Why not make an airplane black box that floats?

Think about it: if it floats, then it could drift. Which means it could get far away from the wreckage. And that is assuming that the recorder would come free from whatever it is attached and secured to--and that involves a fair amount of wiring--which is likely to sink. Unless you want to make the whole plane out of floating material?

You state "you'd think someone would have thought about it". Well, judging by the recent Yahoo Answers questions lately, I'd say about a couple hundred times within the last week alone.

And presumably by a few among us, aerospace engineers. The fact we did not implement this is perhaps because this is not that good an idea?

As for the "recording over itself ever(y) 20 minutes", you should know that today's FDR units record 20 to 60 hours worth of data. This is used to track down progressive trends in slowly emerging faults and failures, among other things. 20000 airliners broadcasting everything they do all the time, including while flying over the pole which is not that well covered by satellites, is a costly and technically challenging solution that probably would cost a lot more than the remote controlled submarines that are required only once per several years.

Edit: yes it would matter, because

1- the flight data recorder sound beacon is one of the thing that helps find the bulk of the wreckage (and the flight data recorder simply tell what happened, not necessarily why and how, the wreckage is often needed for that)

2- the sound beacon that the FDR emits is best preceived if the FDR is under water, on the surface, the waves and other sounds will reduce the range that it can be picked

ELT are radio emitters, which do not work well under water.

As for the boracasting issue, there are a few things you are overlooking.

1- the polar region is not frozen year round everywhere

2- having a broacasting signal that carries the FDR data being interrupted because the plane enters a zone that is not adequately covered by satellites could trigger a false "airplane crash, it is not transmitting anymore" alert, and could also introduce another interesting challenge when transmission resumes.

Again, a continuous braocasting system will likely me far more trouble than it will solve. It would be yet one more system that could fail, that would have to be maintained, and regulated. Pontential savings is likely going to be a big fat zero, when compared with the cost of renting submarines for the one FDR that is at the bottom of the ocean, which occurs once or twice per 10 years.

Good concepts, but may be difficult to implement. They want to record everything up to the moment of impact. Ejecting the black box before that time might miss some important information. Keeping it in the tail section makes it easier to find because it's easier to find a large tail section than a device that isn't much larger that a shoe box. The locating beacon is only good for about 30 days.

It would probably require explosive charges to separate the black box from the aircraft along with the electrical connections. Explosives on a passenger airplane is not a good mix. To make it float, the black box will have to be larger to contain enough buoyancy material.

In a crash, the current black box has the most chance of survival from a design standpoint. It's a good idea to try to make it float, but, as Eric said, it is bolted in to the airframe.

As I understand it, the U.S. is sending devices that will be able to locate the black box, as it sends out signals for about 30 days, and these devices the U.S. is sending should be able to detect the signal, even if it is on the ocean floor..

The black packing packing containers are produced from heavy cloth to guard the contents in caso of a crash. they are continuously on the rear of an airplane, form of under the tail, and screwed to the form. even some thing like an ejection gadget wouldn´t help plenty, because of the fact they have been given each and all of the airplane shape around. And the main significant subject in commercial airplane is weight. desire this enables slightly.

Well, there are a lot of pros and cons to this question. An airplane black box is made so that it can withstand extremely high temperatures, and to shield impact higher than 10g. To make it buoyant, you would have to make it out of a lightweight floating material, but this probably wouldn't withstand temperatures more than 1000 F. But, hopefully we will be able to find this technology some day.

Because the current would move the black box away from the plane wreckage.

The could make it eject from the plane and float. The problem would then be finding the thing. Right now, if they find the plane, they find the box.

With current technology no material has been found/made to stand up to 600 G's of impact force that could float.

A satellite/server would still be impractical and subject to MANY failure points.

The black box could be bouyant and it would still go down with the plane, because they're bolted together.

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