A cockpit voice recorder (CVR) is one of two flight recorders ("black boxes"), used to record audio in the cockpit for the purpose of investigation of accidents and incidents.
A cockpit voice recorder (CVR) is one of two flight-recorders (popularly, though inaccurately, known as "black boxes"), used to record audio in the cockpit to aid in accident-investigations; the other flight recorder is the flight-data-recorder, which records aircraft parametric data. Some newer recorders store both audio and parametric data in a single memory module (but still have two separate recorders); this provides redundancy, as, even if one recorder is lost or destroyed, all audio and parametric data can still be recovered from the other recorder. Such a combined CVR/FDR is known as a cockpit voice and data recorder, or CVDR.
CVRs typically have multiple channels of audio data, each recording audio from different sources:
- One sound channel is connected to the cockpit area microphone (CAM), a microphone (usually mounted in the cockpit roof) which records all sounds audible in the cockpit, both spoken (such as flightcrew conversations or radio-communications) and not (such as engine and wind noises or the sounds of things exploding or breaking apart). The CAM channel has the advantage that it records everything that can be heard in the cockpit, but the disadvantages that all this sound is mixed together (rather than different sounds being recorded separately) and the flightcrew's voices can sometimes be difficult to make out against the background noise.
- The other channels record data from the microphones and earphones of the pilots' headsets; this provides a very-high-quality recording of everything the flightcrew say (or hear over the radio), at the expense of not recording non-voice sounds. A common strategy is to provide two or three channels of single-source audio (one for the headset audio from each of the pilots, plus sometimes a third for the cockpit observer or flight-engineer position on aircraft so equipped), plus a single longer-duration channel containing the audio data from all the headsets mixed together. The headset-audio channel(s) are also sometimes known as the "hot microphone" channel(s) (designated HOT in CVR transcripts), as the headset microphones on most modern aircraft are voice-activated (or "hot"), being active only when spoken to (this improves the quality of the resulting audio by keeping extraneous noise from being recorded when nobody's talking).
Where an aircraft is required to carry a CVR and utilises digital communications, the CVR is required to record such communications with air traffic control unless this is recorded elsewhere. As of 2008, it is an FAA requirement that the recording duration is a minimum of two hours.