Question about power sockets in airplane cabin

Thread Starter

YokoTsuno

Joined Jan 1, 2013
43
Question for aviation experts.

I noticed that the power sockets in an airplane cabin for plugging in your laptop have a hole for earthing pin. Is this actually connected to the frame of the airplane?

If this is the case I presume the aircraft mains voltage is distributed in a TN configuration including RCD instead of IT?
 

Tonyr1084

Joined Sep 24, 2015
6,383
I figured you would "Probably" say that.
I was hoping not to see the word probably.
Aircraft in flight generate static charges. I've seen arcs of static across the hubs of two C-130 engines and their spacing is a good 12 feet or more. I don't know the actual measurement, but I've seen in hot dry dusty conditions a blue arc reaching from the hub of one turbo-prop to the adjacent. You would think it would pass more easily through the fuselage but I can only recount what I saw.

The reason for grounding the ground pin isn't to "GROUND" the plane it's to provide a common ground point which is equal in charge to the aircraft exterior. During refueling the aircraft is first grounded, then the fuel cart is grounded. Then the fuel cart is grounded to the aircraft. I've seen guys disconnect the aircraft ground after the engines have been started. He does so by connecting a rope with a clamp at the end; clamp it to the ground connection on the aircraft, get a good 15 feet away and then yank the ground out, drop the cord and run. Hey! It's what I've seen on the flight line at an aircraft refurbishing plant in Ontario California. That was back in 1980 and 81.

Grounding the outlets to aircraft body reduces the chances of electrical shock from some astonishingly high voltages which can damage electronics and avionics. Two pronged devices don't need to be grounded because they are double insulated. Same as your electric plug in drill or saw. Grounding would be necessary only if your case could become conductive and present an electrical potential to the user. That or static mitigation. That's the reason for the ground pin. Common Ground.
 
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