Dear Sprocket,
What you say is true however on the 214 the magnetic field was so strong that the two standby compasses both pointed towards the centerline of the aircraft sort of looking cross eyed. They were also very slow to respond and they never would point in the correct direction. Another problem on the 214 was the pilots had difficulty in operating their VOR. Bell stated that it was due to rotor flicker interfering with the radio frequncies. They told the pilots that when they wanted to use the VOR they should slow the rotor down almost to the point that the helicopter would want to fall out of the sky. I don't know if Bell was correct or the problem was caused by the high magnetic field.
The problem stemmed from the fact that on the Bell heads that had elastomeric teeter bearings the rotor head was isolated from the mast by the rubber bearings and there were no bonding straps. It is normal for static to dissipate to the fuselage via the transmissions but with the highly magnetized masts the electrical currents are stronger.
We also found the problem on a 412 rotor head and mast, only in this case, the blades were isolated from the mast by the elastomeric elements in the rotorhead.
I presented this problem on another forum and one individual quoted an engineer friend who said that the oil was an insulator.
Technically it is but oil in a helicopter transmission is not pure oil as it has wear metals in it and that is why you do a SOAP analysis on the oil. Also the oil in its' pure form has what is called a puncture voltage. When the voltage differential is high enough the spark will travel from one point to another puncturing the oil to get there. In order to do that the voltage has to build up much like the spark plug in an engine only, not as high a voltage. This build-up causes the spark to be stronger and effecting the discharge wear to a greater extent.
I have seen an engineering demonstration where a bearing on a shaft suffered from static discharge erosion and the electrical potential was supplied by a small battery that could be used in a Sony Walkman.
Spark discharge erosion is common in transmissions
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The Cat