If the blackbox of MH370 were to be found today, would it actually still provide any information, assuming that it was in 5km deep water or so for some 5 years now? If not, why would you still be looking for the missing aircraft and especially the blackbox, if there was nothing to find out about the reason that caused the 777 to disappear?

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    $\begingroup$ Note that the depth of the ocean is very, very variable. If can change from over 7000 meters to less than 2000 in just 100 km, so the actual depth (and pressure the black boxes have been subjected to) is quite unknown. Also, flight data recorders are designed to withstand quite extreme conditions, both at the time of impact (3400 g!) and after impact. You can find datasheets for some listing 20000ft max depth... There's a reason the black boxes are so big compared to the small SSD they contain.... $\endgroup$ – jcaron Jun 21 '19 at 13:07
  • $\begingroup$ @jcaron They use SSDs? I was under the impression, especially from this, that black boxes used their own purpose-specific data storage technology. $\endgroup$ – JoL Jun 21 '19 at 18:38
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    $\begingroup$ @JoL I’m not saying they are using off-they-shelf consumer-grade SSDs. But nowadays they are using solid state drives, as opposed to the magnetic stuff with moving parts they used previously. And this kind of storage is definitely very small compared to the overall FDR size. Note however that in the case of AF447, the storage was actually found separate from rhe FDR and was still functional. $\endgroup$ – jcaron Jun 21 '19 at 21:42
  • $\begingroup$ @jcaron are you saying the FDR disassembled itself? Or are you saying they found a QAR? $\endgroup$ – Harper - Reinstate Monica Jun 22 '19 at 14:31
  • $\begingroup$ @Harper: He's saying that the FDR's memory module separated from the chassis upon impact, and the two were recovered separately. $\endgroup$ – Sean Sep 5 '19 at 21:57

There are precedents: the flight recorders of AF447 spent two years at the bottom of the ocean, and revealed all that had happened after being retrieved. So they had survived being immersed in salty water at high pressure, making it very likely that MH370s boxes have survived as well.

Time of immersion is less relevant: oxidation (rust forming) is much slower at greater depth, due to much less dissolved oxygen and lower temperatures. The corrosion that does take place is mainly anaerobic, through bacterial sulfide formation. As posted in for instance this link.

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    $\begingroup$ For reference, AF447 was found at a depth of 3980 meters. $\endgroup$ – jcaron Jun 21 '19 at 13:14
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    $\begingroup$ +1 for chemistry $\endgroup$ – Travis Jun 21 '19 at 18:00

If not, why would you still be looking for the missing aircraft and especially the blackbox, if there was nothing to find out about the reason that caused the 777 to disappear?

In fact we are concerned with 2 black boxes, the flight parameters box, and the voice recorder, these are complementary. The voice recorder is extremely important too, for instance in the Ethiopian 737 MAX, the voice box recorded the repetitive action of the pilots searching for an adequate procedure in the paper checklist

But not only

When a crash occurs, the debris, and every part of the aircraft is capable to talk. For instance it will tell if the crash occurred while trying a ditching (water landing) or not - such as falling like a stone due to a stall.

But also

Families are concerned, people are concerned, memories are concerned. Don’t be just materialistic, finding the aircraft will help these families to mourn their beloved parent.....

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    $\begingroup$ AF447 is also another good example of why the voice recorder is so important. Without the voice recorder, we wouldn't have had nearly as complete of an understanding of how on Earth they crashed an A330 from 40,000 ft to ocean surface. $\endgroup$ – reirab Jun 21 '19 at 18:31
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    $\begingroup$ @reirab: In contrast, the MH370 CVR, if it's ever found, might not tell us much of anything interesting. It only keeps two hours of recordings, and it seems plausible that most or all of the crew and passengers were incapacitated for more than two hours before the plane finally crashed. $\endgroup$ – Michael Seifert Jun 21 '19 at 18:55
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    $\begingroup$ @MichaelSeifert It's possible, but not necessarily likely. At any rate, it would tell us if that's the case (if you could hear flight noise, but no humans,) which would itself go a long way toward answering questions. You would also be be able to hear automated callouts (or the lack thereof) which could provide useful information. For example, in the AF447 case, hearing the timing of automated callouts and how the crew reacted (or failed to react) to them provided useful information, but they could give us useful information about the aircraft's state even if there were no human voices. $\endgroup$ – reirab Jun 21 '19 at 18:59
  • $\begingroup$ @Michael Seifert, « it seem plausible »! That’s not 100%. But also, May be the recorder lost its supply so many hours ahead of the crash. May be it remained running and recorded nothing in the cockpit. May be some passengers were not incapacitated. If I follow your reasoning ones you make an assumption you stop looking to other colleagues assumptions, and you stop looking for a material proof. If I translate this medically, if you have a health problem and your doctor instead of following a protocol to find the trouble, he relies on a single assumption, would you be satisfied. $\endgroup$ – user40476 Jun 22 '19 at 8:12
  • $\begingroup$ Actually, most doctors do follow a memorized or looked up decision tree to diagnose and treat instead of actually thinking about how things work. If they don’t make a mistake or remember it wrong, this is right for most patients, but the occasional rare case is harmed. $\endgroup$ – WGroleau Jun 23 '19 at 5:46

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