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What is Air Crash Investigation?

  The scene of the violent impact, the tens of thousands of debris scattered on the surface and the ground, and the severely damaged black box, what might they tell us? What factors may lead to an air crash?
  According to international practice, according to the provisions of the “Convention on International Civil Aviation”, the air accident investigation is led by the government of the country where the accident occurred, and the country involved in the accident can apply for participation, including the country of the manufacturer of the aircraft, the country of the airline and the nationality of the aircraft passengers. country etc.
  Air crash investigation is a very long process, which needs to go through three stages: on-site investigation, experimental verification and completion of the report. First of all, the investigators should study the black box, sort out the air-ground call records, draw a track map, and analyze the flight status of the aircraft, the failure status and the operation status of the crew. Secondly, observe and analyze the specific positions of the rudder, elevator, flaps and other specific components and the screw and other control machinery in the wreckage of the aircraft, and judge whether the specific control signal has been implemented by the mechanical structure. Again, investigate other peripheral information such as air traffic conditions, weather conditions, crew flying experience and training, aircraft maintenance records, aircraft performance and subsystem conditions. Finally, it is necessary to closely contact the investigators at the accident scene to find the corresponding physical evidence. Next, stitch this evidence together to construct a model of the accident through which the test is reduced to assess all possible scenarios. Then, simulate the possible flight conditions through the simulator or even the real flight, compare the simulated information with the actual situation during the crash, try to restore the relevant phenomena, and try to restore the entire process of the accident as much as possible, so as to finally get the result. draw relatively complete and scientific conclusions.
Black Box Provides Evidence

  Anthony Brickhouse is an associate professor in the Department of Applied Aeronautical Science, School of Aeronautics, Embry-Riddle Aeronautics and Astronautics, a world-renowned aerospace university. Aircraft accident and safety incident investigation. Air crash investigations are a piece of the puzzle, he said, and investigators need to get information from multiple sources to fit every detail. Every air crash investigation is a unique process. Trying to understand all the evidence and piece it together slowly is a process that investigators must go through.
  Anthony Brickhouse pointed out that one of the important tasks of the on-site investigation was to identify the “four endpoints” of the crashed plane, namely the two wing ends, the nose and the tail. If it is found that these four parts are all at the main crash site, it can be assumed that they all crashed here at the same time. If there is a piece of debris that falls far away, it may have fallen off during the flight, and then it is necessary to investigate why it fell off. In addition to this, at the time of the crash, there was a lot of evidence that was destroyed when it hit the ground, so investigations took longer, sometimes months or even years. After the air crash, the search, reading and decoding of black boxes, the verification and extraction of aircraft wreckage and remains of victims, and peripheral investigations will be advanced simultaneously. Among them, the data from the black box of the aircraft is the most direct, reliable and powerful, and may directly give important investigation directions, and no other evidence can match them.
  On the afternoon of March 24, 2015, a Germanwings Airbus A320 aircraft numbered 4U9525 flew from Barcelona, ​​Spain to Dusseldorf, Germany, at an altitude of about 2,000 meters at the southern foot of the Alps in southeastern France. The crash in the snowy mountains killed all 150 people on board, including 144 passengers and six crew members. After the accident, the first black box airliner cockpit voice recorder was recovered, and two days later the second black box flight data recorder casing was also recovered.
  Investigators from the French National Civil Aviation Safety Investigation and Analysis Agency have found that the crashed passenger plane has turned on the autopilot mode during the climb stage through analysis and research on the data and radio communication records in the two black boxes of the crashed passenger plane. After entering the cruise phase at an altitude of 11,600 meters, Captain Patrick Sandenheimer left the cockpit. The co-pilot Andreas Lubitz, who was left alone in the cockpit, deliberately adjusted the cruise altitude setting of the aircraft from 11,600 meters above sea level to 30 meters above sea level, causing the plane to continue descending until it crashed. The black box recordings showed that Andreas Lubitz had “practiced” the steep descent for about a minute on his previous flight from Dusseldorf to Barcelona.
  The investigation report described the situation and released a portion of the audio recording from the cockpit voice recorder. The recordings helped investigators understand the state of the last time in the cockpit before the crash, and a few key voices revealed the root cause of the crash, which was not caused by a technical problem. Andreas Lubitz has repeatedly said to Patrick Sandenheimer, “You can go to the toilet.” He replied, “You can take over the flight.” Afterwards, the seats were pushed back and the doors closed. the sound of. In the next two minutes, the plane descended more than 600 meters.
  Air traffic controllers at the airport control tower tried to contact the plane, but received no response, and an automatic alarm signal in the cabin reporting the plane’s sharp descent sounded almost simultaneously. Although other crew members used the PIN pad, the cockpit phone to contact Andreas Lubitz, and even tapped the door to request access to the cockpit, he never opened the cockpit door during the descent. Soon after, a loud thud was heard, like someone trying to get into the cockpit. Captain Patrick Sandenheimer could be heard shouting, “For God’s sake, open the door!” while passengers screamed. Two minutes later, there was the sound of the captain hitting the door with an ax, and the plane was only more than 2,000 meters above the ground. About 90 seconds later, the voice of the air traffic controller came: “Pull up! Pull up!” Then Patrick Sandenheimer was heard shouting: “Open the damn door!”
  Andreas Lubitz could be heard breathing for the last two minutes before the plane hit the mountain, but he didn’t say a word. A peripheral investigation of the accident confirmed that he had suffered from depression and had been treated by a neurologist, who had repeatedly issued him a sick note. But he did not report to the airline as required, and was later allowed to return to flying. In the months before the crash, Andreas Lubitz, who had suffered from insomnia and fears of losing his sight, was issued a sick note by doctors on the day of the crash (police found torn sick leave in his apartment). fragments). After the air crash, many European airlines introduced new regulations, in order to prevent accidents, there must be two pilots in the cockpit of the passenger plane during the flight. If one of them needs to go to the toilet, the third person will drive instead.

Wreckage of Germanwings Airbus A320
Splicing the wreckage to reveal the mystery

  Wang Yanan, editor-in-chief of “Aviation Knowledge” magazine and an aviation expert at Beihang University, once described: “The investigation process of an air crash is like archaeology, but also like solving a case.” The investigation of each accident almost starts from the restoration of the scene. The more complete the structure of the aircraft, the more technical information before the impact can be preserved, and the better it is for accident investigation. Once the plane disintegrates into tiny pieces of wreckage, the investigation becomes more difficult, like archaeology. The archaeological team excavated some fragments from the soil and tried to piece them together into a complete artifact, which may last for decades without results, because other fragments may be left in the soil layer. The same is true for air crash investigations. It is difficult to imagine the difficulty of using massive fragments to splicing out the original plane. What’s more, it is even more difficult to find the crux of the accident with the restored “airplane”.

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