The topic of turbulence inevitably pops up when mentioning various flows of gases, liquids or plasmas. Most motions of matter have a turbulent character.
So what is turbulence? Turbulence is the definition of disordered non-linear motion. The concept of "turbulence" has no clear and unambiguous definition. In the general case, this is a vortex movement of flows caused by an increase in their speed.
When calculating other types of aircraft, a flow with a value of the Reynolds hydrodynamic similarity criterion, derived from the Novier-Stokes equation, more than 2320 is considered to be turbulent. holes (tubes) and a decrease in the dynamic viscosity of matter.
An example of a turbulent flow is air currents, which are eddies of various sizes that occur when the wind direction changes sharply: from vertical to horizontal and vice versa. Atmospheric turbulence leads to wind discontinuity, various vertical transfers of steam, condensation nuclei and other particles having 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 flight aircraft. Not everyone knows what turbulence is in an airplane. When vortices are superimposed on each other, aircraft are exposed to multidirectional winds, as a result of which the lift and angles of attack of the wings change. A similar situation overboard leads to shaking and vibration - the so-called "blank".
Distinguish between moderate and strong blanks. At the first shock, the changes in flight altitude and the swaying of the aircraft are not so significant, and the pilots do not experience difficulties in controlling the aircraft.
A strong blank is a more serious situation, consisting in frequent rolls and yaws, accompanied by a deterioration in controllability and stability in flight, as well as a distortion of the readings of on-board instruments. Such a phenomenon, if appropriate measures are not taken, can create stresses in parts and individual components, leading to significant damage and deformation of equipment and airsickness among crew members and passengers.
When entering turbulence zones, passengers often experience anxiety about whether the pilot will cope with the situation. However, the qualifications and skills of the pilot can only come in handy 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 performed on autopilot.
What are turbulence zones? As a rule, this is a space where the probability of getting into long-term turbulence reaches 100%.
Currently, almost any passenger can determine when and where during the flight the ship will shake. This became possible as a result of creating turbulence maps, where calmer zones are marked with a lighter color and vice versa. The online turbulence map was created to reduce the anxiety of passengers and crew, allowing you to predict and prepare if the aircraft is caught in turbulence.
Is turbulence dangerous for aircraft? Of course, such a phenomenon causes anxiety and fear, and if possible, it is bypassed. 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 who did not have time to fasten their seat belts get injured.
The size of the aircraft plays an important role in the feeling of shaking during turbulence. The larger the plane, the less inconvenience. Sooner or later, everyone asks the question of where in the plane the least shakes 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 streams on a 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 descending and ascending flows).
An example of thermal convection is the formation of cumulus clouds.
Before each flight, the crew and the pilot himself familiarize themselves with the weather reports for the near future in order to choose the safest route for movement. 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 updrafts up to 10-15 m/s.
From the point of view of flight safety, it is forbidden to enter such clouds, as well as to fly a ship under them. Especially dangerous are cumulonimbus clouds, because in them, due to the presence of water particles, heavy precipitation and electrical discharges are formed. Therefore, it is recommended to lay a route at a distance of 10 km from thunderclouds at a height of more than 1 km above them. Complicating the flight is not only high turbulence in the aircraft, causing bumpiness, but also poor visibility - up to 45m.
Overlapping zones of updrafts and downdrafts can extend for thousands of kilometers. Most cases recorded Most cases recorded on eastern shores USA.
clear sky turbulence
The absence of any clouds in the sky does not mean that there will be no turbulence. Above 5000 m, so-called clear-air turbulence may 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 rectilinear direction, deforms 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, the aircraft must strictly maintain a certain distance in order to avoid a collision.
Can a plane crash due to turbulence? In all the time, due to clear sky turbulence, five major air crashes. Under conditions of complete absence of clouds, the destruction of an aircraft flying from Tokyo to Hong Kong occurred. Experts have determined that unusually high turbulence near the slopes of Fuji was the cause of the death of all the passengers of the flight and the crew.
Another example is the crash of an airliner landing at one of the airports in Alaska. The version of the tragedy due to turbulence was not immediately considered, since it contradicted the forecasts of the hydrometeorological center. However, an outflow of Arctic masses was subsequently 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 flying from Moscow to Thailand had hit a clear-sky turbulence zone. It was impossible to establish the fact of the approach of the air pocket and avoid the ship getting into it, since not a single device recorded it. As a result of a sharp jump of 200 m, the passengers received multiple injuries and fractures.
According to statistics, there are on average about 1000 cases of precedents per year related to the instability of the atmosphere in a clear sky. Basically, they lead to flight delays, which causes great material damage to carrier airlines.
Actions of pilots when entering the turbulence zone
According to Captain Chesley Sullenberg, who landed a passenger plane on the Hudson, when one of two decisions is made in the cockpit when it enters the turbulence zone: go beyond the instability limits by lowering the height, or go into cloudless space by gaining it.
In case the plane got into turbulence, a set of rules and recommendations for the cockpit and crew has been developed. You need to run the following commands:
- Change the autopilot to manual control.
- Enable the "Tighten belts" command.
- Adjust the speed to 340 km/h.
- Do not allow a sharp drop in altitude, aircraft roll of more than 10 °.
In conditions of impossibility of avoiding the zone of strong blanks, the crew commander is obliged to return the aircraft to the original or the nearest airfield.
Thus, the phenomenon of turbulence in the sky does not pose a strong threat to an aircraft. Like imperfections on highways (bumps, stones), turbulence in the air requires only excessive attention from the aircraft commander.
Several dozen passengers were injured and fractured when on May 1, 2017, a plane flying from Moscow to Thailand hit a turbulence zone. Almost everyone who flies by planes has encountered this phenomenon at least once in their life. the site tells what turbulence is, what is the peculiarity of clear sky turbulence and what does climate change have to do with it.
What is turbulence?
The term "turbulence" is usually understood as 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 non-linear waves with an increase in the speed of the flow of a liquid or gas in a medium. This phenomenon is usually 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: with the movement of their fins and wings, they destroy surface waves and create a special structure of turbulence.
Atmospheric turbulence, in which air masses are constantly moving both in the horizontal plane and in the vertical plane, 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 several factors affect the occurrence of turbulence, mainly orography and air currents. In turn, the conditions of turbulence depend on the height of the mountainous relief, speed, directions and intensity of flows.
What causes clear sky turbulence
At an altitude above five kilometers, a phenomenon such as clear sky turbulence (CAT) can be observed. Unlike other types of atmospheric turbulence, it occurs in clear weather or in the presence of upper clouds, and is difficult to notice in advance. Scientists have found that much more often this phenomenon occurs over mountainous terrain, especially on the leeward side of the slope.
At the same time, clear-air turbulence is difficult to predict due to the sharp localization in the surrounding flow, the dynamics of the size and duration of the phenomenon. Moreover, clear-air turbulence cannot be captured by radar. To date, it is predicted through indirect signs indicating the likelihood of a phenomenon, and predictive models are built based on a number of factors.
The main work on the development of a clear-sky turbulence forecasting technique took place in the 1990s, and since then practically nothing has changed. Thus, according to the method compiled by the Hydrometeorological Center of Russia, the main varieties of the hydrodynamic instability mechanism are the hydrodynamic instability of the main flow stratified by wind and temperature, the instability of internal waves in a steady flow, and the instability of the critical level.
The success of the forecast is also due to the fact that the frequency of CAT largely depends on the region. Clear sky turbulence indices are also calculated abroad, in particular in Great Britain, the USA and Canada.
Over the past 50 years, there have been five air crashes caused by clear-sky turbulence. So, in 1966, a plane flying from Tokyo to Hong Kong, collapsed in the air in the complete absence of clouds. As a result, all passengers on board were killed. As the investigation showed, the cause of the accident was abnormally strong turbulence near the slopes of Fuji, which exceeded the allowable loads on the structure. In the same year, a similar plane crash occurred in the United States, in the state of Nebraska: the plane bypassed a powerful thunderstorm, got into turbulence and also collapsed in the air.
Two years later, in December 1968, an airliner landing at Iliamna Airport (Alaska) suddenly fell apart. Pilots flying near the crash site said they encountered severe turbulence. This contradicted the official weather forecast, so an independent expert was involved in the investigation, who concluded that due to the outflow of Arctic air masses, a air wave, in which the turbulence zone was formed.
One of the largest accidents occurred in 2001 in New York. When the airliner took off from the airport, he got into the air current, which was created by another aircraft. The air current left by the airliner in the form of vortices breaking off the wingtips of a flying aircraft (in aviation this phenomenon is called wake or wake) caused turbulence. The resulting g-force caused the vertical tail stabilizer to come off and the aircraft crashed into a residential area.
The number of precedents for falling into clear sky turbulence, according to various sources, ranges from up to 1500 cases per year. Fortunately, most of them do not cause any harm to passengers and crew, but flight delays and interruptions due to turbulence are hurting airlines. So, only in the United States damage
However, not all climatologists 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 influence, but very indirectly.
This is scary. It is not comfortable. Because of this, coffee and tomato juice are spilled on the pants. This is called "turbulence". And how dangerous is it really?
One day the plane I was on got into severe turbulence. This situation is a great way to feel like a tiny grain of sand on which nothing depends. After that incident, I avoided planes like the plague for a year.
Fortunately, our flight ended safely. The same cannot be said for some other cases. Last February, a flight from Denver to Billings for four passengers and one flight attendant ended up in the intensive care unit. And in December, due to turbulence, 14 passengers of the Seoul-Dallas flight were injured, the plane made forced landing in Tokyo.
These are just three examples that I could think of offhand. And what do experts think about the real danger of an aircraft getting into a turbulence zone? Are belts a 100% guarantee of our safety?
Can an airplane lose control and crash due to turbulence?
In short, the answer is “no”. And don't roll your eyes, looking for killer arguments against such an answer. You have probably heard that an airplane is the safest means of transportation. This is despite the fact that ground transport, unlike airplanes, cannot fall by definition. It seems more reliable than moving in an iron pipe dangling 10 kilometers above the ground.
But, despite the very unpleasant subjective sensations, turbulence itself will never cause the plane to fall to the ground. Pilot Patrick Smith at AskThePilot.com explained that even the most violent movements of air masses cannot flip the plane or break it into several pieces.
Turbulence can cause damage. But this happens very rarely. A frequently cited incident in this regard was a 1966 incident when severe turbulence tore apart a Boeing 707 near Mount Fuji, to which the pilot wanted to fly closer to get a better view of the Japanese landmark. Wind gusts in that place reached 140 miles per hour, which killed everyone on board.
But since then, engineers have done some serious work. Aircraft design has become more resistant to such loads. Modern passenger liners they are able to take off at an angle of 90 degrees to the horizon, so they are not afraid of any gusts of wind on Earth. The Dreamliner 787, for example, is equipped with special sensors to accurately predict the location of turbulence zones. However, a combination of adverse weather conditions and other factors (such as pilot error) can lead to disaster.
Professor Robert Sherman of the National Center for Atmospheric Research (USA) says that history has recorded a couple of cases when very strong gusts of air ripped the engines from the wings. But even in these circumstances, the plane landed safely at the airfield.
If the turbulence is very strong, then the pilots can make adjustments to the route or land in a different place. But even in this scenario, the situation develops very rarely. In this case, the conditions may not be so terrible as to cause harm to the aircraft. Usually emergency landing is committed due to the fact that one of the passengers neglected the “fasten seat belts” command and now he needs urgent medical attention.
How often do passengers get injured due to turbulence?
The official statistics are silent here. Of course, national aviation agencies collect relevant data from airlines. But, as a rule, they report only serious injuries.
Professor Sherman says that in the US, a turbulence injury is included in the statistics if the passenger died within 30 days of the incident or was confined to a hospital bed for more than 48 hours. In addition, bone fractures, severe hemorrhages, torn nerves and ligaments, second or third degree burns involving more than 5% of the body surface, or damage to internal organs are taken into account.
More “minor” injuries, if the patient spends no more than a day in the hospital, are not taken into account. Therefore, official statistics can give a greatly underestimated.
According to a report from the Federal Office civil aviation United States in 2013, 24 people were injured due to the plane hitting the turbulence zone. Of these, 13 were crew members. Most of the injuries are received by those who did not buckle up. Therefore, two-thirds of the victims are flight attendants.
How do pilots perceive an aircraft entering a turbulence zone?
They care about two things: passenger comfort and their own safety.
It should be borne in mind that in the air, pilots of different aircraft communicate with each other “in real time”. They report on observed phenomena in the atmosphere. If someone gets into a "chatter", then his neighbors in the sky will immediately find out about it. This information is also transmitted to controllers on the ground.
Pilots may change their route slightly to avoid turbulence. But this results in additional fuel and time costs. Therefore, some of them do not pay much attention to turbulence.
The situation becomes truly threatening in the case of the so-called "clear sky turbulence". Sudden and strong blows of air masses are like thunder from a clear sky. They are the source of most turbulence-related injuries. The pilots are unaware of the threat that awaits them.
Professor Sherman states that clear-sky turbulence most often occurs over mountainous regions.
Last year, five passengers on United Airlines Flight 1676 were injured due to sudden and severe air strikes. The plane went down sharply, and unbelted passengers "soared" up from their seats, hitting their heads on the compartments for hand luggage and break their bottom. One child jumped out of his chair and landed in a nearby spot.
Another incident involving an American Airlines flight from Seoul to Dallas has made the news. The plane made an emergency landing in Tokyo to take more than 10 passengers to hospital after being injured by a winter storm. The turbulence was so strong that drinks and food flew around the cabin like birds.
Such cases are very rare, but they have every chance of becoming a YouTube hit if one of the passengers has time to film what is happening on a smartphone camera.
Should I be afraid?
The short answer to this question is “no”. But if he did not reassure you, then know that the numbers are on the side of your safety.
Professor Sherman says the chance of an aircraft hitting a zone of severe turbulence is one in a million. The actual occurrence of such hazardous areas in the atmosphere is higher, but pilots try to bypass them.
But do not forget to follow the recommendations of the flight attendants. Fasten your seat belts when prompted to do so, and try not to unfasten them unnecessarily. So you will remain unharmed even if you get into the turbulence of clear skies.
Experts advise not to rush to unfasten and run to the toilet immediately after leaving the turbulence zone or takeoff.
The safest position during a flight is to relax in your seat with your seat belt fastened. Breathe evenly and deeply. Remember: turbulence is normal. Modern aircraft are very reliable. You are completely safe.
MOSCOW, May 1 - RIA Novosti. An Aeroflot plane hit "clear sky turbulence" on its way from Moscow to Bangkok. As a result, 27 people were injured, including 24 Russians. All received medical attention, some of the victims required surgery.
The Boeing 777, operating flight SU 270, on approach to Bangkok's Suvannapum airport, 40 minutes before landing, hit air pocket.
The footage taken on board the liner shows that some passengers are lying on the floor, things are scattered throughout the cabin. Almost three dozen people, including children, received injuries of varying severity.
At 3:38 Moscow time, the plane landed safely at the Bangkok airport. In total, there were 313 passengers on board. All the injured were taken to Samitivet Sinakkarin hospital. "This is a large and well-equipped modern hospital, geographically closest to the Suvannaphum airport," RIA Novosti reported. Russian ambassador Kirill Barsky in Thailand.
No serious injuries
According to the latest data, 15 Russians remain in the hospital. Their list is published on the website of the Russian Embassy in Thailand.
Employees of the consular hotel of the embassy are in the hospital, communicating with doctors, helping the victims with translation, establishing contact with relatives and clarifying information about the severity of injuries.
At the same time, as noted in the message of Aeroflot, there were no patients in serious condition and with injuries that pose a threat to life.
According to the Ministry of Health of Russia, the condition of all the victims is assessed by doctors as of moderate severity.
Most received bruises, a few people - fractures. Nine passengers, including four children, received medical assistance on an outpatient basis. Four victims required surgery. According to the doctors, their lives are out of danger, but the operations themselves are quite complicated, the head of the department told RIA Novosti. consular department Embassy of Russia in Thailand Vladimir Sosnov.
The Embassy has opened a hotline where you can get information about the incident: +66 90 403-3645 . Aeroflot also organized a special line in its contact center for relatives of the victims: +7-495-664-0000 .
clear sky turbulence
Most of the passengers were injured due to the fact that they were not wearing seat belts.
As Aeroflot explains, the so-called "clear sky turbulence" became the cause of the emergency. The main feature of such turbulence is that it "occurs not in clouds, but in clear skies with good visibility, where weather radar cannot catch its approach."
“Therefore, the crew does not have the opportunity to warn passengers about the need to return to their seats,” the carrier said in a statement.
Aeroflot also promised that, if necessary, they would cancel hotel reservations, postpone check-in dates, and also reissue tickets for the next flights for transfer passengers.
"All expenses related to the reissuance, as well as the expenses for the treatment of passengers, were completely covered by the airline," Aeroflot said.
The insurers will pay for the treatment.
Aeroflot's liability is insured by Russian insurance companies, AlfaStrakhovanie is the leader of the contract. The contract limit is sufficient for all compensations, said Igor Yurgens, president of the All-Russian Union of Insurers.
"We are in constant contact with AlfaStrakhovanie, the company interacts with medical institutions in Thailand, and we keep this case under special control," the press service of the Union of Insurers quotes Yurgens.
Investigators started checking
The Moscow Interregional Investigation Department for Transport of the Russian Investigative Committee has begun a pre-investigation check on the fact of injury to passengers.
"The investigation is carrying out a set of necessary verification measures aimed at establishing all the circumstances and causes of what happened. So, immediately after returning to Moscow, the aircraft crew members and passengers will be interviewed," the ministry said in a statement.
In addition, the Moscow Prosecutor for Supervision of the Execution of Laws in Air and Water Transport was instructed to conduct an audit.
The moments that the passengers of the Moscow-Bangkok flight had to endure can be called terrible without exaggeration. The plane hit a trap - what pilots call "clear air turbulence". Fractures, injuries - people had a feeling that the plane began to fall. 27 people are injured, 15 of them remain in hospitals in Bangkok.
The first minutes after shaking. Inside the plane - a terrible picture. Bloody passengers lie in the aisles, sit at the emergency exits. Many are asked not to get up - it is not known how serious the injuries are. As it turns out later, fractures, severe bruises.
“On one side lay a woman, moaning, she was very hurt. And the man groaned. He was apparently doubly sick. The girl, when it was all over, walked around the salon, her eye was blackened, her cheek was all torn. There were many such people who suffered greatly. Almost no one was wearing a seatbelt and did not have time to buckle up,” says passenger Elena Tregubets.
The plane had not yet begun its descent, so the "fasten your seat belts" sign was off. People calmly walked around the cabin - warming up in the aisles after a nine-hour flight. Flight Moscow-Bangkok was coming to an end. 40 minutes before landing - sharp aftershocks. The 300-ton Boeing 777 fell into the air pocket by almost 250 meters.
“We were strongly shaken two or three times. And somehow I immediately intuitively began to buckle up. And literally a couple of seconds, and 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.
At the airport, the plane was met by doctors. There were 313 people on board. 27 - among them both Russians and foreigners - were immediately sent to a local hospital. Some of the victims had to undergo surgery there. Embassy staff and an interpreter were sent to the hospital to help the Russians.
The weather in the skies over Thailand did not bode well. According to experts, the liner got into the so-called clear sky turbulence.
“It does not occur in clouds, but in a clear sky with good visibility. And it is not fixed devices. The main danger is that the crew does not have the opportunity to warn passengers about the need to buckle up. This situation is extremely dangerous for passengers who remain unfastened seat belts,” Aeroflot explained.
Such chatter also occurs in the skies over Russia, but much weaker than in tropical latitudes.
“In tropical latitudes, it is more developed and characterized by very large gradients, that is, power and unpredictability. It was impossible to avoid it. Although you need to keep your eyes open, ”commented the commander of the aviation squadron, pilot Sergei Matrosov.
Ideally, you should be wearing your seatbelt for the entire flight, just like the crew on that flight. Job description. At the helm was an experienced pilot Alexander Ruzov, flying over 23 thousand hours. Co-pilot Artem Unanov - more than 10 thousand flight hours. They took the car out of the turbulence zone, landed in normal mode. According to them, the shaking intensified due to the actions of the autopilot.
“The autopilot was not able to respond correctly in time, which is why such aircraft throws turned out. Therefore, after hitting the air pocket, we turned off the autopilot and smoothly brought the plane into a horizontal, even flight,” said Alexander Ruzov.
Travelers noted the work of flight attendants. They provided assistance and did everything to avoid panic. Although they themselves pretty much got it.
“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 badly injured, they applied tourniquets,” says Elena Tregubets.
Such cases in civil aviation are not uncommon. Almost 750 such incidents are recorded every year in the world. Thirty people were injured on an Etihad Airways flight from Abu Dhabi to Jakarta. And these are footage from the flight from Lima to Buenos Aires - even the crew members got it. But perhaps the loudest case is in the sky over Hong Kong. In August 2013, two airliners hit the turbulence zone at once. One of the passengers then pierced the plastic lining of the passenger compartment with his head. More than fifty people were taken to hospitals.
Passengers of 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 phone +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, reissuing tickets and hotels.
At the same time, after landing, the airport services checked the Boeing itself, which fell into an air pocket. No damage was found. The plane immediately went back to Moscow.
