Cockpit Voice Recorder (CVR) is a device used to record the audio in the flight deck for accident and incident investigation purposes. The CVR records and stores the audio signals of the microphones and earphones of the pilots' headsets and of an area microphone installed in the cockpit, thereby capturing the flight crew's communications and the aural setting of the cockpit for the last 2 hours of operation.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a Cockpit Voice Recorder in aviation?
A Cockpit Voice Recorder (CVR) is a device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents, and it records audio signals from the cockpit. The CVR stores audio signals and captures the audio in the flight deck, including voices.
The CVR preserves the last sounds inside the flight deck before an incident. Early models stored only thirty minutes, while most newer ones are two hours. After a string of accidents in which vital material vanished, regulators extended the required recording duration to twenty-five hours, matching the 2015 EU amended regulations and the later FAA published final rule for modifications. The device resides inside a crash-survivable container that must be bright orange or bright yellow so investigators locate it quickly even under debris or water.
What is the purpose of a Cockpit Voice Recorder?
A Cockpit Voice Recorder records audio in the flight deck so investigators can hear pilot conversation, alarms, and sidetone that appears only when radio transmitters, the public address system, or the interphone is in use. The recording lasts at least the last 25 hours, and a G switch stops recording in a crash. Investigators then read all the way around the loop until they reach the accident again and locate where along the loop the accident occurred. ICAO amendments state data from CVRs is used only for safety-related purposes, while parallel ICAO amendments that took effect in 2019 state that data from flight data recorders is used for criminal proceedings. Each recorder container must be bright orange or bright yellow, must have reflective tape affixed to its external surface, and must have an underwater locating device when required; some aircraft have a marker button on the instrument panel to mark the event.
The main function of a CVR is to record voices within an aircraft that can aid investigators in the event of an incident or crash. Because human elements are sometimes a substantial part in air crashes, this device allows investigators to retrace the series of occurrences preceding a disruption. I believe a CVR to be an individual component of aircraft safety.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
What is the difference between a Cockpit Voice Recorder and a Flight Data Recorder?
The difference between a CVR and an FDR is the type of data being stored. The FDR preserves the recent history of the flight by recording dozens of parameters including altitude, airspeed, vertical speed, control-surface inputs and engine settings collected several times per second for at least the last 25 hours of operation. A CVR captures the last two hours of cockpit voice along with any aural warnings, making human factors audible. Although DVDRs combine both capabilities into one box, the FDR and CVR are normally separate physical devices that can be installed independently.
How does a Cockpit Voice Recorder work?
A Cockpit Voice Recorder works by recording on a continuous loop. The solid-state memory overwrites the oldest data once its capacity is reached. Older ones record 30 minutes, while newer ones record 2 hours. The latest models provide 25-hour recording capacity.
The unit starts the moment the first engine is started and continues until the engines are shut down. If the aircraft electrical system fails, a battery allows recording to continue until flight termination. A G switch stops recording in a crash, and an independent power source provides 10 minutes of backup power so the final sounds are preserved on the loop.
Inside the crash-protected housing, the CVR includes means of converting the analogue audio signals to a digital format. Channel 1 is the pilot microphone, Channel 2 is the co-pilot microphone, Channel 3 is an extra channel for other crew, and Channel 4 is the cockpit area microphone (CAM). The first 3 channels record radio transmissions and ambient sounds, and Channel 4 records from the cockpit area microphone. A marker button on the instrument panel can be pressed to preserve the recording, but the erasure feature is used to erase information recorded more than 30 minutes earlier only when the aircraft is on the ground and the parking brake is set, satisfying EASA and FAA requirements.
Investigators download the solid-state memory after an accident and read all the way around the loop until they reach the accident again. They can locate where along the loop the accident occurred because the recorder timestamps every sound sample.
Where is a Cockpit Voice Recorder located?
The physical CVR box is normally placed as far aft as practicable, so in everyday transport aircraft it is found near the aircraft's tail. A rear location keeps the unit away from the main crush-zone of a forward impact, and the tail area generally suffers the least damage during an accident and limits the length of wiring from the cockpit audio sources.
If, instead of separate CVR and DFDR boxes, two separate combination digital flight data recorder and cockpit voice recorder units are installed, the combination unit that is installed to comply with the cockpit voice recorder requirements is located near the cockpit. A forward-mounted recorder has the advantage of shorter cable distances, but it is still required that the container be located and mounted to minimize the probability of rupture of the container as a result of crash impact and consequent heat damage to the recorder from fire, so the aft position remains preferred whenever practicable.
Inside the flight deck, the audio is captured by a cockpit-mounted area microphone. This microphone is mounted in the centre of the cockpit above the windshield, or installed in the roof of the cockpit, positioned to register voice communications originating at the first and second pilot stations and voice communications of other crew-members on the flight deck when directed to those stations.
When is the CVR automatically energized?
CVRs are normally active as soon as one of the basic electrical buses, like the battery bus or the emergency bus, is energized. The unit is energized automatically when the aircraft is in the Emergency Electrical Configuration and, in flight, it remains powered continuously regardless of engine status. On the ground the recorder is powered continuously while at least one engine is running, and it is also energized for five minutes following initial electrical power application. AUTO mode powers the cockpit voice recorder from first engine start until five minutes after last engine shutdown and the same five-minute wind-down applies if the aircraft is still receiving electrical power on the ground, provided the CVR jack is not used. To guard against total power loss, the CVR must be fitted with an independent 10-minute power source that is located with the recorder and automatically engages whenever normal supply to the recorder ceases.
What are the components of a Cockpit Voice Recorder?
A Cockpit Voice Recorder includes a drive unit, reel and tape, circuit board assemblies and an insulation assembly.
The microphone used is an area microphone mounted on the overhead instrument panel between the two pilots and its signals pass through a pre-amplifier to the recorder. This microphone senses flight deck sounds, conversations, engine noise, stall warnings, landing gear extension and retraction, and other clicks and pops. Memory boards are housed within a crash-survivable memory unit that stores the last two hours of recorded audio. CVR weight is not specified in the approved phrase list.
What material is used in a Cockpit Voice Recorder?
The first cockpit voice recorders stored data with a threaded steel wire, chosen because it did not fling a magnetic recording head off the reel under vibration. Early designs replaced the wire with sterilised copper foil, a thin metallic strip housed in a crash-survivable box at the aft end of the airplane. Many first-generation recorders used metal foil as the recording medium. Analogue magnetic tape followed: the most widely employed backing materials were mylar, kapton and plain metallic tapes transported in coplanar and coaxial reel-to-reel, endless-loop reel packs or endless-loop random storage cartridges.
Present-day units are solid-state. The memory unit is a heavy stainless-steel shell wrapped inside layers of high-temperature insulating material and covered by a light aluminum housing. Some housings are double-wrapped in corrosion-resistant stainless steel, whereas other modern devices use an outer shell of titanium. Circuits store data on stacked digitally encoded memory boards, a technology that is lighter, draws less power and tolerates wider temperature variations than earlier recording-medium materials. All of these materials are selected for extreme durability. The stainless-steel core can survive impacts of thousands of g and remain intact even when a jet strikes the ground at transonic speed. The titanium or steel outer shell keeps seawater out for months and withstands deep underwater pressures encountered on the ocean floor, while an ultrasonic beacon emits a locating ping for at least thirty days under water. Inside, the insulation keeps the memory boards at beneath-threshold temperature for more than an hour in a 1,100°C (2,012°F) flame. This layered combination of fire, impact, pressure and immersion resistance means a CVR will almost certainly survive any conceivable crash scenario long enough to be found and decoded. The exterior shell is high-strength metal steel, chosen specifically for its capacity to endure huge force and intense heat. Inside, the memory portion is a solid-state storage card, isolated within a careful metal casing and wrapped in sophisticated fire-resistant stuff.
When is a Cockpit Voice Recorder required?
A Cockpit Voice Recorder is required on any multi-engine, turbine-powered airplane or rotorcraft that has a passenger-seating configuration of six or more and for which two pilots are required by certification or operating rules. The same obligation applies to any airplane with twenty or more passenger seats. In general-aviation operations, the recorder is not mandatory for light, single-pilot aircraft. The rule is triggered when the flight is conducted under commercial, charter, or air-taxi rules that already demand a flight data recorder.
Airplanes manufactured before 7 April 2010 that are required to carry both recorders had to have a compliant cockpit voice recorder installed by 7 April 2012. Airplanes and rotorcraft manufactured on or after 7 April 2010 must be equipped with an approved CVR that operates continuously from the first pre-flight checklist to the final post-flight checklist and that retains at least the last two hours of audio using a recorder that meets TSO-C123a or a later revision. Datalink messages generated after 6 December 2010 must be recorded.
Any aircraft with a maximum certificated take-off mass above 27,000 kg (59,524.8 lbs) that is manufactured after 1 January 2021 (or about 1 January 2022 under some national rules) must carry a 25-hour recorder. The U.S. imposed the same 25-hour standard on all new U.S.-registered aircraft manufactured after 16 May 2025, while existing aircraft must be retrofitted with 25-hour CVRs by 2030.
What is a CVR test in aviation?
A CVR test in aviation verifies the functionality of the Cockpit Voice Recorder, which records and stores audio signals from the pilots' headsets and an area microphone in the cockpit. This device is used to capture the audio in the flight deck for accident and incident investigation purposes. A CVR test in aviation verifies that the Cockpit Voice Recorder is serviceable before flight and that every recorded channel can later yield intelligible audio for investigation.
The daily functional test is performed before the first flight of each day as part of an approved aircraft checklist: on the flight-deck, with the CVR energized and the parking brake on, the crew pushes and holds the CVR TEST button. A low-frequency tone is heard through the cockpit loud-speakers, the hot-mic circuit is confirmed, aural alerts and autopilot-disconnect tones are checked, and crew-members speak a short intercom phrase - “This is the beginning of the CVR Flight Test for aircraft” - to confirm that microphones and headsets are heard on all channels.
A separate periodic CVR recording inspection is a regulatory and maintenance requirement performed at regular intervals by an audio specialist or qualified analyst. A sample of in-flight recording is examined for evidence that the signal is acceptable on each channel, that adequate signal-to-noise ratio exists for inputs, and that recorded levels and signal quality are balanced between tracks. The inspector checks that Passenger Address, Cockpit Area Microphone, aural alerts, warnings, AUTOPILOT DISCONNECT, SAS alerts and radio side-tone are recorded, that required input sources are connected, that the nominal recording duration is honoured, and that channel synchronization and phase shift between channels are correct.
Interference tests detect CAM recording pollution by aircraft power supply, internal CVR power supply, hyper-frequency bursts from Wi-Fi or GSM pulses, audio popping, mechanical vibration or electrical/mechanical saturation, while miscellaneous checks verify start-stop function, hot-microphone function, FSK signal presence and absence of abnormal signal interruption. The inspection report is prepared and retained, results ranging from good to poor are reported to the oversight authority so that missing sources, uncommanded interruption or saturation are rectified promptly and the recorder remains fit for accident and incident investigation.
Who invented the Cockpit Voice Recorder?
The Cockpit Voice Recorder was invented by David Ronald de Mey Warren AO, an Australian scientist and chemist specialising in aviation fuels at Melbourne's Aeronautical Research Laboratories. Warren conceived the idea in 1953 while investigating the crash of the world's first commercial jet airliner, the Comet. The catalyst was a miniature voice recorder he saw at a trade show that same year, which inspired him to capture cockpit voices as a data parameter.
Between 1956 and 1958 he built two prototypes, the second was the first flight recorder able to store both voice and flight data in one unit. Although the prototype he designed in the late 1950s met with indifference in Australia, it was greeted with enthusiasm elsewhere. British firm S Davall & Sons Ltd accepted the device in the early 1960s, obtained production rights and produced a commercial flight recorder based on Warren's invention.
Independently, American aeronautical engineer Edmund A. Boniface Jr. invented and patented a Cockpit Sound Recorder while at Lockheed Aircraft Corporation, and James J. Ryan filed United States patents for flight-recorder coding apparatus in 1953 and 1963. Australian researcher Robert Henry Orgill test-flew his own Orgill Air Safety Unit in 1956, yet Warren stated he was unaware of Orgill's demonstration. Warren's invention, known as the black box, made a huge contribution to air safety and he was ultimately appointed an Officer of the Order of Australia for services to aviation.
Why is the CVR called a black box?
The CVR is called a black box despite not being colored black but is required to be painted bright orange. This high-visibility vermilion colour, known as international orange, helps locate the unit easily in case of a crash. The misnomer ‘black box’ entered English around 1945, a few years after the first flight data recorder was built. Early prototypes were sometimes housed in egg-type casings painted red, while other early units were painted black simply to prevent reflection. The phrase echoes the pitch-black interior of the housing, because once sealed the inside is never lit again. Regardless of the exact origin, the label stuck, and the bright orange design now aids recovery after accidents, making the once-apt nickname nothing more than historical shorthand.
