2m with strong wind. Flying and non-flying weather

Beaufort scale - a conditional scale that allows you to visually assess the approximate strength of the wind by its effect on ground objects or by waves at sea. Developed by the English admiral and hydrographer Francis Beaufort (Eng. Francis Beaufort) in 1806.

Since 1874, it has been officially accepted for use in international synoptic practice. Since 1926, the Beaufort scale has additionally indicated wind strength in meters per second at a height of 10 meters from the surface. In the USA, in addition to the international 12-point scale, since 1955, a scale expanded to 17 points has been used, which is used for more accurate gradation of hurricane winds.

Absolutely non-flying weather from the passenger's point of view can be only a minor inconvenience for the pilot, while at the same time quite tolerable weather in the traditional sense can be non-flying. Of course, in the latter case, delays and cancellations of flights cause understandable anger on the part of the passenger. In fact, a number of meteorological phenomena can interfere with the safe operation of a flight. It often happens that flights of some airlines take off and land, while others wait for hours for the weather or are canceled altogether. We have already touched on the topic of weather conditions in, in this article we will talk in more detail about what kind of weather and how it affects aviation activities, what is meteorological minimum and how the crew decides to take off.

So, let's start with the fact that before trying to determine whether the weather is flying or not, you need to establish the appropriate criterion. This criterion is called meteorological minimum, takeoff and landing minima apply to wind speed and direction, visibility, cloud base, runway conditions.

As such, there are no minima for flying along the route, but we must not forget that there are a number of meteorological conditions that are a priori dangerous for aviation, we are talking primarily about thunderstorms and related phenomena, such as hail, lightning, heavy icing, severe turbulence. Of course, most thunderstorms can be bypassed, but when it comes to frontal thunderstorms that stretch for hundreds of kilometers like a solid wall, it is often not possible to bypass them.

As a rule, when talking about minima, we are talking about the minimum visibility on the runway and the decision height (CHL). Decision Height is the height at which the pilot must perform a go-around if he cannot see the runway.

There are three types of minima:

• Aircraft minimum.

  This is the minimum set by the aircraft manufacturer, that is, a list of acceptable weather conditions under which the manufacturer guarantees the safe operation of the aircraft.

• Airfield minimum.

  This is the minimum set at this airport for each particular runway. It depends on the ground-based radio navigation, lighting and technical equipment installed at the airport and the terrain surrounding the airport (mainly the terrain and artificial obstacles).

• Crew minimum.

  The crew minimum is the personal admission of each pilot to perform a flight in certain weather conditions. Pilot minimums are achieved by passing a special training program and confirmed by flight checks.

The basic rule for the application of meteorological minima is that the worst minimum of the three is applied: airplane, airport, and crew.

Let's take an example. The aircraft manufacturer set the minimum visibility on the landing strip for this aircraft at 200 meters, the crew, as a result of checks, confirmed their qualifications and has a landing clearance with a horizontal visibility of 200 meters, however, for the aerodrome on which the flight is performed, a minimum of 800 meters is set. As mentioned above, the worst minimum is selected, that is, in this case, a minimum of 800 meters will be applied. Everything is extremely logical, in this case, despite the excellent equipment of the aircraft and the high qualification of the pilots, the airport has less advanced equipment that will not allow you to perform a landing approach with such high accuracy, so the final minimum will correspond to the minimum of the airfield.

Let's talk in more detail about weather phenomena that limit the activities of aviation.

Visibility.

Probably the most common reason for weather delays is limited visibility. This group includes such meteorological phenomena as fog, rain, snow, dust, smoke, in general, everything that somehow reduces visibility. From an aviation point of view, it is not particularly important what the visibility is limited to, the main parameter determining the possibility of taking off and landing is the runway visual range, or RVR (Runway visual range). The second landing minimum parameter is decision height. For example, 60x550, where 60 meters is the decision height and 550 meters is the runway visual range. Sometimes a third parameter is added - the height of the cloud base.

As already mentioned, the minimum airfield depends, among other things, on the radio navigation equipment of the runway, most often on the category of the course-glide path landing system ILS. Most Russian airports have a basic ILS system of the first category, which provides a minimum 60x550, often the airfield is not equipped with a HUD at all, then the landing approach is carried out according to the so-called inaccurate systems and the airfield minimum is much higher. ILS equipment of the second category is currently installed at several airports in the Russian Federation such as Ufa, Vnukovo, Novosibirsk, Krasnoyarsk, the minimum is 30x300 meters. And only three airports have Category IIIA HUD equipment, the minimum for which is 15x200 meters, these are Sheremetyevo, Domodedovo and Pulkovo.

Mountain airfields are a special case, where the minima can be much higher despite the ground equipment installed.

If we talk about aircraft minimums, then most of the foreign-made aircraft, which are the majority today, are allowed to fly under the category IIIB and IIIC, that is, they can land in automatic mode when visibility is close to zero, but in Russia so far not a single airport has the appropriate equipment, which is not surprising because of its huge cost. As for the pilots, most of them have a landing clearance of at least 15x200, less often you can meet crews with a 60x550 clearance, as a rule, these are those who have only recently performed solo flights.

Airport minimums for takeoff depend mainly on the characteristics of the lighting and technical equipment of the runway and obstacles around the runway and are usually about 150-250 meters.

Wind.

Usually, the wind limits are the limits set by the aircraft manufacturer, very rarely airport regulations require these values ​​to be adjusted upwards. The wind speed is decomposed into two components - lateral and longitudinal. Airplanes are taking off and landing against the wind, or with a small associated component. The reason for this is security, because take-off and landing against the wind can significantly reduce the speed of landing and take-off, and therefore reduce the take-off and run distances. For most modern civil aircraft, the maximum tailwind component during takeoff and landing is 5 meters per second, and the side wind component is about 17-18 meters per second.

The wind speed of 11 m/s is decomposed into two components: lateral and tailwind.

side wind is dangerous, because in order to compensate for it, it is necessary to turn the aircraft slightly against the wind, to the so-called drift angle the stronger the wind, the larger this angle. While the plane is flying, drift does not cause problems, but at the moment it touches the runway, the plane acquires grip with its surface and tends to move in a direction parallel to its axis, at this moment the pilot needs to sharply change the direction of movement, which is not always easy. Of particular danger is the gusty wind, which can “blow” at the most inopportune moment, creating a large roll, which is very dangerous in conditions of proximity to the ground.

Landing with a strong side wind.

Recall that we are talking about the wind components decomposed for a particular runway direction, the value of the wind speed itself can be much higher.

Wind that would blow strictly perpendicular to the runway at a speed of about 20 meters per second is an infrequent phenomenon, usually such a strong wind is associated with the passage of powerful cyclones. As for the tailwind, for the vast majority of airports this problem is solved by simply changing the operating threshold of the runway, but there are a number of airports where this is not possible. For example, Sochi and Gelendzhik. These airfields are located in close proximity to the mountains, which excludes the possibility of taking off towards the mountains and landing from the side of the mountains, that is, you need to take off at sea. If the wind blows towards the sea, often the tail component excludes the possibility of a safe takeoff. That is, in fact, you can sit down, but you can’t take off anymore.

Adler Airport in Sochi.

Runway condition.

If the runway is covered with a layer of ice, whatever one may say, it is impossible to take off and land. In aviation, such a concept is used as adhesion coefficient, which is regularly measured by the aerodrome service, if its value falls below 0.3, the runway is not suitable for takeoff and landing. In case there is a side wind, this threshold value is adjusted upwards. A friction coefficient below 0.29 means that the lane is covered with a layer of ice, snow or slush and needs cleaning. Unfavorable weather conditions such as heavy snowfall or freezing precipitation can derail all runway clearance work, causing the airfield to be closed for many hours.

How is the decision to fly made?

The decision to take off is the exclusive right of the aircraft commander. To decide to fly or not to fly, first of all, you need to familiarize yourself with the meteorological information on the aerodromes of departure, destination and alternate. For this, weather reports of the actual weather are used. METAR, which are issued for all airports with a frequency of 30 minutes and forecasts TAF, the frequency of release of which is usually 3 or 6 hours. METAR and TAF reflect in standard form all meteorological information that is somehow significant when flying to a given aerodrome.

As an example, let's take the METAR of Krasnoyarsk Airport:

UNKL 181830Z 00000MPS 4600 BCFG SCT046 BKN240 11/09 Q1012 TEMPO 0500 FG RMK QFE733 29////65

For an uninitiated person, this is just a set of letters and numbers, but one glance is enough for a pilot to understand that the weather is “not very good”. The following information is encoded in the report: at the Krasnoyarsk airfield on the 18th at 18:30 UTC, the following conditions existed: wind - calm, visibility 4600m, fog in places, scattered clouds at 1500 meters, broken at 800 meters, temperature 11 degrees, dew point 9 degrees, fog at times with visibility of 500 meters, pressure 733 millimeters of mercury column, friction coefficient on the runway 0.65.

When deciding on a departure, all flights are conventionally divided into two categories: less than two hours and more than two hours. For flights less than two hours, it is allowed to ignore the forecast and take off if the actual weather at the moment is above the minimum. If the flight lasts more than two hours, on the contrary, the actual weather at the aerodrome is not taken into account, and the decision is made based on the TAF forecast. By the way, Russian legislation allows you to make a decision to take off if the weather at the destination airfield is predicted to be below the minimum if there are two alternate airfields with acceptable weather conditions, but this opportunity is rarely used, which is quite reasonable.

Why do some take off and land, while others wait for the weather?

There are many reasons. Let's give examples. For example, fog below the minimum is predicted in Samara, while the actual weather is still above the minimum. Flights from Moscow take off and land, and flights from St. Petersburg are delayed. The fact is that the flight from Moscow lasts less than two hours, and the decision to take off is made based on actual conditions, while the flight from St. Petersburg takes more than two hours, which means that it will be possible to fly only under the predicted improvement.

Some sat down, while others went to the alternate airfield, why? Again, different planes, different crews. It is possible that the flight that was diverted was operated by a crew with a poor personal minimum, or the aircraft was not allowed to land in these conditions. By the way, even two outwardly identical aircraft of the same manufacturer may have different restrictions, for example, some A320 aircraft are allowed to operate with a tailwind component of 7 meters per second, while the rest have a limit of 5 meters per second.

Often, from passengers waiting for the departure of a flight delayed due to weather conditions, one can hear statements like “I just called my aunt, she said that there is no fog and never was! We are being deceived!" We hasten to assure that no one is deceiving anyone. For some reason, many citizens think that if there is fog in Sheremetyevo, then all of Moscow, exactly along its border, should be covered with fog. Not at all. Many weather events are very local in nature. It happens that visibility on parallel runways differs by several kilometers.

The horizontal movement of air above the Earth's surface is called wind. The wind always blows from an area of ​​high pressure to an area of ​​low pressure.

Wind characterized by speed, strength and direction.

Wind speed and strength

Wind speed measured in meters per second or points (one point is approximately equal to 2 m/s). The speed depends on the baric gradient: the greater the baric gradient, the higher the wind speed.

The force of the wind depends on the speed (Table 1). The greater the difference between adjacent areas of the earth's surface, the stronger the wind.

Beaufort scale- a conditional scale for visual assessment of the strength (speed) of the wind in points according to its effect on ground objects or on waves at sea. It was developed by the English admiral F. Beaufort in 1806 and at first was used only by him. In 1874, the Standing Committee of the First Meteorological Congress adopted the Beaufort scale for use in International synoptic practice. In subsequent years, the scale has changed and refined. The Beaufort scale is widely used in marine navigation.

Direction of the wind

Direction of the wind is determined by the side of the horizon from which it blows, for example, the wind blowing from the south is south. The direction of the wind depends on the pressure distribution and on the deflecting effect of the Earth's rotation.

On the climate map, the prevailing winds are shown by arrows (Fig. 1). The winds observed near the earth's surface are very diverse.

You already know that the surface of land and water heats up in different ways. On a summer day, the land surface heats up more. From heating, the air above the land expands and becomes lighter. Over the pond at this time the air is colder and therefore heavier. If the reservoir is relatively large, on a quiet hot summer day on the shore you can feel a light breeze blowing from the water, above which it is higher than above land. Such a light breeze is called daytime. breeze(from the French brise - light wind) (Fig. 2, a). The night breeze (Fig. 2, b), on the contrary, blows from the land, since the water cools much more slowly and the air above it is warmer. Breezes can also occur at the edge of the forest. The scheme of breezes is shown in fig. 3.

Rice. 1. Scheme of distribution of prevailing winds on the globe

Local winds can occur not only on the coast, but also in the mountains.

Föhn- a warm and dry wind blowing from the mountains to the valley.

Bora- gusty, cold and strong wind that appears when cold air rolls over low ridges to the warm sea.

Monsoon

If the breeze changes direction twice a day - day and night, then seasonal winds - monsoons— change their direction twice a year (Fig. 4). In summer, the land warms up quickly, and the air pressure over its surface hits. At this time, cooler air begins to move to land. In winter, the opposite is true, so the monsoon blows from land to sea. With the change of the winter monsoon to the summer monsoon, dry, slightly cloudy weather changes to rainy.

The action of monsoons is strongly manifested in the eastern parts of the continents, where they are adjacent to vast expanses of oceans, so such winds often bring heavy rainfall to the continents.

The unequal nature of the circulation of the atmosphere in different regions of the globe determines the differences in the causes and nature of the monsoons. As a result, extratropical and tropical monsoons are distinguished.

Rice. 2. Breeze: a - daytime; b - night

Rice. Fig. 3. Scheme of breezes: a - in the afternoon; b - at night

Rice. 4. Monsoons: a - in summer; b - in winter

extratropical monsoons - monsoons of temperate and polar latitudes. They are formed as a result of seasonal fluctuations in pressure over the sea and land. The most typical zone of their distribution is the Far East, Northeast China, Korea, and to a lesser extent Japan and the northeastern coast of Eurasia.

tropical monsoons - monsoons of tropical latitudes. They are due to seasonal differences in the heating and cooling of the Northern and Southern hemispheres. As a result, pressure zones shift seasonally relative to the equator to the hemisphere in which it is summer at a given time. Tropical monsoons are most typical and persistent in the northern part of the Indian Ocean basin. This is largely facilitated by the seasonal change in the atmospheric pressure regime over the Asian continent. The fundamental features of the climate of this region are associated with the South Asian monsoons.

The formation of tropical monsoons in other regions of the globe is less characteristic when one of them, the winter or summer monsoon, is more clearly expressed. Such monsoons are observed in Tropical Africa, in northern Australia and in the equatorial regions of South America.

Earth's constant winds - trade winds and westerly winds- depend on the position of atmospheric pressure belts. Since low pressure prevails in the equatorial belt, and near 30 ° N. sh. and yu. sh. - high, near the surface of the Earth throughout the year the winds blow from the thirtieth latitudes to the equator. These are trade winds. Under the influence of the rotation of the Earth around its axis, the trade winds deviate to the west in the Northern Hemisphere and blow from the northeast to the southwest, and in the Southern they are directed from the southeast to the northwest.

From the high pressure belts (25-30°N and S), the winds blow not only towards the equator, but also towards the poles, since at 65°N. sh. and yu. sh. low pressure prevails. However, due to the rotation of the Earth, they gradually deviate to the east and create air currents moving from west to east. Therefore, westerly winds prevail in temperate latitudes.

Leading specialist of the Phobos Center Evgeny Tishkovets told REN TV that at the time of the crash of the Boeing-737 in Rostov-on-Don, the weather conditions were critical for landing the aircraft.

"Wind west-southwest, 12-14 m/s, in gusts up to 17 m/s. As to the actual weather, none of the above are weather hazards that restrict or prohibit the take-off or landing of aircraft. At least - such type as Boeing. It remains to understand what course it came in. The fact is that in Rostov-on-Don the direction of the runway is northeast-southwest. You need to understand what restrictions it had. If draw an analogy with our domestic types of aircraft, then a side wind of 10, maximum 17 m / s is, for example, critical for the Tu-154. Anything above this prohibits landing ", - explained Tishkovets.

An eyewitness to the Boeing crash told REN TV about what the plane had seen coming in to land. According to the man, at that moment he was sitting in the car, which.

Let's remind, Boeing-737-800 of FlyDubai airline crashed today at 3:50 Moscow time. According to preliminary data, the plane caught fire while still in the air. This is confirmed by the frames,. They show how a bright object falls to the ground, after which a powerful explosion is heard.

Before the crash, the liner circled over the airport for about two hours. There were 55 passengers and 7 crew members on board, all of them died.

The Boeing-737-800 is one of the latest models in the 737th line of the most widely used passenger aircraft in the history of civil aviation. The Boeing-737 is so widely used that 1,200 aircraft of this family are in the air at the same time, and one 737 takes off or lands every 5 seconds. Over the entire history of operation, more than 170 liners of this type have been lost, almost 4,000 people have died in accidents.

In Russia, four such aircraft were lost, and all the crashes occurred during landing. The first disaster occurred in Perm in September 2008. Then 88 people died, among the victims of the crash were Hero of Russia Colonel-General Gennady Troshev, First Vice-President of the All-Russian Sambo Federation Vladimir Pogodin. The second incident in Kaliningrad in October of the same 2008 was without casualties - during landing, the crew forgot to release the landing gear. There were 144 people on board, all of them survived. The disaster on November 17, 2013 in Kazan claimed the lives of 50 people. Boeing-737 crashed while entering the second circle. Everyone on board died, including the son of Tatarstan President Rustam Minnikhanov and the head of the local FSB Alexander Antonov.

Many people ask the question: at what wind speed do planes not fly? Indeed, there are certain speed limits. Compared to the speed of the aircraft, which reaches 250 m/s, even a strong wind with a speed of 20 m/s will not interfere with the aircraft during flight. However, a crosswind can interfere with an airliner when it is moving at a slower speed, namely at the time of takeoff or landing. Therefore, under such conditions, planes do not take off. Air currents affect the speed of the aircraft, the direction of movement, as well as the length of the roll and takeoff run. In the atmosphere, these streams are present at all altitudes. This movement of air in relation to a flying airliner is a portable movement. If a strong wind is blowing, the direction of movement of the airliner in relation to the ground does not coincide with the longitudinal axis of the aircraft. Strong air currents can blow the plane off course.

Airliners always land and take off against the direction of the wind. In the case of takeoff or landing with a tailwind, the length of the takeoff run and run increases significantly. When taking off or landing, an airliner penetrates the lower atmosphere so quickly that the pilot does not have time to respond to a change in the wind. If he does not know about a sharp increase or, conversely, a weakening of air flows in the lower layers of the atmosphere, this is fraught with a plane crash.

During takeoff, when an airliner is gaining altitude, it enters a zone of strong headwind. As the aircraft climbs, the lift force of the aircraft increases. Moreover, the increase occurs faster than the pilot can control it. The flight path in this case may be higher than the calculated one. If there is a sharp increase in wind, this can cause the airliner to fall into a supercritical angle of attack. This can lead to airflow stall and collision with the ground.

Generally, the allowable maximum wind force is determined for each aircraft individually, depending on the specifics of its specific characteristics and technical capabilities. Sets the maximum wind speed at which takeoff or landing can be made, by the manufacturer of the airliner. More precisely, the manufacturer sets two maximum speeds: passing and lateral. Tail speed for most modern airliners is the same. During takeoff and landing, the tail speed must not exceed 5 m/s. As for the lateral speed, it is different for each airliner:

• for TU-154 aircraft - 17 m/s;
• for AN-24 - 12 m/s;
• for TU-134 - 20 m/s.

On average, airliners are set to the maximum lateral speed 17 m/s. At higher speeds, the vast majority of aircraft do not take off. If there is a sharp increase in wind speed in the arrivals area, the speed of which exceeds the permissible values, the planes do not land at this airport, but make an emergency landing on another runway, where conditions allow the airliner to land safely.

Answering the question in what wind the planes do not fly, it can be said with confidence that at a speed of more than 20 m / s, if the wind blows perpendicular to the runway, takeoff cannot be carried out. Such a strong wind is associated with the passage of powerful cyclones. Below you can watch a video of landing an aircraft in a strong crosswind to see how difficult it is to do even for a professional experienced pilot with a long experience. Of particular danger in this case is the gusty wind in the lower layers of the atmosphere. It can begin to blow at the most inopportune moment, forming a large roll, which poses a great danger to the aircraft.

Crosswind is dangerous because it requires the pilot to take certain actions that are very difficult to perform. In aviation, there is such a thing as a "drift angle". This term refers to the amount of angle an airliner deviates from a given direction due to the wind. The stronger the wind, the larger this angle. Accordingly, the more effort is required for the pilot to turn the airliner to this angle in the opposite direction. As long as the aircraft is in flight, even such a strong wind does not cause any problems. But as soon as the plane makes contact with the surface of the runway, the airliner acquires traction and begins to move in a direction parallel to its axis. At this moment, the pilot must abruptly change the direction of the aircraft, which is very difficult.

As for the problem of a strong tailwind, it is easily solved by changing the operating threshold of the runway. However, not every airport has such an opportunity. For example, Sochi and Gelendzhik are deprived of such an opportunity. If a strong wind blows towards the sea, landing can be carried out, but taking off under such conditions is unsafe. That is, landing an aircraft in strong winds is possible, but not in all cases.

Runway condition

Even if the wind speed allows you to take off or land, there are still a number of factors that can affect the final decision. In particular, in addition to weather conditions, visibility, the condition of the runway is taken into account. If it is covered with ice, landing or takeoff cannot be carried out. In aviation, there is such a term as "traction coefficient". If this value is below 0.3, the runway is not suitable for landing or takeoff and needs to be cleaned. If the decrease in friction coefficient was due to heavy snowfall, in which cleaning is not possible, the entire airport is closed until the weather improves. Such a break in work can last several hours.

How is the decision to take off made?

This decision must be made by the aircraft commander. To do this, first of all, he must familiarize himself with the meteorological data on the air hubs of departure, landing and alternate airports. For this, METAR and TAF forecasts are used. The first forecast is issued for all airports every half hour. The second is given every 3-6 hours. Such forecasts reflect all relevant information that may influence the decision to take off or cancel a flight. In particular, such forecasts contain data on wind speed and its changes.

To make a decision, all flights are conditionally divided into 2-hour and longer ones. If the flight lasts less than two hours, it is enough for the actual weather to be acceptable (above the minimum) for takeoff. If the flight is longer, the TAF forecast must be additionally taken into account. If the weather conditions at the destination do not allow landing, in some cases, the decision to take off may be positive. For example, if the weather conditions at the destination are below the minimum, however, there are two airfields in the immediate vicinity with optimal weather conditions. But a positive decision is almost never made in these cases, given the danger of such a flight.

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