The Black Box 08.08.11

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It was the death of his father in a plane crash that inspired David Warren to invent the flight data recorder. While it may not be much to look at, it's a design that's built to endure.

The most memorable words spoken in the cockpit by the captain of the passenger plane that crash-landed on the Hudson river in January 2009 came just after it took off from LaGuardia airport. "And what a view of the Hudson today," Chesley Sullenberger said to his co-pilot, Jeffrey Skiles. It was a very striking winter afternoon in New York, but those were the only words spoken by either of the pilots that weren't related to the business of flying. The pre-flight banter between the two men was about wind speeds, passenger lists, and a door that proved difficult to close. Once the flight began, the communication of Sullenberger and Skiles was all about flight and routine – except for that one observation about the Hudson and how it appeared.

Then, 50 seconds later, the plane flew into a line of geese above the Bronx, lost almost all power in both of its engines, and left the pilot and co-pilot with the unenviable job of gliding it back to earth. The river that Sullenberger had noticed and remarked upon only seconds earlier was the one available place for their craft to land. This was, as the accident was subsequently named, the miracle on the Hudson.

We know Sullenberger said those words about the river to Skiles because one of the plane's two "black boxes", the recorders housed under the tail of each commercial and military plane, preserved every word spoken in the cockpit that day. The cockpit voice recorder along with its companion, the flight data recorder, were extracted from the plane after it was hauled out of the Hudson several days later. The cockpit voice recorder is important when investigating an accident because it captures the atmosphere on the flight deck. The flight data recorder reveals what the plane was up to before and after an accident – the position of its wings, the power of its engines, the speed it was flying, and the effects that damage to any part of the plane had on its ability to fly. The information from both recorders was processed by the National Transportation Safety Board, the authority that investigates airplane accidents in the US, and with all that they now had, along with the testimony of the pilots and the evidence of the wrecked plane, the entire flight and the cause of the accident could be recreated and replayed.

Both instruments are indebted to the invention of an Australian, David Warren, who died earlier this year. In 1934, 
when Warren was a boy, his father died in a plane crash: 20 years later, Warren came up with the idea of a recording device that would make it easier for those examining an air crash to determine its likely cause. Recordings of what pilots were saying before and during an emergency could be played back to the investigators. Warren named his black box the "flight memory unit", but amazingly no one was interested by his idea. Then, a British government official turned up and persuaded Warren to go to London to explain his work. Why the unit was called a black box is mysterious, since these devices are usually housed in steel boxes painted bright orange or red. Early versions were called "red eggs".

Fifty years later, and Warren's invention is a requirement for every commercial plane. Now there are two boxes, one for voice recordings, the other for data, and many more aspects of flight are now recordable than was the case in the late 1950s. Before Warren's invention, many plane crashes were mysteries, or only partially understood; afterwards, they became the critical evidence that explained the cause of a crash. Warren's design helps us to better understand failure.

 

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The UK Air Accidents Investigation Branch (AAIB)

 

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Inigo Thomas

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Before Warren's invention, many plane crashes were mysteries, or only partially understood; afterwards, they became the critical evidence that explained the cause of a crash

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