It's not black. It's bright orange — international orange, specifically — designed to be visible in wreckage, underwater debris, and charred fuselage. The name stuck from the early days of prototype flight recorders when the casing was literally painted black.
Every misconception about this device starts with the name.
A modern aircraft carries two black boxes. The Flight Data Recorder (FDR) captures up to 88 parameters — altitude, airspeed, heading, control surface positions, engine thrust, autopilot mode, landing gear state — sampled multiple times per second for a minimum of 25 hours on a continuous loop.
The Cockpit Voice Recorder (CVR) captures the last two hours of audio from four channels: the captain's microphone, the first officer's, the area microphone in the overhead panel, and a fourth channel for the observer seat.
Two hours. Then it overwrites.
That constraint is deliberate. Pilot unions negotiated the two-hour limit to prevent routine surveillance of cockpit conversations. The CVR exists for accident investigation, not performance monitoring. If the overwrite window were longer, every casual remark would become a liability.
Both boxes are built to survive what the aircraft cannot.
The crash survivability standard — EUROCAS ED-112A — requires the recorder to withstand an impact of 3,400Gs for 6.5 milliseconds. That's equivalent to being hit by a train at 600 kilometres per hour. It must then survive a 1,100°C fire for 60 minutes, followed by immersion in 6,000 metres of saltwater for 30 days.
The underwater locator beacon — a small device attached to each box — emits a 37.5 kHz acoustic pulse once per second for a minimum of 90 days. After Air France 447 disappeared into the Atlantic in 2009, the pingers expired before searchers located the wreckage. The boxes were recovered two years later from the ocean floor at a depth of 3,900 metres.
The data inside was intact. Every parameter. Every word.
Bright orange. Nearly indestructible. Overwriting itself every two hours.
The most important device on any aircraft is the one built to survive the aircraft's destruction.