Magneto Check; Spark Plugs; Engine Controls; Throttle Control - Cessna T182 Series Service Manual

MODEL 182 & T182 SERIES SERVICE MANUAL
11-79. MAGNETO CHECK. Advanced timing set-
lower spark plugs in upper portion of cylin-
tings in some cases, is the result of the erroneous
ders and install upper spark plugs in lower
practice of bumping magnetos up in timing in order
portion of cylinders. Since deterioration of
to reduce RPM drop on single ignition.
NEVER AD- lower spark plugs is usually more rapid than
VANCE TIMING BEYOND SPECIFICATIONS IN OR- that of the upper spark plugs, rotating helps
DER TO REDUCE RPM DROP.
Too much impor- prolong spark plug life.
tance is being attached to RPM drop on single ignition.
RPM drop on single ignition is a natural character- 11-81.
ENGINE CONTROLS.
istic of dual ignition design. The purpose of the fol-
lowing magneto check is to determine that all cyl-
11-82. DESCRIPTION. The throttle, mixture, pro-
inders are firing. If all cylinders are not firing, the
peller and carburetor heat controls are of the push-
engine will run extremely rough and cause for investi- pull type. The propeller and mixture controls are
gation will be quite apparent. The amount of RPM
equipped to lock in any position desired. To move
drop is not necessarily significant and will be influ-
the control, the spring-loaded button, located in the
enced by ambient air temperature, humidity, airport
end of the control knob, must be depressed.
When
altitude, etc. In fact, absence of RPM drop should
the button is released, the control is locked. The
be cause for suspicion that the magneto timing has
propeller and mixture controls also have a vernier
been bumped up and is set in advance of the setting
adjustment. Turning the control knob in either direc-
specified. Magneto checks should be performed on a
tion will change the control setting. The vernier is
comparative basis between individual right and left primarily for precision control setting. The throttle
magneto performance. control has neither a locking button nor a vernier ad-
a. Start and run engine until the oil and cylinder
justment, but contains a knurled friction knob which
head temperature is in the normal operating range.
is rotated for more or less friction as desired. The
b. Place the propeller control in the full low pitch friction knob prevents vibration induced "creeping" of
(high rpm) position. the control. The carburetor heat control has no lock-
c. Advance engine speed to 1700 RPM.
ing device.
d. Turn the ignition switch to the "R" position and
note the RPM drop, then return the switch to NOTE
"BOTH" position to clear the opposite set of plugs.
e. Turn the switch to the "L" position and note the
Some controls have intricate parts that will
rpm drop, then return the switch to the "BOTH" fall out and possibly be lost if the control is
position. pulled from the housing while it is discon-
f. The rpm drop should not exceed 150 RPM on
nected.
either magneto or show greater than 50 RPM differ-
ential between magnetos.
A smooth RPM drop-off 11-83. RIGGING. When adjusting any engine control,
past normal is usually a sign of a too lean or too it is important to check that the control slides smooth-
rich mixture. A sharp rpm drop-off past normal ly throughout its full travel, that it locks securely if
is usually a sign of a fouled plug, a defective harness equipped with a locking device and the arm or lever
lead or a magneto out of time. If there is doubt con- which it operates moves through its full arc of travel.
cerning operation of the ignition system, RPM checks
at a leaner mixture setting or at higher engine speeds
will usually confirm whether a deficiency exists.
Some engine controls have a small retaining
NOTE ring brazed (or attached with epoxy resin)
near the threaded end (engine end) of the con-
An absence of RPM drop may be an indication
trol. The purpose of these retaining rings is
of faulty grounding of one side of the ignition
to prevent inadvertent withdrawal of and pos-
system, a disconnected ground lead at mag-
sible damage to the knob end of the controls
neto or possibly the magneto timing is set
while jam nuts and rod ends are removed.
too far in advance.
Whenever engine controls are being discon-
11-80. SPARK PLUGS. Two spark plugs are in-
nected, pay particular attention to the EXACT
stalled in each cylinder and screw into hellcoil type
position, size and number of attaching washers
thread inserts. The spark plugs are shielded to pre- and spacers. Be sure to install attaching parts
vent spark plug noise in the radios and have an inter-
as noted when connecting controls.
nal resistor to provide longer terminal life. Spark
plug service life will vary with operating conditions. 11-84.
THROTTLE CONTROL.
A spark plug that is kept clean and properly gapped
will give better and longer service than one that is
NOTE
allowed to collect lead deposits and is improperly
gapped.
Before rigging throttle control shown in fig-
ure 11-7, check that staked connection (7)
NOTE between rigid conduit (6) and flexible conduit
(5) is secure. If any indication of looseness,
Refer to Section 2 for inspection intervals. (total linear movement exceeds . 050 in.) or
Remove, clean, inspect and regap all spark
breakage is apparent, replace the throttle
plugs at these intervals. At this time, install
control before continuing with the rigging
procedure.
11-28