US United States




As the effort to find Malaysian Airlines flight MH370 moves inexorably towards the recovery stage, the challenge of finding the plane’s flight recorder (called the “black box” even though it’s actually bright orange) on the ocean floor will become a game of blind man’s bluff spread over thousands of kilometres.


In a nutshell, the problem is that seawater is opaque to electromagnetic radiation, such as radio waves, microwaves and X-rays. This means that almost none of our normal techniques to “see” over long distances can be used in the ocean.



The bright colour of black boxes doesn’t help when submerged in 4,000m of seawater. AvgeekJoe/Flickr, CC BY-SA



But oceanographers who want to study the deep ocean can’t use most common tools, such as satellites or radio waves.

Listen to this


It’s no surprise, then, that black boxes on aeroplanes have “pingers” that transmit a sound signal. But while sound travels long distances under water, it isn’t a very efficient way of transmitting information: you can’t pack too much information in it and it costs much more energy than electromagnetic radiation.


As sound bounces around under water it can change intensity and create confusing reflections. RA Zingarelli and DB King


Oceanographers have been struggling with this lack of a good way to transmit signals through the ocean for decades. It means that submarines can’t use GPS to get their position, and that data from subsurface instruments need to be either locally stored on logging devices (which then need to be retrieved) or transmitted via cables to land or ship.

What happens when the pings stop?


A diagram of seafloor sonar ‘pictures’ taken by a ship. NOAA's National Ocean Service/Flickr, CC BY

The real dilemma for the search team is how high above the ocean floor to take the sonar “pictures”:


In this sense, it doesn’t help that we don’t have any good maps of the ocean floor already. If we would have such maps, we could simply put post-plane crash maps on top of them and see where they differ. These locations could then be scrutinised for possible wreckage, and regions where there are no differences can initially be skipped.

The problems faced by the search time of the MH370 are very similar to those of the Air France AF447 flight that went down in the Atlantic Ocean in 2009. Back then, the search team was not able to locate the black boxes with a pinger signal.

The search took two years, and it was only through months of scouring the ocean floor with submarines and sonar that the black box was finally found.

Let’s hope MH370’s black box can be located sooner and provide some much-needed insight to the flight’s mystery.