Servicing Seabee pitch trim system
This is a discussion of the Seabee pitch trim system cables, how to
service and maintain them.
The fundamental problem is that the cables are routed inside a metal
bowden sheath, and the failure mode is going to be internal.
At some point in time, one of the wires of the 1/16 cable is going to
wear enough to the point that it will break. During the normal operation of the trim system,
that broken wire is going to unwind, double back on itself, and jam the trim system.
You have to keep in mind that this is inevitable. It is only a question
So, what do you do?
The first thing is to get those cables out of your airframe and clean
and service them. After they are pristine, you can examine them for
The easiest way to clean the trim cables is the kerosene routine as
outlined in the instructions for servicing push-pull controls.( __here__ )
Once the cables are cleaned up and free of all foreign material, you
should carefully examine the individual strands of wire. This really
has to be done with a 5X loop. Closely examine the wire where it
exits the sheath. The only visible signs of wear will appear
If you see wires that are worn to the point that the flat is as wide
as the strand, that means the wire is now 1/2 it's thickness. The
internal cable must be replaced.
What you have to keep in mind is you are looking at the only portion
of the wire rope where damage is visible. Just think about the strands
inside the sheath, where it has been rubbing against the inside of the
metal sheath. If what you can see on the outside is poor, the inside
Lets suppose there is no visible wear. Now what?
You have to get these parts absolutely clean internally, and
lubricated internally. The fact that you have removed the cables, and
the roller chains, and moved everything about, means you have
repositioned the wires internally with respect to the sheath. This
will serve to redistribute the wear points, and the cables should last a
The disassembled cable should move freely inside the sheath with no rough
spots or binding whatsoever. If you feel any snags, the wire rope has
to be replaced.
What about the sheath? It will be rusted, and some of the coils might
be somewhat open. As long as the sheath is still elastic enough that
it can be reinstalled, it can probably be reused. It only serves as a
guide for the wire rope. But if it is so rusted that bending the
sheath breaks it, it will have to be replaced.
This may seem like a lot of effort to attend to something that works
now, but it really has to be done. The downside risk is just too
Link back to Servicing Push-Pull Controls