EXPLANATOR: What’s the next step in the East China plane crash investigation?

Even after the discovery of the two ‘black boxes’, it may be a long time before investigators find out what caused a China Eastern Airlines Boeing 737-800 to plunge into the ground last week, killing all 132 people on board. .

BEIJING — Even after the discovery of the two “black boxes,” it may be a long time before investigators uncover what caused a China Eastern Airlines Boeing 737-800 to crash to the ground last week, killing all 132 people at home. edge.

WHAT IS A BLACK BOX?

Most commercial airliners carry two recorders to help investigators determine the cause of accidents. Despite their name, they are usually orange to make them easier to find.

The cockpit voice recorder captures the voices of pilots and other people in the cockpit, audio alerts and the sound of moving engines or switches. It stores at least two hours of sound before it starts recording on itself.

Flight data recorders continuously capture at least 88 pieces of information, including speed, altitude, direction, and whether the plane’s nose is pointing up, down, or level. They can also record the position of the wing flaps and whether the aircraft is flying on autopilot. They typically log 25 hours of data.

Both stop recording when the power is off. They are designed to withstand fire and powerful impacts and are usually installed at the rear of the cargo bay. They are equipped with radio beacons that activate underwater but not on land.

Flight recorders once used magnetic tape, but are now digital, allowing them to hold more information.

WHAT DID THE RESEARCHERS FIND?

Searchers found the cockpit voice recorder first, then the flight data recorder. The two orange cylinders, the size of a large elongated can, were covered in dirt. The second was found under 1.5 meters (5 feet) of soil.

Officials said the exterior of the cockpit voice recorder was damaged but gave no indication whether the recording was intact. Both will be reviewed and analyzed in Beijing.

WHAT CAN RECORDERS TELL ACCIDENT INVESTIGATORS?

Recorders can tell investigators what pilots were doing before a crash, whether they knew about problems, and how engines and other equipment were operating. They are particularly important following disasters such as the China Eastern crash in which no survivors were found and air traffic controllers heard nothing from the pilots.

When a Lion Air Boeing 737 Max crashed in Indonesia in 2018, the flight recorder showed the pilots struggling to keep their noses up, fighting off an automated system pushing them down. An Ethiopian Airlines 737 Max crashed in the same way four months later. The crashes led to the grounding of the plane, which is a different model from the 737-800.

WHAT WILL THE SURVEY LOOK LIKE?

Investigators will review the aircraft’s maintenance history, pilot training and records, and weather data. They will examine pieces of the wreckage for clues. Even the size of the debris field matters. When the wreckage is spread over a very large area, it could indicate that the plane was falling apart before it touched down.