The role of two black boxes in the Chinese plane crash

The two black boxes contain the most important clues, which could help Chinese investigators find out what happened before the MU5735 plane crashed.

The first black box of the Boeing 737-800, bearing the number MU5735, was found on March 23, two days after the China Eastern Airlines plane crashed in Guangxi. This is the black box containing the cockpit voice recorder, recording the last conversations of the pilot and the warning sound of the plane before the crash.

Officials said the outer shell of the black box was damaged, but it was not clear whether the protected data inside was intact. The device stores a recording of every noise in the cockpit, even the engine and the pilot’s switches, for at least two hours before being overwritten.

The remaining black box of the plane was discovered under 1.5 m of land on February 27, recording the flight data. This is a device that stores flight data, continuously recording at least 88 parameters, including flight speed, altitude, flight direction and position of the aircraft’s nose up, down or balance.

The device can record the position of the flaps and whether the plane is on autopilot or not, typically storing 25 hours of flight data.

Both black boxes of the crashed Boeing 737-800 were brought to Beijing for inspection and data download. The process can take weeks to months, experts say, to analyze all the data and begin to find answers.

These two black boxes, which are found on most commercial aircraft, are considered the most important clues to help investigators determine the cause of the crashes. Despite the name black box, the device is usually orange in color to make it easy to find.

Both black boxes stopped recording when the plane suddenly lost power. They are designed to withstand fire and high impact, usually located behind the cargo hold. They are equipped with radio navigation devices that activate when they fall underwater, but do not operate on land. Black boxes used to use magnetic tape, but manufacturers have now switched to storing data in digital form to hold more information.

The black box can tell investigators what the pilot was doing before the plane crashed, whether they noticed problems with the plane, as well as the working condition of the engine and other equipment.

Rescue workers rescue at the scene of the crash of a Boeing 737-800 in Teng county, Guangxi autonomous region, China on March 26. Photo: Xinhua.
Rescue workers rescue at the scene of the crash of a Boeing 737-800 in Teng county, Guangxi autonomous region, China on March 26. Photo: Xinhua.

These devices are especially important after aviation tragedies like the China Eastern Boeing 737-800 crash, when no one on board survived and air traffic controllers heard no reports from the plane. when the plane went down.

During the 2018 Lion Air crash of a Lion Air Boeing 737 Max in Indonesia, data from the black box showed that the pilots struggled to balance the nose of the plane as the autopilot repeatedly sent it down. An Ethiopian Airlines Boeing 737 Max crashed four months later for the same reason. These accidents caused all Boeing 737 Max aircraft to be grounded.

China is leading the investigation into the cause of the MU5735 plane crash, in addition to representatives of the US National Transportation Safety Board (NTSB), aircraft manufacturer Boeing and engine manufacturer. CFM. The NTSB said it is negotiating with the Chinese side about the Covid-19 prevention requirements to facilitate the entry of its staff to assist the investigation.

Investigators will look at the plane’s maintenance history, training and records of the three pilots, as well as weather data on the day of the crash.

They also examined the wreckage of the Boeing 737-800 for clues, because their size is also important information. If the plane’s debris was spread over a very large area, the plane would most likely have broken up before hitting the ground. In contrast, if the debris is mainly concentrated in a small area, the aircraft may be intact before the impact with the mountainside.