>A question about shielding.
>
>The manual says the P-leads should be shielded at the switch end only. I
>have noticed production aircraft that have the shield grounded at the mag
>(to the case itself). I know not to ground at both ends or else one may
>produce a ground loop, but is there a reason to use one method over another?
. . . I recommend that the ignition switch shields be used to
produce a ground for the ignition switch and that the shield be
grounded to airframe at the magneto or ignition box. Two reasons
for this:
(1) it insures that no ground loop currents flow in the shield
conductor which degrades its performance as a nose attenuator.
(2) should your crankcase jumper become disconnected and/or
you forget to hook it back up after maintenance -AND- you
try to crank the engine, the starter will seek a ground through
ANY wires that might close the path between battery(-) and
crankcase. If this happens to be your p-lead (or any other
shields/grounds) then you get instant smoke and foul smells
from under the instrument panel. Had two mechanics generate
a lot of work for themselves while I owned the airport at
Benton, KS about 10 years ago . . . not a pleasant sight.
Bob . . .
////
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