The indestructable box on airplanes

[beccabee52000]

Why don't they make the whole plane out of that material?

[Q.E.D.]

Weight. An entire plane made out of steel would be extremely heavy and expensive to operate. Besides, even if the the plane itself was indestructible (which it wouldn't be, due mainly to its every large size--the small black boxes survive because they are small and the overall stresses on them are proportionally smaller), the people inside would be subject to the same forces of acceleration and would not fare much better.

[Antonius Block]

Originally posted by beccabee52000
Why don't they make the whole plane out of that material?

The Perfect Master has already addressed this.

[Irishman]

The steel is maybe a quarter inch thick and the boxes are so heavy in consequence that the designers don't even bother enclosing the accompanying electronics, which in a crash generally meet the same fate as the passengers.

What is that supposed to mean? I can't decypher it. What does the thickness of the steel box have to do with whether or not the electronics are enclosed?

[Nametag]

'Cause if you enclose the electronics, the box will be even bigger and heavier -- too big and heavy.

[CurtC]

I agree - I can't decipher it either. Is he saying that they don't put the accompanying electronics inside the black box? Or that the electronics in the black box are not in sub-enclosures? It just seems like the bit about the electronics meeting the same fate is a non sequitur to the heavy steel sides part.

[nodope4us]

Maybe the electronics they refer to are the wiring for the equipment inside the box. Just speculation though

[Irishman]

What is in the black box - the recording device itself.
What is the electronics outside the box? The circuits and batteries and signal processors from the sensors? Maybe that's what it means.

[CurtC]

I think what he means is that since the electronics die whether they're inside the box or out, the designers make the box as small as possible by putting the electronics outside the box, therefore putting the minimal amount of stuff inside it. The wording made that confusing, though.

[Irishman]

But my question was what is in the box? Apparently electronics is being differentiated from something. I finally figured out that something is the recording itself - electromagnetic tape, probably. So what are the electronics, if not the recording medium and recorder (device making the recording)? That is what I was guessing at.

[scr4]

Originally posted by Irishman
But my question was what is in the box? Apparently electronics is being differentiated from something.

A "black box" is a data acquisition and recording system. I'm not familiar with the actual designs, but it makes sense that the two functions require separate components. The "electronics" performs data acquisition, which means communicating with sensors and other avionics, deciphering the received information (which may include analog-to-digital conversion) and formatting the data into a single data stream suitable for recording. This is not a trivial task. The recorder itself is just a dumb device that needs properly formatted data for input, just like an external hard drive for a PC. It used to be magnetic tape but IIRC they are starting to use solid state memory.

It's possible to put both the electronics and recorder into a metal box so they both survive the crash. But what's the point? The electronics is not needed after the crash, and it makes the box much larger (and therefore heavier) than necessary. The recorder is the only component that needs to survive.

[Broomstick]

HowStuffWorksTM is your friend:

Several pages on Flight Data Recorders

Even has a picture of a post-crash box - specifically the one from Egypt Air 990

[Telemark]

Originally posted by beccabee52000
Why don't they make the whole plane out of that material?

Because interstate overpasses aren't high enough to let the planes through.

[scr4]

It occurs to me that "because it'd be too heavy" is a misleading answer. I think the more valid answer is that the strength (survivability) of an object depends on size as well as material. An 8x8x4 inch box made of 1/4" steel will survive a fall from a few thousand feet, but a 100x15x15 ft tube of the same material will not.

[Bryan Ekers]

In the same sense, if you suddenly had to run for the border because the brownshirts were coming for you, there's no point grabbing your entire computer when your life's work is stored on the much smaller and more portable hard drive, so get a screwdriver, open the case, pocket the drive and go. The rest of the computer is just the means to get information on and off the hard drive, and it's replacable. Your essays on individual rights might not be.

So, in a black box, the recording medium is critical but all the electronic stuff that lets you write to and read from that medium isn't. Since the crash investigators are going to bring their own power supplies and whatnot, there's no need to make sure the black box has extraneous stuff that will survive the crash.

[C K Dexter Haven]

I apologize for the delay, I been on vacation without computer. This question should probably be in the General Questions forum, so I'm moving it there.

beccabee, it's no big deal, and welcome to the Boards (a little belatedly). You might take a look at the forum descriptions, it will help you in future know where to put what. Glad to have you with us!

[N9IWP]

scr4 exactly. In order for an airplane fuselage to be as strong, it would have to be (WAG) 4 inches thick (possibly more) in which case the plane gets very heavy.

Strength is proportional to the (IIRC) square of the thickness, but mass is proportional to the cube. If this is right something 10x as thick is 100 times stronger but 1000 times as massive.

Brian

[sailor]

No offense but this is a pretty dumb question to be asked by an adult. I have heard it more than once from some comedian, I forget who.

A) An airplane built to withstand a crash without structural damage could not fly so building it is quite pointless. You can't even build cars and trains which will not suffer damage when they crash at a fraction of the speed of an airplane.

B) Even if it were possible it would be pretty pointless because, you see, airplanes are used to carry people and there's not much point in building an airplane, or a car, or a train which can crash without structural damage when all the people inside would be just as dead.

Now, if you can build *people* who can survive after being dropped on concrete from 1000 ft up, that would be *something*.

[Rick]

Furthermore even if you built the plane out of Unobtainum (the strongest material know to man) the it wouldn't help much. the sudden stop at the end of the flight would still kill the softies inside the plane. (that's you)
It just like the description of what happens when you fall off a cliff. It isn't the fall that kills you, it's the sudden stop at the end.

[BobLibDem]

The black boxes are not always indestructible, as witnessed by the WTC boxes being completely obliterated.

[Tarantula]

Originally posted by Rick
Furthermore even if you built the plane out of Unobtainum (the strongest material know to man) the it wouldn't help much. the sudden stop at the end of the flight would still kill the softies inside the plane. (that's you)
It just like the description of what happens when you fall off a cliff. It isn't the fall that kills you, it's the sudden stop at the end.

You can just imagine them swinging open those huge heavy doors after the crash, and all this ragu with bits of hair floating in it, flows out onto the ground - gross...

:barf smilie:

[Rick]

But hey look you could get someone with a very strong stomach to hose out the inside, dust off the outside and you could use the plane again.

: Barf smilie:

[Trigonal Planar]

Hey, it worked for WWII tanks.

[Q.E.D.]

Originally posted by Trigonal Planar
Hey, it worked for WWII tanks.

Yes, but they aren't known for cruising at 600+ MPH at 35,000 feet.

[Broomstick]

Originally posted by Q.E.D.
[b]Weight. An entire plane made out of steel would be extremely heavy and expensive to operate.

Hmm.... well, if the steel was a porportionally thick on the plane as for the black box, yes, but if the steel was only as thick as it needed to be to provide the proper in-flight structural strength...sure, it could fly. Would take a little more power than an aluminum or cloth plane, but it would fly just fine. In fact, I think there might have been a production airplane or two built largely of steel (early Beechcraft Baron? Don't quote me - very vague recollection there).

[Q.E.D.]

I didn't say it wouldn't fly, I said it would be heavy, and expensive to do so.

[UncleBeer]

But what if, in this theoretical airplane, I jumped at the exact moment of impact? Snicker.

[sailor]

Originally posted by Broomstick
Hmm.... well, if the steel was a porportionally thick on the plane as for the black box, yes, but if the steel was only as thick as it needed to be to provide the proper in-flight structural strength...sure, it could fly. Would take a little more power than an aluminum or cloth plane, but it would fly just fine. In fact, I think there might have been a production airplane or two built largely of steel (early Beechcraft Baron? Don't quote me - very vague recollection there).

You might be able to build an airplane of steel which will fly but you cannot build an airplane which will fly AND not suffer any damage when flown into the side of a middle sized mountain. Heck, ships are build much more solidly and they will suffer a lot of damage if they hit a rock or another ship. You cannot build a practical ship which will not be damaged in a collision, much less an airplane.

[Broomstick]

Fact remains, abuse any object enough it comes apart.

Even those "black boxes" aren't indestructable, as has been pointed out - the WTC pair went through a crash, a fire, and a major building collapse and simply didn't survive. Sorry, we only figure on one catastrophic event, not three in a row!