The Australians have reported that a Chinese ship has reported hearing a ping, a pulse signal for a second time, just hours after they reported hearing a pulse that could have come from the black box recorders.  Jon Donnison from the BBC says: Given that not a single piece of debris from the missing plane has been found, it would be remarkable if the Chinese ship had managed to stumble across signals from the black box flight recorder without any real idea of where the plane crashed. Some will ask whether the Chinese know more than they are letting on. After thousands of man-hours spent searching the ocean he has a point, could a Chinese vessel just have gotten lucky and happened upon the site? The Haixun 01 picked up the first ‘ping’  at 25° south latitude and 101° east longitude, about 1,000 miles northwest of Perth, Australia, on the same frequency used by the black box recorders, 37.5Hz. They were using a hand-held device called a hydrophone. Mounted on the end of a pole it was held over the side of a very small Chinese boat. Experts have said that discovering the wreckage with this method is not entirely impossible but is extremely unlikely. More