NEC in Aircraft Hangars

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madmike

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Article 513 makes no mention of the aircraft service 400-Hz power systems used either within hangars or at airport jetways. <Howcum>? These systems are grounded wye 200/115v, 4-wire services. The problem is that few know that the aircraft electrical systems use the fuselage for a Neutral conductor to save weight. The service cable grounded conductor simply bonds to the aircraft structure at the power service connector shell. Now, the problem is that many of the hangar services are not "derived" systems, so when multiple aircraft are on the circuit, circulating currents may flow. Also, if you connect another service trailer, say an air-conditioner powered from the hangar or airport 480v 60-Hz system, a ground loop is formed between the 60-Hz ground wire and the 400-Hz Neutral, resulting in circulating currents through the aircraft. Shouldn't the NEC address this?
r,
Mike
 
charlie

charlie

Senior Member
Location
Indianapolis
Re: NEC in Aircraft Hangars

I think section 513.10 covers your concerns (italics mine):

513.10 Special Equipment.
(A) Aircraft Electrical Systems.
(1) De-energizing Aircraft Electrical Systems. Aircraft electrical systems shall be de-energized when the aircraft is stored in a hangar and, whenever possible, while the aircraft is undergoing maintenance.
(2) Aircraft Batteries. Aircraft batteries shall not be charged where installed in an aircraft located inside or partially inside a hangar.

Of course, you can't stop there, the rest of 513.10 applies as well. This area is well outside my expertise but it seems to me that you should be shutting the power off to the aircraft whenever possible. :D
 
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madmike

Member
Re: NEC in Aircraft Hangars

charlie, earlydean,

All true guys, but I would hate to have to board a plane and find my seat in the dark, with no A/Cs running in the summertime.

And since today's aircraft are becoming mostly fly-by-wire, it bothers me to know that the neutrals are grounded to the fuselage. If this were a mobile home, it would be considered a fire hazard. Granted, NEC sez de-energize where ever possible, but this seems to dodge the issue. I think if the Code folks knew the situation, they would require individual derived systems for aircraft ground power. Scary to think this is a fuel tank crammed with computers and people, with load current flowing through the structure.
r,
Mike
 
charlie

charlie

Senior Member
Location
Indianapolis
Re: NEC in Aircraft Hangars

Let's see, how do they wire automobiles? I don't know about modern cars but the old ones used the chassis and I don't remember my cars blowing up on me. HMMM

How safe are the large aircraft around lightning? Doesn't it hit planes on a regular basis? HMMM

90.2(B) Not Covered. This Code does not cover the following:
(1) Installations in . . . aircraft, or automotive vehicles . . . HMMM :D
 
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