An underwater locator beacon (ULB) such as the one on the black boxes (CVR) Cockpit Voice Recorder and FDR (Flight Data Recorder) of Malaysia Airlines Flight 370 on 37.5 kHz for about 30 days at 4°C temperature. They run on lithium-ion batteries, and “mileage” may vary; 30 days is the minimum expectation. This is all relevant to today’s news because the Chinese patrol ship Haixun 01 which is one of the ships equipped with a pinger locator, has heard a ping in the South Indian Ocean.
The particular frequency was selected because it is not one that occurs in nature.
Although Malaysia Airlines told the public that “This battery is not replaceable,” the ULB batteries had been scheduled for battery replacement in 2012, but were not replaced by Dukane Seacom, the original equipment manufacturer of the beacons. (Dukane Seacom either replaces the entire pinger or installed new batteries.) If replacement was not performed by toe OEM or other parties, the actual ping time may be less than 30 days.
One ping in an ocean does not a discovery make. The wreckage has not been located, nor the ping confirmed. But we can still hope this is a step in the right direction.