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Comment by amichail | Hacker News Reader

While I highly doubt this, I do wonder why we rely on black boxes for crash investigations. Airbus already received some data from the plane after problems developed. Why not develop this technology further to make black boxes redundant?

And if you really do want to keep black boxes, why not develop an ejection mechanism for them so that they would separate from the plane at the last second and float in the ocean?

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Because it's simply not possible to make black boxes redundant.

You can fly into a storm or into a canyon where radio/satellite uplinks won't work. Hence you need to store the data on sturdy local storage aka a black box.

As much as people love to think that technology can completely tame mother nature, it can't. It's still a brutal place, with nasty conditions. While the uplink data is great, you still need backups (Higher resolution is a nice bonus too)

A better way to explain it would be to point out that the remote telemetry and the black boxes are already examples of redundant design. The black box has fewer failure modes recording data, but requires recovery. The telemetry is more easily disrupted, but can get data out even in the face of a total loss of the aircraft.

Redundancy doesn't always mean the same thing as simple duplication.

"Why don't they make the whole plane out of that black box stuff?"

-steven wright

This question was previously asked here:

http://news.ycombinator.com/item?id=640289

I have thought about an ejection mechanism too. Maybe a combined system of ejecting small beacons and the main one, that stays in the plane, would work better. The beacons could be located in multiple locations on the plane, e.g. nose, tail, wings, and when an inevitable crash is detected they could start firing off at regular time intervals, depending on the altitude. If they are light-weight enough maybe some of them could be combined with an expandable helium balloon for easier spotting. Of course this requires having weather data available for the crash area so that one could deduct their starting position. (Disclaimer: I'm not an engineer so I don't know if my idea is stupid.)

That seems to be the direction...

http://en.wikipedia.org/wiki/Flight_data_recorder#Future_dev...

I know nothing about flight recorders, but offhand it would make sense to me for them to have some sort of transponder. Maybe the requirement of having a power source is unrealistic.

They do - they've got a pinger that sends out a signal after a crash has been detected to aid in locating the box, similar to an avalanche beacon.

Problem is that it's not all that strong, and is likely under a few tons of airplane and a few kilometers of water.

To make things even worse, sea water strongly attenuates electromagnetic radiation at radio frequencies...

It uses sonar. Radio would be useless under water.

I suppose it emits both in radio and sonar, right? What if the airplane crashes over land?

It only activates the sonar if it is under water:

http://trueslant.com/milesobrien/

And it only pings for 30 days.

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