I’ve always been a proponent of wiring being tightly tied down on an RC airplane. You certainly don’t want the wires to flop around and catch on servo arms, linkages and the like. This would likely result in the wires pulling loose, abrading against the internal structure of the plane or just breaking due to repeated bending. Worst of all if the wire starts to break inside the insulation where you can’t see it, the connection is likely intermittent and therefore difficult to troubleshoot.
Usually folks control this by tying the wires to the internal structure with cable/wire ties. These are usually made from flexible nylon with locking teeth built in that make them hold nice and tight and just about impossible to loosen. That’s all well and good but take a look at what happens when you pull these up, perhaps a bit to snug, against your servo wires.
As you can see the insulation on the red and black wire (for instance) has been pinched and cut through down to the conductor. It’s not impossible that somewhere down the road these two wires would touch or simply be cut and as a result a short or open circuit would occur with unfortunate results. Since this is the power lead on an ignition for a small gas engine… at best an open circuit occurs and the engine quits unexpectedly. At worst… well the flaming parts of airplane falling out of the sky probably won’t win you any “Club Member of the Year” awards. (Hey, I did say “worst”)
So my suggestion is this: Continue to use wire ties as needed but only do so with proper protection around the wires. For instance, wrap the wires first in a spiral wire wrap like the material provided by the ignition manufacturer. Then use your cable tie and tighten it down just enough to get a good grip on the wrap material. Something like this:
This wrap is also useful to protect the braided ground wire on the outside of the spark plug lead from getting abraded by the edge of a fiberglass cowl. You only want to protect the necessary part of that lead however as this nylon material is typically not made to withstand the temperatures of your exhaust or cooling fins on a gas engine. Here is an example:
Of course, this is just one option. I’m also a big fan of Velcro but that’s for another post.