ORIGINAL: preivers
See rule number tree in my previous post. Rephrasing that rule to omit dB: Signals are reduced in strength by the inverse cube of the distance. Meaning, that when a servo is 16"away, its radiation level is 1/16th of the servo placed at 4"distance radiation power level is:
(4/16)^2=0.0625 times. Quite a large reduction, giving the transmitter signal a fighting chance.
I do not know why some plane builders do not care where that nearest servo or receiver connected lead is.
I do know, that Engine and ignition manufacturers advocate as large a distance as is feasible.
From my own background and limited knowledge, I am very much biased to believe the ignition/engine manufacturers. There always will be exceptions to the rule, but that does not change best practice.
It just makes sense to keep your radio system as far as possible from the ignition system. However, I have to agree that if you have a brakedown of the shielding system you will not be safe if you are 8' away. That spark in your spark plug has as much RF energy as the transmitter and it is much closer than the trransmitter.