We know about the Black box, but what is the QACVR?

The second black box was recovered last week from the disastrous China Eastern crash that happed in Wuzhou, China. The black boxes are set to arrive in the U.S. for decoding and investigation today on the 5th of April. Whilst it will take up to months and even years before anything significant can be revealed from the crash, there might be a quicker way for the airline to retrieve recordings and data, according to a former pilot who used to work for a Chinese airline.

What is a Black Box, again?

Anyone who is slightly interested in aviation is aware of what a black box is. A black box is a colloquial name for a flight recorder that contains mainly two components, the flight data recorder (FDR), and the cockpit voice recorder (CVR). It was colloquially called the black box due to the components being encased in a non-reflective black housing. In modern-day, the “black box” is painted in a fluorescent and bright hue of “safety orange” for easier identification after an accident. The FDR preserves the recent history of flight parameters such as airspeed, attitude, altitude, etc. while the CVR records the recent history of various sounds in the cockpit via the boom headsets, including the conversations of pilots. The combined records were proven to be detrimental to accident and incident investigations in the aviation industry and it is a mandatory requirement for commercial airliners to have a functioning CVR before the aircraft can be dispatched.

Honeywell is the leading black box manufacturer in the industry|© Honeywell Aerospace

Limitations of the standard CVR

The black box is seemingly the one crucial component in reviving the scenario before impacts. However, it is not without flaws and limitations, continuous upgrading of the black box has been suggested by ICAO after some recent crashes.

The black box is designed to survive an impact of 3400g and a temperature of over 1000°C required by the European Organization for Civil Aviation Equipment (EUROCAE) ED-112. The minimum physical strength of the housing would allow the black box to withstand an impact at roughly 270 kt and the crushing depth of 4.5km (15,000ft) underwater. The recent MU5735 recorded a surprisingly high speed right before impact at 450kts, which is more than the cruising speed of an airliner. If the speed data on FlightRadar24 were correct, it would have been a miracle for the black box to be found unscathed.

“Safety Orange” painted on the “black” box for easier identification among debris|©BBC

Besides the FDR and CVR, the black box is also equipped with an emergency locator beacon transmitter (ELT) that emits ultrasonic signals for 90days that is detectible down to 2km from the surface. This means if the black box is not recovered before the battery drained, the chance of finding it is just doing to be slimmer as time goes by. Air France’s flight 447 had its black box sink to the depth of the Atlantic Ocean and the CVR was not recovered after 2 years of search. The recording and data were eventually recovered. This particular accident prompted the extension of the battery life of the ELT.

The standard FDR is able to record up to 25 hr of flight parameters specified by aviation authorities. However, the standard CVR can only record up to 30 or 50 mins before the end of the recording depending on the model and make of the device. In recent years, the requirement for the amount of time was extended to 2 hours as it has been deemed not enough for incident investigations where the flights landed safely and the incident was more than 30mins from landing. In 2018, the NTSB had proposed to FAA to extend the duration of the CVR to up to 25hr to aid in investigations.

Last but not least, to retrieve data from the black box, the device will need to be sent back to the manufacturer for decoding before information can be released. This feature has led to the development of the QACVR, which is capable of streaming live data to ground stations without the need for decoding.

The Civil Aviation Authority of China (CAAC) celebrates the QACVR being installed on the Boeing 787|© caacnews.com.cn

Quick Access Cockpit Voice Recorder (QACVR)

Since there were numerous accidents where the black box was never recovered, the need for real-time access of flight data and voice recording comes to light. From 1970, a new detachable recorder called Quick Access Recorder (QAR) became popular among airliners as it is readily removable and can be connected to a desktop computer.

However, since it is not standard equipment or an optional item from the OEM (Original Equipment Manufacturer e.g. Airbus or Boeing etc.), the installation of the QACVR is controversial as it also violates privacy issues with its prolonged recording time. With SSD memory installed, a QACVR can record up to 3000hr of cockpit sounds. Unlike the CVR, the recordings in the QACVR are not erasable by the pilots through a button. The latest generation of QACVR is also compatible with 4G and Wifi, making the data readily accessible for airline operators.

Recordings are readily accessible via a USB port from the QACVR| ©Donica

Privacy Issues

From 2018, all airliners in China are required to be equipped with the QACVR, including the Boeing 737 that crashed as flight MU5375. According to EASA, the sole purpose of the QACVR is to aid in accident and incident investigations and shall not be used for the monitoring of flight operations. There have been talks that Chinese airlines are using the QACVR as a means to monitor cockpit behaviour. Grounding of pilots due to the use of non-standard phraseology is not uncommon and eventually, this culture to eavesdrop on pilots became a management style among Chinese airlines.

Could China Eastern had already retrieved the recording right after the crash? Do you think pilots can do their jobs properly if they are being monitored as soon as they enter the cockpit? Would the installation of QACVR add unnecessary stress to the flight crew? Let us know what you think below. For more aviation news from Travel Radar, click here.



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Leo Cheung
Leo Cheung
Aviation Reporter - Born and raised in Hong Kong, Leo has decided to pursue a career in aviation under the influence of the old Kai Tak Airport back in the days. With a degree in aviation, he has joint Travel Radar as an aviation reporter to diversify his views and apply professional knowledge to anyone who is interested in commercial aviation. He regularly contributes articles with 'inside the cockpit' knowledge.



  1. Good article. One typo: “The combined records were proven to be detrimental to accident and incident investigations in the aviation industry and it is a mandatory requirement for commercial airliners to have…”

    I think you mean “essential” instead of “detrimental”.


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