Electricity Over Glass

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."

Comments

Intrinsic Safety.

[GrpA]

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.

[IcePop456]

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.

Formidably silly article

[Ancient_Hacker]

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?

[element-o.p.]

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...

Re:Is this needed?

[speculatrix]

steam? in the 2nd world war when magnesium was used for fire bombs it was quickly discovered steam would in fact allow magnesium to burn - worse still, the Mg "stole" the O2 when burning, leaving free H2 to then burn separately. Moral: don't try to put out a magnesium fire with water!