In rectilinear horizontal flight, the aircraft's angle of attack increases with increasing speed, adding lift to the aircraft, which is created by the wing. However, the inductive reactance also increases. The angle of attack of an aircraft is denoted by the Greek letter "alpha" and means the angle that is located between the chord of the wing and the direction of the air flow speed.
Wing and flow
As long as there is aviation in the world, so many aircraft are threatened by one of the most frequent and terrible dangers - stalling into a tailspin, because the angle of attack of the aircraft becomes higher than the critical value. Then the smoothness of the air flow around the wing is disturbed, and the lifting force decreases sharply. Stall usually occurs on one wing, as the flow is almost never symmetrical. It is on this wing that the plane stalls, and it’s good if the stall does not turn into a tailspin.
Why do things like this happenwhen the angle of attack of the aircraft increases to its critical value? Either speed was lost, or maneuvering overloaded the aircraft too much. This can also happen if the height is too high and close to the "ceiling" of possibilities. Most often, the latter occurs when thunderclouds are bypassed from above. Velocity pressure at high altitudes is small, the ship becomes more and more unstable, and the critical angle of attack of the aircraft may increase spontaneously.
Military and civil aviation
The situation described above is very familiar to pilots of maneuverable aircraft, especially fighters, who have the theoretical knowledge and sufficient experience to get out of any situation of this kind. But the essence of this phenomenon is purely physical, and therefore it is characteristic of all aircraft, of all types, of all sizes and for any purpose. Passenger aircraft do not fly at extremely low speeds, and energetic maneuvers are not provided for them either. Civilian pilots most often do not cope with the situation when the angle of attack of the aircraft wing becomes critical.
It is considered unusual if a passenger ship suddenly loses speed, in fact, many believe that this is generally out of the question. But no. Both domestic and foreign practice shows that this happens not even very rarely, when a stall ends in a catastrophe and the death of many people. Civilian pilots are not well trained to overcome such a situation.aircraft. But the transition into a tailspin can be prevented if the angle of attack of the aircraft during takeoff does not become critical. At low altitude, it is almost impossible to do anything.
Examples
So it happened in the crashes that occurred with TU-154 aircraft at different times. For example, in Kazakhstan, when the ship was descending in the stall mode, the pilot did not stop pulling the steering wheel towards himself, trying to stop the descent. And the ship should have been given the opposite! Lower your nose to pick up speed. But until the very fall to the ground, the pilot did not understand this. Approximately the same thing happened near Irkutsk and near Donetsk. Also, the A-310 near Kremenchug tried to gain altitude when it was necessary to gain speed and watch the angle of attack sensor in the plane all the time.
Lift force is formed as a result of an increase in the speed of the flow that flows around the wing from above compared to the flow speed under the wing. The greater the speed gained flow, the less pressure in it. The difference in pressure on the wing and under the wing - that's it, lift. An aircraft's angle of attack is a measure of normal flight.
What to do
If the ship suddenly rolls to the right, the pilot deflects the steering wheel to the left, against the roll. In this case, the aileron on the wing console deviates downward and increases the angle of attack, slowing down the air stream and increasing pressure. At the same time, the flow from above on the wing accelerates and reduces the pressure on the wing. And on the right wing, at the same moment, the reverse action occurs. Aileron - up, the angle of attack decreases and liftingforce. And the ship comes out of the list.
But if the angle of attack of the aircraft (during landing, for example) is close to critical, that is, too large, the aileron cannot be deflected down, then the smoothness of the air stream is disturbed, starting to swirl. And now this is a stall, which sharply removes the speed of the air flow and also sharply increases the pressure on the wing. The lift force quickly disappears, while everything is fine on the other wing. The difference in lift only increases the roll. But the pilot wanted the best… But the ship starts to descend, go into rotation, into a tailspin and fall.
How to act
Many practicing pilots talk about the angle of attack of an aircraft "for dummies", even Mikoyan wrote a lot about it. In principle, everything is simple here: there is practically no complete symmetry in the air flow, and therefore, even without a roll, the air flow can stall, and also only on one wing. People who are very far from piloting, but who know the laws of physics, will be able to figure out that this is the angle of attack of the aircraft has become critical.
Conclusion
Now it is easy to draw a simple and fundamental conclusion: if the angle of attack is large at low speed, it is impossible, absolutely impossible to counteract the roll with the ailerons. It is removed by the rudder (pedals). Otherwise, it is easy to provoke a corkscrew. If a stall still occurs, only military pilots can get the ship out of this situation, civilians are not taught this, they fly according to very strict restrictive rules.
And you need to learn! After the plane crashesthe recordings of conversations from the "black boxes" are always carefully analyzed. And never once in the cockpit of a plane crashed in a tailspin did the “Steering wheel away!” sound, although this is the only way to save. And "Leg against roll!" didn't sound either. Civil aviation pilots are not ready for such situations.
Why is this happening
Passenger planes are almost completely automated, which, of course, facilitates the actions of the pilot. This is especially true for adverse weather conditions and flights at night. However, this is where the great danger lies. If it is impossible to use the ground system, if at least one node in the automatic system fails, then manual control must be used. But pilots get used to automation, gradually losing their piloting skills "the old fashioned way", especially in difficult conditions. After all, even the simulators for them are set to automatic mode.
This is how plane crashes happen. For example, in Zurich, a passenger plane could not land properly on the drives. The weather was minimal, and the pilot did not taxi out, collided with trees. All died. It often happens that it is automation that causes a stall into a tailspin. The autopilot always uses ailerons against a spontaneous roll, that is, it does what cannot be done if there is a threat of stalling. At high angles of attack, the autopilot must be turned off immediately.
Autopilot action example
Autopilot hurts not only whenthe beginning of the stall, but also when the aircraft is pulled out of a spin. An example of this is the case in Akhtubinsk, when an excellent military test pilot Alexander Kuznetsov was forced to eject, and he understood what was the matter. He attacked the target with the autopilot turned on when he broke into a tailspin. Twice he managed to stop the rotation of the aircraft, but the autopilot stubbornly manipulated the ailerons, and the rotation returned.
Such problems, which constantly arise in connection with the widest spread of programmed automatic control of aircraft, are extremely worrying not only for domestic specialists, but also for foreign civil aviation. International seminars and rallies dedicated to flight safety are held, where it is certainly noted that the crews are poorly trained in flying an aircraft with a high degree of automation. They get out of dire situations only if the pilot has personal ingenuity and good manual piloting technique.
The most common mistakes
Even the ship's automation is often not well understood by pilots. In 40% of flight accidents, this played a role (of which 30% ended in a disaster). In the USA, evidence of disharmony among pilots with highly automated aircraft has begun to be compiled, and a whole catalog of them has already accumulated. Very often, pilots do not even notice the failure of the autothrottle and autopilot at all.
They also control the state of speed and energy poorly, because this state is not saved. Some pilots don't realize that rudder deflection is no longercorrect. It is necessary to control the flight path, and the pilot is distracted by programming the automatic system. And many more such errors occur. Human factor - 62% of all serious accidents.
Explanation "on the fingers"
What is the angle of attack of an aircraft, probably everyone already knows, and even people who are not related to aviation realize the importance of this concept. However, are there any? If there are, then there are very few of them on Earth. Almost everyone is flying! And almost everyone is afraid of flying. Someone internally worries, and someone right on board falls into hysterics at the slightest turbulence.
Perhaps, it would be necessary to tell passengers about the most basic concepts regarding the aircraft. After all, the critical angle of attack of the aircraft is not at all what they are experiencing now, and it is better if they understand this. You can instruct flight attendants to convey such information, prepare appropriate illustrations. For example, to tell that there is no such independent quantity as lifting force. It just doesn't exist. Everything flies thanks to the aerodynamic force of air resistance! Such excursions to the basics of science can not only distract from the fear of flying, but also interest.
Angle of attack sensor
The plane must have a device that can determine the angle of the wing and the horizontality of the air flow. That is, such a device, on which the well-being of the flight depends, is worth demonstrating to passengers at least in the picture. With this sensor, you can judge how far the nose of the aircraft looksup or down. If the angle of attack is critical, the engines do not have enough power to continue the flight, and therefore a stall occurs on one wing.
It can be quite simply explained: thanks to this sensor, you can see the angle between the plane and the ground. The lines should be parallel in flight at an already climbed altitude when there is still time before descent. And if a line running along the ground tends to a line mentally drawn along the plane, an angle is obtained, which is called the angle of attack. You can’t do without it either, because the plane takes off and lands at an angle. But he can't be critical. This is exactly how it should be told. And that's not all passengers need to know about flying.
