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Electricity Over Glass

CmdrTaco posted more than 6 years ago | from the still-no-sandwiches-over-plastic dept.

Power 187

guddan writes "Running a live wire into a passenger jet's fuel tank seems like a bad idea on the face of it. Still, sensors that monitor the fuel tank have to run on electricity, so aircraft makers previously had little choice. But what if power could be delivered over optical fiber instead of copper wire, without fear of short circuits and sparks? In late May, the big laser and optics company JDS Uniphase Corp., in San Jose, Calif., bought a small Silicon Valley firm with the technology to do just that."

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Is this needed? (4, Insightful)

inject_hotmail.com (843637) | more than 6 years ago | (#21724500)

"Running a live wire into a passenger jet's fuel tank seems like a bad idea on the face of it. Still, sensors that monitor the fuel tank have to run on electricity, so aircraft makers previously had little choice. But what if power could be delivered over optical fiber instead of copper wire, without fear of short circuits and sparks? In late May, the big laser and optics company JDS Uniphase Corp., in San Jose, Calif., bought a small Silicon Valley firm with the technology to do just that."

What, no one ever heard of vacuum lines? Or maybe pressurized lines? I'm not a rocket scientist, or even a plane scientist, and I could figure that out before I was finished reading the frickin' summary, let alone the frickin' article.

People love to make work for themselves...

Setting that aside, the idea sounds awesome!...what with all the planes we lose every year to short-circuiting wires...BUT, I'll wait to see if this materialized before I get all excited about it.

Re:Is this needed? (5, Insightful)

morgan_greywolf (835522) | more than 6 years ago | (#21724550)

Who even says that the sensor necessarily needs to be fully electronic? You can have a mechanical piece that sticks in the fuel tank and have an electronic control piece that's outside of the fuel tank. In fact, this is exactly how the gas gauge in your car works [howstuffworks.com] . This design has, quite frankly, worked well for decades. Sure there's a few disadvantages, but, uh, who cares?

Re:Is this needed? (0)

DeeQ (1194763) | more than 6 years ago | (#21724594)

Who even says that the sensor necessarily needs to be fully electronic? You can have a mechanical piece that sticks in the fuel tank and have an electronic control piece that's outside of the fuel tank. In fact, this is exactly how the gas gauge in your car works. This design has, quite frankly, worked well for decades. Sure there's a few disadvantages, but, uh, who cares?

And Plenty of people run out of fuel while driving the cars. Last thing we need is airplanes falling out of the sky.

Re:Is this needed? (1)

somersault (912633) | more than 6 years ago | (#21724796)

That's because they forget to fill up their tanks, numbnuts. I doubt transatlantic pilots get halfway across and go "oh shit honey, I forgot to fill up the gas tank again!! >.". They have people for that kind of thing.

Re:Is this needed? (5, Funny)

Hitto (913085) | more than 6 years ago | (#21724902)

You trust PEOPLE more than machines?
Hand over your geek card!

Re:Is this needed? (0)

Anonymous Coward | more than 6 years ago | (#21725122)

you propose a plane that fills itself?

Re:Is this needed? (1)

somersault (912633) | more than 6 years ago | (#21725294)

Actually they already have those, but if we keep giving human jobs to machines then we'll have nothing left to do but eat and have sex.. hmm..

Re:Is this needed? (3, Funny)

Rulke (629278) | more than 6 years ago | (#21725478)

I really doubt that there would be an "again!!" in that sentence ;)

Re:Is this needed? (0)

Anonymous Coward | more than 6 years ago | (#21725262)

That's because they think they have enough to get where they're going, despite the gauge reading E. I've never heard of some one running out of gas when the gauge was not on E.

Re:Is this needed? (4, Informative)

Renegade88 (874837) | more than 6 years ago | (#21724626)

I've replaced the gauge on a mid-eighties Buick a number of times and I can tell you live wires go into the gas tank. The transducer was a one-piece unit. Did you ever consider there is more than one way to design something? Your point, therefore, is invalid.

Re:Is this needed? (3, Informative)

schnikies79 (788746) | more than 6 years ago | (#21725300)

Unless they have changed something very recently (in the last couple of years), the guage controlling unit is inside the tank, wires and all. The only thing outside is the plug to go into the wiring harness. I've changed plenty of sending units.

The wires for your electric fuel pump are inside the tank too.

Re:Is this needed? (1)

schnikies79 (788746) | more than 6 years ago | (#21725604)

Oh yea, I forgot to add that the electric fuel pump is itself submerged in fuel to keep it cool. It's not a fully sealed unit either.

Oh course when you run your tank low the pump is above the fuel level.

Avionics Tech Saves /. (5, Informative)

WED Fan (911325) | more than 6 years ago | (#21725318)

Speaking as a former USAF Avionics Specialist, who worked on C-5's, C-141's, and C-130's, and who personally saw a parked C-141 burst into flames on the ramp because of a fuel probe maintenance accident, let me explain things simply.

Design considerations:

  • There are many fuel tanks on an air craft.
  • The criticality of accurate fuel readings in any attitude is much higher than with any other vehicle on the planet.
  • Large tanks have many 8+ fuel probes running into them. Some have 12+.
  • The criticality of fuel quality readings in the tank is very high.
  • Weight and simplicity are a vital factor.
  • The system has to work in extreme temperatures.
  • The system has to work in extreame teperature changes over short periods of time.

JP4, the fuel that makes most jets run, is difficult to ignite. It needs a heat source. You could run a bare wire into a full tank and not have a problem. However, heat that wire up, and get the fuel/air mixture just right, and you have a problem. Big Boomba Problem, to quote JJB.

The big problem is the mostly empty tank and exposed heat sources. The C-5 has a nitrogen purging system. Basically, as fuel empties from a tank, it is replaced by nitrogen. The only way that wing is going to explode is if something other than a bare wire acts on it. Then, you've got bigger problems.

The big problem comes when you open the tank for maintenance. So, there are massive safety considerations. The C-141 that exploded in the mid-90's at Travis AFB in California blew because a jackass tech did not follow lockout/tag out procedures. The 141 doesn't have the nitrogen purge, but the tanks were open anyway. Two senior specialists were standing on top of the aircraft when the wing blew. Several others were in the cargo box. Luckily, aside from bumped elbows and bruised body parts, everyone got out o.k. We towed nearby aircraft to safer distances. There was precious little left of the burnt aircraft that identified it as such.

Most amatuers could make a good guess at a practical design for fuel sensors, but most of the solutions developed as such will end up being to costly, too heavy, will introduce other problems such as high maint., or simply won't work in 3-d, or extreme temperatures.

Re:Is this needed? (2, Informative)

JonTurner (178845) | more than 6 years ago | (#21724588)

>>Running a live wire into a passenger jet's fuel tank seems like a bad idea

Why? it's extremely difficult to ignite liquid gasoline, or jet fuel. An air-fuel mix ignites quite easily, however. So moral of the story: if you're paranoid that wires in your fuel tank are freyed, keep your fuel tank full. Or get your crappy car fixed.

(In fact, nearly every automobile built in the past 20 years has not one, but two powered devices in the fuel tank -- a fuel pump and a level sensor.)

Re:Is this needed? (1)

MortenMW (968289) | more than 6 years ago | (#21724602)

When jet-fuel gets warm, some of it turns into gas. Gas is unstable and very easy to ignite...

Re:Is this needed? (3, Insightful)

Gregb05 (754217) | more than 6 years ago | (#21724764)

Not without oxygen it isn't.

So what replaces gas when it's pumped out (1)

Nicolas MONNET (4727) | more than 6 years ago | (#21725590)

Has to be air, doesn't it? 20% oxygen, from what I hear.

Re:Is this needed? (0)

Anonymous Coward | more than 6 years ago | (#21724866)

When jet-fuel gets warm, some of it turns into gas. Gas is unstable and very easy to ignite...

All gases are easily flammable!

Maybe planes should do something to counteract the risk of jet fuel getting too warm. Like flying in the upper atmosphere.

Re:Is this needed? (2, Insightful)

Chrisq (894406) | more than 6 years ago | (#21724914)

All gases are easily flammable! Carbon dioxide? Nitrogen? Argon?

Re:Is this needed? (4, Funny)

jrp2 (458093) | more than 6 years ago | (#21724978)

"All gases are easily flammable! Carbon dioxide? Nitrogen? Argon?"

I doubt it is "easy" to ignite steam ;)

Re:Is this needed? (2, Insightful)

Captain Nitpick (16515) | more than 6 years ago | (#21724918)

Why? it's extremely difficult to ignite liquid gasoline, or jet fuel. An air-fuel mix ignites quite easily, however. So moral of the story: if you're paranoid that wires in your fuel tank are freyed, keep your fuel tank full.

One cannot keep the fuel tanks on any operating vehicle continuously full without shape-changing tanks. Even if one allows for a partial drop in fuel level (with the resulting fuel-air mixture being too rich to burn), this will result in reduced range, and hauling a lot of extra fuel around.

Better to remove potential ignition sources from the tank.

Re:Is this needed? (5, Insightful)

TheBearBear (1103771) | more than 6 years ago | (#21724880)

What, no one ever heard of vacuum lines? Or maybe pressurized lines?

I'm no rocket scientist either, and I'm sure that those rocket scientists has already consider those options you've mentioned. Perhaps because it is on an airplane going over 500mph and you have all sorts of physics and temperature considerations that vaccuum/pressurized lines are just not best suited for.

Re:Is this needed? (1)

vertinox (846076) | more than 6 years ago | (#21724992)

What, no one ever heard of vacuum lines? Or maybe pressurized lines?

1. Airplanes often travel at 30,000ft which may make it more difficult to do this on the wings (where they keep the fuel)
2. Airplanes have a whole problem with weight versus lift ratio. If you can squeeze a few more passengers by using fiber optics instead of the gear required for the pressurized/vacuum lines then the Airline executives would prefer that.

Old, ignorant, and out of touch with ... (5, Funny)

Futurepower(R) (558542) | more than 6 years ago | (#21725346)

OLD: The deal was finished on May 26, 2005 [compoundsemi.com] . The article referenced by the Slashdot story is from October 2005.

NOT NEW TECHNOLOGY: They are merely piping light using fiber optics, and then using the light with photocells to create small amounts of power for use with measuring devices. The measurements are communicated back through the fiber optics, using a different wavelength.

PATENTS? The article says, "Photonic Power owns key patents..." Can the generation of power using light be patented again? Can sending information using fiber optics be patented again? Maybe the company has patents, considering that the U.S. government has become corrupt, but it is difficult to believe that any patents could be valid.

IGNORANT: See this quote from the article referenced in the Slashdot story: "... the company's fastest growing sector is currently electric power transmission. One important application is eliminating the transformers used to step down high currents and voltages to measurable levels."

The article should have said, "... the company's fastest growing sector is currently powering and connecting the measuring devices used in electric power transmission."

The writer does not understand that the idea does not change the measuring system, only the method of transmitting the data. If step down transformers are part of the method of measurement, they will still be required. The "senior research analyst" who was quoted, Vincent Lui, doesn't understand that, either, apparently.

REALITY RULES: If you play video games too much, your brain will become partly useless for other things, and, if then try to be a Slashdot editor, you won't be able to do a good job. (This is a theory that seems to fit the facts.)

This is a useful idea for computer professionals in some cases where voltage isolation is needed, but the Slashdot story was mishandled, as often happens.

Re:Is this needed? (2, Informative)

russ1337 (938915) | more than 6 years ago | (#21725410)

What, no one ever heard of vacuum lines? Or maybe pressurized lines?


Aircraft are required to operate at various altitudes (which have various temperatures and pressures) making compensating for differences in pressures and temperatures in a system that requires vacuum lines more difficult (and more difficult to maintain and keep calibrated). Early aircraft had a sight glass on the outside of the tank, but these are only good for reading volume and at a specific aTTitude (i.e on the ground) intrinsic safety [omega.com] is a well understood practice within electrical engineering and has proven to be extremely safe and reliable when proper maintenance and operational maintenance procedures are used.

Modern aircraft fuel quantity measurement is through it's capacitance, as this compensates for temperature / volume, when it is the 'mass' (and hence energy) of the fuel decides which just how far you will fly. You are only interested in the mass of the fuel.

what with all the planes we lose every year to short-circuiting wires.
I don't recall this happening very often. Last one i remember was the center tank on an airliner that they suspected had developed a fault, and also had NO fuel - (blamed the vapor) but IIRC the fault being pinned on the fuel measurement system was not conclusive... I think they looked more closely at the fuel pump which normally sits submersed in the fuel with the electrics outside the tank. Run a pump dry and it gets hot. Heat + Oxygen + ignition source (vapor) = boom.

Re:Is this needed? (2, Interesting)

kestasjk (933987) | more than 6 years ago | (#21725532)

I watched a documentary about the only case I know of where a plane went down due to a short circuit in the fuel tank, and after I tell you how it happened maybe you'll see why this new tech will be a welcome addition to aircraft safety.

I think it happened a few months after 9/11 and happened to a plane leaving JFK airport, so everyone initially assumed it was terrorists. (Just to help jog anyone's memory, not making a point here)

IIRC the power cables that went into the fuel tanks weren't at a high enough voltage to cause sparks, which is what makes sense of course. The problem was that there were two short circuits; one was a short circuit in the instruments in the fuel tank, and the other was a short circuit in the main power cables which run down the plane.
One of the short circuits caused there to be a higher voltage in the fuel tank, and this caused the spark.

By itself even this wouldn't be enough to cause an explosion because liquid jet fuel won't ignite with just a spark, it needs to be in vapor form, but doesn't vaporize until it gets hot.
As it happened the plane was waiting in the airport for a very long time before takeoff and had the air-conditioners running, and the air-conditioning units were underneath the fuel tanks. Staying on the ground for far too long on a hot day with the A/C on caused the fuel to heat up enough to vaporize, so that soon after takeoff when the two short circuits caused a spark there was something to ignite.


Moral of the story; if you think four unlikely things won't happen one after the other to cause a disaster you're dead wrong. Any extra fail-safes are a very welcome addition to an aircraft's design.
I don't think a relative of someone who died in that crash would agree that the people working on this new tech are just making work for themselves. It's hard to think of any other area where a single failure in 20 years and thousands of uses isn't acceptable.

friggin laser beams (4, Funny)

stinky wizzleteats (552063) | more than 6 years ago | (#21724506)

So, firing laser beams into fuel tanks is a safety feature now?

Re:friggin laser beams (2, Funny)

ByOhTek (1181381) | more than 6 years ago | (#21724532)

yes, but will they run on sharks?

Re:friggin laser beams (0)

Anonymous Coward | more than 6 years ago | (#21724586)

I doubt that enough of the energy of the kind of laser used for this can be transformed into heat to be a safety concern.

Re:friggin laser beams (1)

mlush (620447) | more than 6 years ago | (#21725438)

I doubt that enough of the energy of the kind of laser used for this can be transformed into heat to be a safety concern.

Light is a form or radiation, all forms of radiation are Evil and hence a safety concern.

Re:friggin laser beams (1)

wattrlz (1162603) | more than 6 years ago | (#21725466)

TFA says the receiver end of the circuit's 40-50% efficient. That means half of whatever power you're sending into the fuel tank ends up as heat. Depending upon how well the chip's cooled, that might be enough.

Re:friggin laser beams (1)

Phil06 (877749) | more than 6 years ago | (#21725390)

Haven't they seen how much damage a photon torpedo can cause?

Sounds like a bad idea. (5, Insightful)

Jason1729 (561790) | more than 6 years ago | (#21724510)

But what if power could be delivered over optical fiber instead of copper wire, without fear of short circuits and sparks?

You're stilling bringing as much power into the fuel tank. High-power beams of light aren't any safer, a laser can cut inch thick steel.

At least electricity is very well understood, we know how to insulate the wire, we know how much voltage will spark in a given medium, and the low voltage for sensors is very safe.

High energy lightbeams are not at all well understood. Will the fiber heat up? What about light leakage, will that cause an explosion? What if the fragile fiber breaks while the beam is on?

Re:Sounds like a bad idea. (1)

Lally Singh (3427) | more than 6 years ago | (#21724528)

And how much power do you need to run a sensor?

Re:Sounds like a bad idea. (4, Insightful)

Rob the Bold (788862) | more than 6 years ago | (#21724606)

And how much power do you need to run a sensor?

Not much, at least compared to what it takes to run a pump motor. And at least jet fuel isn't nearly as volatile as gasoline, which is pumped every day with submersible electric turbine pumps at nearly every gas station in the developed world. It's a PITA to make intrinsically safe electric circuits, but it's well understood and done every day.

The light powered device might be useful in planes if they could achieve the same degree of intrinsic safety at a lower weight.

Re:Sounds like a bad idea. (1)

Sen.NullProcPntr (855073) | more than 6 years ago | (#21724936)

The light powered device might be useful in planes if they could achieve the same degree of intrinsic safety at a lower weight.
I think that makes sense, lower weight means higher overall efficiency.
But it's the safety aspect that they seem to be pushing, Quote TFA;

...has developed a system that uses a laser to inject power in the form of light into a fiber-optic cable and a photovoltaic (PV) array to convert the light back into electricity for powering devices...
I might be wrong but I think large aircraft fuel tanks are part of the wings so there is no choice but to put wires through the cavity that holds the fuel.
The article links to a picture of the 1996 TWA flight 800 [wikipedia.org] reconstruction to drive the point home.

Re:Sounds like a bad idea. (2, Informative)

russ1337 (938915) | more than 6 years ago | (#21725560)

I might be wrong but I think large aircraft fuel tanks are part of the wings so there is no choice but to put wires through the cavity that holds the fuel.


Most of the wing is the tank, but not all of it. There is room behind the 'leading edge' and the trailing edge (between the aft of the tank and the front of the flaps/ailerons. ) This is where other services go, such as air ducts for the leading edge De-Icing (heating) systems, and wires that run to those little navigation lights way out there on the wingtips. Not to mention all the wires to and from the wheelwell (undercarage).

Not a good picture - but it shows what I mean: here [bst-tsb.gc.ca]

Could run off a watch battery for months (3, Informative)

JonTurner (178845) | more than 6 years ago | (#21724636)

Millivolts. Most level sensors are variable resistors, so you only need to exceed the forward min. bias of the resistor (see the spec. sheet) to have accurate results. Above that, it's just a matter of calibration and maintaining a well-regulated power supply.

The issue is power limiting (2, Informative)

FuzzyDaddy (584528) | more than 6 years ago | (#21724800)

You're stilling bringing as much power into the fuel tank. High-power beams of light aren't any safer, a laser can cut inch thick steel.

It's a lot easier to ensure the power is properly limited. Running a sensor is a low power application (you wouldn't be using a "steel cutting" laser), and the power is limited with the size of the laser diode. There's no other way to get power through the line.

With electric lines, the issue is whether the wire to the sensor is going to short to another wire somewhere else in the wiring harness that will accidently put a lot more power on the line. There are a TON of wires on an aircraft, going every which way, some of which can deliver a lot of power. Short one of those to the sensor line and you can get a spark in the fuel tank.

Re:Sounds like a bad idea. (2, Insightful)

kmac06 (608921) | more than 6 years ago | (#21724986)

No, no and no. Some (very high power) lasers can cut steel. Those lasers have many orders of magnitude more power than your standard laser pointer, which is probably amount the amount of power necessary to work a couple of sensors. High energy lightbeams are very well understood, I don't know how you could think otherwise. No, the fiber will not heat up (fibers can safely carry kilowatts or more of laser light without melting). Light leakage would be very small. If the fiber breaks, the light will be dispersed in the fuel rather than absorbed in one spot. The ONLY thing you would have to worry about in this case is if the light from the fiber is focused onto something that absorbs the relevant wavelength, and can heat it up enough to ignite the fuel (which may be impossible depending on the input power). Well, that and the problems with the electricity after the light is converted (which of course are there anyway).

Re:Sounds like a bad idea. (4, Insightful)

TubeSteak (669689) | more than 6 years ago | (#21725082)

You're stilling bringing as much power into the fuel tank. High-power beams of light aren't any safer, a laser can cut inch thick steel.
Technically, since their solar cell is only 40%-50% efficient, they're pumping in twice as much "power" into the fuel tank. So yes, while there are lasers that can cut steel, there are also lasers that can be safely shined into your eyeball without causing any harm.

About the only valid sentence in your post starts with "electricity is very well understood". The rest of it just reflects your ignorance.

"High energy lightbeams are not at all well understood" by you. Light leakage causing an explosion? Seriously?

Light Sensors in cameras... (2, Informative)

pryoplasm (809342) | more than 6 years ago | (#21724522)

...have been using similar technology for some time.

however, there is a problem with what is called dark current. that is when there is no light hitting the transducer, and there is still a current being developed...

Re:Light Sensors in cameras... (1)

ByOhTek (1181381) | more than 6 years ago | (#21724568)

how does that mesh with thermodynamics? (Is it from ambient vibrations? What makes it so that we aren't causing a violation of the underlying laws of the univers such that a catastrophic cascading implosion of all existance won't happen?)

Re:Light Sensors in cameras... (4, Funny)

Rob the Bold (788862) | more than 6 years ago | (#21724630)

What makes it so that we aren't causing a violation of the underlying laws of the univers such that a catastrophic cascading implosion of all existance won't happen?

Don't cross the beams.

Re:Light Sensors in cameras... (3, Informative)

tomz16 (992375) | more than 6 years ago | (#21725034)

Dark current is the signal detected from the ambient blackbody radiation around the sensor. This includes the radiation off the detector itself. It is so ridiculously small compared to the scales we are talking about here that it is not even worth mentioning.

as far as I can understand it.. (1)

legoman666 (1098377) | more than 6 years ago | (#21724540)

...They're shooting a laser through fiber into a small solar cell that's inside the fuel tank. explain to me how that is innovative.

Re:as far as I can understand it.. (2, Funny)

youthoftoday (975074) | more than 6 years ago | (#21724570)

I think you're mixing up innovation and patent-worthiness. You must be new here.

Re:as far as I can understand it.. (1)

legoman666 (1098377) | more than 6 years ago | (#21724620)

you got me there. *bows in apology*

You're right, nothing new here (1)

IvyKing (732111) | more than 6 years ago | (#21725600)

Carrying power through glass fibers was one of the main themes of the eco-fantasy 'YV88' written in 1977 - they also had data transport over glass fibers and multi-user chat program. ASEA was using glass fibers to send trigerring pulses to stacked thyristors in the early 70's.

Intrinsic Safety. (5, Interesting)

GrpA (691294) | more than 6 years ago | (#21724556)

There is nothing wrong with running wires into petrol tanks for sensors... Take a good look at how badly made the rheostats in everyone's pertol tanks are made. Most engineers freak out when they see them for the first time.

However the design is what is known as "Intrinsically Safe"... ie, it can't cause an explosion.

Currents, voltages are limited. Components are overrated by a set amount.

I've never heard of any intrinsically safe circuit igniting gasoline.

So what if you use fiber optics to provide the power. It's still electronic circuits in the tank, except now they are a whole lot more complicated and have power generation and regulation circuits, which make it a whole lot more dangerous...

And please don't just say encapsulate the dangerous stuff, because I'm sure that won't explode with a pressure build up if a component dies (as they tend to do in regulated power circuits).

It really scares me how such "great" ideas like this seem sane, when the original technology was probably safer.

GrpA

Re:Intrinsic Safety. (0)

Anonymous Coward | more than 6 years ago | (#21724638)

It really scares me how such "great" ideas like this seem sane, when the original technology was probably safer.


Next you'll be saying my "fill-your-home-with-helium to prevent death by fire" is worse than our current nitrox-filled houses too, won't you?

Re:Intrinsic Safety. (2, Informative)

Rob the Bold (788862) | more than 6 years ago | (#21724658)

There is nothing wrong with running wires into petrol tanks for sensors... Take a good look at how badly made the rheostats in everyone's pertol tanks are made. Most engineers freak out when they see them for the first time.

Good point. Note that electronic sensors are also used in underground (and above-ground) storage tanks. Electric turbine pumps, too.

Re:Intrinsic Safety. (1)

SatanicPuppy (611928) | more than 6 years ago | (#21724828)

Well, the reality of it is, gasoline won't burn without a ready source of air, so the danger of a spark inside a tank of gas is minimal until the tank itself is ruptured. And if you can keep the bulk of the components outside the tank anyway, then it doesn't matter if they're more prone to failure.

Other than that, I tend to agree. Stick with the reliable, proven method, until the alternative offers enough benefits to make the risks worthwhile.

Re:Intrinsic Safety. (1)

MightyYar (622222) | more than 6 years ago | (#21724872)

I've never heard of any intrinsically safe circuit igniting gasoline.
Ahh, but flight 800...

The source of ignition energy for the explosion could not be determined with certainty, but, of the sources evaluated by the investigation, the most likely was a short circuit outside of the CWT that allowed excessive voltage to enter it through electrical wiring associated with the fuel quantity indication system."

The problem wasn't the safe circuit, it was that the wires made a path into the fuel tank. Sometimes circuits don't stay the way you built them :) An optical path would offer no chance that stray current could get into the tank.

Re:Intrinsic Safety. (1)

GrpA (691294) | more than 6 years ago | (#21725054)



Yes, TWA 800.

Well, the biggest problem with Intrisically Safe designs is that they don't tend to be nearly as safe when they get struck by missiles... :)

I thought it was interesting though. I don't actually know enough about that aircraft to know if it was an intrinsically safe design that went wrong or just bad design.

Of course, Avtur - or Kerosene, doesn't ignite with a spark or even a flame - try it. It takes a LOT more, so I'm not really sure how the middle tank went up. You need heat and pressure too. I would have to read the accident report to fully understand it, which is something I haven't done.

Or of course, it might really have been that the wires became frayed after being struck by a missile :)

GrpA

Re:Intrinsic Safety. (3, Interesting)

IcePop456 (575711) | more than 6 years ago | (#21724890)

It really scares me how such "great" ideas like this seem sane, when the original technology was probably safer.

It also bugs me, as an engineer, when people want better, faster, cheaper, but then refuse change. I hear numerous stories from my coworkers who used to design parts for the automotive industry. Apparently they had to come up with improvement plans and present them only to have the "what we have works, why change it?" mentality. Follow this with, now do it for less because we are going to buy the same system for less money each year...but remember, don't change or improve anything. Sounds dumb? Obviously the company no longer makes those parts.

Re:Intrinsic Safety. (4, Informative)

Cassini2 (956052) | more than 6 years ago | (#21724900)

Intrinsically safe circuits can ignite gasoline when they are hit by lightning. The concern in aircraft applications isn't that the fuel ignites in normal operation. Rather, it is suspected that some airplanes have exploded after being hit by lightning.

If enough power hits just the right wire, and the tanks are near empty (with lots of explosive fuel vapors), and enough planes get hit by lightning in flight in a sensitive location, then potentially disaster can happen. The accident data says fuel tank explosions occur, and this might be a possible cause. Safety problems demand a precautionary approach. Hence the desire to eliminate the wire going to the fuel tank.

Further resources:
http://www.epa.gov/fedrgstr/EPA-GENERAL/1997/April/Day-03/g8495.htm [epa.gov]
http://easa.europa.eu/doc/Events/fueltanksafety_24062005/easa_fueltanksafety_24062005_large_transport_ppt.pdf [europa.eu] [pdf]

Note: a widespread consensus exists that many possible ways for fuel tanks to ignite exist. As such, most of the focus is on minimizing the likelihood of ignition, rather than one specific cause, like the fuel tank wires themselves.

Re:Intrinsic Safety. (1)

ajs318 (655362) | more than 6 years ago | (#21725518)

A lightning strike is pretty extreme. There's enough potential difference there to ionise the insulation on the wires (especially if it's PVC; a chlorine atom attached to every other carbon atom looks "just polar enough"). Under which circumstances, it tends to stop insulating.

Even fibre optic cable -- or its outer protective sheath -- can potentially become conductive.

Re:Intrinsic Safety. (1)

Skweetis (46377) | more than 6 years ago | (#21724904)

In order to ignite the gasoline or jet fuel (essentially high-octane kerosene), you need two other things: a spark which brings the temperature of the fuel to its flash point, and oxygen. You're absolutely right, a low-voltage/current sensor would never be able to spark enough to bring the fuel to its flash point, and if it's submerged in the fuel, it doesn't matter anyway, there's no oxygen available for ignition. Properly insulate the sensor, and it's extremely safe.

Actually, gasoline can be used to put out a fire under certain conditions (I wouldn't recommend it as a practical use, as there are plenty of substances better-suited to the task).

Re:Intrinsic Safety. (2, Interesting)

GrpA (691294) | more than 6 years ago | (#21725004)

Actually, there's a lot of air in the tank anyway, especially when it's nearly empty, so a spark would be bad news.

Intrinsic Safety [wikipedia.org] is better explained on the Wikipedia that I did in the post.

And the insulation doesn't exist in the rheostat - just wires rubbing together in the presence of fuel and air, but as I mentioned, it's extremely rare for car fuel tanks to spontaneously explode, which is probably a good example of why intrinsic safety designs work so well :) (Yes, the wires in a fuel tank have no insulation, and they sit in the air/vapour part of the tank)....

I designed some intrinsically safe stuff for a company I worked for once... Sensors that were designed to sit inside the petrol tank and relay information through RFID to an external reader... Which is even lower power than lasers, and actually worked quite well (Credit card information located in the fuel tank or near the filler to be read by the pump handle).. In the end I think they just went with straight commercial stuff, which would have been IS also..

GrpA

Re:Intrinsic Safety. (1)

ledvinap (412654) | more than 6 years ago | (#21724932)

IMHO the problem is not with power required for sensor. The problem is (probably) conductive wire entering the tank. This wire can act like antenna or conduct static charge. And where you are trying to estimate static charge/EMI, you should have good crystal ball at hand. It's nearly impossible to be ABSOLUTELY safe.
(Once i tried to solve EMI problem with small CPU board ... So i put it in sturdy aluminum box .. Works great as long as no wires go out of the box, but MAY be much worse otherwise. And in my case the CPU got burned in first encased test)

The power needed for new sensors is probably in mW range. The sendor capacitance is bounded (so no unknown stored electrical energy), the thermal conductivity can be estimated (no thermal buildup). And no unexpected interference ...

On the idea of shining laser into fuel tank - do you thing you could ignite anything with 1mW laser pointer? it's hard to ignite match with 200mW one ...

Re:Intrinsic Safety. (1)

GrpA (691294) | more than 6 years ago | (#21725134)

Just out of interest, I wonder how many watts will a laser pointer diode put out for microseconds or less if it gets hit by lightning.

The pulse would be short but I wonder if it might be enough to cause damage/ignition at the other end.

Diodes seem really easy to overdrive in my experience.

GrpA

Re:Intrinsic Safety. (1)

noidentity (188756) | more than 6 years ago | (#21725144)

There is nothing wrong with running wires into petrol tanks for sensors. [...] Currents, voltages are limited. Components are overrated by a set amount. [...] So what if you use fiber optics to provide the power.

If the wires short with something outside the tank (even far away), that power is now going inside the tank where it could cause sparks. With fiber optics it's virtually impossible to cause a spark via light. I'm assuming the fiber would carry very weak light, on the level a solar calculator uses, not on the level of CD burner.

Re:Intrinsic Safety. (1)

GrpA (691294) | more than 6 years ago | (#21725278)

See my comment above.

If the diode driver circuit is hit by lighting, the output will be in the order of watts before the diode disappears... Way more than a CD burner. Anyone who's worked with LEDs knows how easily you can overdrive them if you have the duty cycle low enough. Basically, the power limitation in LEDs is based on how quickly they can dissipate the heat. This is the same for many electronic circuits.

But having thought it through, I'm thinking that even with wires inside the tank, I've heard of cars being struck by lightning before and not exploding.

And if there is enough of a potential difference between the tank and the wiring anyway for lightning to cause arcing, then the arc even to the outside of the tank will generate enough heat inside to ignite fuel/air... Just like an arc welder...

GrpA

Re:Intrinsic Safety. (1)

nahdude812 (88157) | more than 6 years ago | (#21725308)

Just curious, is there a reason that fuel levels can't be read entirely by fiber optic? Place a fiber end every few millimeters, place a light source (also carried by fiber optic) at the top of the tank, and measure the total light coming back on the incremental fiber. If the fuel is not opaque enough to accommodate (gasoline is pretty clear, I don't know about jet fuel but for some reason I think it is not), put a floater in front of the return fibers and identify which ones are blocked.

Re:Intrinsic Safety. (0)

Anonymous Coward | more than 6 years ago | (#21725448)

I had the same thoughts. Whatever happened to the good old fashioned float that could be read from outside the tank, perhaps by optical or magnetic properties. If you want to make it high tech, I am sure the old fashioned floats can be replaced with MEMS devices.

What is the electrically read sensor inside the tank doing anyway to measure the amount of gas?

Re:Intrinsic Safety. (1)

meatspray (59961) | more than 6 years ago | (#21725502)

Or weight sensors under the tank, or optically via shooting visible light through the tank top to bottom and reading the loss, or acoustic range finding from top down or PSI sensors at the bottom of the tank.

There are a million ways to do this. Some tech firm just came up with an idea to combine laser transponders with solar cells and is trying to find something to do with it.

I saw once on TV that they add agents to the fuel to make it even less flammable and a red dye of some sort but it was years ago and that might be outdated information shouldn't really matter for your plan you could use light diffraction.

Put a window at the top of the tank, shoot a narrow beam of light at 45 degrees, place light sensing material on the bottom and side of the tank, as the level recedes, the beam will split more toward the true 45 degree slant it's initial path was set to.

Fuel Gauges (1)

dunc78 (583090) | more than 6 years ago | (#21725536)

People always complain about battery monitors being inaccurate (spending 90% of their time at full charge and 10% of their time on the way down). I always wonder why people can't build a reasonable fuel gauge, as they seem to suffer the same problem. It would seem like these measurement biases could be calibrated out, but I guess it isn't that easy.

what exactly are they sensing? (1)

ftsf (886792) | more than 6 years ago | (#21724584)

why do they need electricity? if it's to monitor the level of the tanks you could use a purely mechanical device surely?

Re:what exactly are they sensing? (1)

Stonent1 (594886) | more than 6 years ago | (#21724674)

Or you could just pump in Nitrogen gas or CO2 to fill the empty space so it can't ignite.

Re:what exactly are they sensing? (1, Informative)

Anonymous Coward | more than 6 years ago | (#21724792)

How does a purely mechanical device transmit the information back to the pilot/cockpit?

It can be done, but doing it electronically is much easier and lighter.

Re:what exactly are they sensing? (1)

Broken scope (973885) | more than 6 years ago | (#21725020)

An electrical device can give a more accurate and precise reading, as the tanks get lighter certain things change., you need to know with a fair amount of accuracy how much is in those tanks.

They could go farther (2, Informative)

Anonymous Coward | more than 6 years ago | (#21724592)

Why bother with electricity at all. A piece of fiber to an optical encoder would do the job just fine. I can't think of any sensor that couldn't be implemented optically.

Having said the above, the product seems like a solution in search of a problem. I can't recall any incidents where a fire or explosion was caused in an airplane because of faulty wiring in the fuel tank. There are lots of places where an electrical spark could cause an explosion. For instance in a mine, or factory, dust explosions are an ever present danger. To deal with that, we have explosion proof wiring. http://en.wikipedia.org/wiki/Electric_actuator#Explosion_protection [wikipedia.org] In other words, the problem was solved long ago.

Re:They could go farther (1, Informative)

Anonymous Coward | more than 6 years ago | (#21724680)

I can't recall any incidents where a fire or explosion was caused in an airplane because of faulty wiring in the fuel tank.

I can. [wikipedia.org]

Ok, so I read the article... (2, Interesting)

inject_hotmail.com (843637) | more than 6 years ago | (#21724616)

...and found that they said "Such transformers are large and necessarily heat up, which can lead to hot spots. To prevent equipment temperatures from rising to dangerous levels and to reduce power leaks, oil and gas are used as insulators. But oil is flammable and can make the transformers explode at high temperatures. The transformers are also expensive to install and maintain."...

Say what?!? Ok...so, yes, I'd much rather have the manufacturer disclaim that they can't be sure that their product won't explode (thusly guaranteeing all hands lost), than use wires that have have never caused a problem in the manner in which the manufacturer of said bomb-like device.

Still...there might be some application for this device, but it certainly WON'T be in a fuel tank.

By the way, millions or even billions of fuel level sending units have been in use in anything with gas gauge for years. How many users of such devices have been killed due to electric failures? I'm guess very very VERY few, if any at all.

I agree with another commenter when they said that they don't want frickin' lasers pointing at their frickin' gas tanks.

Re:Ok, so I read the article... (1)

DigiShaman (671371) | more than 6 years ago | (#21724952)

I'd much rather have the manufacturer disclaim that they can't be sure that their product won't explode (thusly guaranteeing all hands lost), than use wires that have have never caused a problem in the manner in which the manufacturer of said bomb-like device

I'm not defending this new technology, in fact I agree with you. However that said, they're was at least one documented case of a plane blowing up because of a failed fuel sensor. Actually, it wasn't the sensors fault, but rather it's low current wire crossed a high voltage line somewhere in the plane. Last I remember, it was the outer plastic sheath cracked in places exposing the copper. When two wires are running next to each other both cracked at the point they intersect, bad things can happen.

I've already invented such a gadget (1, Funny)

Anonymous Coward | more than 6 years ago | (#21724640)

I've already invented a device to tell the level of a fuel tank without using electricity!

Through advanced hydrostatics, I found the level of the fuel tank could be remotely monitored via a capillary tube, from which the fuel level can be calculated from an ocular spectrogram in the VIS range.

Okay, okay.. so it's just looking at the level in a hose connected to the tank... and it's not new.

Re:I've already invented such a gadget (2, Informative)

ArieKremen (733795) | more than 6 years ago | (#21725368)

You're going to overestimate your remaining fuel if you are relying on a capillary. Unless, of course, your ocular spectrogram can automatically correct for the capillary rise [wikipedia.org] .

Sounds bogus (1)

RobinH (124750) | more than 6 years ago | (#21724646)

Power is still power. Whether you're pumping 100 mW of electricity or light into a fuel tank, I don't see a difference.

We already have intrisically safe electrical technology for such things. As long as you limit the power so that there isn't enough to create an ignition source, you're golden.

Personally I'd prefer new sensor technology that allows sensing the desired quantity with either less power or from a safe distance, like ultrasonic level sensors and such.

Re:Sounds bogus (1)

artg (24127) | more than 6 years ago | (#21724766)

So electrical and optical power is power, but acoustic power isn't ?

Re:Reading and understanding the article.. (1)

Technician (215283) | more than 6 years ago | (#21725266)

Power is still power. Whether you're pumping 100 mW of electricity or light into a fuel tank, I don't see a difference.

There isn't much diffrence between feeding 100 mW opticaly or not.

"where electromagnetic interference is more than just an inconvenience"

Feeding 100 mW sensor and getting a 50 nW signal back with 25 mW of induced ground radar or cell telephone signal on top is the problem. It swamps the signal. In extreme cases such as a close lightning strike, the induced power could be enough to create a spark. The optical is for noise rejection and less for fire safety.

"Already, a Photonic Power device is replacing instrument transformers used in the power grid to measure high currents."

The optical in power substations doesn't have insulation breakdown failures in a lightning strike.

Stupid solution to a simple problem (1)

jimmydevice (699057) | more than 6 years ago | (#21724650)

What's the problem with all the other solutions? Load cells, surface reflectivity, refraction with a modified optical fiber, acoustic ( ever tapped on a gas tank?), a current limiter on old school sensors? I'm glad I got out of aerospace in the 90's. It looks like idiots have taken over.

Re:Stupid solution to a simple problem (1)

Heped on caffine (1204006) | more than 6 years ago | (#21725260)

and people wounder why planes crash into mountains...>.>

Galvanic isolation. (2)

Ihlosi (895663) | more than 6 years ago | (#21724690)

One of the main applications for this will be when galvanic isolation of the components is required. This has fairly little to do with fuel tanks, but is interesting for various medical applications, applications in humid environments, and so on.

How much Power? (2, Interesting)

sadtrev (61519) | more than 6 years ago | (#21724710)

This development would be great for Intrinsically Safe (EEx etc) instrumentation applications.
Current ATEX regs make it awkward to supply anything above about 1Watt at 6V.
Most people resort to pneumatics and/or keeping the computational logic outside the zoned areas.

Disappointingly for IEEE, he article is sparse in terms of technical details, such as the power/size ratio.

get rid of oxygen, instead of wires (1, Insightful)

Anonymous Coward | more than 6 years ago | (#21724718)

How about keeping the empty space in the fuel tank full of an inert gas?
After all, an electric spark can't ignite jet fuel if there's no air to burn it in.

Danger Will Robinson! (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#21724740)

This is actually far more dangerous than it first appears. Check out what happened when this technology was tested in this town [myminicity.com]

Re:Danger Will Robinson! (1)

greebowarrior (961561) | more than 6 years ago | (#21724852)

will you please stop spamming that crap!

So much safer (2)

mitchskin (226035) | more than 6 years ago | (#21724752)

Right, so instead of running electrical cables into the fuel tanks, we'll just shoot lasers into them instead.

NOT the issue! (1, Informative)

Anonymous Coward | more than 6 years ago | (#21724968)

Tank probes are capacitive and use a very weak signal for excitation. The spec is 25uJ maximum which is WELL under the energy required to ignite fuel. Typical systems use way less energy to make measurements. The problem is more that wiring for OTHER more power consumptive things is routed through the tanks in some designs. Also I agree, optical isn't any better or worse of a method.

That could lead to... (2, Funny)

RyoShin (610051) | more than 6 years ago | (#21725040)

I dunno, electricity in glass could lead to some shocking panes.

Acoustic impulse pneumatic probes (1)

Skapare (16644) | more than 6 years ago | (#21725050)

A small tube is lightly pressurized with a known gas. A mechanical sensor at the far end moves a tiny piston in or out of the tube to measure fuel level or temperature. At the near end, a device emits an acoustic pulse into the gas and measures the return reflection timing. This timing gives the length the piston has moved in the tube. The tube can be made of metal (well grounded to the tank frame at many points) or other reasonably rigid materials.

One tube can even be used for multiple sensors. This would be sorted out by the timings of multiple pulses returned from the various sensors at different distances along the tube. Some of those sensors measure temperature of the gas in the tube itself to maintain calibration. A low angle tube splitter can be used to greatly minimize the impulse reflections between sensors (which would otherwise appears as ghost sensors to the firmware scanning the pulse train, which can easily eliminate them at low levels).

If this has never been done before, this posting hereby constitutes public disclosure of the idea on Monday, 17 December, 2007.

Glass fiber = static electricity? (2, Insightful)

dpbsmith (263124) | more than 6 years ago | (#21725176)

No, probably not, although friction on glass does develop a static charge, and under the exact right bad conditions could conceivably cause a spark. As others have observed in this thread, premise, as presented in the posting, is stupid and promotional.

The safety of stuff in a fuel tank depends on a) how well the risks are understood, and b) how well the engineering to mitigate them is performed.

It's a standard rhetorical ploy to assert that because something is different from an older technology, it is automatically free from the problems of the older technology... and, without saying so in so many words, allowing the listener to infer that it does not have equivalently bad new problems of its own.

The first time I heard groove-skipping on a CD, I laughed out loud. With all the promotion of the digital perfection of the CD, the fact that it suffered from exactly the same problem as a vinyl LP was... delightful.

Obligatory... (0)

Anonymous Coward | more than 6 years ago | (#21725228)

The goggles! Zey do nothing!

High Transmission Lines? (2, Interesting)

Anonymous Coward | more than 6 years ago | (#21725268)

If they can scale this technology up to usable levels, would the power loss of the conversion outweigh the power loss to heat/resistance in High Transmission Lines? Obviously not over short distances, but imagine how it would play out over the thousands-millions of miles in the electrical grid.

For an idea of the scale of loss versus cost of power: some power companies are currently willing to take the hit in lost power by using aluminium lines instead of copper, because they can engineer the towers holding the lines up to use less steel. (ie: This is possibly an argument against doing this). The cost savings in the tower construction outweighs the power lost in the lines.

Lousy Science (2, Insightful)

ajs318 (655362) | more than 6 years ago | (#21725328)

Running a live wire into a passenger jet's fuel tank seems like a bad idea on the face of it.
Only if you don't understand the basics of electronics or chemistry. One would hope that aircraft designers and constructors would have studied the science in these fields (mind you, if they're Americans, they probably think that God Did It, End Of Story; and if they're British, they probably think that All Beliefs, Even Demonstrably Untrue Ones, Are Equally Valid).

Still, sensors that monitor the fuel tank have to run on electricity, so aircraft makers previously had little choice.
You can use a low enough voltage that it won't spark; and you can use sufficiently-close contacts that even if it does spark, there will be insufficient energy to ignite the fuel.

Unless those techniques are patented?

Does not solve the problem? (1)

Jumphard (1079023) | more than 6 years ago | (#21725366)

Existing sensors I've worked with typically require ~5V and low low amperage and when properly insulated the chances of sparking are very minimal.
With this solution, there still is electronics inside the fuel tank, so I do not see how this solves the problem. The light is converted into electricity inside the tank, so potentially even more problems with the conversion circuitry. However this tech is pretty cool and may have other applications. The 50% efficiency is bothersome as well, that's crap given todays electrical standards.

What interests me for fuel tanks is why they couldn't use some sort of a camera or sonar sensor from the outside of the tank to measure it. Perhaps having a tonight sealed porthole to view into, or maybe even sonar through the metal could determine the amount of fuel.

Formidably silly article (4, Interesting)

Ancient_Hacker (751168) | more than 6 years ago | (#21725404)

Formidably silly article, for many reasons:
  • Exploding gas tanks are very low on the list of problems, sorted by frequency and severity. If we spend money on these less severe problems, we're taking money away from figting more serious and cost-effectively attakcable problems.
  • The problem is having explosive mixtures in gas tanks. Rather easily solved by plumbing a little engine exhaust gas into the tanks to displace the oxygen. Done for decades on tanker ships.
  • The typical sensors in airplane tanks are capacitive dielectric guages. These can easily be made to run on microwatts of signal, not enough to cause ignition.
  • Even if the sensors were a problem, which they're not, and you replaced them all with some new method, you'd still have all the other sources of ignition, including sulfur chemical catalsys, static discharges, lightning, friction, and more. You need to make the stuff non-explosive or ignitable, see point #1.

What about capacitance fuel sensors? (3, Interesting)

element-o.p. (939033) | more than 6 years ago | (#21725586)

I thought capacitance based fuel sensors solved most, if not all, of the problems of sparking inside fuel tanks by keeping the powered components on the *outside* of the fuel tank. Is there some problem with accuracy or reliability that makes them unsuitable for commercial aviation that I'm not aware of or is this a solution searching for a problem?

And for all of the people asking how often sparking inside a fuel tank causes a tank to explode, yes, it *does* happen sometimes. The final NTSB report on the airliner that crashed off New York about a decade ago (you know, the one that the conspiracy theorists said was shot down by a hand-held SAM) was due to sparking inside the fuel tank. I'd link to it, but I can't recall the flight number, and I don't have time to search for it right now...
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