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What's a black box? Well it's not black for starters.

Transport Accident Investigation chief investigator Tim Burfoot said the black box is in fact orange - to make it easier to find - and planes have two of them on-board.

One records the voices of the pilot and co-pilot in the cockpit while the other records the details of the instruments, including altitude, speed, fuel levels and the condition of the engines and landing gear.

Mr Burfoot said black boxes - or flight data recorders - had two layers. The outer layer houses the electronics while the inner layer - known as the crash proof module - holds the recorded data, usually of the last half hour or hour of the flight.

"All the data comes in, everything that has happened to that plane is recorded," Mr Burfoot said.

"Everything the pilots do - every time he moves the controls to do something to the aircraft, whether it's to make it go up or down or turn - is all recorded," he said.

Mr Burfoot said the exact route of the plane can be mapped.

The boxes are 60cm long, 30cm high and 20cm wide while the crash proof module component is fire proof, crash proof and water proof.

"It's an amazing bit of kit," Mr Burfoot said.

So why are they called black boxes?

"I think the history of it was because they revealed all the dark secrets but that goes back a long way," Mr Burfoot said.

According to the website - the crash survivable memory unit is housed by a layer of dry silica about 2.64cm thick to protect it from high temperatures. There is also a stainless steel shell - sometimes made from titanium - which is 0.64cm thick.