended
that the
magneto on the engine
and secure, then remove the
magneto be checked internally
only at 500 hour inter-
timing pin from the magneto.
Be sure to remove
vals. It is normal for contact
points to burn and the
this pin before turning the propeller. cam to wear a comparable amount so the magneto
c. Connect a timing light to
the capacitor terminal
will remain in time within itself.
This is accom-
at the front of the magneto and to a good ground. plished by having a good area making contact on the
d. Turn propeller back a few degrees to close the surface between the points and the correct amount of
contact points.
spring pressure on
the cam. The area on the points
should be twenty-five percent of the area making
NOTE contact. The spring pressure at the cam should be
10.
5 to 12. 5 ounces.
When the
contact points
burn,
Do not turn the propeller back
far enough to the
area becomes irregular, which
is not detrimental
engage the impulse coupling or the propeller to the operation of the points unless metal transfer is
will have to be turned in normal direction of too great which will cause the engine to misfire.
rotation until the impulse coupling releases, Figure 11-6 illustrates good and bad contact points.
then backed
up to slightly before the firing
A small dent
will appear on the nylon insulator
be-
position. tween the cam follower and the breaker bar. This is
normal and does not require replacement.
e. Slowly advance the propeller in normal direction
of rotation until timing
light indicates the position
of
NOTE
contact point breaking. Magneto mounting clamps
may be loosened so that the
magneto may be shifted
If ignition trouble should
develop, spark plugs
to
break the points
at the correct
firing position.
and ignition
wiring should be
checked first.
f. Tighten
magneto mounting
nuts,
recheck timing.
If the
trouble definitely
is associated
with a
g. Repeat steps
"a" through "f" for the other
mag- magneto, use
the following to help disclose
neto.
the source of trouble
without overhauling
the
h. After
both magnetos
have
been timed,
check
magneto.
synchronization of both magnetos. Magnetos must
11-20