Aircraft have become the first choice for more and more people to travel, and its safety has always been the focus of attention. The 2016 movie "Captain Sully", based on the true events of the 2009 US Airways 1549 forced landing, tells the story of Captain Sully who successfully landed to save 155 passengers and crew members in the event of engine failure.
Image source: Douban Movie
In the film, the plane takes off two minutes after being hit by a bird, and the two engines are turned off at the same time, completely losing power. Faced with the question of "turning back to the take-off airport or landing somewhere else", Captain Sully gave his choice with years of flying experience - an emergency landing to the Hudson River.
Captain Sully was relieved to board the rescue vessel after confirming that all passengers had been evacuated safely. However, after such a successful emergency, Captain Sully was greeted by an investigation by the National Security Transportation Agency.
The focus of the investigation was on whether Captain Sully's forced landing on the surface was correct. In machine simulation experiments to review hearings, Flight 1549 was considered safe to return to the airport, rather than performing an "impossible task" of a surface landing. Captain Sully's approach was questioned as more likely to cause the plane to be destroyed.
Captain Sully, based on the actual situation, pleaded that the machine simulation be changed to a manual simulation, and asked to take into account the human factor and increase the reaction time by 35 seconds. In simulations under these conditions, the plane crashed directly into the city complex.
Although the story does not give an investigation conclusion at the end, the "emergency landing surface" chosen by Captain Sully throws us a flight safety question: Why is the surface landing considered an "impossible task"?
When an aircraft encounters an accident and needs to land, there are generally two options: land landing and surface landing. In people's daily cognition, the land is harder, so the risk of forced landing is large, and it seems that the survival rate of water forced landing will be higher. In fact, it is not true that the forced landing of aircraft on the surface of the water is more dangerous than the forced landing on land.
Although the surface of the water looks mild, at the moment of high-speed contact, the water surface is a hard and undulating land surface. Compared with the land surface, the water surface is constantly changing, the structure is more loose, the vibration conduction ability is very strong, once the nose or wing first touches the water surface, the aircraft is very prone to local fragmentation or disintegration. And when the speed decreases, the plane will sink into the water. If the aircraft has been damaged or disintegrated, it is likely to sink when the speed stops.
The design structure determines that the aircraft cannot float in the water. When the aircraft is forced to land on the surface of the water, due to the damage to the fuselage, the cabin will quickly enter the water, and the escape time left for passengers according to the angle of the aircraft is generally only a few minutes.
The safety instructions on the back of the aircraft seat also mention that if the water surface is forced to land, be sure to inflate the life jacket after exiting the aircraft hatch. Because, with the rapid sinking of the aircraft, if the life jacket is opened in the aircraft cabin, it will prevent passengers from escaping from the aircraft. In addition, the pressure of the water will also make it more difficult to open the hatch.
If the person is still alive when he falls into the water, the water temperature will directly affect the survival rate of the person. People lose their body temperature in cryogenic water much faster than in cryogenic air. Compared with land rescue, surface rescue has a certain delay, and exposure to cold water for several hours can also be life-threatening, just as in the well-known Titanic shipwreck, most people were not drowned, but frozen to death.
In general, the risk factor for a forced landing on the surface is much higher than that of a forced landing on land. When modern aircraft choose a landing site, airports are preferred, followed by highways or leveling the ground, and finally the surface of the water.
"Captain Sully" is not only a film that promotes heroism, but also the professionalism and professionalism it conveys have become the spiritual core of the film. As Captain Sully said: I just did what I was supposed to do!
The author is an engineer in the Network Science Popularization Department of China Science and Technology Museum
Source: Popular Science Times
Author: Li Dawei
Editor: Wu Tong
Review: Wang Fei
Final Judge: Chen Lei
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