The Mysterious Black Box

Whenever there is an accident involving an airliner, news reporters immediately begin talking about “the Black Box.”

“Where is the Black Box?”
“Investigators are looking for the Black Box”
“What’s the condition of the Black Box?”
“What did the investigators find in the Black Box?”

What exactly is the “Black Box” and why is it so important?

 

It’s (Usually) Not One Box and It’s Not Black

It’s confusing when the news media talks about The Black Box. The term is a misnomer. The Black Box is usually two different boxes with different functions. Ironically, neither of these boxes are black. They’re bright yellow or day-glow orange. The bright color is used to assist in locating the boxes after an accident. Here’s what the mysterious boxes do:

Black Box #1 – The CVR: The first box is the Cockpit Voice Recorder, or CVR. The CVR is a multi-track audio recorder that continuously captures every audible sound in the cockpit. CVRs are required to save at least two hours of audio (FAA regulation). Some recorders can save more audio. Early CVRs used magnetic wire or metal tape as a recording medium. Modern recorders are digital and use solid state memory, similar to a thumb drive or solid state hard drive.

The Cockpit Voice Recorder captures sounds on the flight deck with an area microphone, usually mounted on the cockpit overhead panel. It’s a sensitive mic that captures voices, sounds of switches, audible warnings, and other cockpit noise. The CVR also records audio from each pilot’s headset microphone, oxygen mask mic and handheld mic. If a mouse squeaks in the cockpit, it’s recorded.

Black Box #2 – The FDR: The Flight Data Recorder, or FDR, is also a solid state recording device. Instead of recording sounds, the FDR records aircraft system and flight data. Flight Data Recorders are required to captured at least 88 defined parameters. These include the position of control surfaces (flaps, elevator, rudder, ailerons), barometric data (altitude, airspeed, vertical speed), engine performance, G-loading, and many more.

Flight Data Recorders typically capture 17 to 25 hours worth of data. This is enough information for investigators to look at not only the accident flight data but data from several previous flights.

Black Box #3 – The All-In-One: Recent advances in digital technology have allowed both the CVR and FDR to be combined into one, bright orange box. So, in some cases, there really is just one box (it’s still not black). This combined unit is called a Cockpit Voice and Data Recorder (CVDR). Modern airliners have either two separate recorders or the CVDR.

Recorders Are Required For Airliners

The FAA requires that aircraft with 10 or more passenger seats have both a CVR and FDR installed. Smaller turbine powered aircraft require only a CVR. Regulations in other countries are similar. Simply put, if you buy a ticket on an airline, your aircraft will be equipped with these devices.

Flight Data and Voice Recorders are usually installed in the tail section of the aircraft. This area provides the equipment with the most protection. In the event of an accident or incident, investigators can use the CVR and FDR data to reconstruct the events leading up to the event. This helps the aviation community avoid similar accidents in the future.

Why does the media call it a Black Box?

The origin of “Black Box” when referring to a CVR and FDR is unclear. There are several theories, but my favorite is the reference to engineering and design jargon used since the mid 1940’s: A black box is an electronic device, system, or programming object which the user has no control. The device accepts inputs and has outputs, but what happens inside cannot be altered or seen by the operator – it’s a “magic box” or “black box.”

At some point in the late 60’s, the media started using “black box” and has used it ever since. I’ve had reporters tell me “If I use the correct terminology, viewers won’t know what I’m talking about.” Nonsense. The reason the public accepts the incorrect terminology is because the press has been feeding it to them for so long. The general public is pretty smart – use the correct terminology and they’ll catch on.

It’s important to note that no one in the flight safety or airline industries use the term “black box.” These are very important devices and we always use the correct terms for them. Because there may be two different devices that investigators need to recover after an accident, it’s helpful when the media uses the correct terminology to avoid confusion.