CORRECTION Aircraft Down

In plane crash investigations, the “black boxes” are crucial forensic tools.

These robust devices, actually orange, consist of a cockpit voice recorder and a flight data recorder.

Federal investigators retrieved the flight recorders Friday from the passenger jet that crashed in the Potomac River near Washington on Wednesday, while the search for similar devices from the downed military helicopter continues. This accident resulted in 67 fatalities, marking the deadliest U.S. aviation disaster since 2001.

Here’s an explanation of their function and capabilities:

What are black boxes?

The cockpit voice recorder and flight data recorder help investigators reconstruct the events preceding a plane crash.

Their orange color aids in wreckage location, even at significant ocean depths. Typically housed in the aircraft’s tail—the most impact-resistant section—they’re equipped with underwater beacons that transmit from depths up to 14,000 feet (4,267 meters). Although the beacon’s battery life is about one month, the data itself has no definitive lifespan, according to NTSB investigators.

For example, black boxes from an Air France flight that crashed in the Atlantic in 2009 were recovered from over 10,000 feet two years later, yielding most of their data.

Seawater-submerged boxes undergo freshwater rinsing to remove corrosive salts. If water intrusion occurs, careful drying using a vacuum oven is necessary to prevent memory chip damage.

Electronics and memory are inspected, repairs undertaken, and chips are microscopically examined.

What does the cockpit voice recorder do?

This recorder captures radio transmissions and sounds within the cockpit, including pilot conversations and engine noises.

Investigators analyze engine sounds, stall warnings, and other audio cues to determine engine speed and system failures. Pilot-crew conversations and air traffic control communications are transcribed, a process which can take up to a week.

What does the flight data recorder do?

The flight data recorder tracks altitude, airspeed, and heading, among at least 88 parameters mandated for new aircraft.

Some recorders monitor over 1,000 characteristics, from wing flap position to smoke alarms. The data allows for computer-animated flight reconstructions.

The recorder stores 25 hours of data, encompassing prior flights, which can reveal clues about mechanical failures. Preliminary data is available within 24 hours, but analysis continues for weeks.

What are the origins of the black box?

Two individuals are credited with the development of flight data recording devices.

French engineer François Hussenot developed a system in the 1930s to record aircraft speed, altitude, and other parameters onto photographic film for Airbus.

In the 1950s, Australian scientist David Warren conceived the cockpit voice recorder, inspired by the 1953 Comet crash. His prototype, built in 1956, was initially slow to gain widespread adoption. Warren’s father died in a plane crash in 1934.

Why the name “black box”?

One theory links it to Hussenot’s film-based device, operating within a light-tight enclosure. However, the orange color was chosen for visibility.

Other suggestions include post-crash charring.

The term likely originates from post-World War II electronics terminology, referring to self-contained devices whose function was more important than their internal workings.

The term persists due to the air of mystery it adds to post-disaster investigations.