Turbulence in the skies over Bangkok: investigators have a lot of work ahead of them. “There is one TIAN”: what is clear sky turbulence What is clear sky turbulence

Several dozen passengers were injured and fractured when on May 1, 2017, a plane flying from Moscow to Thailand encountered turbulence. Almost everyone who flies by plane has encountered this phenomenon at least once in their life. the site explains what turbulence is, what makes clear-sky turbulence special, and what climate change has to do with it.

What is turbulence?

The term “turbulence” usually refers to a situation in which the aircraft begins to shake very violently. From the point of view of physicists, turbulence is the formation of linear and nonlinear waves when the speed of flow of a liquid or gas in a medium increases. Typically, this phenomenon is typical for near-wall layers of low-viscosity liquids and gases, as well as for the case when bluff bodies are located at some distance from each other. In nature, turbulence manifests itself not only in the air, but also in the oceans. Thus, animals have learned to extract energy from the flow: by moving their fins and wings, they destroy surface waves and create a special structure of turbulence.

Atmospheric turbulence, in which masses of air constantly move both horizontally and vertically, is characterized by the formation of air pockets due to sudden changes in temperature and wind speed. Irina Gorlach, leading researcher at the Department of Meteorology and Climatology, Faculty of Geography, Moscow State University, said that the occurrence of turbulence is influenced by several factors, mainly orography and air flows. In turn, turbulence conditions depend on the height of the mountainous terrain, speed, directions and intensity of flows.

What are the dangers of clear sky turbulence?

At altitudes above five kilometers, a phenomenon called clear air turbulence (CLT) can be observed. Unlike other types of atmospheric turbulence, it occurs in clear weather or in the presence of upper clouds, and is quite difficult to notice in advance. Scientists have found that this phenomenon occurs much more often over mountainous terrain, especially on the leeward side of the slope.

However, clear-sky turbulence is difficult to predict due to its sharp localization in the ambient flow, the dynamics of the size and duration of the phenomenon. Moreover, clear-air turbulence cannot be detected by radar. Today, it is predicted through indirect signs indicating the likelihood of the phenomenon, and predictive models are built based on a number of factors.

The main work on developing a methodology for predicting clear-sky turbulence occurred in the 90s of the twentieth century, and since then practically nothing has changed. Thus, according to the method compiled by the Hydrometeorological Center of Russia, the main types of the mechanism of hydrodynamic instability are hydrodynamic instability of the main flow, stratified by wind and temperature, instability of internal waves in a stable flow and instability of the critical level.

The success of the forecast is also due to the fact that the recurrence of TJN largely depends on the region. Clear air turbulence indices are also calculated abroad, in particular in the UK, USA and Canada.

Over the past 50 years, there have been five plane crashes caused by clear air turbulence. Thus, in 1966, a plane flying from Tokyo to Hong Kong disintegrated in the air in a complete absence of clouds. As a result, all passengers on board died. As the investigation showed, the cause of the accident was abnormally strong turbulence near the slopes of Mount Fuji, which exceeded the permissible loads on the structure. In the same year, a similar plane crash occurred in the USA, in the state of Nebraska: the plane avoided a powerful thunderstorm, got into turbulence and also disintegrated in the air.

Two years later, in December 1968, an airliner landing at Iliamna Airport (Alaska) suddenly collapsed. Pilots flying near the crash site said they encountered severe turbulence. This contradicted the official weather forecast, so an independent expert was brought in to investigate, who concluded that due to the outflow of Arctic air masses, an air wave had formed in the region, in which a zone of turbulence had formed.

One of the largest accidents occurred in 2001 in New York. When the airliner took off from the airport, it fell into an air current created by another plane. The air current remaining from the airliner in the form of vortices breaking off from the wingtips of a flying aircraft (in aviation this phenomenon is called a wake or wake) caused turbulence. The resulting overload caused the vertical tail stabilizer to break off and the plane crashed into a residential area.

The number of precedents of falling into clear-air turbulence, according to various sources, ranges from up to 1,500 cases per year. Fortunately, most of them do not cause any harm to passengers and crew, but flight delays and disruptions due to turbulence are crippling airlines. So, only in the United States the damage

However, not all climate scientists agree with this study. Irina Gorlach commented: “There is a very distant connection between climate change and turbulence, since turbulence is primarily related to the distribution of flows. The chemical composition, of course, can have an effect, but very indirectly.”

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The moments that the passengers of the Moscow-Bangkok flight had to endure can be called, without exaggeration, terrible. The plane was trapped in what pilots call “clear air turbulence.” Fractures, injuries - people had the feeling that the plane began to fall. 27 people were injured, 15 of them remain in Bangkok hospitals.

The first minutes after the shaking. There is a terrible picture in the cabin of the plane. Bloodied passengers lie in the aisles and sit at emergency exits. Many are asked not to get up - it is unknown how serious the injuries are. As it turns out later, there were fractures and severe bruises.

“On one side there was a woman lying, moaning, she was in great pain. And the man moaned. He was apparently in doubly pain. The girl, when it was all over, walked around the salon, she had a black eye, her cheek was all torn. There were many such people who suffered greatly. Almost no one was wearing a seat belt or had time to do so,” says passenger Elena Tregubets.

The plane had not yet begun its descent, so the “Fasten seat belts” sign was not on. People calmly walked around the cabin - warming up in the aisles after a nine-hour flight. The Moscow-Bangkok flight was coming to an end. 40 minutes before landing - sharp shocks. The 300-ton Boeing 777 fell almost 250 meters into the air pocket.

“We were rocked two or three times. And somehow I immediately intuitively began to buckle up. And literally a couple of seconds, and it was as if we began to fall. And the passengers flew up to the ceiling, and with a roar they all fell down,” says Elena Tregubets.

Doctors met the plane at the airport. In total there were 313 people on board. 27 - among them both Russians and foreigners - were immediately sent to a local hospital. There, some victims had to undergo operations. Embassy staff and a translator were sent to the hospital to help the Russians.

The weather in the skies over Thailand did not promise anything bad. According to experts, the plane encountered so-called clear-air turbulence.

“It does not appear in the clouds, but in a clear sky with good visibility. And it is not recorded by instruments. The main danger is that the crew has no way to warn passengers about the need to buckle up. This situation is extremely dangerous for passengers who do not fasten their seat belts,” Aeroflot explained.

Such chatter also happens in the skies over Russia, but much weaker than in tropical latitudes.

“In tropical latitudes it is more developed and is characterized by very large gradients, that is, power and unpredictability. It was impossible to avoid this. Although we must keep our eyes open,” the commander of the aviation squadron, pilot Sergei Matrosov, comments on the situation.

Ideally, you need to be buckled up for the entire flight, like the crew of this flight. Job description. At the helm was experienced pilot Alexander Ruzov, with over 23 thousand flight hours. Co-pilot Artem Unanov - more than 10 thousand flight hours. They took the car out of the turbulence zone and landed it in normal mode. According to them, the shaking intensified due to the actions of the autopilot.

“The autopilot was unable to react correctly in time, which is why the plane was thrown like that. Therefore, after hitting an air pocket, we turned off the autopilot and smoothly brought the plane into horizontal, level flight,” said Alexander Ruzov.

Travelers noted the work of the flight attendants. They provided assistance and did everything to avoid panic. Although they themselves got it pretty bad.

“It was clear from them that they were injured, they were also scratched, they were also not ready for this. They gave painkillers to those who were very seriously injured and applied tourniquets,” says Elena Tregubets.

Such cases are not uncommon in civil aviation. Every year, almost 750 such incidents are recorded around the world. 30 people were injured on an Etihad Airways flight from Abu Dhabi to Jakarta. And this is footage from the flight from Lima to Buenos Aires - even the crew members got it. But perhaps the loudest incident is in the skies over Hong Kong. In August 2013, two airliners entered the turbulence zone at once. One of the passengers then hit the plastic trim of the cabin with his head. More than fifty people were taken to hospitals.

Passengers on the Moscow-Bangkok flight continue to receive assistance in Thai clinics. Their lives are not in danger. A hotline has been opened for relatives - by calling +66904033645 you can find out all the latest information about the condition of the victims. Meanwhile, it became known that all victims will receive compensation. In addition, they will be paid for treatment, re-issuance of tickets and hotels.

At the same time, after landing, airport services checked the Boeing itself, which had fallen into an air pocket. No damage was found. The plane immediately flew back to Moscow.

The topic of turbulence inevitably comes up when talking about various flows of gases, liquids or plasma. Most movements of matter are turbulent in nature.

So what is turbulence? Turbulence is the definition of disordered, nonlinear motion. The concept of “turbulence” does not have a clear and unambiguous definition. In general, this is the vortex movement of flows caused by an increase in their speed.

When calculating other types of aircraft, a flow is considered turbulent if the value of the Reynolds hydrodynamic similarity criterion, derived from the Novier-Stokes equation, is more than 2320. Reynolds in his studies indicated the factors influencing the movement of the fluid: the flow becomes turbulent with increasing linear velocity and flow density, diameter holes (tubes) and reducing the dynamic viscosity of matter.

An example of a turbulent flow is air flows, which are vortices of various sizes that arise when the wind direction suddenly changes: from vertical to horizontal and vice versa. Atmospheric turbulence leads to intermittency of wind, various vertical transfers of vapor, condensation nuclei and other particles with mass and shape, as well as energy in the form of heat from one layer of the atmosphere to another.

Turbulence in aviation

Turbulence is of particular importance during aircraft flights. Not everyone knows what turbulence is on an airplane. When vortices overlap each other, airplanes are exposed to multidirectional winds, resulting in changes in lift and angles of attack of the wings. A similar situation overboard leads to shaking and vibration - the so-called “blank”.

There are moderate and strong blanks. During the first shock, changes in flight altitude and rocking of the aircraft are not so significant, and pilots do not experience difficulties in controlling the aircraft.

A strong bump is a more serious situation involving frequent rolls and yaws, accompanied by deterioration of controllability and stability in flight, as well as distortion of on-board instrument readings. Such a phenomenon, if appropriate measures are not taken, can create stress in parts and individual components, leading to significant breakdowns and deformations of equipment and air sickness among crew members and passengers.

When encountering turbulence, passengers often worry whether the pilot will be able to handle the situation. However, the qualifications and skills of the pilot can only be useful in the case of a very strong blank. In other cases, the turbulence zone does not have a strong effect on the flight - it is carried out on autopilot.

What are turbulence zones? As a rule, this is a space where the probability of getting into long-term turbulence reaches 100%.

Nowadays, almost any passenger can determine when and where the ship will shake during the flight. This became possible as a result of the creation of turbulence maps, where calmer zones are marked with lighter colors and vice versa. The online turbulence map is designed to reduce the anxiety of passengers and crew, allowing you to predict and prepare if the plane encounters turbulence.

Is turbulence dangerous for an airplane? Of course, such a phenomenon causes concern and fear, and, if possible, it is avoided. As a rule, atmospheric instability is not dangerous for the aircraft itself, since its design provides for such overloads. Most often, in 30% of cases, flight attendants are injured because they did not have time to fasten their seat belts in time.

The dimensions of the aircraft play an important role in the feeling of shaking during turbulence. The larger the plane, the less inconvenience it will be. Everyone sooner or later wonders where on the plane it shakes the least during turbulence? When choosing a place, you should be guided by the intensity of shaking in the cabin: the strongest is in the tail section.

Causes of turbulence

The following causes of turbulence are distinguished:

• thermal convection (due to uneven surface heating or mixing of cold and warm air with significant vertical temperature changes);
• due to friction of moving air currents on rough terrain;
• due to the heterogeneity of the nature of air flows in direction and speed, wave movements on inversion and isothermal layers (there are alternating downward and upward flows).

An example of thermal convection is the formation of cumulus clouds.

Before each flight, the crew and the pilot himself familiarize themselves with weather reports for the near future in order to choose the safest route. Particular attention is paid to the presence of cumulus clouds.

Cumulus clouds are dense atmospheric formations, most often separately located, with a lower boundary height of up to 1200 m and a length of up to several hundred meters. They are formed as a result of powerful vertical flows and have internal upward flows of up to 10-15 m/s.

From a flight safety point of view, it is prohibited for a ship to enter such clouds, as well as to fly under them. Cumulonimbus clouds are especially dangerous because, due to the presence of water particles, heavy precipitation and electrical discharges form in them. Therefore, it is recommended to lay a route at a distance of 10 km from thunderclouds at an altitude of more than 1 km above them. The flight is complicated not only by the high turbulence in the plane, which causes bumpiness, but also by poor visibility - up to 45m.

Zones of overlap between ascending and descending flows can extend over thousands of kilometers. Most cases recorded Most cases recorded on the eastern shores of the United States.

Clear sky turbulence

The absence of any clouds in the sky does not mean that there will be no turbulence. At altitudes above 5000 m, so-called clear-air turbulence can occur. This phenomenon is typical for mountainous areas on the leeward side of the slope. When flowing around mountains, the air flow deviates from the straight direction, becomes deformed and forms zones of increased turbulence. The distribution of zones varies in height: in the lower and upper parts it is maximum, and in the middle it is minimum.

If it is not possible to change the flight course, aircraft must strictly maintain a certain distance to avoid a collision.

Can a plane crash due to turbulence? Over the entire period, five major plane crashes occurred due to clear air turbulence. In conditions of complete absence of clouds, a plane flying from Tokyo to Hong Kong was destroyed. Experts have determined that the death of all flight passengers and crew was due to unusually high turbulence on the slopes of Mount Fuji.

Another example is the crash of an airliner landing at an airport in Alaska. The version of the tragedy due to turbulence was not immediately considered, since it contradicted the forecasts of the hydrometeorological center. However, subsequently an outflow of Arctic masses was recorded, which led to the formation of an anomalous air wave and a zone of turbulence.

On May 1, 2017, all domestic news channels reported that a Boeing 737 on a flight from Moscow to Thailand entered a clear-sky turbulence zone. It was impossible to establish the fact of the approaching air pocket and avoid the ship getting into it, since not a single instrument recorded it. As a result of the Boeing's sudden jump of 200 m, passengers received multiple injuries and fractures.

According to statistics, on average about 1000 cases of precedents arise per year related to atmospheric instability in clear skies. They mainly lead to flight delays, which cause great material damage to airline carriers.

Actions of pilots when entering a turbulence zone

According to Captain Chesley Sallenburg, who landed a passenger plane on the Hudson, when a turbulent zone is encountered in the cockpit, one of two decisions is made: to go beyond the limits of instability by reducing altitude, or to enter cloudless space by gaining it.

In case the aircraft encounters turbulence, a set of rules and recommendations has been developed for the cockpit and crew. You need to run the following commands:

1. Switch the autopilot to manual control.
2. Enable the “Tighten belts” command.
3. Adjust speed to 340 km/h.
4. Do not allow a sharp change in altitude or aircraft roll of more than 10°.

If it is impossible to avoid the heavy bump zone, the crew commander is obliged to return the aircraft to the original or nearest airfield.

Thus, the phenomenon of turbulence in the sky does not pose a strong threat to the aircraft. Like imperfections on highways (bumps, stones), turbulence in the air requires only excessive attention from the aircraft commander.

The Aeroflot flight Moscow-Bangkok, on board of which unbelted passengers were injured, encountered “clear-air turbulence” - it is so unpredictable that the crew did not have time to warn passengers and flight attendants.

“The turbulence that the Boeing 777 encountered is known in aviation as “clear-sky turbulence.” Its main feature is that it does not occur in clouds, but in clear skies with good visibility, where weather radar cannot detect its approach. Therefore The crew does not have the opportunity to warn passengers about the need to return to their seats,” Aeroflot said.

Indeed, in world aviation, more than 750 cases of aircraft of all classes and sizes encountering “turbulence in a clear sky” are recorded annually.

“At 3.38 Moscow time, the crew landed safely at Bangkok airport, and assistance was provided to the victims,” the airline said. The consular department of the Russian Embassy has already reported that “out of 313 passengers on the plane, 27 passengers needed medical assistance and were taken to Bangkok hospitals. At this time, 11 people have already been discharged.

Also, the company, citing doctors, also denied some media reports that several passengers suffered a compression fracture of the spine, but confirmed that “several victims were urgently operated on.” Thai doctors assured us that there is no threat to the life of any of the victims now.” - added the national air carrier, which pledged to pay for the treatment of all victims.

“The injured passengers were not wearing seat belts when they hit the air pocket; some were walking around the cabin,” they shared. Aeroflot employees. They also reported that despite the feeling that “the plane was falling apart,” it did not suffer any damage and had already flown back to Moscow.

“The closer to the tail, the stronger the blows were. When we asked to see what happened to the people in the rear of the plane, it was a terrible sight: blood on the ceiling, on the shelves, people with broken noses. All this was visible to the naked eye from afar. It was almost impossible to hold on. It seemed that if these tremors did not stop, we would simply fall. Fortunately, after the fifth or sixth tremors everything stopped. It was a very scary sight, such that people simply cried and fainted from stress," she said vesti.ru one of the passengers.

“The incident occurred before descent and landing, so many were not wearing seat belts. It felt like the plane was thrown up 100-200 meters, and oxygen masks were released over some seats,” eyewitnesses add.

“There was blood everywhere: on the armrests, and on the ceiling, which they hit. Since I am involved in medicine, I couldn’t, of course, just sit still,” a medical girl who helped the flight attendants examine and treat the injured told Life . The cabin crew gave her a first aid kit, with which she “went around to all the injured.”

“When I provided first aid and nothing depended on me, all I had to do was wait for the boarding and the ambulance,” she modestly shared. By the way, as it turned out, Thailand “slowed down” and after landing in Bangkok “there were no rescuers or doctors on the runway, who arrived only an hour later.”

What is clear sky turbulence? There is a calm, clear sky and in it there is a strong ascending or descending current. Typically, such flows are visible by radar as water droplets, since water (rain/steam) reflects the radar beam. In this case, this stream is not visible, since there is no water in it. Air is simply moving at high speed up or down. When a plane flies into such a flow, it carries it along with it,” said aviation expert.

“People who are accustomed to uniform linear motion and who are not fastened while sitting in seats (although this is recommended) fly out of them. And the higher the wind speed, the more “qualitatively” people fly out of their seats. But this phenomenon happens extremely rarely and "Mainly in regions close to the equator, since there are powerful movements of air currents. In northern latitudes, this practically does not happen," he added.

“It’s practically impossible for an airplane to fall apart from something like this, it has operational strength and is “prepared” for such things, plus a margin of safety. Of course, they have limits, but in history there are practically no cases when turbulence in a clear sky broke up an airplane - this is not at the epicenter thunderstorms fly, in the end, that’s where death is,” the expert believes.

“Well, if you are flying, you are shaking, the plane rises and falls in altitude, and the bumpiness does not decrease - that means it is at all levels and you need to be patient. Don’t worry, the plane will not fall apart, but what seems to you like a fall or approach hundreds of meters, in reality it is a “pit” or “slide” of 10-30 meters and this is acceptable, airplanes are not designed for such loads,” a pilot from one of the leading Russian airlines told the site.

“Over the entire existence of civil aviation, it was turbulence “in the sky” at the flight level that caused the death of aircraft a vanishingly small number of times - it was necessary to fly into the epicenter of a thunderstorm, and on an airliner that cannot come out of a flat spin,” he added.

“Pilots are not afraid of turbulence - the kind that passengers are afraid of. They know the strength limits of the aircraft and in the event of turbulence they do not panic, but turn on the “fasten your seat belts” (by the way, before departure we tell the flight attendants at the briefing whether there will be bumpiness, what kind, where and for how long Li) and take the plane away from this area,” the PIC shared.

“Always buckle up in your seats while you’re flying. When the “fasten your seat belts” sign lights up, don’t think, just immediately sit down and/or buckle up. It may shake or start chattering, the most common injuries from turbulence are when those who are not fastened fly headfirst into the shelves in an “air pocket.” ", they become injured, starting to "fly" around the cabin. Also, when the sign is not lit, and you are in a seat, fasten your seat belt. It's not difficult for you, but if it suddenly shakes (sometimes "clear-sky turbulence"), you will not fly out of the seat and will not you will break your neck, arms, legs or other passengers,” the pilot advises.

By the way, earlier journalists found out what civil aviation pilots are doing and how flight attendants of various airlines “get a kick out of it.”

In particular, the worst thing for pilots is not even a failure of the engine or engines (planes can land and have landed with all engines turned off), but a fire in the cabin or luggage compartment. Well, flight attendants “have fun” not only by “conning” passengers for extra surcharges or stealing expensive alcohol, but also by having sex with passengers and working for competitors.