What is clear air turbulence. A clear-sky disaster: how dangerous turbulence is. Technical Sciences - Indicator. “In our case, the consequences were minimal”

The Aeroflot flight Moscow-Bangkok, on board of which unbelted passengers were injured, encountered “turbulence” clear skies" - she 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 were hit." air pocket"Some walked around the salon," 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 shock, 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 - it means that 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.

"During the entire existence 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 are injured, starting to "fly" around the cabin. Also, when the display 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.

Crew actions Russian plane, investigators will evaluate. They will interrogate the pilots and passengers on board, after which they will decide whether to open a criminal case or not.

As a result of the aircraft hitting an air pocket. All of them were not wearing seat belts at the time of the turbulence. Eight had to be operated on. Why didn't the crew warn passengers about the danger zone? About “clear sky turbulence,” a phenomenon that causes injuries to hundreds of passengers every year, report NTV correspondent Alexey Kvashenkin.

The flight to Bangkok was already coming to an end, less than an hour remained, but the “fasten seat belts” sign had not yet lit up. 7 hours of flight left. Someone was finishing breakfast, someone was waiting in line for the toilet when the plane shook for the first time.

Olga Tarasova, passenger of flight SU270: “Nothing predicted. It was light outside the window, we were flying above the clouds. The sky was clear, and suddenly we felt like we were falling into some kind of abyss, as if on a roller coaster.”

For a few seconds, the liner seemed to freeze, and then the most terrible seconds in the lives of passengers began.

Tamara Sipko, passenger of flight SU270: “The plane was falling, it was shaking, some things were flying.”

Margarita Dovgaya, passenger of flight SU270: “We were thrown up, torn from our seats, very strong shaking began. People fell, panic and screams began.”

And at this time the pilots did everything possible to hold the huge airliner.

Ilya Kuzma, flight simulator instructor: “Turbulence is an unpredictable thing. We don’t know which way the liner will throw now, right, left, up, down. Piloting becomes quite problematic."

It's just a simulator, but the feeling is quite authentic. And here, in the cockpit, the question arises: could this situation have been prevented at all? Having stopped the simulation of turbulence, the pilot instructor explains: there is indeed a special radar on board, but it is not an all-seeing eye.

Ilya Kuzma: “Turbulence zones, if they are created by cloud fronts, thunderclouds, precipitation, then they will be displayed on the radar. If there is no precipitation or suspended matter, turbulence zones are not visible.”

Most people are accustomed to thinking that turbulence is a companion to bad weather. But like this, at a height of many kilometers, in the middle of a clear sky? Most passengers have never even heard of this. And flight 270 encountered exactly this phenomenon.

Maxim Fetisov, press secretary of Aeroflot: “The locator cannot detect its approach, so our pilot could not anticipate this turbulence and turn on the “fasten seat belts” signal in time.”

And military meteorologist Evgeny Tishkovets believes that local weather services could have identified the danger zone.

Evgeniy Tishkovets, meteorologist: “Ground services did not predict this dangerous phenomenon, although it is predicted. It was said that it is supposedly not predicted, it is invisible. It is not true".

But this is not the crew’s fault. Even by indirect signs, the pilots could not notice the danger in advance: the tropical climate is very treacherous.

Victor Zabolotsky, Honored Test Pilot of the USSR: “These are tropical latitudes. This is very harsh. I encountered this phenomenon once. To be honest, it’s not very pleasant.”

"Clear-sky turbulence" it's not that big of a deal a rare event. Planes hit it more than 700 times a year. As a rule, without consequences for passengers.

Did you pay attention the other day to the news about the Moscow-Bangkok plane that got into turbulence?

About 40 minutes before landing, the plane hit an air pocket. In 15 seconds, the plane was first thrown 200 meters. And then it fell back the same meters. As a result, those who were not wearing seat belts were simply thrown out of their seats, thrown up, and then fell down.

According to some reports, 27 people were injured, including serious fractures. According to the news, 10 people have already been operated on in Bangkok.

Cause of incident - clear sky turbulence. The instruments on board the aircraft cannot predict its appearance. But why in a clear sky?!

As we know, air turbulence is a powerful disturbance of air flows, multidirectional movements of air masses up, down, and sideways. The speeds of gusts and currents reach colossal values. Ascending and descending currents rush a huge mass of air in different directions. An airplane caught in such a mess will be thrown like a chip in a stormy mudflow. The main reasons for such bumps are the heterogeneous composition of the atmosphere, which is influenced by temperature, pressure, and humidity.

Very often, such up-down-sideways flows form not only in thunderclouds, but also above the boundaries - joints various types earth's surface: land-sea, steppe-forest, plain-mountains, etc. This is due to different degrees of heating of these surfaces and air masses above them, evaporation. So the cycle begins - the larger the area of ​​these adjacent surfaces and the temperature difference, the higher the turbulence above their boundary.

And more about clear skies:

You may believe it or not, but it is a fact (like the fact that the earth is round) that there are rivers, rivulets, and streams in the sky. Only the size of these rivers and streams is monstrous! Thousands of kilometers long, tens of kilometers high and hundreds of kilometers wide. The flow speed in these currents can reach half a thousand kilometers per hour!

And now imagine, you are riding a bicycle along a path between residential areas, whistling your favorite melody, suspecting nothing, and suddenly the houses end, and you jump out at speed around the corner, and there is a gusty wind! How will you feel? That's it!

If you know that there will be wind around the corner (and this can often be determined visually by dust, leaves, and debris rushing around the corner), then of course you will take action. Either don't go there, go around, or be prepared for the wind to blow!
So it is with “clear sky turbulence.” This phenomenon has long been known and easily explained and, alas, it is not uncommon! There are even signs and places where you are likely to run into it, but they are too unpredictable.

Where are you most likely to encounter this phenomenon?
Typically, this is the boundary of the air flow at the entrance and exit to and from the flow. But the trouble is that it is almost impossible to see this flow with a modern radar, but to feel its influence on yourself is even very...

On May 1, an Aeroflot Boeing 777 entered a zone of severe turbulence. 27 people were injured, mostly unfastened, while, according to passengers, the “Fasten seat belts” sign was not lit. The reason for what happened was the so-called TYAN - this is not a girl in anime slang, but clear-sky turbulence. In English it is called CAT - Clear Air Turbulence.

What it is? “Normal” turbulence is associated with cloud cover and its occurrence is easy to predict both visually and using weather radar. But the TYAN is not visible until you get into it: it arises due to collisions of air masses moving with a large difference in speeds. There are three main reasons:

Why is TIAN dangerous? As you already understood - serious injuries to passengers. Despite the fact that, according to information from medical institutions in Bangkok, where medical care 27 Aeroflot passengers applied; there were no patients in serious condition with life-threatening injuries, and information about patients with compression fractures of the spine was not confirmed; 15 Russian citizens and two Thai citizens are currently hospitalized. Patients who remain under the supervision of doctors suffered bruises, and several people had broken limbs.

An unbelted passenger's head turns into a powerful sledgehammer

There are known cases of more serious injuries and even deaths due to traction accidents, as well as plane crashes: for example, in 1966, a Boeing 707 flying from Tokyo to Hong Kong simply suddenly disintegrated in the air, killing 124 people.

Buckle up.

In addition, severe bumpiness makes it impossible for pilots to perform even the simplest operations, such as reading instrument readings.

What to do? After the “Fasten your seat belts” sign turns off, it’s not without reason that they say: “You can move freely around the cabin, but for your safety we recommend that you remain buckled throughout the flight.” It is not necessary to tighten it tightly: in this case, it will not restrict movement, but still will not allow you to break through the ceiling with your head.

An unbelted passenger can play as an astronaut and fly around the cabin in zero gravity.

Also, it's always better to fold hand luggage under the chair: when the shelf opens during turbulence, the suitcase will not fall on your head. By the way, for the same reason, there is less chance of running into your neighbor’s suitcase.

And you certainly shouldn’t pretend to be a hero while valiantly standing in line for the toilet with the signs on: according to statistics, the most deaths not during disasters are people who sat on the potty during turbulence and unsuccessfully hit their heads.

It's not what you think. Just coffee on the ceiling. Or it could be on your lap.

If you're not wearing a seatbelt, remember to avoid carts.

Today, turbulence is a very pressing problem for aircraft, at the same time, a person, unfortunately, cannot control the vortex chaotic wind flows. As a rule, turbulence poses a serious danger to aircraft, however, for the most part, any negative consequences for aircraft can be avoided, but passengers often suffer, receiving a number of injuries and injuries due to the strong shaking of aircraft.

Turbulence after.

It is still possible to reduce the threat to the life and health of passengers by applying in practice very interesting idea, based on a number of laws of hydrodynamics. The idea is very simple and lies in the fact that the passenger seats available in the aircraft cabin should be provided with hydraulic dampers, which will operate at the slightest vibration of the passenger airliner, thereby reducing inertia and saving hundreds of passengers from injuries and possible injuries.

Schematic diagram of the operation of a damping passenger aircraft seat

As is known, liquid is an incompressible medium, and the use of a hydraulic damper built into the passenger seat will avoid shaking of the passenger seats if the aircraft enters even a zone of strong turbulence. The chaotic movements of the aircraft will be dampened by the hydraulic medium, that is, if the plane swings sharply down, then according to the laws of physics, the passenger in the seat must remain for a moment at the point from which the plane deviated, and vice versa, with a sharp rise, the passenger will begin to squeeze into the seat. The two cases considered are rather particular, however, given the chaotic movement of the aircraft during turbulence, strong vibration will be created, during which a person may be injured. The use of a hydraulic damper will dampen these vibrations, thereby minimizing any possible harm, creating safe conditions for passengers.

Among other things, the current development has another very interesting purpose - passenger seats equipped with damping elements are extremely effective in the event of forced or emergency landing, for example, when the landing gear fails, when the aircraft lands on unprepared terrain, etc. Hypothetically, the seats used will also make it possible to protect passengers in the event of a plane crash, however, only in a situation where there is no subsequent fire, explosion, etc.

Kostyuchenko Yuri especially for the site

Atmospheric turbulence

The speed of movement of air and particles suspended in it changes in space and time. Ordered and turbulent movements of air masses differ primarily in scale. Large-scale motion is considered orderly, while small-scale motion is considered turbulent. It is impossible to draw a clear boundary between them: it is conditional and depends on the task and measurement methods.

Turbulent movement of air masses is characterized by disorder of the velocity field in time and space, the presence of inhomogeneities or turbulent vortices that affect the behavior of the aircraft. A spectrum of vortices of different sizes (scales) is created. The reciprocal of the scale is called the spatial frequency, similar to how the circular frequency w in radio engineering is the reciprocal of the oscillation period. The distribution of turbulent energy over spatial frequencies, which is called the turbulence spectrum, is its sufficient full description. The value of e, as a dimensional parameter of the turbulence spectrum, characterizes its intensity.

The nature of turbulent motion in the atmosphere is such that the energy of large-scale vortices is transferred to smaller-scale vortices - the vortices seem to be crushed. This continues until the vortices become so small that their kinetic energy is entirely used to overcome the viscosity of the air and turns into heat. This process of turbulent motion occurs continuously as long as large-scale vortices are replenished with energy from atmospheric energy sources associated with differences in temperature and pressure. The conversion of turbulence kinetic energy into heat is called turbulence kinetic energy dissipation (TKED). The quantity e, in its physical content, is the rate at which the kinetic energy of turbulence of minimal scale is converted into heat. The higher the v, the higher the intensity of the turbulence.

Turbulence is not observed throughout the entire atmosphere at the same time and not at all altitudes. It occurs under the influence of thermal and dynamic factors. Therefore, it is customary to distinguish between thermal and dynamic turbulence.

Thermal turbulence occurs as a result of uneven heating of the earth's surface and large vertical temperature gradients. This type of turbulence is typical for the lower half of the troposphere (up to 3-4 km). Its intensity depends on the time of year, the period of day and the stability of the atmosphere. Greatest intensity is observed during the day in the warm season in cold unstable air masses, as well as in a blurred pressure field - in saddles and cyclones.

With thermal turbulence in the atmosphere, both disordered and ordered ascending and descending air movements occur, creating cumulus and cumulonimbus clouds, modocumulus and cumulonimbus clouds.

Dynamic turbulence is created due to the friction of moving air against the rough relief of the earth's surface and the heterogeneity of air flows in speed and direction.

The friction of air against the earth's surface in flat and mountainous areas causes the occurrence of dynamic turbulence mainly in the lower layer of the troposphere (up to 1-1.5 km). In mountainous areas it can spread much higher (up to 7-9 km).

Dynamic turbulence occurs in layers of the free atmosphere with great variability in wind characteristics and is observed more often where there is convergence or divergence of air flows, curvature of their direction, as well as in areas of jet streams. It can also occur in the form of ascending and downdrafts as a result of wave movements at the boundary of the inversion and isothermal layers. Its intensity depends on the speed of vertical and horizontal wind shears.

Although thermal and dynamic turbulence are created as a result of the action of different factors, they can influence the nature of air flows both separately and simultaneously, increasing the intensity of the turbulent state of the atmosphere.

Turbulence causes the vertical transfer of heat, water vapor and solid particles in the atmosphere, and wind gustiness. Turbulent exchange significantly influences the conditions of formation, evolution and microstructure of clouds, precipitation and fogs, which create difficult meteorological conditions for flights.

Intense turbulence occurs under clear and cloudy skies. Since it is one of the cloud-forming factors, let us consider its physical characteristics in a clear sky (“turbulent field”).

There are several types of clear air turbulence:

    1) mechanical turbulence, caused by the influence of unevenness of the earth's surface on air currents and sometimes enhanced by its unequal heating;

    2) mountain waves, which by origin are a special form of turbulence of the first type (due to the specific impact on aircraft flights, mountain waves are considered separately);

    3) turbulence of jet streams;

    4) turbulence in the layers internal to the free atmosphere.

Turbulence in a clear sky is a meteorological phenomenon dangerous for aviation due to its sudden impact on the aircraft. Some aviation accidents occurred as a result of aircraft entering areas of dangerous turbulence under cloudless skies.

Turbulization of air flows in a clear sky is associated with the existence in the atmosphere of layers with significant vertical and horizontal gradients of wind speed and air temperature.

Under conditions of stable temperature stratification, the occurrence of TJN can be explained by the loss of stability (increase in amplitude and subsequent destruction) of gravity or gravity-shear waves (over mountains - mountain waves) and the transfer of energy from wave movements to turbulent ones.

In the troposphere, the probability of an aircraft hitting a nuclear power plant is quite high; it depends on geographical latitude. In the middle and upper tropospheres of temperate latitudes, this parameter is approximately 10% of the total aircraft flight time, in southern latitudes - 15-20%. In the stratosphere, this probability is much lower and in the 10-20 km layer is approximately 1%.

When entering the PTZ zone, aircraft are most often subject to weak and moderate bumpiness, the integral frequency of which in the troposphere is 95%, and only in 5% of cases can strong bumpiness be observed.

Turbulence video

The horizontal dimensions of the nuclear power plants vary within fairly wide limits, especially in the troposphere, reaching in some cases several hundred kilometers. However, for 80% of cases in the upper troposphere of temperate latitudes, the length of turbulent zones does not exceed 140 km. In the stratosphere, TN zones have significantly smaller horizontal dimensions. At an altitude of 10-20 km, the horizontal length of turbulent zones (80% of cases) in the temperate latitudes of the CIS territory is less than 80 km, and in the lower stratosphere over the USA - up to 40 km. This means that when a supersonic aircraft crosses PTZ zones in cruising mode, bumpiness is observed for several seconds or tens of seconds.

TN zones can be continuous (solid) and in the form of separate intermittent cells with quite sharp boundaries. Continuous zones of TAN have greater repeatability.

The thickness of the TAN zones, as well as the horizontal dimensions, fluctuates within significant ranges depending on the geographic latitude, altitude and aerosynoptic conditions. In the middle and high latitudes of the CIS (85-90% of cases), the thickness of turbulent zones in the troposphere does not exceed 1000 m, and in the stratosphere - 350 m, therefore, the TNT zones have a pronounced spatial anisotropy. These are flat formations, the coefficient of spatial anisotropy of which (the ratio of the thickness of the turbulent zone to its horizontal length) with an 80% integral repeatability is for the upper troposphere of mid-latitudes.

Turbulence video 2

 

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