March 25, 2014 3:50 pm
Updated: March 25, 2014 4:07 pm

Flight MH370: What is a black box and how does it work?

Airplane’s actually have two black boxes, made up of two separate pieces of equipment – a cockpit voice recorder and a flight data recorder.


TORONTO – Now that investigators have concluded the missing Malaysia Airlines jet crashed into the Indian Ocean, the race is on to find the wreckage and recover the black box in hopes of solving the mystery of flight MH370.

Story continues below

But search crews are on a tight deadline to find the so-called black boxes before a battery-powered ping the devices emit fades away. The devices are designed to send out those signals for at least 30 days after a crash – but it has already been 17 days since flight MH370 went missing and poor weather is hampering search efforts.

READ MORE: Race is on to find Malaysia airliner’s black boxes

Why is finding the black boxes so important to the investigation?

Because without it investigators may never be able to piece together exactly what happened to flight MH370.

What is a black box?

Black boxes may be one of the most important pieces of technical equipment on board a plane, despite the fact they do nothing to help the plane while it’s in the air.

Airplanes actually have two black boxes, made up of two separate pieces of equipment – a cockpit voice recorder, which records all of the sound and conversations that happen in the cockpit, and a flight data recorder, which records the planes operating functions.

Each unit is fitted with an underwater locator beacon (ULB) that is activated as soon as the recorder comes into contact with water – this is what creates the “ping” that investigators use to locate the device.

It is usually located in the tail of the plane because it is usually the last part of the plane to make impact.

Despite its name the device is actually bright orange, making it easier to spot in wreckage.

The flight data recorder from Air France flight 447 is displayed in front of journalists during a press conference in 2011.


Cockpit voice recorder

Obviously, the point of having a cockpit voice recorder is so investigators can play back conversations between the pilot, copilot, and whoever else may have entered the cockpit to piece together what went wrong.

But trained investigators are also able to listen for engine sounds, stall warnings, or emergency alarms that could provide evidence into a mechanical problem.

According to the U.S. National Transportation and Safety Board, the cockpit voice recorder must hold at least two hours of audio.

Flight data recorder

Flight data recorders can record a number of parameters including, the time, altitude, airspeed, direction, and vertical acceleration of the flight, as well as more technical things like the movement of individual flaps on the wings.

According to National Geographic, the data saved on this recorder can help investigators to eventually produce computer-generated re-enactments of the crash.

The recorder must hold a minimum of 25 hours of flight information.

How does the black box survive a crash?

Black boxes are designed to withstand catastrophic events.

According to National Geographic, one black box recorder called the L-3 FA 2100 underwent testing that included being exposed to a 1,110°C fire for an hour and 260°C heat for 10 hours. The devices are also designed to operate from -55° to +70°C. This is done with high-temperature insulation.

Black boxes are also encased in corrosion-resistant stainless steel or titanium shells.

The ping transmitted from the ULB is able to transmit from as deep as 14,000 feet.

Can the black box survive underwater?


The black box from Air France flight 447 wasn’t found until two years after the plane crashed into the Atlantic on route from Rio De Janeiro to Paris in June 2009. It remained intact despite being lost beneath two miles of ocean.

© 2014 Shaw Media

Report an error


Want to discuss? Please read our Commenting Policy first.