According to the Global Times quoted by foreign media, a black box of flight MU5735, which is touching, has recently entered the decoding stage, and the US National Transportation Safety Commission will assist China in decoding. This black box is a "CVR", which is also known as a cockpit voice recorder.
The U.S. National Transportation Safety Board recently confirmed the news, and said that they are working hard to recover the relevant data, and the details of the pilot exchange recorded by this "CVR" in the future will bring great help to the investigation of the cause of the accident. This means that we are one step closer to the truth of the cause of the accident.
The reason why "CVR" needs the help of the United States to be able to decode is actually very simple. That's the technical reason. According to CCTV News, as early as the beginning of the discovery of "CVR", the black box data storage chip was found to be damaged. Usually according to the recommendations of the logger manufacturer, the relevant memory chip may require the assistance of the manufacturer to be able to carry out further repair processing.
In fact, it is not surprising that the black box is damaged. According to the current black box manufacturing industry standard, its fire resistance strength only needs to persist for 30 minutes at a high temperature of 1100 degrees Celsius. According to the data, the temperature of the air crash explosion is usually as high as 3,000 degrees Celsius, which is far more than the black blind man's ability to bear, so the CVR found in the accident is completely understandable.
At present, the CVR configured on the aircraft basically uses a new solid-state memory and digital recording technology, although it can better resist shock and vibration, but also causes its hardware to be damaged, basically there is no other way but to return to the manufacturer for recovery.
Unfortunately, from the current situation, the damage to the CVR on the MU5735 seems to be more serious, and there is indeed a lack of relevant technology for decoding in China. It is worth noting that the black boxes used on the crashed aircraft 737-800 are all products from honeywell in the United States, so this black box was finally repaired and decoded by the United States.
Compared with another black box "FDR" that records flight data, the decoding process of "CVR" is relatively simpler, after the audio file is extracted, only the spectrum needs to be analyzed to remove the interference band, and the integrity of the signal is screened, and all the recordings stored by the aircraft before the crash can be restored.
It does not need to be read like FDR parameters, and it needs to be repeatedly verified and checked. At the same time, the audio data stored by the CVR is almost zero compared to the flight data stored by the FDR, and the possibility of tampering with it during the reading process is almost zero. According to the relevant requirements of ICAO, the CVR carried on the passenger aircraft must be able to complete at least 2 hours of recording time.
The flight process of the crashed plane was only more than an hour, completely within the scope of the CVR record. I believe that our investigation team will soon be able to obtain this crucial recording data. Of course, after obtaining this recording, it is necessary to wait for the FDR data to be decoded and corroborated to finally find the cause of the accident. Usually there are 5 to 6 microphones in the cockpit for recording sound.
After the recording is read, on the one hand, we have to listen to the pilot's dialogue to analyze the accident process, on the other hand, in the background sound recorded by the microphone, we can also understand the state of the aircraft engine and the status of the entire cab from the side. These analysis processes will take some time.
At present, based on known information, it can be roughly inferred that the main cause of the mu5735 crash is likely to be on the left wing of the aircraft. Mu5735 crash during the continuous rolling flight status, flight trajectory data, etc. are in line with the situation after the wing fracture or damage, of course, until enough evidence is found, all the causes of the accident can only stay in a speculative stage. I believe that our investigation team will definitely restore the real accident process, and find the cause of the accident, and give everyone an explanation.