Black Box Science: Everything you wanted to know about the flight data recorder

Monday, January 12, 2015, 3:53 PM - News reports are flooding in about one of the flight data recorders from AirAsia flight 8501 now on its way to Jakarta after being recovered, with the other found trapped under heavy debris, but exactly what are these devices - typically called 'black boxes' - where are they located in the plane, what, exactly, can investigators learn from them, and might there be a better way of recovering this information?

'Black' Box?

The first detail to know about these devices is that they're not actually black. They're painted bright orange, so that they're easier to find amongst the debris of a crashed aircraft.

A flight data recorder (left) and a cockpit voice recorder (right). Credit: National Transportation Safety Board

'Black box' is an informal nickname for the flight data recorder because it describes how the data it contains treats the entire plane as if it's a black box system. That is to say, one where the interior workings of the system aren't important to find out what happened - the inputs into the system, along with the system outputs are enough to figure anything out. In the case of an aircraft, the inputs would be the actions of the pilots, while the outputs would be the data displayed on the pilots' instrument panel.

More than one, and more than one kind

At one time, there was only the one 'black box' on any flight. These days, though, there are usually two, as shown above. The flight data recorder handles the inputs and outputs of the aircraft - the positions of the wing flaps (used to change how much lift the wing generates), the aileron (the small flap-like parts closer to the tips of the winds, which help the plane bank or roll), and the rudder, the position of the landing gear, and the speed of the engines - while the cockpit voice recorder keeps at least a two hour record of everything said inside the aircraft's cockpit. While just one of these can provide a good amount of information to investigators, having both available greatly increases their chances of discovering the cause of the accident.

Tough Enough

With the invaluable information these recorders contain, they are built to withstand some extreme conditions.

The interior workings of the recorder look like a fairly standard computer, with a processor, circuit boards and power supply.

The inside of a flight data recorder. Credit: Wikimedia Commons

However, the exterior of the device is a hardened shell of either stainless steal or titanium, that can withstand the crushing forces of impact, and resist the corroding effects of exposure to sea water. Meanwhile, the memory module, which resides in the cylindrical section of the device, is not only wrapped in this metallic shell, but also a layer of insulation inside the shell to protect it from the intense heat of explosions and fires caused by jet fuel.

Maximum survival

Even with the sturdy construction, aircraft engineers leave nothing to chance when it comes to recovering these data recorders.

In order to reduce the impact of the forces that the recorders are subjected to, both the flight data and cockpit voice recorders are bolted into the tail of the aircraft. This works on the assumption that the tail will experience the least amount of stresses (as the nose and fuselage will take the brunt of the impact) and thus be the most likely part of the aircraft to survive intact.

One of the times when the recorders are difficult to retrieve, no matter what, is the case of a water crash, when the wreckage sinks beneath the waves. However, each recorder is fitted with a radio beacon (the small silver cyclinder at the 'front' of the unit), which sends out a periodic 'ping' that search and rescue personnel can use to hone in on. Even this has its limitations, though, as the beacon only has a certain amount of battery power - typically lasting around 30 days. A month may seem like a sufficiently long time, but in the case of some crashes, like Air France Flight 447 in 2009 and Malaysia Airlines Flight 370, it can take significantly longer than that to find the wreckage and recover the recorders. In the case of Air France Flight 447, it wasn't until nearly two years after the accident that the recorders were located and brought to the surface. For Malaysia Airlines Flight 370, although there were several false alarms that they'd been located, the search continues even now, and may go on for some time before they're found.

A better way, perhaps?

With these kinds of limitations hampering the recovery of vital clues to the cause of flight accidents, there might be a better way to go about this, especially now, in the digital age.

Flyht Aerospace Solutions, a company based on Calgary, has designed a new type of flight data recording system, called FLYHTStream, which uses a device called the Automated Flight Information Reporting System (or AFIRS) to transmit the contents of a flight data recorder, as well as GPS data, when the aircraft experiences an in-flight accident.