How Things Work

Once in a while we hear news about an air crash that killed many people. As news spreads about this catastrophic event and fingers start to point at the people responsible, safety investigators point toward a different source: the well-known “black box” in the plane.

In reality, black boxes aren’t really black: Most are bright orange in color to aid investigators in their recovery. The term is used by physicists to refer to a device whose internal workings are deliberately hidden or ignored while the input and output are well understood.

The technology behind black boxes is in a state of transition. Black boxes are moving from the traditional use of magnetic tapes to the use of solid state technology boards.

The solid state technology boards are the result of significant advances in black box technology in planes, and offer increased durability, robustness and memory capacity among other things.

Solid state uses stacked arrays of memory chips, so unlike magnetic tapes, there are no moving parts and therefore fewer maintenance issues and a decreased chance of something breaking during a crash.

Another advantage is that magnetic-tape recorders can track about 100 parameters, while solid-state recorders can track more than 700 in larger aircrafts, according to

For instance, the Solid State Flight Data Recorder (SSFDR) developed by Honeywell, a leader in black box technology and manufacturing, retains the most recent 25 hours of digital flight data and timing information.

Similarly, according to Honeywell’s website, the “Solid State Cockpit Voice Recorder retains the most recent 30 minutes or two hours of audio, digital, and timing information.”

Both these devices use a modular crash survivable memory unit (CSMU) for protection of the memory board.

The use of black boxes has found its way into other industries, too. Black boxes have been used in automobiles for a long time — GM has been installing black box technology in its cars for more than a decade. These have helped police gather information about traffic accidents.

So what’s next for black boxes? We could soon expect to see cockpit video recorders, which will provide a more detailed peek at the events before a crash.

Also, small heat-resistant black boxes for space probes are being developed. NASA recently signed a deal with the Aerospace Corporation to develop black boxes called Reentry Breakup Recorders (REBRs).
Black boxes are not usually used on spacecraft such as the shuttle, which experiences extreme heating when roaring back into Earth’s atmosphere.

The planned REBRs would quietly take data during the flight, but would only activate in the event of a major disaster. The heat from the craft’s explosion would trigger the boxes to detach, and, as they fall to Earth, the boxes would transmit their data, eliminating the need to retrieve the recorder later.