P-lead splicing

[glenn654]

Is it acceptable to splice a P-Lead?


Glenn Wilkinson

[Rick S.]

Since the lead is a shielded wire I would caution against it.

Here is what Aeroelectric connection says about the P-lead.

"Note that I show shielded wire between the
magnetos and the magneto switches. Spark plug wires and
magneto p-lead wires are the ONLY wires in the airplane
which are ALWAYS shielded. Further, p-lead shields should
be grounded to the airframe/engine only at the engine end. The
shield is used to provide a ground for the "GRD" terminals at
the switch but no other connection to the shields should be
made at the instrument panel end.
Noise sources, noise victims and noise propagation control is a
large topic for another time. For now, understand that shielded
wire has limited capability and reduces or eliminates only two
of three common noise propagation modes in vehicular power
systems. Shielding of most other wires in an airplane, unless
specifically recommended by equipment manufacturers, is
unnecessary"

[lrfrey]

Shielded wires can be spliced, but must be done with care so as to insure there is no short between the wires. The easiest way to do this IMO is to "push back" the shield a fair ways after striping to allow a piece of shrink wrap to be slid over one of the center wires. The center wires are then spliced and in this case must be lightly soldered before the heat shrink is slid over the splice and shrunk. (I don't want to hear about no solder joints in an airplane ).

The shields are then slid back together and sort of "hand woven" back together. A larger piece of heat shrink is then slid over the entire cable and shrunk. Since this joint is not as prone to vibration as a wire soldered to a fixed plug etc and the external shrink tube is acting like a damper, there should not be a large problem with the joint failure.

Having said all this, for the price of the wire and the short amount needed, I would opt for a single, jointless wire. Just my experience.

Larry