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Ok maybe not everyone, but in two examples after the crash of Oceanic flight 815 we see survivors claiming that the rescue planes will find them and the reason the give is "the plane had a black box". First is Shannon talking to Boone "the plane had a black box, stupid..." and the other is Ana Lucia talking to the survivors of the tail section.

My understanding is that a black box can only be used after a crash to identify what might have caused it, like a sort of log of the machinery, communication, and environmental readings and such. But the crash victims seem to think that its some kind of beacon. Am I missing something in the way black boxes work? Or are these victims simply making an assumption that isn't supported by facts?

I guess the more pointed question would be, can a plane's black box be used to locate a missing plane?

  • Black box ~= tracking device. so search party(s) can find their crash location – Vishwa Jun 8 at 6:43
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Black Boxes do in fact contain a tracking component that would assist in authorities finding a crashed plane.

From the National Transportation Safety Board:

Each recorder is equipped with an Underwater Locator Beacon (ULB) to assist in locating in the event of an overwater accident. The device called a "pinger", is activated when the recorder is immersed in water. It transmits an acoustical signal on 37.5 KHz that can be detected with a special receiver. The beacon can transmit from depths down to 14,000 feet.

From another article:

Every flight data recorder contains a tool called an underwater location beacon (ULB). This makes it possible for investigators to find it if a plane crashes into a body of water. Once underwater, it sends out an acoustic signal that searchers can detect with a special receiver.

Finding the FDR and CVR from a plane that's crashed into an ocean can still be tricky. In order for the signal to be heard, one has to be within a 15-mile range of the beacon. On top of that, the battery life only lasts for 30 days after it's been submerged.

However, it's not impossible. Two years after the 1987 crash of South African Airways 295, investigators found the plane’s cockpit voice recorder 16,000 feet below the surface.

Because these devices are designed to activate when submerged in water, it seems that the ULB from Flight 815 would only help if the tail section survivors knew enough to locate the black box and activate it. The other members likely assumed that the tail section did end up in the water, or they wouldn't have known about this requirement.

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    Interesting stuff, thanks for a great answer. – sanpaco Jun 4 at 5:17
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    Worth noting is that they are not that reliable. We never found Malaysia flight 370, after all. – Davor Jun 4 at 10:10
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    It's worth noting that 15 miles is a tiny range when considering the size of the ocean. The plane going even slightly off course could make it really hard to get within 15 miles of all the places the plane could be. – NotThatGuy Jun 4 at 10:57
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    @NotThatGuy Exactly! If you don't know where to look approximately, the black box won't help you because of the limited range. And if you do know where to look, you are close enough to find the survivors directly without locating the black box (they may have drifted apart very far). So the beacon only helps to find the black box itself, not survivors. – Weirdo Jun 4 at 12:15
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    Many aircraft also have an ELT ( en.wikipedia.org/wiki/… ) which uses satellite communication to transmit the location of a crashed plane anywhere on the planet. But it is usually separate from the black box and made so that it floats to surface if it gets into water. – jpa Jun 4 at 15:38
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This question already has an excellent answer from GendoIkari, but I see two separate questions. They overlap considerably, but they also don't overlap entirely.

The title question is "Why is everyone so focused on the black box in LOST?", which morphs in the body of the question into "can a plane's black box be used to locate a missing plane?" I find the original question interesting, and I believe it adds something to answer that, apart from the question it became. To wit:

Characters don't always have complete nor correct information about the world they inhabit. Lots of people believe that things about which they aren't experts behave in ways they don't, or even which would be impossible. And technology is ripe for this misunderstanding.

So, regardless of whether or not a black box can help authorities find Oceanic 815, some of the characters in LOST are obsessed with it because they believe that's something that black boxes can do. Per GendoIkari's answer, they are partly correct, but tragically mistaken on the details.

e.g., Shannon seems to think the black boxes are magical, guaranteeing that they will be rescued so quickly that they don't even need to worry about shelter, food, water, or organizing.

True, this question is tagged with realism and my answer is all about unrealistic things characters might expect; on the other hand it is very realistic for a story to portray the unrealistic expectations, ignorance, or belief-in-the-face-of-counter-evidence that real people exhibit in real situations in the real world.

A much shorter answer for "Why is everyone so focused on the black box in LOST?" therefore would be : because they are desperate people, in a desperate situation, desperately in need of a reason to not give up hope.

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    I totally agree with this point and although I don't think there was much he could of done with it, on it's own, Sayid is very knowledgeable with tech/communication devices, so he might be a character who "believed" that he could do something with it. – Darth Locke Jun 5 at 0:47
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    This reminds me of the scene in Alive where the downed passengers think that reconnecting the plane's radio equipment would be like wiring-together a home stereo system. – Dai Jun 6 at 1:38

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