[sirlegin]

I was recently enjoying lunch outside at the Blue Cafe at 52F when a pretty Glasair pulled up to the fuelling station. The pilot unrolled a preformed rubber sheet from a towel, placed it over the fuel tank and proceeded to fill up without grounding the plane. I asked nicely if the rubber mat made it that the plane didn't still necessitate grounding to which he stated that an all fiberglass plane does not require grounding.
If anything, I would have thought that a fiberglass plane would generate more static than a metal plane? Needless to say, I finished lunch in one piece and the cafe is still standing.
Anyone have any thoughts on this grounding issue?

 

[Ron Lee]

I do not know but I saw a Cozy refuel today and he had a cap that attached to the plane fuel tank innards with a chain. He then connected a wire from that chain to the fuel pump nozzle.

 

[tomwebster]

I had an experience at Winston-Salem (KINT)
where the re-fueler said they couldn't use the
exhaust pipe for grounding. They refueled
my RV-7A after I screwed in one of the wing
tie-down rings for their grounding. I have
wondered after that if the exhaust is a reliable ground.
If pulled in parallel to fuel pumps, I usually ground to
the tail tie-down ring but don't know if it is necessary.
Tom

 

[noelf]

Composites make an excellent insulator...

...and as such can "store" a considerable static / electrical charge. The only real discharge path when on the ground is through the tires to ground...or through the fuel nozzle when the conditions are right, or through the pilot/passenger when stepping from airframe to ground. It is the classification of the "right" conditions that can cause the problems. And if the composite materials have acquired some static charge, there is no real total surface discharge even though part of the airframe is locally discharged.

Aircraft static discharge fires are real, and I have a severely burned and disfigured friend to always remind me of the probabilities.

As for grounding the exhaust stack...in an absolute-theoretical-sort-of-way...
I can see where there is a possibility of a problem. If one were to attach the fueling hose grounding wire to the end of the exhaust stack, and the exhaust system had slip joints, and if the slip joints were somewhat insulated with non conductive oil residue, then there may not be a "low" enough resistance path for any built-up static to fully discharge.

Or, what if for some reason the engine case was not grounded, as in a hand-prop, no electric system Cub might be. Grounding the airframe seems the best solution for all situations, but then there will always be the exception.

 

[Walt]

I had an experience at Winston-Salem (KINT)
where the re-fueler said they couldn't use the
exhaust pipe for grounding. They refueled
my RV-7A after I screwed in one of the wing
tie-down rings for their grounding. I have
wondered after that if the exhaust is a reliable ground.
If pulled in parallel to fuel pumps, I usually ground to
the tail tie-down ring but don't know if it is necessary.
Tom

I often use the pitot tube, it would be easier than digging out the tie-downs.

 

[jetjok]

I had an experience at Winston-Salem (KINT)
where the re-fueler said they couldn't use the
exhaust pipe for grounding. They refueled
my RV-7A after I screwed in one of the wing
tie-down rings for their grounding. I have
wondered after that if the exhaust is a reliable ground.
If pulled in parallel to fuel pumps, I usually ground to
the tail tie-down ring but don't know if it is necessary.
Tom

Hello Tom!
I am sure that there are lots of opinions, but here is my .02. The exhaust stack definitely provides great continuity to the engine, and the bonding strap that surely everyone has, from the engine to the airframe means that the exhaust stack is a perfectly fine place to ground.
Take Care!

 

[rv9aviator]

I once had a conversation with our airport safety person about the danger of fueling with plastic gas cans as they are more prone to static than steel gas cans. Looks like the same logic would apply to composite airplanes.

 

[txaviator]

Sirlegin...

I also wondered the same thing...why? I saw you and your buddy eating lunch outside at the picnic tables, as I drove into the parking lot. I saw the aircraft in question when it began its taxi from the southern end of the field. I was in the white, four-door Chevy truck that rolled past you guys, and parked just to the north of you. I wanted to see the Glasair lift off, and when he stopped for fuel first, I noticed (and wondered) the exact thing you did!

I was thinking that you and your buddy were the ones who flew in in the C-172 a few minutes before? (if so, DARN nice slip on final )

Good observation on the Glasair, and great question you have posed to the group!

Take care,

 

[KRviator]

From my old Army Aviation days, the reason for grounding (as opposed to bonding) is to dissipate any static charge the aircraft has developed in flight prior to the removal of the fuel caps.

Any static charge the aircraft is holding will be immediately grounded when you place the nozzle into the filler port if you haven't already grounded the aircraft. Naturally bad things then tend to happen if it is a hot day and fuel vapours are present.

The small earth strap on the fuel gun is (technically) a bonding strap, that is used to dissipate any static charge that builds up (between the aircraft and the fuelling equipment) during the fuelling process as a result of the fuel being moved rapidly across the rubber hose.

It also serves double-duty as a backup to the normal ground strap (which in turn does double-duty in case the internal metal windings in the fuel hose seperate and then fail to provide a conductive path from the fuel gun to the hose reel and bowser).

That Glasair pilot is completely misinformed. ALL aircraft need to be grounded and bonded to the refuelling equipment before the removal of the fuel filler caps.

 

[Calvin25]

Would it work to check the ohm's from the exhaust tip to the bare aluminum on the inside of a tank?

I would think that would give you a 100% accurate indication of a true ground.

 

[RVbySDI]

That Glasair pilot is completely misinformed. ALL aircraft need to be grounded and bonded to the refuelling equipment before the removal of the fuel filler caps.

Well, I am going to serve as devil's advocate for a minute.

The question is this (sayeth the devil): Why is it important to ground our aircraft when we refuel but not important that we ground our automobiles when doing the same thing?

Ok, second question; If the person fueling the aircraft is standing on the ground and is touching any metal component on the aircraft is he not supplying a ground circuit for discharging any static electricity? In deed, this is what is preached to the auto fueling masses when they are fueling their cars. It is recommended that before one grabs the pump hose one should ground oneself effectively by touching a metal part of the car which should then appropriately discharge buildup.

These are the "Devil's" thoughts so what say you?

 

[Larry Stokes]

Grounding

Well, I am going to serve as devil's advocate for a minute.

The question is this (sayeth the devil): Why is it important to ground our aircraft when we refuel but not important that we ground our automobiles when doing the same thing?

Ok, second question; If the person fueling the aircraft is standing on the ground and is touching any metal component on the aircraft is he not supplying a ground circuit for discharging any static electricity? In deed, this is what is preached to the auto fueling masses when they are fueling their cars. It is recommended that before one grabs the pump hose one should ground oneself effectively by touching a metal part of the car which should then appropriately discharge buildup.

These are the "Devil's" thoughts so what say you?

Well, I have been a electronics tech most of life and I WOULD AGREE, with your statement.
But, for SAFETY SAKE, I always ground the aircraft, mostly because I know there are GREMLINS out there to make your day terrible.

 

[DEWATSON]

I always ground to the exhaust stack and I always touch the fuel nozzle to the fuel cap before I take it off. If it's going to spark, it will do it with the cap on and the fuel enclosed away from the spark. In 29 years of fueling aircraft, I've never had one spark, BUT I'm going to keep doing it.

 

[Rick S.]

Just recalling the old USAF guidance regarding fueling, when you connect the fueling vehicle to the aircraft it is bonded not grounded together.

Second every aircraft I have worked on had a dedicated grounding points similar to a stereo plug jack except with a solid metal plug that connected to a ground wire that would plug into the aircraft.

Lastly the fuel truck and the aircraft were grounded with the "triangle" method, wherein the truck and airecraft were attached to the same earth ground in the ramp, and the truck had an additional ground cords that ran to the aircraft creating a triangle.

The sequence of who gets connected to where first must have changed 4 times over the years I worked on them.

On auto fueling, the hose is conductive and grounded from the nozzle to within the pump, when you touch the nozzle to the inlet I understand it grounds and bonds the pump the the fuel tank. IIRC.

And yes static charges can pack a whollop...I was heading to take out the impulse carts from a centerline rack on an F-4, as I headed in I ran my hand across the fuel tank and bam...huge shock, then I crawled back out and completed the checklist, step one, aircraft positioned, chocked and GROUNDED...The impulse carts in bomb racks are electrically primed, coulda been worse, lesson learned and never did that again.

 

[Caveman]

Try this link

I was recently enjoying lunch outside at the Blue Cafe at 52F when a pretty Glasair pulled up to the fuelling station. The pilot unrolled a preformed rubber sheet from a towel, placed it over the fuel tank and proceeded to fill up without grounding the plane. I asked nicely if the rubber mat made it that the plane didn't still necessitate grounding to which he stated that an all fiberglass plane does not require grounding.
If anything, I would have thought that a fiberglass plane would generate more static than a metal plane? Needless to say, I finished lunch in one piece and the cafe is still standing.
Anyone have any thoughts on this grounding issue?

Scroll down at this link. Go to the fuel handling safety report, 4th one down. It answers most of your questions.

http://cafefoundation.org/v2/research_reports.php

 

[TThurston]

Wool Jacket

In cold weather, I normally fly with a wool jacket. I believe that wool tends to build up static, and I've seen and felt sparks from wool in cold dry weather. I've wondered if I should be concerned about my jacket as a potential source of static discharge sparks when fueling.

 

[Mel]

A word of caution here!

I always touch the fuel nozzle to the fuel cap before I take it off. If it's going to spark, it will do it with the cap on and the fuel enclosed away from the spark.

This could be a "not good practice" for a vented fuel cap.
It's the fumes that are explosive, not the liquid fuel.
You might try touching the nozzle to another part of the aircraft instead of the fuel cap.

 

[sirlegin]

Glasair specific

It would appear that when all is said and done, all planes regardless of material should ground the frame during re fuelling. As Mel stated the fuel vapor is the combustible agent for sparks.
This site explains how the Glasair tank has a strap built into the tank which connects it to the landing gear for grounding I believe. It helps when you build your own plane as you are familiar with every component.
http://www.contactmagazine.com/Hangar_Talk/August-08/Fuel-Tank-Bonding.html
Thanks for all the responses. I may suggest to the Blue Cafe folks to put a sign saying mandatory grounding so their nosey patron(s) can enjoy their great food without worrying about being blown up.
Besides which, my RV9A is almost complete.

 

[jetjok]

No pun intended here. But, to add fuel to fire here is another point that has not been mentioned.
Another reason for grounding the aircraft and keeping the nozzle grounded is that flowing fuel will generate a static charge and could generate a spark. This is not a huge issue in most places, but when there is lots of static in the air, there is a possibility of a spark.

 

[ddurakovich]

Another reason for grounding the aircraft and keeping the nozzle grounded is that flowing fuel will generate a static charge and could generate a spark. This is not a huge issue in most places, but when there is lots of static in the air, there is a possibility of a spark.

Actually, this is a huge issue anywhere solvents are transferred.

I have been personally involved with 2 static discharge explosions over the last 35 years. Fortunately, there were no significant injuries in either incident, but substantial loss of property and business interruption. The possibility of serious injury or death was very real. We were very, very lucky in both cases. I am also very familiar with explosions from similar circumstances that resulted in multiple deaths.

The chemical industry has been dealing with the issues of static induced explosions for decades, and have come up with very specific requirements for the transfer of flammables from container to container, tanks, and vehicles. OSHA, NFPA et. al. have very specific criteria for the handling of flammable liquids. This is not a random, isolated issue amongst aircraft operators.

The use of static chains on trucks to dissipate static charges while running down the roads have been generally considered of little real value, but doing no harm.

The equalization of potential across the two transfer points is what is required, both before starting the transfer, and during the transfer. A substantial amount of charge can develop during the transfer process, hence the need to maintain the bonding circuit. And while the term "grounding" is not entirely accurate, it is does apply to tank farms systems where the tanks are interconnected.

It has been found that the greatest static charge occurs on the droplets of solvents that are free falling through the air. The smaller the droplet size and the greater the freefall distance exacerbates the issue. Good engineering practice dictates that a downcomer pipe extend to the bottom of the the receiving tank so that while filling, the liquid is being introduced below the liquid surface to reduce static charge development. The same technique is used in transport tankers that handle flammable liquids.

When filling your tanks, make sure that the nozzle is below the surface as much as possible.

Dry (low humidity) conditions aggravates the development of static charges. You guys in the desert are much more susceptible than the guys along the gulf coast.

But we are all at risk!

 

[az_gila]

For a long time....

......
The question is this (sayeth the devil): Why is it important to ground our aircraft when we refuel but not important that we ground our automobiles when doing the same thing?
.......
These are the "Devil's" thoughts so what say you?

...ago, from my high school days, we were told that auto tyres (school in England......) had carbon in their composition so static charges would not build up on the car. It was explained more in a electrical storm scenario, but would still be effective for fuelling.

I don't think our plane tires are made the same way...

gil A - in Bardstown, KY