How black boxes flight recorders work

Originally published on March 12, 2014

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On March 7, at 1:30 a.m. Malaysian Airlines flight MH370 lost all communications and vanished with 239 people on board.

Now, five days later, search crews are racing to find the plane's black boxes in order to solve the mystery of its disappearance, the South China Morning Post reported.

Black boxes are able to record a huge amount of data and therefore can help, in case of a crash, to understand the causes of the accident.

To locate a black box, the underwater locator beacon switches on automatically after a crash and sends out an ultrasonic pulse that allows its detection with special equipment.

As of Wednesday however, no signal from the missing Malaysian Airlines plane has been picked up by the searching teams.

The battery life of the locator lasts 30 days, aerospace expert professor Alan Lau Kin-tak of Hong Kong Polytechnic University's mechanical engineering department was quoted by the South China Morning Post as saying. "If they cannot find it within this window, it will become very hard to locate," he said.

When found, black boxes are transferred to a lab in a water-filled cooler that allows investigators to retrieve and copy all the recorder data that is then examined to understand the nature of the accident.

This animation explains how black boxes work.