Squally wind 20 m s. Technical Library

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 runway and decision height (VPR). 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 radio navigation, lighting and technical equipment installed at the aerodrome and surrounding airport terrain (mainly we are talking about the relief 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 heading and 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.

Speaking of minimums aircraft, then the majority of foreign-made aircraft, of which the majority are today, are approved for flights 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 conditionally 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 in this moment 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? Yet again, different aircraft, 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 one manufacturer may have different restrictions, for example, part of the A320 aircraft is 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.

Wind- this is a horizontal movement (air flow parallel to the earth's surface), resulting from uneven distribution of heat and atmospheric pressure and directed from a high pressure zone to a low pressure zone

The wind is characterized by speed (strength) and direction. Direction is determined by the sides of the horizon from which it blows, and is measured in degrees. Wind speed measured in meters per second and kilometers per hour. The strength of the wind is measured in points.

Wind in boots, m/s, km/h

Beaufort scale- conditional scale for visual assessment and recording of wind strength (speed) in points. Initially, it was developed by the English admiral Francis Beaufort in 1806 to determine the strength of the wind by the nature of its manifestation at sea. Since 1874, this classification has been accepted for widespread (on land and sea) use in international synoptic practice. In subsequent years, it was changed and refined (Table 2). The state of complete calm at sea was taken as zero points. Initially, the system was thirteen-point (0-12 bft, on the Beaufort scale). In 1946 the scale was increased to seventeen (0-17). The strength of the wind in the scale is determined by the interaction of the wind with various objects. IN last years, wind strength, more often, is estimated by speed, measured in meters per second - at the earth's surface, at a height of about 10 m above an open, flat surface.

The table shows Beaufort scale adopted in 1963 by the World Meteorological Organization. The sea disturbance scale is nine-point (the parameters are given for a large sea area; in small areas - less excitement). Descriptions of the action from the movement of air masses are given "for the conditions of the earth's atmosphere near the earth's or water surface", and above zero temperature. On the planet Mars, for example, the ratios will be different.

Wind strength in points on the Beaufort scale and sea waves

Table 1

To make it easier to remember(compiled by: site author site)

3 - Weak - 5 m / s (~ 20 km / h) - leaves and thin branches of trees sway continuously
5 - Fresh - 10 m / s (~ 35 km / h) - pulls out big flags, whistles in the ears
7 - Strong - 15 m / s (~ 55 km / h) - telegraph wires are buzzing, it is difficult to go against the wind
9 - Storm - 25 m / s (90 km / h) - wind knocks down trees, destroys buildings

* The length of the wind wave on the surface of water bodies (rivers, seas, etc.) is the smallest distance, horizontally, between the tops of neighboring ridges.

Dictionary:

Breeze– a weak coastal wind with a strength of up to 4 points.

normal wind- acceptable, optimal for something. For example, for sports windsurfing, you need sufficient wind thrust (at least 6-7 meters per second), and when parachuting, on the contrary, calm weather is better (excluding lateral drift, strong gusts near the earth's surface and dragging the dome after landing).

storm is called a long and stormy wind up to a hurricane, with a force of more than 9 points (gradation on the Beaufort scale), accompanied by destruction on land and strong waves at sea (storm). Storms are: 1) squall; 2) dusty (sandy); 3) dust free; 4) snow. Squall storms start suddenly and end just as quickly. Their actions are characterized by enormous destructive power (such a wind destroys buildings and uproots trees). These storms are possible everywhere in the European part of Russia, both at sea and on land. In Russia, the northern border of the distribution of dust storms passes through Saratov, Samara, Ufa, Orenburg and the Altai mountains. Snow storms of great strength occur on the plains of the European part and in the steppe part of Siberia. Typically, storms are caused by the passage of an active atmospheric front, a deep cyclone, or a tornado.

Squall- a strong and sharp gust of wind (Peak gusts) with a speed of 12 m/s and above, usually accompanied by a thunderstorm. At a speed of more than 18-20 meters per second, a heavy wind blows away poorly fixed structures, signs and can break billboards and tree branches, cause power lines to break, which creates a danger to people and cars under them. A gusty, squally wind occurs during the passage of an atmospheric front and with a rapid change in pressure in a baric system.

Vortex- atmospheric formation with rotational movement of air around a vertical or inclined axis.

Hurricane(typhoon) - a wind of destructive force and considerable duration, the speed of which exceeds 120 km/h. "Lives", i.e. moves, a hurricane usually lasts 9-12 days. Forecasters give it a name. The hurricane destroys buildings, uproots trees, demolishes light structures, breaks wires, and damages bridges and roads. Its destructive force can be compared to an earthquake. Homeland hurricanes - ocean expanses, closer to the equator. Cyclones saturated with water vapor from here leave to the west, more and more twisting and increasing speed. The diameters of these giant whirlwinds are several hundred kilometers. Hurricanes are most active in August and September.
In Russia, hurricanes most often occur in the Primorsky and Khabarovsk Territories, Sakhalin, Kamchatka, Chukotka, and the Kuril Islands.

Tornadoes are vertical vortices; squalls are more often horizontal, included in the structure of cyclones.

The word "tornado" is Russian, and comes from the semantic concept of "twilight", that is, a gloomy, thunderous situation. The tornado is a giant rotating funnel, inside which there is low pressure, and any objects that are in the way of the tornado are sucked into this funnel. As he approaches, a deafening roar is heard. A tornado moves above the ground at an average speed of 50–60 km/h. Deaths are short-lived. Some of them "live" seconds or minutes, and only a few - up to half an hour.

On the North American continent, a tornado is called tornado, and in Europe thrombus. A tornado can lift a car into the air, uproot trees, cripple a bridge, destroy the upper floors of buildings.

The tornado in Bangladesh, observed in 1989, was included in the Guinness Book of Records as the most terrible and destructive tornado in the entire history of observations. Despite the fact that the inhabitants of the city of Shaturia were warned in advance about the approach of a tornado, 1,300 people became its victims.

In Russia, tornadoes are more frequent in the summer months in the Urals, Black Sea coast, in the Volga region and Siberia.

Forecasters classify hurricanes, storms and tornadoes as emergency events with a moderate propagation speed, so most often it is possible to announce a storm warning in time. It can be transmitted through civil defense channels: after the sound of sirens " Attention everyone!"must listen to the message of the local television and radio.

Symbols on meteorological maps of weather phenomena associated with wind

In meteorology and hydrometeorology, the direction of the wind ("where it blows from") is indicated on the map in the form of an arrow, the type of plumage of which shows the average speed of the air flow. In air navigation - the name of the direction is different to the opposite. In navigation on the water, the unit of speed (knot) of a ship is taken to be one nautical mile per hour (ten knots correspond to approximately five meters per second).

On the weather map, a long feather of the wind arrow means 5 m/s, a short one - 2.5 m/s, in the form of a triangular flag - 25 m/s (follows after a combination of four long lines and 1 short one). In the example shown in the figure, there is a wind with a force of 7-8 m/s. With an unstable wind direction, a cross is placed at the end of the arrow.

The picture shows the symbols for the direction and speed of the wind used on weather maps, as well as an example of drawing icons and fragments from a hundred-cell matrix of weather symbols (for example, a snowstorm and a blowing snow, when there is a rise and redistribution of previously fallen snow in the surface air layer).

These symbols can be seen on the synoptic map of the Hydrometeorological Center of Russia (http://meteoinfo.ru) compiled as a result of the analysis of current data on the territory of Europe and Asia, which schematically shows the boundaries of the zones of warm and cold atmospheric fronts and the direction of their movements along the earth's surface.

What to do if there is a storm warning?

1. Close and secure all doors and windows tightly. Glue strips of plaster crosswise on the glass (so that fragments do not fly apart).

2. Prepare a supply of water and food, medicines, a flashlight, candles, a kerosene lamp, a battery receiver, documents and money.

3. Turn off gas and electricity.

4. Remove items from balconies (yards) that could be blown away by the wind.

5. From light buildings, move to more durable or civil defense shelters.

6. In a village house, move to the most spacious and durable part of it, and best of all - to the basement.

8. If you have a car, try to drive as far as possible from the epicenter of the hurricane.

Children from kindergartens and schools must be sent home in advance. If the storm warning comes too late, the children should be placed in basements or the center of buildings.

It is best to wait out a hurricane, a tornado or a storm in a shelter, a pre-prepared shelter, or at least in a basement. However, often, a storm warning is given just a few minutes before the arrival of the elements, and during this time it is not always possible to get to the shelter.

If you were outside during a hurricane

2. You can not be on bridges, overpasses, overpasses, in places where flammable and toxic substances are stored.

3. Hide under the bridge, reinforced concrete canopy, in the basement, cellar. You can lie down in a hole or any depression. Protect eyes, mouth and nose from sand and earth.

4. You can not climb onto the roof and hide in the attic.

5. If you are driving in a flat area, stop but do not leave the vehicle. Close its doors and windows more tightly. Cover the radiator side of the engine during a snow storm. If the wind is not strong, you can shovel the snow from the car from time to time so as not to be buried under a thick layer of snow.

6. If you are in public transport, leave it immediately and seek shelter.

7. If the elements caught you on an elevated or open place, run (crawl) towards any shelter (to rocks, forest) that could extinguish the force of the wind, but beware of falling branches and trees.

8. When the wind has died down, do not immediately leave the shelter, as a squall may repeat in a few minutes.

9. Stay calm and don't panic, help the injured.

How to behave after natural disasters

1. Leaving the shelter, look around for overhanging objects and parts of structures, broken wires.

2. Do not light gas and fire, do not turn on electricity until special services check the state of communications.

3. Do not use the elevator.

4. Do not enter damaged buildings, do not approach broken electrical wires.

5. The adult population provides assistance to rescuers.

Devices

The exact wind speed is determined using an instrument - an anemometer. If there is no such device, you can make a home-made wind-measuring "Wild board" (Fig. 1), with sufficient measurement accuracy for wind speeds up to ten meters per second.

Rice. 1. Homemade Wind Measuring Board-Wild Vane:
1 - a vertical tube (600 mm long) with a welded pointed upper end, 2 - a front horizontal weather vane rod with a counterweight ball-weight; 3 - weather vane impeller; 4 - upper frame; 5 - horizontal axis of the board hinge; 6 - wind board (weighing 200 g). 7 - lower fixed vertical rod with indicators of the cardinal points fixed on it: C - north, south - south, 3 - west, B - east; No. 1 - No. 8 - wind speed indicator pins.

The weather vane is installed at a height of 6 - 12 meters, above an open flat surface. Under the weather vane, arrows indicating the direction of the wind are fixedly fixed. Above the weather vane to the tube 1 on the horizontal axis 5 is hinged to the frame 4 wind board 6 measuring 300x150 mm. Board weight - 200 grams (adjusted according to the reference device). Extending back from frame 4 is an arc segment attached to it (with a radius of 160 mm) with eight pins, of which four are long (140 mm each) and four are short (100 mm each). The angles at which they are fixed are with the vertical for the pin No. 1-0 °; №2 - 4°; No. 3 - 15.5°; #4 - 31°; No. 5 - 45.5 °; #6 - 58°; #7 - 72°; No. 8-80.5°.
The wind speed is determined by measuring the angle of deflection of the board. Having determined the position of the wind board between the arc pins, refer to Table. 1, where this position corresponds to a certain wind speed.
The position of the board between the pins gives only an approximate indication of the wind speed, especially since the wind strength changes quickly and often. The board never remains long in any one position, but constantly fluctuates within certain limits. Observing the changing inclination of this board for 1 minute, its average inclination is determined (calculation by averaging maximum values) and only after that the average minute wind speed is judged. For a high wind speed exceeding 12-15 m/s, the readings of this device have low accuracy (in this limitation, this is the main drawback of the considered scheme).

Application

Average wind speed on the Beaufort scale in different years its application

table 2

The Hurricane Scale was developed by Herbert Saffir and Robert Simpson in the early 1920s to measure the potential damage from a hurricane. It is based on numerical maximum wind speeds and includes an estimate of storm waves in each of the five categories. IN Asian countries, given a natural phenomenon called a typhoon (translated from Chinese - "great wind"), and in the North and South America is called a hurricane. When quantifying wind flow speed, the following abbreviations apply: km/h / mph- kilometers / miles per hour, m/s- meters per second.

table 3

tornado scale

The tornado scale (Fujita-Pearson scale) was developed by Theodore Fujita to classify tornadoes according to the degree of damage caused by wind. Tornadoes are typical mainly for North America.

table 4

Glossary of terms:

Leeward side of the object (protected from the wind by the object itself; an area of ​​increased pressure, due to strong flow deceleration) faces where the wind blows. In the picture - on the right. For example, on the water, small boats approach more large ships from their leeward side (there they are protected by the hull of a large ship from waves and wind). "Smoking" factories-enterprises should be located, in relation to residential urban buildings - on the leeward side (in the direction of the prevailing winds) and separated from these areas by fairly wide sanitary protection zones.


windward side object (hill, sea vessel) - on the side where the wind blows. On the windward side of the ridges, ascending movements of air masses occur, and on the leeward side, a downward airfall occurs. Most of the precipitation (in the form of rain and snow), due to the barrier effect of mountains, falls on their windward side, and on the leeward side, a collapse of colder and drier air begins.

Approximate calculation of dynamic wind pressure per square meter of a billboard (perpendicular to the plane of the structure) installed near the road of the carriageway. In the example, the maximum storm wind speed expected at a given location is assumed to be 25 meters per second.

Calculations are carried out according to the formula:
P = 1/2 * (air density) * V^2 = 1/2 * 1.2 kg/m3 * 25^2 m/s = 375 N/m2 ~ 38 kilograms per square meter (kgf)

Note that the pressure increases with the square of the speed. Take into account and include in the construction project sufficient margin of safety, stability (also depends on the height of the support post) and resistance to strong gusts of wind and precipitation, in the form of snow and rain.

At what wind force cancel flights civil aviation

The reason for violation of the flight schedule, delay or cancellation of flights - may be a storm warning from weather forecasters, at the airports of departure and destination.

The meteorological minimum required for a safe (regular) takeoff and landing of an aircraft is the allowable limits for changes in a set of parameters: wind speed and direction, line of sight, the state of the airfield runway, and the height of the cloud base. Bad weather, in the form of intense precipitation (rain, fog, snow and blizzard), with extensive frontal thunderstorms, can also cause cancellation of flights from the air harbor.

The values ​​of meteorological minimums - may vary for specific aircraft (by their types and models) and airports (by class and the availability of sufficient ground equipment, depending on the features of the terrain surrounding the airfield and the existing high mountains), as well as due to the qualifications and flight experience of the crew pilots , commander of the ship. The worst minimum is taken into account and for execution.

Departure ban - possible in case of bad weather at the destination airport, if there are not, nearby, two alternative air harbors with acceptable weather conditions.

In strong winds, aircraft take off and land against the air flow (by taxiing, for this, to the appropriate lane). In this case, not only safety is ensured, but also the takeoff run and landing run are significantly reduced. Limitations on the lateral and tailwind components of the wind speed, for most modern civil aircraft, are approximately: 17-18 and 5 m/s, respectively. The danger of a large roll, demolition and reversal of an airliner, during its takeoff and landing, is represented by an unexpected and strong gusty wind (squall).

https://www.meteorf.ru - Roshydromet (Federal Service for Hydrometeorology and Monitoring environment). Hydrometeorological Research Center of the Russian Federation.

Www.meteoinfo.ru - new site of the Hydrometeorological Center of the Russian Federation.

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 crosses 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 effect of the monsoons is strong in eastern parts 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 areas 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 area of ​​their distribution is Far East, Northeast China, Korea, to a lesser extent - Japan and northeast coast 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 basin indian ocean. 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.

Takeoff is the most difficult part of flying. Of course, the automatic takeoff mode after the release of the brakes is not difficult, but the crew of the aircraft, led by the commander, must be tuned to critical moments. Can a flight be canceled due to rain? ? You will find out in the process of reading the article.

Objective assessment

Do planes fly in the rain? Yes. But in order for the flight to be successful, there are strict regulations for pilots and controllers who allow the aircraft to fly and land. For each side and airfield, the rules are individual, but with similar indicators:

• minimal visibility. Determined both vertical and horizontal visibility with the level of illumination;
• runway coverage. Ice on the airfield is unacceptable;
• the ability of pilots to receive instrument signals of adverse weather conditions.

Normally, the weather forecast should correspond to the meteorological minimum so that the pilot has the opportunity to take emergency action in the event of a critical situation.

Paramount parameters

What is meant by meteorological minimum? These are the conditions that apply in relation to visibility, cloudiness, wind speed and direction. These criteria can be dangerous when flying, especially when it comes to thunderstorms, downpours and severe turbulence. Of course, most thunderclouds can be bypassed, but frontal thunderstorms stretching for hundreds of kilometers are almost impossible to bypass.

If we are talking about minima, then the criteria for visibility at the aerodrome and the decision height (CHL) are determined. What is this indicator? This is the level of altitude at which the aircraft crew is required to make an additional turn when the runway is not defined.

There are three types of minima:

• air transport - acceptable criteria for the safe flight of an aircraft under adverse weather conditions, established by the manufacturer;
• airfield - depends on the type of installed navigation and technical systems on the runway and in the surrounded area;
• crew - admission of pilots in accordance with their training program for specific weather conditions and practical flying skills.

Do planes fly in the rain? To allow an aircraft to take off or not, is determined only by the aircraft commander. To make a decision, you should first familiarize yourself with the provided meteorological data for the destination aerodromes, as well as alternate ones, and evaluate them.

Thunderstorm is not a hindrance to flight

A thunderstorm is a rather dangerous phenomenon, but for modern liner it is not the cause of the disaster. Technique and people have learned to overcome huge distances safely in all weather conditions.

In his practice, every experienced pilot has repeatedly encountered thunderclouds, which significantly complicate the landing and takeoff of an aircraft in the rain. During the "entry" into the clouds, the crew loses the visual perception of the machine in space. Therefore, flight in "non-flying" weather can only be carried out according to technical instruments. In some cases, an unpleasant situation may arise - the electrification of the aircraft. Here, radio communication deteriorates sharply, which causes great inconvenience even to professional pilots.

But most of all, "non-flying" weather complicates the landing of liners. In such a crew is maximally loaded. The captain, even in modern rain, glances at aviation equipment up to 200 times per minute, focusing on each fixture up to 1 second. Low cloud cover in combination with a thunderstorm is a serious obstacle to the correct movement of the aircraft. Therefore, it is extremely important to have a good knowledge of the clouds, their state and the nearest changes. The deterioration of the weather begins if there is:

• accelerated drop in atmospheric pressure;
• a sharp change in the direction and speed of the wind;
• an increase in various types of cloudiness and its rapid movement;
• "growth" of cumulus clouds in the evening;
• the formation of colored circles around the satellites of the Earth.

You can’t play with a thunderstorm, you need to bypass it as far as possible, according to the regulations. In addition, when climbing or descending, the pilot must correlate information on the development of the elements with the capabilities of the aircraft.

When there are clouds in the sky

Is it dangerous to fly in the rain on an airplane? The passenger liner passes the way along the given air routes. In case of bad weather, the coordinates may change upon agreement with the controller at the flight control center. The flight altitude is about 11,000 meters. For this reason, it becomes comfortable with more. It is this flight altitude that allows the aircraft to rise above the clouds - the sources of rain or snow. Therefore, the movement of the aircraft at high altitude is completely independent of weather conditions. Often you can observe how the rays of the sun enter the window of the liner, and when landing it is dark and it is raining.

Do planes fly in the rain? Yes. Theoretically, raindrops can affect aircraft engine performance. But rain is not the amount of water that can provoke a short circuit. In tests, the engine compressors are subjected to a good "gulf", which is not compared with natural phenomena.

We take into account

Do planes fly in thunderstorms? The precipitation itself does not pose any danger to the flight. Another thing is visibility. But when it rains, windshield wipers come to the rescue. Aircraft windshield wipers are different from car wipers. First, they have a completely different design. Secondly, the windshield wipers operate at a very high rate, which provides a perfect view.

How do planes land when it rains? The most critical in bad weather are "atmospheric disturbances". The landing aircraft has a low speed and can easily be affected by the movement of air masses. To overcome the adverse effects during this phenomenon, pilots spend a lot of time "in simulators", honing their skills. If in such weather the danger of an accident is great, then the landing is postponed or the ship is sent to another airfield.

Another important factor in rain is traction. Wet coating reduces its coefficient, but this situation is not recognized as critical. It is much more dangerous if the water on the asphalt freezes, and the value of the coefficient decreases. Most similar cases The airport does not allow aircraft to take off or land.

Other natural barriers

In addition to the main weather phenomena, there are other important criteria that limit the capabilities of aviation:

• wind - requires special care and dexterity from the pilot, especially on the runway;
• remu - vertical movement of air, throwing up an aircraft, forming "air pockets";
• fog is a real enemy during flights, limiting visibility and forcing pilots to navigate by compasses;
• glaciation - on the ice-covered runway, the movement of aircraft is strictly prohibited.

Thanks to the developed electronic devices and systems, she is ready to overcome any weather conditions. The movement on the runway is safe, because in critical situations the liner simply does not depart for the flight or remains in certain waiting areas.

Heavy flight criteria

Cumulus clouds in cold weather and at high altitude in summer can be a hazard to aircraft. It is here that the probability of aircraft icing is quite high. In cumulus clouds, the flight of heavy aircraft is complicated by turbulence. If the likelihood of adverse events persists, the flight is postponed for several hours.

Indicators of bad stable weather are:

• atmospheric pressure with low rates, which practically do not change or even decrease;
• high wind speed;
• clouds in the sky are predominantly of a scatter or scatter-rain type;
• prolonged precipitation in the form of rain or snow;
• small fluctuations in temperature during the day.

If the problem with rain can be solved more quickly, then heavy precipitation, especially in the form of drizzle, will create difficulties. They occupy very large areas, and it is almost impossible to bypass them. In such a zone, visibility is significantly reduced, and at low temperatures, icing of the aircraft body occurs. Therefore, at low altitude in such situations, flight is classified as difficult.

On duty

In order not to expose themselves and passengers on board to danger and fear, the crew of the aircraft must perform a number of important actions before departure:

• listen to information from the duty meteorologist about the upcoming weather conditions along the established route: cloudiness data, wind speed and direction, the presence of dangerous zones and ways to bypass them;
• receive a special bulletin containing information about the state of the atmosphere, the weather forecast along the route and at the landing site;
• if the flight is delayed by more than an hour and a half, the pilot must receive new information about the state of the weather.

However, the duties of the crew do not end there.

Additional terms of commitment

During the flight, the pilot must carefully monitor the weather, especially if the route passes near dangerous areas or worsening weather is expected soon. The attentiveness and professionalism of the navigator will allow you to correctly assess the state of the atmosphere and, in which case, make the right decision.

In addition, a few hundred kilometers before the landing point, an inquiry should be made about the meteorological situation at the aerodrome and the safety of the landing should be assessed.

The natural "opponent" of the flight

It's great when the flight takes place in a clear sunny weather. But if it snows or rains, and overboard low temperature? Here begins the icing of the body of the aircraft.

Ice, like armor, increases the weight of an aircraft, reducing its lift by several times and reducing engine power. If suddenly the crew captain, studying the meteorological situation, determined that the hull of the liner was covered with a crust, then a command comes to clean the ship. The processing of the aircraft is carried out. Moreover, attention is paid to the entire hull of the vessel, and not just the wings and nose.

Reliability above all

Thunderstorm or rain is a romantic phenomenon only in literature. Aviation considers a natural phenomenon as an emergency. The elements can bring great human casualties, so it is extremely important to approach flights with high accuracy and literacy. A flight in adverse conditions is a great responsibility and great worries not only for your life, but also for the life of hundreds of passengers.

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.