why are planes not made out of the same material as the black box is???

Question

this is a question that has been bugging me for a while now please can someone shed some light on this sugbject!!!

Answer 1

consider a 777 and a 787. you can do the rest of the math on 767, 757, 747, etc if you wish....

777 first....

empty weight = 315000 lbs
composition is 15% SS, 50% Al, 18% Ti, 12% CFRP, 5% other.
density of SS= 7.85g/cc, Al = 2.7g/cc, Ti = 4.5g/cc, CFRP = 1.6g/cc, other = ?? say 1.

lbs SS = 47k, lbs Al = 158k, lbs Ti = 57k, lbs CFRP = 38k, lbs other = 16k

let's say we switch all aluminum and all CFRP to SS and leave parts the same size.... weight from Al switch = 7.85/2.7 x 158k = 458k lbs, from CFRP = 185k lbs

new weight of aircraft = 763,000 lbs

if we switch from Al to Ti and from CFRP to Ti, new weight = 489,000 lbs

max takeoff weight = 768,000 lbs according to boeing. Given a 777 holds about 320,000 lbs of fuel
an all SS 777 won't fly. Meanwhile, given if we say the average weight of people plus luggage = say 200 lbs per passengar, then at 280 passengers / plane the passenger weight would be about 56k lbs. meaning the max fuel weight would be < 70% of full. with no extra cargo...

for a 787......

empty weight = 242000 lbs
composition is 10% SS, 20% Al, 15% Ti, 50% CFRP, 5% other.....

weight of plane with SS instead of Al and CRFP = 806k lbs
with Ti instead of Al and CRFP = 493k lbs

max takeoff weight = 484,000 lbs
max payload = 100,000 lbs
max fuel load = 224000 lbs fuel

both SS and Ti planes are too heavy.

again, that assumes same size parts right? since Ti is stronger than Al, perhaps the parts can be shrunk and some weight saved. Sounds like a decade of redesign at the least....

by the way, aluminum goes for about $1.20/lb. Ti goes for about $22/lb currently. so making a plane out of Ti would increase the price of the plane by about.....oh 20 or 30 million dollars. Given a 777 costs about 250 million, it's may a 10% increase. Plus fabrication costs as well.

Airplanes are designed to minimize weight, maximize efficiency, minimize maintenance, minimize costs to airlines and passengers. and of course maximize safety. Switching from the current compositions to titanium or SS (the materials a CVR or FDR are composed of) doesn't accomplish any of those. it increases weight, cost, maintenance, and doesn't increase safety (most airplane fatalities are cause by either smoke/fire or by physical trauma SS or titanium won't eliminate either).

Answer 2

First of all it is. The Black Box is a dayglow orange ARINC-404 ATR box, just like most electronics packs in the plane, other than the color since the rest really are black. LRUs, or Line Replaceable Units as we used to call them.

The Black Box is built a bit tougher than the other LRUs, but not a heck of a lot. The main thing is that it is built to protect the recording device, in old machines that was a metal wire, in new recorders it's a solid state 'disk' made of memory devices in a tough shell filled with a 'potting' compound. They also place the recorders in the tail, which is usually the last part of the aircraft to hit the ground, so it has been slowed by the rest of the aircraft crumpling in front of it.

The forces an electronic device can stand are also a lot higher, we used electronics in fuzes which would stand being accelerated to 2,000 mph in about 15 feet. Humans can survive a few tens of g's for a couple of seconds, electronics can survive hundreds of times as much.

In the end the black boxes still get broken and burned, but they provide enough protection to the recordings that they can be recovered with forensic techniques.

If you put a human in a black box and crashed it you'd still get nothing out except a bloody pulp.

Answer 3

The real answer is...they are. If you were to propel the black box, on its own, into the ground at the same speed that the aircraft is flying when it hits, it would be damaged significantly. The sick fact is that the aircraft is part of the protective structure of the black box. The aircraft absorbs much of the energy of the crash. The black box, being surrounded by the structure of the aircraft, and positioned at the tail (usually the last part to hit the ground after the majority of the plane has absorbed energy and slowed everything else down), receives significantly less energy, and usually survives. In numerous high speed crashes, the black box has been irreparably damaged.

Answer 4

With strength comes weight.
And with size you lose strength.
A blackbox cant survive a direct impact of a jet crash, but its strong enough to be thrown clear of the wreckage.
Even if you were to build a jet that could withstand a nosdive into the ground, the people on board could never be protected against the instant decceleration.
The challenger shuttle cockpit hit the ocean at the same sort of speeds an airliner could hit the ground at. It suffered a 200g decceleration.
Passengers organs would be turned to paste and every bone would be broken into many pieces.
The best option is to incorporate crumple zones into the underside of the jet to absorb impacts.

And its not materials that make something strong, its shapes. If you build a frame with triangular shapes it will be stronger then something built with square shapes in the structure.
I could make you a box made out of aluminium thats stronger structually then a box made out of titanium. It all depends on the shapes.

Answer 5

One lesser known fact is that the location of the FDR and CVR play a big factor in its durability. On Boeing aircraft, they are typically located near the rear of the aircraft.

Three reasons for this. By the time the CVR and FDR get to the scene of the crash, the rest of the aircraft's impact has slowed everything down. Less of an impact. Also, these items are more likely to be on top of the pile, not buried under the rest of the plane. Additionally, Boeing aircraft don't store fuel in the rear of the plane on passenger aircraft(except the MD-11...but that was a Douglas design), so the chance of being in a puddle of fuel is reduced.

Answer 6

There are a few reasons why the black boxes are not completely destroyed during a crash. One is the materials they are made of , if you were to make an aircraft in them it would be too heavy to fly. Also where they are located in the aircraft doesn't take the full impact of the crash.

Answer 7

not only would it be to heavy to fly, just because it's made of the same material, the force on the plane in a crash or emergency landing would be the same or even higher....if the plane crumbles up a bit on impact, it will produce a smaller force over a greater time on the passengers. (from the equation: net force * time = mass * velocity) the longer time of impact, the less force needed to equal the momentum. Not to mention the black box makes it heavier which also increases it momentum/force.
But, either way you'd need some very powerful engines to lift it.

Answer 8

Ok, to all you people who think that it would be too heavy to fly, because you think it is made of some indestructable fortress force field thing...do some research.

The black box only survives (sometimes) because it is usually kept in a section of the aircraft that suffers (statistically) the least amount of damage. To those of you who are ignorant on the topic, but choose to post anyway...it is actually orange in color (so it is easier to find in the event of a crash), and the only required design specifications are that it must be able to withstand a decceleration of 3,400 g's for 6.5 milliseconds, and various other temperature, pressure, weatherproofing requirements. It is usually made out of stainless steel, or titanium.

Answer 9

like the weight, it is just the same reason why cars have crumple zones. If the plane was built of such material which it is so hard and dense, then the fuselage would not absorb/dissapate the crash energy, instead send it throughout the passenger cabin and making the force greater, and resulting in more deaths.

Answer 10

also, the fact is that even with the material it is made out of, if the black box had the same mass, and had the same impact as the airplane during a crash, instead of being in an area where it is intentionally placed to try and insure its survival, it would also likely be destroyed during impact of a crash, so the plane would have no particular advantage being constructed of the same materials.