18 days left to locate missing MH370's black box

As the desperate search for the missing Malaysian Airline Flight 370 continues for the 11th day, authorities are running out of time before the crucial black box stops giving a signal to unlock the mystery.

The black box, a piece of aviation technology which holds the key to unlocking the unanswered questions about why flight MH370 went missing, will only transmit a signal for 30 days.

The authorities, therefore, are left with only 18 days to comb the dense 600,000 square kilometres sea and retrieve the black box, news.com.au reports.

According to the report, if ever a plane crashes into the water, an underwater locator beacon sends out an ultrasonic pulse that cannot be heard by human ears but can be detected by sonar and acoustic-locating equipment.

There is a submergence sensor on the side of the beacon, and when this sensor touches water the beacon activates and it begins 'pinging,' once per second for 30 days.

However, in rare and severe crashes, the beacon might get snapped off during a high-impact collision, while underwater terrain such as deep trenches could also affect how easily the beacon's signal can be detected.

Search teams must be about 25km in range of the beacon to locate the beacon's pings, which are sent out at 37.5 kilohertz (kHz) to transmit sound as deep as 14,000 feet, the report added.