FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 8. Engines, Fuel, Exhaust, and Propellers | 1. Engines | 8-19. Magneto Inspection
9/27/01
AC 43.13-1B CHG 1
checklist for isolating some of the malfunc-
tions inherent to ignition harnesses.
a. Carefully inspect the lead conduit or
shielding. A few broken strands will not affect
serviceability, but if the insulation in general
looks worn, replace the lead.
function quickly. However, conduct any inter-
nal inspection or repair of a magneto in accor-
dance with the manufacturer’s maintenance
and overhaul manuals.
a. Inspect the distributor block contact
springs. If broken or corroded, replace.
b. When replacing a lead, if the dressing
procedure is not accomplished properly,
strands of shielding may be forced through the
conductor insulation. If this occurs, a short
will exist in the conductor; therefore, it is es-
sential this task be performed properly.
c. The high-temperature coating used
on some lightweight harnesses is provided for
vibration abrasion resistance and moisture
protection. Slight flaking or peeling of this
coating is not serious, and a harness assembly
need not be removed from service because of
this condition.
b. Inspect the felt oil washer, if applica-
ble. It should be saturated with oil. If it is dry,
check for a worn bushing.
c. Inspect the distributor block for
cracks or a burned area. The wax coating on
the block should not be removed. Do not use
any solvents for cleaning.
d. Check the spark plug contact springs
for breaks, corrosion, or deformation. If pos-
sible, check the lead continuity from the dis-
tributor block to the contact spring.
e. Check the insulators at the spark plug
end of the lead for cracks, breaks, or evidence
of old age. Make sure they are clean.
f. Check to see that the leads are posi-
tioned as far away from the exhaust manifold
as possible and are supported to prevent any
whipping action.
g. When lightweight harnesses are used
and the conduit enters the spark plug at a se-
vere angle, use clamps as shown in figure 8-8
to prevent overstressing the lead.
8-19. MAGNETO INSPECTION. When-
ever ignition problems develop and it is deter-
mined that the magneto is the cause of the dif-
ficulty, the following are a few simple inspec-
tion procedures which may locate the mal-
FIGURE 8-8. Typical method of clamping leads.
d. Look for excess oil in the breaker
compartment. If oil is present, it may indicate
a bad oil seal or bushing at the drive end. This
condition could require complete overhaul, as
too much oil may foul and cause excessive
burning of the contact points.
e. Look for frayed insulation on the
leads in the breaker compartment of the mag-
neto. See that all terminals are secure. Be sure
that wires are properly positioned.
f. Inspect the capacitor visually for gen-
eral condition, and check the mounting bracket
for cracks or looseness. If possible, check the
capacitor for leakage, capacity, and series re-
sistance.
Par 8-16
Page 8-15