With the tragic disappearance of flight MH370 over the sea, there is much discussion about the difficulty of finding the Flight Data Recorder or "black box" of a crashed plane. These things are incredibly well-engineered and will send out a signal for up to 30 days even immersed at depth but eventually fail.
Like all battery powered devices there is the inevitable trade-off between balancing strength of signal with the need to conserve battery power. I'd suggest tweaking the current design so it emits the ongoing signal at usual strength but then twice every 24 hours it squawks at maximum strength. This should be synched to 0 hours and 12 hours UTC so searchers know when to pay special attention because attention fatigue affects people listening for the signals no matter how urgent the search.-- AusCan531, Mar 11 2014 Add a depth guage that self-releases on hitting the ocean floor, inflates a small bladder, and then floats back up to report ia how deep the black box lies, and the search could be narrowed a bit more, too.
In fact a lot of black box data would fit on a micro-SD card, these days, so why do they still sink? You should even be able to get the GPS coordinates of the splash, surely?
=== Edit === [21] said pretty much the same thing almost simultaneously, which leads me to the not so astonishing conclusion that in all probability this idea has been raised time and again by the people who design black boxes.-- skoomphemph, Mar 11 2014 Black boxes I suspect are protectively wrapped in miles of red tape. Bringing them up to the state of technology of at least 2007 would be a great start.-- RayfordSteele, Mar 11 2014 They are actually orange.-- sqeaketh the wheel, Mar 13 2014 Not quite done. They have to survive things like high G impacts, ridiculous temperatures, and such.-- RayfordSteele, Mar 14 2014 There's probably an application in quintuplicate to amend the specification at this very moment being returned to the proposer, because the new blue form was not used, and someone forgot to initial every page.-- skoomphemph, Mar 14 2014 It misses the point. The technical problems are tiny. However the aircraft recovery industry will never go along with the idea because it would be like turkeys voting for christmas.-- bhumphrys, Mar 16 2014 But wait! I like it! [+]-- Grogster, Mar 16 2014 The question could be addressed in a Darwinian manner. I am interested to read of all the transmitters on this plane, each muttering it's own mantra. Some under human control and some not. Thinking about 21st " just before they crash" scenario, load a plane with a bunch of different boxes just before just before it crashes. See which proves most helpful.-- bungston, Mar 16 2014 A 600,000 lb black box which absolutely, positively prevents crashes.
Now we just have to invent some other way to transport the people and cargo.-- lurch, Mar 16 2014 Chance and happenstance are your biggest enemies for this idea. If something is visible within a certain radius all of the time, that is better than having it visible from a larger radius some of the time, even if those larger radius points are regular.
It is easier to ramp up the detecting ability of rescuers than it is to increase the detectability of the device. For this reason it is best to go with ULF, SLF and ELF signals, and then get better at detecting those signals from a search point. Of course, those frequencies have their own problems, nothing to do with power however.-- 4whom, Mar 16 2014 See this is what confuses me. I own a personal EPIRB (emergency position indicating radio beacon), which is GPS enabled. It's about the size of a large packet of cigatrettes. If I pull the cord, the satellite network will be notified nearly instantaneously that I'm in trouble, and my position will be transmitted as well. They don't come looking for you anymore, they send a helicopter directly to your position. (I really don't understand why anyone, ever, needs a search party when hiking etc now that this technology exists).
Why don't commercial aircraft have a half-dozen ruggedized EPIRBS distributed about the fuselage and wings, rigged to come loose on impact with the ocean or ground? At least one could be expected to remain functional.-- Custardguts, Mar 16 2014 random, halfbakery