Interesting. But I’m skeptical.
I understood that aviation fuel was more flammable than automobile gasoline.
I know from my brother who served on Aircraft Carriers that they took very serious precautions around the ‘avgas’.
Understandable. The Car Talk guys might be great (-ly entertaining) mechanics, but sometimes their science is a bit off. Let’s see what else my google-fu can come up with…
Here’s a long and mostly relevant paper about the merits of carbon fiber that has a few choice quotes:
Bah. That should be irrelevant. That’s pretty much the only mention of tire conductivity in the whole thing.
Your suspicion is correct. They are conductive straps designed ot let any charge that builds up on the vehicle dissipate through the ground. I’ve seen people use metal chains for the same purpose.
The term “grounding strap” is used in a more general sense to mean a wire or piece of metal braid used to ground something. Like this, for example: http://www.international-auto.com/images/originals/ground_strap.jpg
Note that the term “ground” is often used in a somewhat incorrect manner to refer to the common voltage reference of something. For example, a car’s electrical system is “grounded” to the metal frame of the car even though there’s no physical connection to earth ground present. The metal braid connecting the car’s battery to the frame might be called a “grounding strap” even though it doesn’t connect to earth ground.
When civil aircraft refuel, they do not need to be grounded, where the device is attached to the ground to disperse static.
They must, however, be bonded. Bonding is where a cable is connected between the fueling device (fuel truck, hydrant cart, or fixed fueling island) and the aircraft. This equalizes the static charge between both the aircraft and the fueling device, minimizing the possibility of a static spark.
The fueler also does not need to bond or ground him/herself. They are supposed to touch an overwing nozzle to the chain holding the fill neck cap before starting to fuel when filling through an overwing port (as opposed to single-point fueling, where the nozzle is connected to one spot under the wing and fills the aircraft under pressure). Once the nozzle contacts the fill cap chain, the static potentials between the hose and the aircraft are essentially equalized. For single point fueling, they only need to attach the bonding cable to a bonding point on the aircraft, usually part of a landing gear strut assembly. Nothing else needs to be done.
For everything you ever wanted to know about aircraft refueling: NFPA 407 - the document I use to inspect aircraft fueling trucks every month.
As for fueling cars, the filler hose is conductive (next time you fill up, read the embossed writing on the side of the hose). When you touch the nozzle to the fill neck, you’re bonding the car to the dispenser island. That gets rid of the static charge as far as the gasoline is concerned, minimzing the spark potential nearly as much as grounding would, but without the added “inconvienence” of grounding.
Thanks!
When I was working out in Production at the computer factory, we had to place our work on static-dissipative mats and ground ourselves with wrist-straps so static shocks didn’t fry the workpieces. Those straps and mats were tied to earth ground through a high-value resistor (10 megohms or so) so that excess charge would bleed off, but we weren’t connected directly enough for large currents to flow. This also equalised voltage between us, our tools, and the frame of the workpiece.
Planes are no longer required to be grounded when refueling, just bonded. Bonding the plane to the fuel truck equalizes the static between the two vessels, eliminating the chance for a spark.
These are the same type precautions taken when working with explosives. Conductive floor, leg and arm stats to make as much of your body as possible conductive down to the conductive floor so as to reduce your accumulated charge. They are also high resistance so that you are not directly grounded in case you accidently touch the electric power line.
There’re lots of words that usually (not always) are tossed around indiscriminately to mean the same thing, as engineer_comp_geek says. “Neutral” (usually for AC), “common,” “ground,” “earth.” We don’t use “earth” so much in the US, but if the British are consistent in meaning a true earth ground, then I’d nominate it to always mean ground, err, earth potential, rather than “ground” which, as you see, is really just a common.
What do the Brits (Australians, whoever else) use for common? Will the say “earth” when the mean a common that’s not earthed?
Neutral
We also wore conductive smocks. They were blue. I called them Smurfcoats.
Ah, no. The Brits will (or at least they used to) refer cars as bing positive earth or negative earth. In 1968 When the British Leyland changed to a negative ground, MGs came with a very prominent sticker under the hood (bonnet) that said Warning: Negative Earth
Avgas is short for aviation gasoline - it’s gas, petrol. Some of the additives are a little different (avgas is not to have ethanol in it and autogas is not to have tetraethyl lead for example) but on a practical level it’s neither more nor less flammable than what you put in your car. In fact, I’ve flown aircraft that run quite happily on premium autogas, and back when cars took leaded gas they ran quite happily on standard avgas.
I think maybe the 130 octane aromatic fuel might have been a little more volatile and like some of the racing fuels it burned with a barely visible flame. I suspect such fuel is now rare since most of the planes that would have used it are jets. Some of the firefighting aircraft might still require aromatic fuels.
I thought the higher the octane the lower the volatility.
And to clarify, jets burn “jet fuel”, also commonly caled “aviation kerosene”. There are many speciific blends with the common ones in US & Western international usage being “Jet-A” or the military “JP-4”. There ar a few other terms for rare or special purpose blends. At a laymen’s level they’re all not much different from diesel fuel or lantern kerosene.
Jets do not / cannot burn “avgas”, and non-diesel internal combustion engines cannot, period, burn jet fuel.
The fellow upthread who said his friend served on an aircraft carrier & they were being careful with avgas either served during the Viet Nam days or before or something was lost in translation.
then what is JP-5, its jet fuel, but is it the same gas that is in our vehicles?
A word on automotive grounding straps:
I used to see these on about 20% of cars in the 1970s. They looked like a flat black strip of some rubberised material hanging from the rear of the car. I can remember my dad scoffing at them as being “useless”. Given that I can’t recall seeing one for over twenty years, was my dad right?
Really? Hmmm. Maybe someone will be along who knows.
Anyone?