(Health Times reporter Zhao Weide)
On April 20, the Civil Aviation Administration of China issued the "3.21" Preliminary Report on the Investigation of the Mu5735 Aircraft Flight Accident of China Eastern Airlines, which is based on the factual information obtained at present, excluding the analysis and conclusion of the cause of the accident, and the report mainly includes factual information such as flight history, crew maintenance personnel, airworthiness maintenance, and wreckage distribution.
Wang Yanan, editor-in-chief of "Aviation Knowledge" and an aviation expert at Beijing University of Aeronautics and Astronautics, said in an interview with the People's Daily health client reporter that the preliminary investigation report released at present is mainly a summary of the factual information that has been made public, and the past factual information is confirmed in the form of a document report, indicating that there is a confirmation process behind each information, which is convenient for the next step of in-depth investigation.
Search and rescue personnel searched the scene of the accident on March 24. Xinhua News Agency photo
The preliminary investigation report is a review and summary of the past public facts
Wang Yanan told reporters that the civil aviation accident investigation generally lasts a long time, and the preliminary investigation report given within one month often does not involve the speculative analysis and conclusive opinions of the cause of the accident, because it is too early to make analysis and speculation on the cause of the accident within one month, which is also considering the seriousness of the investigation, and the current reports are confirmed facts.
Residual items. Photo by Xinhua News Agency reporter Lu Bo'an
"However, the preliminary investigation report is still valuable for the follow-up investigation, because the past factual information is confirmed in the form of a document report, indicating that there is a process of confirmation behind these facts." Wang Yanan introduced, for example, for the aircraft maintenance records, the aircraft's latest A inspection (31A) and the last C inspection (3C) did not exceed the inspection time limit specified in the maintenance plan, there was no fault report before the flight and the short parking line on the same day, there was no problem with the release and signing of the aircraft, the weather was not abnormal, and the radio communication and control command were not abnormal. This can largely rule out these reasons in subsequent investigations.
"Another noteworthy point is that the last time the radar recorded the aircraft information: the standard air pressure altitude of 3380 meters, the ground speed of 1010 km / h, which is extremely abnormal, has been far away from the cruise altitude, in 4 minutes to drop more than 5000 meters, and the speed is also more than 200 kilometers faster than the normal cruising speed, if you take into account the dive attitude of the aircraft, the actual speed may be even greater, indicating that the aircraft is in a very dangerous state." Wang Yanan said.
Follow-up investigations may focus on crew and wreckage analysis
Silence for the dead. Photo by Xinhua News Agency reporter Zhou Hua.
Wang Yanan told reporters that the preliminary investigation report does not explain much about the situation of the flight crew, and the follow-up investigation, on the one hand, will focus on the crew, such as resume and social relations, which need to be explained.
On the other hand, the wreckage analysis, according to the current investigation, the aircraft maintenance situation and so on have not found a fault, the next step to see whether some signs of failure can be found from the wreckage that has been found. This would allow the investigation to be redirected in important directions, such as whether the wreckage was a technical problem or a crew environmental problem.
According to the preliminary investigation report, the technical investigation team will continue to carry out in-depth investigation work such as wreckage identification, classification and inspection, flight data analysis, and necessary experimental verification in accordance with relevant procedures.
Wang Yanan introduced that wreckage identification is to confirm the debris fragments collected at the scene, which part of the aircraft it comes from, and restore it on the spot after cleaning, so as to analyze the possible hidden dangers of failure.
"Experimental verification is a follow-up, generally speaking, after grasping a large amount of evidence, the investigation tends to a certain conclusion, and then use the experimental method to verify our investigation speculation." For example, Wang Yanan said that if the aircraft engine fails, the fault state is set on the simulator to restore the original appearance of the accident. This is like a criminal investigation experiment, which is a very important part of accident investigation.
Black box data is still a difficult point for investigation
According to the investigation report, the two recorders on board were seriously damaged due to the impact, and the data repair and analysis work was still in progress.
Wang Yanan told reporters that the next step of the investigation may be the data record of the black box, the current civil aviation department has not announced the progress of the relevant repair and restoration information, no news behind the recovery work may be more difficult.
In addition, the proportion of data recovery after data corruption is difficult to determine, and the extent to which the recovered data can support the follow-up investigation work is not easy to determine, so it is expected that the progress of data recovery will be disclosed.
Wang Yanan suggested that whether it is possible to set up an activation device for the black box, which can activate the cloud mechanism of the black box when the altitude of the aircraft changes drastically or fails, and quickly transmit data information to the cloud before the accident occurs, which should be technically achievable at present.