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
AC 43.13-1B
g. Examine the points for excessive wear
or burning. Discard points which have deep
pits or excessively burned areas. Desired
contact surfaces have a dull gray, sandblasted
(almost rough) or frosted appearance over the
area where electrical contact is made. Fig-
ure 8-9 shows how the normal contact point
will look when surfaces are separated for in-
spection. Minor irregularities or roughness of
point surfaces are not harmful (see fig-
ure 8-10), neither are small pits or mounds, if
not too pronounced. If there is a possibility of
the pit becoming deep enough to penetrate the
pad (see figure 8-11), reject the contact assem-
bly.
9/8/98
FIGURE 8-11. Point with well-defined mound.
CAUTION: When inspecting the con-
tact points for condition, do not open
further than absolutely necessary.
Excess tension on the spring will
weaken it and adversely affect the
performance of the magneto.
FIGURE 8-9. Normal contact point.
i. Adjustment of magneto point gaps
must be correct for proper internal timing of a
magneto. See applicable manufacturer’s pub-
lications for internal timing procedures.
j. Check the breaker cam to assure
cleanness and smoothness. Check the cam
screw for tightness. If new points have been
installed, blot a little oil on the cam. In addi-
tion, check contact point assembly to ascertain
that the cam follower is securely fastened.
k. If the impulse coupling is accessible,
inspect for excessive wear on the contact edges
of the body and flyweights. In addition, check
the flyweights for looseness on the axles.
FIGURE 8-10. Point with minor irregularities.
h. Generally, no attempt should be
made to dress or stone contact point assem-
blies; however, if provided, procedures and
limits contained in the manufacturer’s manuals
may be followed.
l. Further examination of the impulse
coupling body may disclose cracks caused by
exceedingly-tight flyweight axle rivets.
m. Check the magneto ventilators for
proper functioning and obstructions. If drilled
plugs are used, they should be in the lowest
vent hole of the magneto to serve as a drain for
condensation and oil.
Page 8-16
Par 8-19