Elephant News reporter Zhang Ziqi
On March 27, according to CCTV news, the second black box (flight data recorder) on board the MU5735 was found.
According to public information, the Boeing 737-800 aircraft is equipped with two flight recorders, one of which is a data recorder (FDR), installed in the tail of the cabin, recording a period of about 25 hours, recording important parameters such as altitude, speed, heading, pitch angle, roll angle, vertical speed and the operation of the crew such as the amount of steering wheel rod, throttle and so on. The other is the cockpit voice recorder (CVR), installed in the tail of the cargo compartment, which can record four channels of sound, namely the captain's channel, the co-pilot channel, the backup channel, and the ambient sound channel, and the recording time is about two to three hours.
The first black box found earlier, image source: Xinhua News Agency
So when will you find two black boxes to extract the information? What is the focus of the next on-site search? In response to related questions, Elephant News interviewed Li Hanming, a senior civil aviation industry analyst, and Yao Fei, director of the Air Traffic Control and Signing Faction Department of the Civil Aviation College of Zhengzhou Aviation Industry Management College, to interpret it.
The interpretation of black box data can take several weeks at the earliest, and the search for aircraft wreckage is equally important
The first black box previously found has been sent overnight to a civil aviation professional agency in Beijing for decoding. "If the interpretation of the black box information is smooth, it may take a few weeks at the shortest", Yao Fei introduced, after the air crash, for the damage to the recorder, the follow-up may need to be cleaned, vacuum drying, data download and repair and other steps, and then the data interpretation can be carried out, and the specific repair time should be determined according to the degree of damage.
"The black box is just an airborne device that provides investigators with the richest amount of information." Yao Fei said that with the help of the black box, investigators can analyze the details like "scene reproduction" and look for evidence chains. However, the final result needs to be obtained after comprehensive analysis and argumentation by the investigation team.
Image source: People's Daily
Investigators' on-site surveys and the collection of important wreckage are also very important during the search. Yao Fei introduced that some of the aircraft wreckage that was cleared out at the accident site will be preliminarily classified and treated, and then will be judged by experts. On-site investigation and evidence collection of important wreckage will do a good job of the basic work for the next step of identifying the cause of the accident.
Why is the black box so "difficult to find"?
"Judging from the first black box found so far, it has only one cylinder left, and the beacon is gone, indicating that it was damaged by the structure during the crash of the aircraft." Li Hanming introduced that the black box itself is a wireless transmitter, but this time it fell on the mountain, and the beacon basically did not have much effect. Because the signal transmission characteristic of the wireless transmitter on the black box is straight-line propagation, it increases the difficulty of searching in the valley, because its signal will be constantly reflected, "even if the signal transmitter can work normally, the search help is very limited." ”
Li Hanming introduced that the cockpit voice recorder can record the operation carried out by the pilot of the crashed aircraft at that time, and what his operation intention was. "The pilot has a standard operating procedure when operating the aircraft, that is, he must say all the actions of the operation, and the person next to him must confirm the pilot's operation, and this important information will be recorded by the recorder."
It is naturally best to obtain data information on the two black boxes on the plane at the same time, Li Hanming said, with the current black box information, investigators can combine the information on the wreckage of the aircraft to draw a more reliable conclusion.