Before taking off in winter, the plane must be deiced. Why are planes so afraid of freezing?

The cold wave sweeping across the country has brought a lot of inconvenience to passengers. Many times, after boarding the plane, the back door was closed for a long time without seeing their plane take off. On the contrary, something like a sprinkler will spray an unknown liquid on the plane. This process is called "deicing" in the aviation industry. Sometimes on flights, there are not enough deicing equipment to ensure that every plane can deice in time. After the de-icing vehicle ended, it met the peak period of departure and entry. After a long wait, the plane slipped into the deicing plane again for deicing. Since then, time and time again, the departure time has been postponed helplessly. Many passengers are frustrated by this inconvenience: if the snow on the car can be swept away, why fly? Can't the airline sweep the ice in advance?

An airplane is a vehicle that flies with the help of the lift generated by air. During the flight, ice accumulation will destroy the aerodynamic characteristics of the aircraft. If there is ice and snow on the surface of the fuselage, it will increase the resistance; The ice on the wing will lead to a sharp drop in lift; Adding ice may also block the rudder surface and reduce the handling quality of the aircraft. However, the uneven distribution of accumulated ice may destroy the stability of the aircraft and lead to unstable flight. These will lead to very serious consequences, even collapse.

In addition, ice accumulation will reduce the efficiency of the internal power plant of the aircraft and even lead to its failure. Ice can also affect instruments and communications. As safety first, AirAsia has made detailed regulations on aircraft icing. The company's policy clearly stipulates that when snow or ice adheres to the wing, control surface, engine intake or other important surfaces of the aircraft, it is not allowed to take off unless an external inspection is carried out within 5 minutes before take-off. Once the ice accumulation risk is determined, all AirAsia flights will be strictly de-iced. For an A320, the whole deicing process takes 10 minutes, and the deicing liquid alone costs nearly 10,000 yuan.

So far, the most commonly used deicing method in civil aviation industry is spraying deicing liquid, which is often called "hot bath on board" by passengers. The preheated liquid is sprayed on the plane at a temperature of about 82 degrees Celsius, and the ice and snow on the plane are removed at high temperature and high speed. In addition, the main components of deicing liquid are ethylene glycol and propylene glycol. After mixing with water, the freezing point can be reduced to below MINUS 50 degrees, which can prevent secondary ice accumulation. The specific retention time depends on the label of the deicing fluid used at that time. However, due to the limited time for deicing liquid to prevent secondary icing, the deicing plane should take off as soon as possible, otherwise the deicing liquid must be deiced for the second time when it fails. This is why airlines can't clear the ice and snow on the plane in advance, and can only clear it after passengers board the plane and the cabin door is closed.