Experts have reconstructed the take-off scheme of the Tu-154 according to the flight recorder, according to the Kommersant newspaper. The obtained result seemed unusual to the experts - it turned out that when the navigator warned the pilots about the fall, they did not react to it. The airliner's sensors did not register a "pulling" movement of the steering wheel, which was logical in the current situation.
ON THIS TOPIC
Moreover, a source close to the investigation said that "prior to the collision with water, they reacted to the crew's control actions in a timely and regular manner." An emotional statement by the pilot about the flaps may indicate an uncritical delay in the order to remove them, but not a technical malfunction.
Aviation experts suggested that the pilots' behavior was strongly affected by the fact that the flight was made at night. "A few seconds after taking off from a well-lit and marked strip, you cross the also illuminated coastline and immediately you get into a black hole, "- said one of the specialists. In such a situation, the pilot must trust only the readings of the sensors, and not his own vestibular apparatus.
Nevertheless, the onboard systems of the Tu-154 recorded that the commander had been manually adjusting the flight path for a long time. This indicates his loss of orientation. Many experts criticize the inaction of the co-pilot Alexander Rovensky, but his behavior is explained by the fear of taking the steering wheel away from the senior Major Volkov.
However, a number of experts deny the "illusory" version of the fall of the Tu-154. They explain the resulting scheme of the tragedy by a malfunction of the parameter registration system.
We add that the behavior of the pilot's organism has long been studied by such a science as aviation psychology. However, experts have still not been able to establish why the captain of the aircraft instinctively violates the flight path. Experts say that fatigue, stress and malaise can contribute to disorientation. According to statistics, every tenth plane crash in the world is caused by illusions.
Many people are afraid of flying. Psychologists say that there is even such a thing as "aerophobia". Patients with this diagnosis experience real horror at the mere thought of taking off. The strongest negative emotions are caused by getting into air pockets and turbulence. Such moments are unpleasant even for those who have no fear of flying. However, pilots claim that this is actually quite common. a natural phenomenon, which can be explained in scientific language, and it will not bring any trouble to the passengers of the airliner. Today we decided to tell you what an air pit really is, and whether it is worth being afraid of.
Explanation of the term
It is quite difficult for an ordinary person to understand what an air pocket really is. Everyone understands that there is no highway or road surface in the sky, and therefore there cannot be any holes. For example, when it comes to driving a car, it is absolutely clear to anyone that an obstacle or a hole may arise on the road, which an experienced driver can ditch. But what if you fell into an air hole? Is it possible to pass it? And how dangerous is it? We will answer all these questions in the following sections of the article. But let's understand this difficult topic gradually.
Scientists have long figured out that air flows are not uniform. They have different directions, temperatures and even density. All this affects the airliners following certain routes. In the case when the plane encounters currents of lower temperature on the way, a complete illusion of a short-term fall is created. Then we usually say that the ship fell into an air hole. However, in reality, this is just an illusion that can be easily explained using modern science.
Downstream and upstream
To understand how air pockets are formed, it is necessary to get a complete understanding of the movement of air currents. According to the laws of physics, heated air always rises up, while cooled air goes down. Warm currents are called ascending, they always strive upward. A cold air it is considered to be descending, and like a funnel it pulls down everything that comes in its way.
It is because of the movement of these streams that air pockets so unloved by passengers are formed during flight. They make travelers experience very unpleasant sensations that many cannot forget for a long time.
The principle of the formation of air pockets
Despite the fact that the modern aircraft industry has long equipped its new liners with an abundance of technological innovations designed to make the flight comfortable and safe, so far no one has managed to relieve passengers of the unpleasant sensations caused by descending air masses. So, the plane fell into an air hole. What happens to him at this moment?
Even while flying in good weather conditions, the airliner can run into cold air. Since it is descending, it begins to significantly slow down the rate of climb of the aircraft. It is noteworthy that in a straight line it goes with the same indicators, but it loses a little height. This usually only lasts a few moments.
The airliner then encounters the updraft, which begins to push it upward. This allows the aircraft to return to its previous altitude and continue its normal flight.
The sensations of passengers
For those who have never fallen into air pockets, it is quite difficult to understand how aircraft passengers feel. Usually people complain that they experience stomach cramps, nausea coming up to the throat, and even weightlessness lasting a fraction of a second. All this is accompanied by the illusion of falling, which is perceived as realistic as possible. The combination of sensations leads to uncontrollable fear, it is he who further does not allow most people to calmly endure flights and causes aerophobia.
Should you panic?
Unfortunately, none of the most highly professional pilots will be able to bypass the air pit. It is impossible to fly around it, and even the make and class of the aircraft will not be able to save passengers from unpleasant impressions.
The pilots claim that the moment it enters the downdraft, the plane temporarily loses control. But you should not panic because of this, such a situation lasts no more than a few seconds and, apart from unpleasant sensations, does not threaten travelers.
However, you need to know that the airliner is under serious pressure in the air pocket. At this point, the plane gets into "bumpiness" or turbulence, which, in turn, adds discomfort to the frightened passengers.
Turbulence at a glance
This phenomenon gives travelers a lot of inconvenience, but in fact it is not dangerous and cannot lead to the crash of the airliner. It is believed that the loads on an aircraft during turbulence are no higher than on a car traveling on uneven roads.
A turbulence zone is formed when air currents with different speeds meet. At this moment, vortex waves are formed, which cause "bumpiness". It is noteworthy that on some routes, turbulence occurs regularly. For example, when flying over mountains, the plane always shakes. Such zones are quite long, and the "bumpiness" can last from several minutes to half an hour.
Causes of turbulence
We have already talked about the most common cause of the "bumpiness", but, in addition to this, other factors can cause it. For example, an airliner flying in front often contributes to the formation of vortices, which, in turn, form a zone of turbulence.
Not far from the earth's surface, the air warms up unevenly, therefore, vortex flows are created, which cause turbulence.
It is noteworthy that pilots compare flying in the clouds to driving on a highway with holes and bumps. Therefore, in cloudy weather, passengers most often experience all the "delights" of a flight in a shaking plane.
Dangers of turbulence
Most passengers in all seriousness believe that turbulence can compromise the tightness of the cabin and lead to a crash. But in fact, this is the safest thing possible. The history of air travel does not know a case when falling into a "bumpiness" would lead to fatal consequences.
Aircraft designers always put a certain margin of safety into the aircraft body, which will quite calmly withstand turbulence and thunderstorms. Of course, such a phenomenon causes anxiety, unpleasant emotions and even panic among passengers. But in fact, you just need to calmly wait out this moment, not succumbing to your own fear.
How to behave during the flight: a few simple rules
If you are very afraid of flying, and the thought of air pockets and turbulence makes you feel terrified, then try to follow a number of simple rules that will greatly facilitate your condition:
- do not drink alcohol during the flight, it will only aggravate unpleasant emotions;
- try to drink water with lemon, it will relieve the attacks of nausea when it gets into the air pockets;
- before the trip, set yourself up in a positive way, otherwise you will all the time suffer from premonitions and negative emotions;
- be sure to fasten your seat belts, while passing through the turbulence zone, passengers may be injured;
- if you are very much afraid of flying, then choose larger aircraft models that are less sensitive to various kinds of shaking.
We hope that after reading our article, your fear of flying will become less acute, and your next air trip will be easy and enjoyable.
Passed the sound barrier :-) ...
Before we start talking on the topic, let's make some clarity about the accuracy of the concepts (what I like :-)). Now two terms are in fairly wide use: sound barrier and supersonic barrier... They sound similar, but not the same. However, it makes no sense to breed a special rigor: in fact, they are one and the same. The definition of a sound barrier is most often used by people who are more knowledgeable and closer to aviation. And the second definition is usually everyone else.
I think that from the point of view of physics (and the Russian language :-)) it is more correct to say the sound barrier. Here's a simple logic. After all, there is the concept of the speed of sound, but, strictly speaking, there is no fixed concept of the speed of supersonic. Running a little ahead of myself, I will say that when an aircraft flies in supersonic, it has already passed this barrier, and when it passes it (overcomes), it passes a certain threshold speed value equal to the speed of sound (not supersonic).
Something like that:-). Moreover, the first concept is used much less frequently than the second. This is apparently because the word supersonic sounds more exotic and attractive. And in a supersonic flight, exotic is certainly present and, naturally, attracts many. However, not all people savoring the words “ supersonic barrier"They really understand what it is. More than once I was convinced of this, looking at the forums, reading articles, even watching TV.
This question is actually quite complicated from the point of view of physics. But we, of course, will not climb in complexity. Let's just try, as usual, to clarify the situation using the principle of "explaining aerodynamics on the fingers" :-).
So, to the (sound :-)) barrier! ... An airplane in flight, acting on such an elastic medium as air, becomes a powerful source of sound waves. I think everyone knows what sound waves in the air are :-).
Sound waves (tuning fork).
This is an alternation of areas of compression and depression, spreading in different directions from the sound source. Roughly like circles on the water, which are also just waves (but not sound ones :-)). It is these areas, acting on the eardrum of the ear, that allow us to hear all the sounds of this world, from human whispers to the roar of jet engines.
An example of sound waves.
The points of propagation of sound waves can be various parts of the aircraft. For example, an engine (its sound is known to anyone :-)), or parts of the body (for example, the nose), which, by compressing air in front of them when moving, create a certain type of pressure (compression) waves running forward.
All these sound waves propagate in air at the speed of sound we already know. That is, if the plane is subsonic, and even flies at low speed, then they seem to run away from it. As a result, when such an aircraft approaches, we first hear its sound, and then it flies by itself.
I'll make a reservation, however, that this is true if the plane is not flying very high. After all, the speed of sound is not the speed of light :-). Its magnitude is not so great and the sound waves need time to reach the listener. Therefore, the order in which the sound appears for the listener and the airplane, if it flies at high altitude, can change.
And since the sound is not so fast, then with an increase in its own speed the plane begins to catch up with the waves emitted by it. That is, if he were motionless, then the waves would diverge from him in the form concentric circleslike circles on water from a thrown stone. And since the plane is moving, in the sector of these circles corresponding to the direction of flight, the boundaries of the waves (their fronts) begin to converge.
Subsonic body movement.
Accordingly, the gap between the aircraft (its nose) and the front of the very first (head) wave (that is, this is the area where there is a gradual, to a certain extent, deceleration oncoming flow when meeting with the nose of the aircraft (wing, tail unit) and, as a result, increase in pressure and temperature) begins to decrease and the faster the higher the flight speed.
There comes a moment when this gap practically disappears (or becomes minimal), turning into a special kind of region, which is called shock wave... This happens when the flight speed reaches the speed of sound, that is, the plane is moving at the same speed as the waves it emits. In this case, the Mach number is equal to one (M \u003d 1).
Sound movement of the body (M \u003d 1).
Compaction shock, is a very narrow area of \u200b\u200bthe medium (about 10 -4 mm), when passing through which there is no longer a gradual, but a sharp (abrupt) change in the parameters of this medium - speed, pressure, temperature, density... In our case, the speed decreases, the pressure, temperature and density increase. Hence the name - shock wave.
In a somewhat simplified way, I would also say so about all this. It is impossible to decelerate the supersonic flow sharply, but it has to do it, because there is no longer the possibility of gradual deceleration to the flow velocity in front of the very nose of the aircraft, as at moderate subsonic speeds. It, as it were, stumbles upon a subsonic section in front of the aircraft's nose (or the toe of a wing) and crumples into a narrow jump, transferring to it the large motion energy it possesses.
By the way, it can be said, and vice versa, that the aircraft transfers part of its energy to the formation of shock waves in order to slow down the supersonic flow.
Supersonic body movement.
There is another name for the shock wave. Moving with the aircraft in space, it is, in fact, a front of a sharp change in the above parameters of the environment (i.e. air flow). And this is the essence of the shock wave.
Compaction shock and a shock wave, in general, are equal definitions, but in aerodynamics the first is more used.
The shock wave (or shock wave) can be practically perpendicular to the direction of flight, in which case they take in space approximately the shape of a circle and are called straight lines. This usually happens in modes close to M \u003d 1.
Modes of body movement. ! - subsonic, 2 - M \u003d 1, supersonic, 4 - shock wave (shock wave).
When M\u003e 1, they are already at an angle to the direction of flight. That is, the plane is already overtaking its own sound. In this case, they are called oblique and in space they take the shape of a cone, which, by the way, is called the Mach cone, after the name of a scientist who studied supersonic flows (he mentioned it in one of the).
Mach cone.
The shape of this cone (its so-called "harmony") just depends on the number M and is related to it by the ratio: M \u003d 1 / sin α, where α is the angle between the axis of the cone and its generatrix. And the conical surface touches the fronts of all sound waves, the source of which was the aircraft, and which it "overtook", reaching supersonic speed.
Besides shock waves may also attachedwhen they are adjacent to the surface of a body moving with supersonic speed or departed, if they do not touch the body.
Types of shock waves in supersonic flow around bodies of various shapes.
The jumps usually become attached if the supersonic flow flows around any sharp-pointed surfaces. For an airplane, for example, this can be a pointed nose, LDPE, a sharp edge of the air intake. At the same time, they say "the jump sits", for example, on the nose.
A retreating jump can be obtained when flowing around rounded surfaces, for example, the front rounded edge of a thick wing airfoil.
Various components of the aircraft body create a rather complex system of shock waves in flight. However, the most intense of them are two. One head on the bow and the second on the tail on the elements of the tail assembly. At some distance from the aircraft, the intermediate jumps either catch up with the head one and merge with it, or the tail one overtakes them.
Compaction jumps on a model airplane during blowing in a wind tunnel (M \u003d 2).
As a result, there are two jumps, which, in general, are perceived by the terrestrial observer as one due to the small size of the aircraft compared to the flight altitude and, accordingly, the small time interval between them.
The intensity (in other words, energy) of the shock wave (shock wave) depends on various parameters (the speed of the aircraft, its design features, environmental conditions, etc.) and is determined by the pressure drop at its front.
As the distance from the top of the Mach cone, that is, from the aircraft, as a source of disturbances, the shock wave weakens, gradually turns into an ordinary sound wave, and ultimately disappears altogether.
And from what degree of intensity will have shock wave (or shock wave) that reaches the ground depends on the effect that it can produce there. It's no secret that the well-known "Concorde" flew supersonic only over the Atlantic, and the military supersonic aircraft go to supersonic at high altitudes or in areas where there are no settlements (at least it seems like they should do it :-)).
These restrictions are very justified. For me, for example, the very definition of a shock wave is associated with an explosion. And the things that a sufficiently intense shock wave can do may well correspond to it. At least glass from windows can come out easily. There is enough evidence of this (especially in the history of Soviet aviation, when it was quite numerous and flights were intense). But you can do worse things. One has only to fly lower :-) ...
However, for the most part, what remains from the shock waves when they reach the ground is no longer dangerous. Just an outside observer on the ground can hear a sound similar to a crash or explosion. It is with this fact that one common and rather persistent misconception is associated.
People who are not too sophisticated in aviation science, hearing such a sound, say that this plane overcame sound barrier (supersonic barrier). In fact, this is not the case. This statement has nothing to do with reality for at least two reasons.
Shock wave (shock wave).
Firstly, if a person on the ground hears a resounding rumble high in the sky, then this only means (I repeat :-)) that he has reached his ears shock front (or shock wave) from an airplane flying somewhere. This plane is already flying at supersonic speed, and not just switched to it.
And if the same person could suddenly be several kilometers ahead of the plane, then he would again hear the same sound from the same plane, because he would have been hit by the same shock wave moving along with the plane.
It moves at supersonic speed, and therefore approaches silently. And after it has had its not always pleasant effect on the eardrums (well, when only on them :-)) and safely goes on, the hum of working engines becomes audible.
Approximate flight pattern of the aircraft at various values \u200b\u200bof the M number using the example of the Saab 35 "Draken" fighter. The language, unfortunately, is German, but the scheme is generally clear.
Moreover, the transition to supersonic itself is not accompanied by any one-time "booms", pops, explosions, etc. On a modern supersonic aircraft, the pilot most often learns about such a transition only by reading the instruments. In this case, however, a certain process takes place, but it is practically invisible to him if certain piloting rules are observed.
But that's not all :-). I will say more. in the form of just some tangible, heavy, difficult-to-cross obstacle against which the plane rests and which needs to be "pierced" (I heard such judgments :-)) does not exist.
Strictly speaking, there is no barrier at all. Sometime at the dawn of mastering high speeds in aviation, this concept was formed rather as a psychological conviction about the difficulty of switching to supersonic speed and flying at it. There were even statements that this was generally impossible, especially since the preconditions for such beliefs and statements were quite specific.
However, first things first ...
In aerodynamics, there is another term that quite accurately describes the process of interaction with an air flow of a body moving in this flow and striving to go to supersonic. it wave crisis... It is he who does some of the bad things that are traditionally associated with the concept sound barrier.
So something about the crisis :-). Any aircraft consists of parts, the air flow around which in flight may not be the same. Take, for example, a wing, or rather an ordinary classic subsonic profile.
From the basics of knowledge about how the lifting force is formed, we well know that the flow rate in the adjacent layer of the upper curved surface of the profile is different. Where the profile is more convex, it is greater than the total flow rate, then, when the profile is flattened, it decreases.
When the wing moves in a stream at speeds close to the speed of sound, there may come a moment when, in such a convex region, for example, the speed of the air layer, which is already greater than the total speed of the stream, becomes sonic and even supersonic.
Local shock wave appearing on transonic during a wave crisis.
Further along the profile, this speed decreases and at some point again becomes subsonic. But, as we said above, a supersonic flow cannot quickly decelerate, therefore, the occurrence of shock wave.
Such jumps appear in different parts of the streamlined surfaces, and initially they are rather weak, but their number can be large, and with an increase in the total flow velocity, the supersonic zones increase, the jumps "get stronger" and shift to the trailing edge of the airfoil. Later, the same shock waves appear on the lower surface of the profile.
Full supersonic flow around the wing profile.
What is all this fraught with? And here's what. The firstIs significant increase in aerodynamic drag in the range of transonic speeds (about M \u003d 1, more or less). This resistance grows due to a sharp increase in one of its components - wave resistance... The one that we previously did not take into account when considering flights at subsonic speeds.
For the formation of numerous shock waves (or shock waves) when decelerating a supersonic flow, as I said above, energy is spent, and it is taken from the kinetic energy of the motion of the aircraft. That is, the plane is simply slowed down (and very noticeably!). That's what it is wave resistance.
Moreover, due to the sharp deceleration of the flow in them, the shock waves contribute to the separation of the boundary layer after itself and its transformation from laminar to turbulent. This further increases the aerodynamic drag.
Profile swelling at different M numbers. Compaction jumps, local supersonic zones, turbulent zones.
Second... Due to the appearance of local supersonic zones on the wing airfoil and their further shift to the tail of the airfoil with an increase in the flow velocity and, thereby, changes in the pressure distribution pattern on the airfoil, the point of application of aerodynamic forces (center of pressure) also shifts to the trailing edge. The result is dive moment relative to the aircraft's center of mass, causing it to lower its nose.
What does all this translate into ... Due to a rather sharp increase in aerodynamic drag, the aircraft requires a tangible engine power reserve to overcome the trance zone and enter, so to speak, real supersonic.
A sharp increase in aerodynamic drag on transonic (wave crisis) due to an increase in wave drag. Сd is the coefficient of resistance.
Further. Due to the appearance of the diving moment, there are difficulties in pitch control. In addition, due to the disorder and unevenness of the processes associated with the emergence of local supersonic zones with shock waves, too difficult to manage... For example, by roll, due to different processes on the left and right planes.
Plus the occurrence of vibrations, often quite strong due to local turbulence.
In general, a complete set of pleasures that bears the name wave crisis... But, it is true, they all take place (had, specific :-)) when using typical subsonic aircraft (with a thick straight wing profile) in order to achieve supersonic speeds.
Initially, when there was still not enough knowledge, and the processes of reaching supersonic were not comprehensively studied, this very set was considered almost fatally insurmountable and received the name sound barrier (or supersonic barrier, if you want to:-)).
When trying to overcome the speed of sound on conventional piston aircraft, there were many tragic cases. Strong vibration sometimes led to structural damage. The aircraft did not have enough power for the required acceleration. In level flight, it was impossible due to an effect of the same nature as wave crisis.
Therefore, a dive was used for overclocking. But it could very well be fatal. The diving moment appearing during the wave crisis made the peak protracted, and sometimes there was no way out of it. Indeed, to restore control and eliminate the wave crisis, it was necessary to extinguish the speed. But doing this in a dive is extremely difficult (if not impossible).
Pulling into a dive from horizontal flight is considered one of the main reasons for the disaster in the USSR on May 27, 1943, the famous experimental BI-1 fighter with a liquid propellant rocket engine. Tests were carried out for the maximum flight speed, and according to the estimates of the designers, the achieved speed was more than 800 km / h. Then there was a delay in the peak, from which the plane did not leave.
Experimental fighter BI-1.
Nowadays wave crisis already well understood and overcoming sound barrier (if required :-)) is not difficult. On airplanes that are designed to fly at high enough speeds, certain design solutions and restrictions are applied to facilitate their flight operation.
As you know, a wave crisis begins when M numbers are close to unity. Therefore, almost all subsonic jet liners (passenger, in particular) have a flight restriction on the number of M... Usually it is in the region of 0.8-0.9M. The pilot is instructed to monitor this. In addition, on many aircraft, when the limit level is reached, after which the flight speed must be reduced.
Almost all aircraft flying at speeds of at least 800 km / h and above have swept wing (at least along the leading edge :-)). It allows you to postpone the start of the offensive wave crisis to speeds corresponding to M \u003d 0.85-0.95.
Swept wing. Principal action.
The reason for this effect can be explained quite simply. On a straight wing, the air flow at a speed V runs almost at a right angle, and on a swept wing (sweep angle χ) at a certain slip angle β. Velocity V can be decomposed into two streams in vector relation: Vτ and Vn.
The Vτ flux does not affect the pressure distribution on the wing, but it does the Vn flux, which determines the wing bearing properties. And it is obviously less in terms of the value of the total flow V. Therefore, on the swept wing, the onset of a wave crisis and growth wave resistance occurs noticeably later than on a straight wing at the same incoming flow velocity.
Experimental fighter E-2A (predecessor of the MiG-21). Typical swept wing.
One of the modifications of the swept wing was a wing with supercritical profile (mentioned him). It also allows you to shift the beginning of the wave crisis at high speeds, in addition, it allows you to increase efficiency, which is important for passenger liners.
SuperJet 100. Supercritical swept wing.
If the plane is intended to go sound barrier (passing and wave crisis also :-)) and supersonic flight, then it usually always has certain design features. In particular, it usually has thin wing and tail profile with sharp edges (including diamond or triangular) and a certain shape of the wing in plan (for example, triangular or trapezoidal with a sag, etc.).
Supersonic MIG-21. Emissary E-2A. A typical triangular wing.
MIG-25. An example of a typical airplane designed for supersonic flight. Thin wing and tail profiles, sharp edges. Trapezoidal wing. profile
Passage of the notorious sound barrier, that is, the transition to supersonic speed such aircraft are carried out at engine afterburner due to the increase in aerodynamic drag, and, of course, in order to quickly pass the zone wave crisis... And the very moment of this transition is most often not felt in any way (I repeat :-)) neither by the pilot (he may have a decrease in the sound pressure level in the cockpit), nor by an outside observer, if, of course, he could observe this :-).
However, here it is worth mentioning one more misconception associated with outside observers. Surely many have seen this kind of photographs, the captions under which say that this is the moment of overcoming the plane sound barrier, so to speak, visually.
The Prandtl-Gloert effect. Not associated with passing the sound barrier.
At first, we already know that there is no sound barrier, as such, and the transition to supersonic is not accompanied by anything so extraordinary (including a pop or explosion).
Secondly... What we saw in the photo is the so-called prandtl-Glauert effect... I already wrote about it. It is in no way directly related to the transition to supersonic. Just at high speeds (subsonic, by the way :-)) the plane, moving a certain mass of air in front of it, creates some rarefaction area... Immediately after the flight, this area begins to fill with air from a nearby space with natural an increase in volume and a sharp drop in temperature.
If air humidityis sufficient and the temperature falls below the dew point of the ambient air, then moisture condensationfrom water vapor in the form of fog, which we see. As soon as conditions are restored to their original conditions, this fog immediately disappears. This whole process is rather short-lived.
This process at high transonic speeds can be facilitated by local shock wavesi, sometimes helping to form something like a gentle cone around the plane.
High speeds favor this phenomenon, however, if the air humidity is sufficient, then it can (and does) occur at rather low speeds. For example, above the surface of water bodies. Most, by the way, beautiful photos of this nature were made from an aircraft carrier, that is, in a fairly humid air.
And so it turns out. The shots, of course, are cool, the spectacle is spectacular :-), but this is not at all what it is most often called. it has nothing to do with it (and supersonic barrier also:-)). And this is good, I think, otherwise the observers who take this kind of photo and video might not be happy. Shock wave, do you know:-)…
In conclusion, one video (I have already used it before), the authors of which show the effect of a shock wave from an aircraft flying at low altitude with supersonic speed. There is, of course, a certain exaggeration there :-), but the general principle is clear. And again, spectacular :-) ...
And that's all for today. Thank you for reading the article to the end :-). Until next time ...
Photos are clickable.
Small unmanned aircrafts every year they are becoming more common - they are used in the filming of TV shows and music videos, for patrolling territories or just for fun. Controlling drones does not require special permission, and their cost is constantly decreasing. As a result, the aviation authorities of some countries decided to study whether these devices pose a danger to passenger aircraft. While the early studies were controversial, regulators generally concluded that private drone flights should be brought under control.
In July 2015 the plane lufthansa Airlines, who was landing at the Warsaw airport, almost collided with a multicopter, flying at a distance of less than a hundred meters from it. In April 2016 pilots passenger aircraft British Airways, who landed at London airport, reported a collision with a drone during the approach to dispatchers. Later, however, the investigation came to the conclusion that there was no drone, and what the pilots mistook for it was most likely an ordinary package lifted by the wind from the ground. However, in July 2017, the plane almost collided with a drone at the British Gatwick airport, after which the dispatchers were forced to close one lane for landing and redirect five flights to reserve lanes.
According to the British research organization UK Airprox Board, in 2016, 71 cases of dangerous convergence of passenger aircraft with drones were recorded in the UK. A dangerous convergence in aviation is considered to be the convergence of an aircraft with another aircraft at a distance of less than 150 meters. Since the beginning of this year, 64 cases of drones approaching aircraft have been recorded in the UK. In the United States last year, the aviation authorities registered just under 200 cases of dangerous encounters. At the same time, how exactly small drones can be dangerous for passenger aircraft, the aviation authorities still have a bad idea. Some experts previously assumed that a collision with a drone for a passenger liner would be no more dangerous than a normal collision with birds.
According to the specialized publication Aviation Week & Space Technology, since 1998, 219 people have died due to collisions in the air of passenger flights with birds around the world, and a significant part of them flew on small private planes. At the same time, airlines around the world spend a total of $ 625-650 million annually to repair damage to passenger aircraft due to bird strikes. By the way, in general passenger liners are considered resistant to direct bird hits. When developing and testing new aircraft, special checks are even carried out - the aircraft is fired at with the carcasses of various birds (ducks, geese, chickens) to determine its resistance to such damage. Checking the engines for casting birds in them is generally mandatory.
In mid-March last year, researchers from the American University of George Mason, which announced that the threat of drones to aviation was greatly exaggerated. They looked at statistics on airplane collisions with birds from 1990 to 2014, including episodes ending in fatalities. As a result, scientists came to the conclusion that the real probability of a dangerous collision of a drone with an aircraft is not so great: just one case in 187 million years should end in a large-scale disaster.
In 2016, the aviation authorities of the European Union and the United Kingdom commissioned two independent studies to try to determine whether drones pose a threat to passenger aircraft. Engineers conducting this research fire various aircraft fragments with drones of various designs or parts in order to cause actual damage that can be sustained by a passenger aircraft in a collision. In parallel, mathematical modeling of such collisions is carried out. Research is carried out in several stages, the first of which have already been completed, and the results are presented to customers. When the work is complete, the aviation authorities are expected to develop new rules for the registration and operation of drones by private individuals.
Drone crashes into the windshield of a passenger plane during testing in the UK
Today in different countries there are no uniform rules for drone flights. For example, in the UK it is not required to register and license drones weighing less than 20 kilograms. Moreover, these devices must perform flights in the line of sight of the operator. Private drones with cameras must not fly closer than 50 meters to people, buildings and cars. In Italy, there are practically no special rules for drones, except for one thing - drones cannot fly on a large crowd of people. And in Ireland, for example, all drones weighing more than one kilogram must be registered with the Authority. civil aviation countries. By the way, in the European Union, Ireland is one of the ardent supporters of toughening the rules for the use of drones.
Meanwhile, while in Europe they plan to tighten the screws, in the USA, on the contrary, they intend to make drone flights more free. So, earlier this year, the US Federal Aviation Administration came to the conclusion that lightweight consumer quadcopters do not pose a great threat to aircraft, although their flights near airports are unacceptable. In February, American companies 3DR, Autodesk and Atkins received permission to operate drone flights at the busiest airport in the world - Hartsfield-Jackson Atlanta International Airport, which handles about a hundred million passengers annually. Here, quadcopters were used to draw up 3D maps of the airport in high definition... They flew in line of sight of the operator and under the control of air traffic controllers.
The first results of the study were published in October last year by a working group of the European Aviation Safety Agency. These researchers concluded that amateur drones do not pose a serious threat to passenger aircraft. During their work, the members of the working group focused on studying the consequences of air collisions between passenger aircraft and drones weighing up to 25 kilograms. For the study, the drones were divided into four categories: large (weighing over 3.5 kilograms), medium (up to 1.5 kilograms), small (up to 0.5 kilograms), and “harmless” (up to 250 grams). For each category, experts determined the degree of danger, which was assessed on a five-point scale: 1-2 - high, 3-5 - low. Devices that received four to five points were considered safe.
To determine the degree of danger, the researchers used data on the flight altitudes of vehicles by category, took into account the likelihood of their appearance in the same airspace with aircraft, as well as the results of computer and field tests of collisions between drones and liners. In addition, the individual degree of danger was assessed for each unmanned vehicle according to four points: damage to the hull, threat to the lives of passengers, threat to the life of the crew, and the threat of disrupting the flight schedule. To simplify the assessment, the researchers performed calculations for aircraft flying at a speed of 340 knots (630 kilometers per hour) at an altitude of three thousand meters or more and at a speed of 250 knots at a lower altitude.
Based on the results of all calculations, the members of the European working group came to the conclusion that small drones at an altitude of up to three thousand meters practically do not pose a threat to passenger aircraft. The fact is that such devices rarely rise to great heights, where they can collide with an aircraft. Moreover, they are very lightweight. Medium drones, according to experts, do not pose a serious threat to liners. Only if a device weighing 1.5 kilograms (this is the mass of most amateur drones) collides with an aircraft at an altitude of more than three thousand meters, it can threaten flight safety. Large aircraft are recognized as dangerous for passenger aircraft at all flight altitudes.
Based on the results of full-scale tests, it turned out that in the event of a collision with drones, the windshields of airliners, nose cones, leading edges of the wing, as well as engines can receive the greatest damage. In general, the damage from drones weighing up to 1.5 kilograms can be comparable to the damage from birds that planes regularly encounter in the air. Now European experts are preparing for an extended study. This time, they will study the damage that drones can inflict on the engines of passenger aircraft, and also evaluate the likelihood of batteries getting into technological holes.
By the way, earlier scientists from Virginia Polytechnic University conducted computer simulations of situations in which various drones get into a working aircraft engine. The researchers concluded that vehicles weighing more than 3.6 kilograms pose a serious danger to engines. Once in the engine, they will destroy the fan blades and collapse themselves. Then the fragments of the fan and drone blades will enter the external air circuit, from where they will be thrown out, as well as into the internal circuit - the compressor, the combustion chamber and the turbine zone. The speed of the debris inside the engine can reach 1150 kilometers per hour. Thus, in a takeoff collision with a 3.6 kilogram drone, the engine will completely stop working in less than a second.
Meanwhile, the results of the British study were summed up in the middle of this year - in July, the company QinetiQ, which carried out the work, submitted a report to the National Air Traffic Control Service of Great Britain. The study, conducted by a British company, used a specially designed air cannon that fired drones and their parts at predetermined speeds at the front of decommissioned aircraft and helicopters. For shooting, quadrocopters weighing 0.4, 1.2 and 4 kilograms were used, as well as aircraft-type drones weighing up to 3.5 kilograms. Based on the results of the shooting, experts came to the conclusion that any drones are dangerous for light aircraft and helicopters that do not have a special certificate of protection against collisions with birds.
Bird-proof passenger aircraft can be severely damaged by drones when flying at cruising speeds of between 700 and 890 kilometers per hour. As serious damage, the researchers attributed the destruction of windshields when colliding with heavy parts of the drones - metal body parts, camera and battery. These parts, breaking through the windshield, can fly into the cockpit, damage control panels and injure pilots. Devices weighing two to four kilograms were considered dangerous for the liners. It should be noted that passenger aircraft develop their cruising speed at a high altitude (usually about ten thousand meters), to which amateur drones are simply unable to climb.
According to QinetiQ, drones weighing four kilograms can be dangerous to passenger aircraft at low speeds, such as when landing. Moreover, the severity of damage to the aircraft largely depends on the design of the drone. So, during the tests, it turned out that drones with a camera placed on a suspension under the hull have a small chance of breaking through the windshield of a passenger plane. The fact is that in a collision with the glass, the camera on the gimbal will first hit, and then the body of the drone. In this case, the camera and its suspension will play the role of a kind of shock absorber, taking on part of the impact energy. The British aviation authorities, which are in favor of dramatically tightening drone rules, are expected to order additional research.
Some of today's mass-produced drones already have the function of geofencing. This means that the device is constantly updating the database of areas closed for drone flights. In such an area, the drone simply will not take off. However, in addition to serial devices, there are home-made drones that can fly into air space airports. And there are quite a few of them. In general, until now, not a single case of a collision of an aircraft with a drone has been recorded, but this is just a matter of time. And even if small drones do not pose a serious threat to passenger aircraft, they can still have a negative impact on aviation, increasing the already considerable costs of companies on aircraft repairs.
Vasily Sychev
Pilots-bloggers tell passengers what is really worth and what not to be afraid of in flight.
The holiday season is in full swing. Many would be happy to rush somewhere to the sea, but the fear of flight overpowers the desire to bask in the southern sun. The story of the crash of a liner near Smolensk with the President of Poland on board further increased this fear: if boards number 1 fall, then there is no reason to hope for the reliability of a simple civilian aircraft. But aviators have a different opinion: the plane is the safest transport. Pilots-bloggers, tired of drunken hysterics on board, decided to fight against the aerophobia of passengers, telling why air pockets are not terrible, and that the liner should "knock, rattle and blink" in flight. The idea came to the head of a former military pilot, and now the captain of a civil aviation aircraft Alexei Kochemasov, known on the Internet under the nickname "pilot-lech." His colleagues from other airlines also supported him.
Turbulence is normal
Most of all, passengers are frightened when the plane gets into a zone of turbulence. In the language of pilots, this is "bumpiness". The plane begins to shake, and sometimes it even "jumps" up and down and alarmingly flaps its wings.
Bumpiness can occur both in the clouds and outside them. It will be turbulence of the clear sky, - says Alexey Kochemasov. “Clouds are to an airplane what bumps on the road are to a car. If there is no wind, the temperature is evenly distributed over the heights, the humidity and pressure are even. The flight is calm and serene. And if there are clouds and wind, there is a difference in the temperatures of the ascending and descending currents, then, most likely, it will shake in flight. Over the mountains and big water always shakes, but not necessarily strongly. But aircraft are designed with turbulence in mind. Therefore, you should not be afraid that the plane, falling into an air hole, will fall apart. Nothing will fall off and will not come off.
Is turbulence dangerous for an airplane? Could it crash?
The bumpiness is unpleasant for many, but it is not dangerous, - the pilot reassures. - However, flights in the area of \u200b\u200bstrong turbulence are not encouraged. Pilots try to avoid getting into turbulence, and if they do, they tend to jump out of these zones as quickly as possible. Entry into the turbulence zone is not unexpected. The pilots are ready for it and know the bypass or exit routes.
What's really dangerous
For dangerous meteorological phenomena, pilots include: thunderstorms, icing, wind shear and its microbursts (also called microexplosions), a squall, dusty or sandstorm, ash clouds from volcanoes (can rise to a height of 14 kilometers), tornadoes, heavy rainfall, ultrahigh and ultra-low temperatures. If one of the above is outside the window, then the weather is considered non-flying. If the crew encounters such a meteorological phenomenon on the flight, then they act according to the instructions.
Thunderstorms
They are different: frontal (warm air displaces cold air), orographic (air rises along mountain slopes), intramass (with uneven heating of the surface layer of air), dry (without precipitation).
Half of all thunderstorms last no more than an hour. Flights in the zone of thunderclouds are dangerous: there are powerful ascending and descending air currents up to 20 - 30 m / s, more intense icing, lightning strikes, hail, heavy rain showers, poor visibility.
We know about thunderstorms and try not to go there, - says Alexey Kochemasov. - The plane has a locator that clearly sees thunderstorms. Depending on the density of the clouds on its screen, a thunderstorm object is highlighted in different colors. Light clouds are barely green, denser clouds are bright green, thunderstorms are bright red, clouds containing hail (ice) are purple-red. Wind shear and strong turbulence - dark cherry.
Depending on the color on the radar, the crew decides whether they are following a given route or choosing a new one.
Icing
It is very dangerous. The outer and frontal surfaces of the aircraft are covered with ice. The liner looks like a supermarket shrimp. Icing occurs when flying in an atmosphere with supercooled water droplets. When icing occurs, the laws of aerodynamics cease to work: the plane becomes heavier with lightning speed, the bearing properties of the wing deteriorate, and the liner becomes uncontrollable. Sometimes the engine can also freeze up.
Aviation knows how to fight this phenomenon.
The most severe icing occurs near the ground or even on the "concrete" itself. If there is a danger of "freezing" at the airport (snow, rain at sub-zero temperatures, frost, ice), the aircraft must be treated with an anti-icing fluid before departure. Poured over everything: wings, tail, stabilizer.
If I was doused with a liquid that is effective for half an hour, but I taxied around the airfield and stood in front of the runway longer, then I will not fly. I will come back and shower again! - our consultant assures. - And let the passengers swear at the airline and "honor the mother" of the commander. Life is more expensive!
Icing in the air is less likely, but more intense if it does. The crew is already working here: they are launching an anti-icing system, pouring hot air over the frozen parts. Once they fought with this byaka, pouring pure alcohol on the body. Up to 200 liters of this invaluable liquid were lifted aboard and sprinkled on the glass like on a car: a tank and a special lever stood in front of the windshield.
If the anti-icing system fails, then the pilots leave the dangerous cloud zone.
We turn around and flee so that the heels sparkle! - Kochemasov admits.
Educational program
The flight is proceeding normally if:
When taxiing, you feel the vibration and squeak of the wheels. This is the flap-slats are released, the hydraulic system and brakes are checked. The flaps move in order to increase lift. After takeoff, they are removed back. Released before landing.
When the engines were started, the lights and air conditioners suddenly turned off and then turned on. This power supplies are switched from an external generator to an onboard generator.
After takeoff, something knocks and creaks under the floor - this is the landing gear.
The engine runs quieter after takeoff and before descending. This reduced the thrust of the engines - it should be so.
During turbulence, the wing flaps. Everything is in order - the wings of the liner are flexible and are designed for turbulence.
Something is blinking in the window. These are flashing beacons mounted on the wings. Often their light is reflected off the clouds, creating the illusion of lightning.
After landing, a "blowing" sound is heard - this is the reverse of the engine thrust with the help of a jet of air, which slows down the aircraft.
After landing, the plane brakes and vibrates sharply. The shorter the bar, the sharper the stop.
In the rain, the plane "slaps" against the concrete - a hard landing provides better grip on the asphalt. Vibration - this is an anti-skid device that prevents slipping.
And at this time
A scandal erupts: Australian flight attendants saw posters on the Internet with naked girls on the plane and were offended. Flight attendants from the Green Continent believe that such a photo triggers a surge of violence towards female workers, as some passengers begin to perceive them as a sexual object.
Who actually made and posted the scandalous nudes on the Web is still unknown.
By the way
On takeoff, the crew reads a "prayer".
Before departure, pilots launch all systems necessary for a safe flight. And after each performed action, they read the Checklist. This document is a kind of "Bible" for the crew or, as the pilots themselves call it, "prayer". As a result of reading it, they check whether everything was done correctly, in order to correct the problems in time if something happens.
