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toddheffley
Joined: 24 Mar 2010 Posts: 8 Location: Fort Worth Texas
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Posted: Fri Dec 17, 2010 6:43 am Post subject: (off topic) Aircraft Ground to the hangar floor when parked |
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ALL
Sorry for the distractor... but I am on a quest for "Simple Science" FACTS to rebuff some "Hanger Talk" about grounding aircraft when parked.
MOST military, some heavy maintenance bases , and a few General aviation facilities provide and use ground wires to the hangar floor when aircraft are parked.
Why is that so???
The reasons I have gathered are:
1. "Grounds Out" static electricity when the aircraft is being polished (sounds reasonable)
2. "Grounds Out" the airplane if the hangar is struck by lightening (sounds like hanger talk)
3. Reduces Galvanic corrosion by dissimilar metals in the landing gear. ( sounds like hanger talk)
4. Provides path to ground in the event of a 220VAC Ground Power Unit being wired wrong and/or failure of the Green ground wire from the Mains supply (sounds reasonable). This has been witnessed by one our staff.
5. Reduces chances of damage to ESD components, for example, when removing Printed Circuit Cards from cages. (sounds reasonable)
6. Some Hanger Keepers insurance policies require it. (I have yet to see one...hanger talk)
7. And finally, the most common answer.... Because the Army told me to ground the airplane 30 years ago and I have been doing it ever since........(hanger talk accepted blindly with no supporting rationale)
The accepted norms from several (Military) documents are: <10K Ohms to SOIL.... and/or ~MilliOhms to the Electrical grounds in the building Mains Supply.
I figure with the brain power and diverse backgrounds here on the list, SOMEONE should be able to add real knowledge to this subject.
Anyone?
Todd Heffley
Maintenance/Avionics background only..... plus a Champ restoration.
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Float Flyr
Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Fri Dec 17, 2010 7:27 am Post subject: (off topic) Aircraft Ground to the hangar floor when parked |
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If all aircraft in a hangar are bonded (grounded) to a common ground there
is no chance of a spark occurring between aircraft and all static is
immediately sent to ground.
The AMO (Authorized Maintenance Organization - Canada) I worked for did in
fact have a stipulation on the insurance requiring all aircraft on the
premises be bonded to ground, even the ones tied down outside. I never
actually saw the policy but I was told by the owner of the company such a
stipulation was in effect. On one occasion the insurance company did send
an inspector and he did check for grounds on all aircraft that may have fuel
in them.
Noel
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lm4(at)juno.com Guest
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Posted: Fri Dec 17, 2010 8:40 am Post subject: (off topic) Aircraft Ground to the hangar floor when parked |
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Tod,
I'll take a shot at this.
On hot,and particularly dry, days the fuel in the tanks will heat up and push the fumes out of the vent. The fumes, being heavier than air, will sink to the ground, asphalt, concrete or whatever. Should you rub against the plane or hit something that will make a spark there is a fair chance the spark will detonate the fume buildup on the ground. If the plane is grounded it will not contribute to a spark. I hope.
Larry
On Dec 17, 2010, at 9:43 AM, toddheffley wrote:
Quote: |
ALL
Sorry for the distractor... but I am on a quest for "Simple Science" FACTS to rebuff some "Hanger Talk" about grounding aircraft when parked.
MOST military, some heavy maintenance bases , and a few General aviation facilities provide and use ground wires to the hangar floor when aircraft are parked.
Why is that so???
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If you owe under $729k you probably qualify for Obama's Refi Program
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Geoff Heap
Joined: 12 Jan 2006 Posts: 266 Location: Lindenwold, New Jersey
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Posted: Mon Dec 20, 2010 11:58 am Post subject: Re: (off topic) Aircraft Ground to the hangar floor when par |
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This would explain all the exploding hangars all over the country...Geoff
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