Now that searchers have found some floating remnants of Air France 447 in the Atlantic 430 miles (700 kilometers) north of the Fernando de Noronha islands, the hard work of trying to locate the Airbus' "black boxes" - the Flight Data Recorder and Cockpit Voice Recorder - can begin. This is actually much worse than the proverbial needle in the haystack, because in that case, the assumption is the needle can be found after expending a lot of time and energy. These boxes might very well be truly lost to the abyss.Long Odds Search for Black Boxes (Trueslant.com)
But of course they still must try to find them as well as any wreckage of the Airbus A-330.
To that end, a French research ship with a submersible capable of diving to a depth of 20,000 feet (6,000 meters) is steaming to the area. The French transport Ministry says the ship carries equipment "able to explore more than 97% of the ocean bed area, specifically in the search area." I some spots, Atlantic is more than 20,000 feet deep in the area where searchers found the floating debris.
The submersible will be listening for the distinctive "pinging" noise that these boxes are designed to emit once they are submerged in water. They are supposed to "ping" for thirty days in water as deep as 20,000 feet. Sonar used by surface ships is only good to about a thousand feet of depth - so it is essential to send some "ears" deep beneath the sea in order to find the boxes. These sonar devices can be towed by ships or ply the deep on their own power.