Inspection Of Magnetos - Piper PA-24 Comanche Service Manual

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PIPER COMANCHE SERVICE MANt:Al
d. When the Idling speed has been stabilized. move the cockpit mixture control" ith a smooth. -acadv
pull toward the "Idle Cut-OFF" position and observe the tachometer for any change during the "leaning
process ". Caution must be exercised to return the mixture control to the "Full Rich" position before the
R PM can drop to a point where the engine cuts out. An increase of more than 50 RPM while "leaning nut"
indicates an excessively rich idle mixture. An immediate decrease in RPM (if not preceded by a
mornentaty
increase) indicates the idle mixture is too lean.
e.
If
the above indicates that the idle adjustment is too rich or too lean, turn the idle mixture
adjustment in the direction required for correction. and check this new position by repeating the
above
procedure. Make additional adjustments as necessary. Each time the adjustment is changed. the engine
should be run up to
1000
RPM to clear the engine before proceeding with the RPM check. Make final
adjustment of the idle speed adjustment to obtain the desired idling RPM with closed throttle. The above
method aims at a setting that will obtain maximum RPM with minimum manifold pressure. In case the
setting does not remain stable. check the idle linkage: any looseness in this linkage would cause erratic
idling. In all cases. allowance should be made for the effect of weather conditions and field altitude upon
idling adjustment.
i.~~.
Ignition
System.
7-.l9. Magneto.
CACTIO,
Ascertain that the primary circuits of both magnetos are grounded
before working on the engine.
7-40. Inspection
Of
Magnetos. At time of engine inspection or when a magneto has been removed from
the engine. the following checks may be performed. Each step in the check list is keyed by number
to
a
pan shown in Figure 7-H.
a.
Inspect distributor block contact springs. If broken or corroded. they should be replaced.
b.
Inspect oil felt washer.
It should be saturated with oil.
If
dry. check for worn bushing. Of 0. K .. add
'0.
JO
oil.
c. Inspect distributor block for cracks or burned areas. The wax coating on the block should not be
rernov
ed. Do not use solvents.
d. Look for excess oil in breaker compartment.
If
present. it may mean a bad oil seal or oil seal
hushing at drive end. Check manufacturer's overhaul procedure.
e. Look for frayed insulation or broken wire strands in leads in back of magneto. See that terminals
are secure. Be sure wires are properly positioned. The position of the leads in the
200
series breaker
compartment must be as shown in Figure 7-9. otherwise chafing or breaking may result.
f.
Inspect capacitor visually. If possible test for leakage. capacity and series resistance. Remember. an
~.
electrical failure of an aircraft capacitor is rare.
g. Adjustment of breakers must be COrrect for proper internal timing of magneto. (Refer to
. . paragraph
"-42.)
h. Check if breaker cam is clean and smooth. if cam screw is tight (25 in.
lbs.).
If new points arc
installed. blot a liule oil on cam.
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ISSl'ED: 8/18/72
2B7
POWER
PLA~T