The flight attendant and passengers were thrown to the ceiling! What exactly is the "clear sky turbulence" encountered by Air China aircraft?

CCTV News WeChat official accountOn the 10th, Air China flight CA1524 from Shanghai Hongqiao to Beijing Capital Airport experienced strong turbulence in the air, causing injuries to flight attendants and passengers. The safety exit indicator light was damaged, and debris was scattered all over the ground

CCTV News WeChat official account

On the 10th, Air China flight CA1524 from Shanghai Hongqiao to Beijing Capital Airport experienced strong turbulence in the air, causing injuries to flight attendants and passengers. The safety exit indicator light was damaged, and debris was scattered all over the ground. On the 11th, Air China responded that flight CA1524 encountered clear air turbulence during its flight, and the crew and crew followed the procedures. During this process, one passenger and one crew member were injured. After the flight landed normally on the day of the incident, a dedicated person was arranged to accompany the injured passengers and flight attendants to the hospital for treatment.

What is clear sky turbulence? What is the reason for its occurrence? The aircraft is usually equipped with Weather radar, can we predict in advance?

01

What is' clear sky turbulence '?

Clear sky turbulence refers to the turbulence of aircraft caused by atmospheric activity at high altitudes without clouds.

Generally, under the action of Earth's rotation, topography, water distribution and solar radiation, the atmosphere will form a sudden and intense disturbance at high altitude (generally above 7000 meters) in some places. When the aircraft encounters such disturbances, it can cause sudden lifting or lowering of the aircraft, ranging from personal injury to potentially affecting aircraft control and posing a threat to flight safety.

Experts introduce that the sudden rise and fall of an aircraft is not a passive response to airflow disturbances, but rather a standard handling method for the crew.

When encountering severe turbulence, the crew will switch the autopilot from conventional mode to "steering wheel control mode", and the aircraft will "drift" in the direction of vertical airflow, thereby reducing the load borne by the body. It is precisely this operation that creates a "roller coaster" like experience for cabin personnel, but it can reduce overload and reduce danger.

02

What are the causes of airplane turbulence?

Is clear sky turbulence a low probability event?

Aircraft turbulence is usually divided into mild turbulence, moderate turbulence, and strong turbulence according to the level. According to the statistics of the International Air Transport Association, in recent years, there have been about 5000 serious bumps encountered by commercial aircraft worldwide every year.

The occurrence of aircraft turbulence is due to the presence of turbulence in the atmosphere. According to the causes of turbulence, it can be divided into dynamic turbulence, thermal turbulence, Clear-air turbulence, etc. Clear-air turbulence is also called upper air turbulence, which is related to the thermal and dynamic factors of the atmosphere in the upper air. When the temperature field and wind field change sharply, strong turbulence will occur. Clear-air turbulence mostly occurs in the upper troposphere and stratosphere, which is an important factor causing clear air turbulence in high-altitude flight.

Wang Yanan, an aviation expert from Beihang University and chief editor of Aviation Knowledge, said that most civil aviation airliners cruise in the stratosphere, and if the aircraft crosses from the troposphere to the stratosphere during ascent and descent, it will encounter atmospheric turbulence. However, the intensity of most turbulence is not high, and the frequency of high-intensity atmospheric turbulence is relatively low, which is an occasional phenomenon. Even rarer is the clear sky turbulence shown in this event

03

Can clear sky turbulence be predicted?

It is understood that the wavelength of the modern passenger aircraft Weather radar is designed for the size of water droplets in the cloud. If the water droplets detected by the airborne radar have severe vertical movement, the navigation screen will display a red bumpy area, prompting the pilot to fly around and avoid.

However, high-altitude jet streams usually do not contain water vapor, so airborne radar cannot detect the clear sky turbulence generated by the jet streams. The meteorological forecast can only roughly infer the possible location of clear sky turbulence.

Wang Yanan introduced that clear sky turbulence is a difficult atmospheric phenomenon to predict and avoid. "Because the Weather radar relies on detecting the scatterers in the atmosphere to investigate the atmospheric movement, but the clear air turbulence is difficult to be accurately captured by the Weather radar because of the large air permeability. This situation will not have a major impact on the structure of the aircraft, but it still poses a great threat to the control of the aircraft and the stability of flight."

Civil aviation expert Qi Qi introduced that in response to clear sky turbulence, flight crew pilots will also receive specialized training in their daily simulator training. Additionally, it is recommended that passengers fasten their seat belts during flight.

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