Some secrets of flying in a passenger plane
Aircraft is an aircraft intended for flights in the atmosphere with the help of a propulsion unit that creates thrust and a wing stationary relative to other parts of the aircraft, creating lifting force. A fixed wing distinguishes the aircraft from a flywalker (ornithopter) and a helicopter, and the presence of an engine differs from a glider. The aircraft differs from the airship and aerostat in that it uses the aerodynamic, rather than the aerostatic method of creating lift.
The word "aircraft" was used to refer to aircraft in the XIX century. So, in 1857, the captain of the 1st rank N. M. Sokovnin used this word to designate a controlled aerostat. In a meaning close to modern, the word “plane” was first used by journalist and writer Arkady V. Ewald in the article “Ballooning”, which was published in 1863 in the newspaper “Golos”, where he first proposed the idea of a similar aircraft in Russia.
Anyone who flew in a passenger plane at least once was surely interested in what is happening now and why it is needed. We will try to answer some of the questions.
Quite often it happens that the first ones are seated for those who are sitting in front of the cabin, and then for those who are sitting in the tail. And this is not a whim of the airline - otherwise the plane can simply roll over, even without having departed from the terminal. This is especially important for those aircraft in which the engines are in the tail and the center of gravity is shifted far back. For example, on the IL-62, an additional tail support and, moreover, a balancing water tank in front of the aircraft, was provided to prevent tipping over.
However, the rear engine has its advantages. First, it reduces the noise level in the cabin during the flight. Secondly, such engines are higher than those located under the wings, and less prone to “sucking” foreign objects from the runway. And finally, if one of the engines fails, the aircraft will maintain better controllability - due to its smaller “shoulder”, it will be less deployed. At the same time, tail engines have quite serious drawbacks: they are more difficult to maintain (especially on Tu-154 or MD-10 aircraft, where the engine is located directly in the fuselage). In addition, in this case, a T-shaped stabilizer is used, which, if the angle of attack is increased, can fall into the vortex trail of the wing, which is fraught with a loss of control. Therefore, in modern aircraft engines are trying to have under the wings. This has serious advantages - easy access to the engines facilitates their maintenance, and due to the even distribution of the load, it is possible to simplify and simplify the design of the wing.
Passengers are seated and fastened, the plane is taxiing to the start of the runway, and the pilots are allowed to take off. Look out the window: the “flared” wing makes an unforgettable impression, although this is not a sight for the faint of heart. Extended wing mechanization changes its profile, increasing lift and shortening the takeoff run. Almost immediately after the ground goes down, a low rumble is clearly audible: the chassis is retracted inside the fuselage or wings. But first, you need to stop the heavy wheels, which, after being taken off the ground, still rotate: the gyroscopic effect creates a heavy load on the landing gear. Then the plane is slightly "squander". But there is no need to be frightened - this happens at the moment when the sliding elements of wing mechanization are folded. This reduces the lifting force of the wing and its resistance, which allows to reach high speeds.
During the climb, passengers lay their ears. Outside pressure drops, and without an oxygen mask already at an altitude of more than 5–6 km (and flights of modern airliners pass at altitudes of about 9–11 km) a person experiences oxygen starvation, altitude decompression and is unable to survive. Therefore, the cabin of the aircraft is relatively hermetic, but you still need to constantly “inflate” it. The cabin pressure is less than “at sea level” (but not lower than 0.75 atm., This corresponds to an air pressure of 2400 m above sea level), and that is why passengers get their ears when they climb (and pressure drops). .
Why not make life easier for passengers and maintain pressure corresponding to sea level? This is due to the strength of the fuselage materials. One of the first passenger aircraft with a sealed cabin - the De Havilland Comet - was inflated to almost normal atmospheric pressure. However, after some time, followed by a series of unexplained accidents - 4 aircraft literally collapsed in the air. One of them fell into the Mediterranean Sea, and when rescuers lifted debris from the bottom, it turned out that the largest fragment was only about half a meter in size. Studies have shown that all these disasters occurred because of the "fatigue" of the metal: the stresses arising from the pressure difference inside and outside the fuselage accumulate and are capable of destroying the aircraft over time.
However, progress does not stand still, and the newer the aircraft, the more advanced materials are used in it and the closer the pressure in the cabin is to normal. And in the new Boeing 787, in the design of which high-strength composite materials are widely used, they promise to maintain pressure at "sea level" during the entire flight.
Finally, the “fasten seat belts” signs go out and the plane goes into horizontal flight, the safest part of the journey. It's time to get up from the chair, stretch your legs, go to the toilet. By the way, we want to dispel the widespread "toilet" myth. Waste in modern airliners is not dumped out at all. They enter the tank, from which they are already pumped out on the ground by a special sewage truck. Therefore, a shot from the film “The Incredible Adventures of Italians in Russia,” when a passport thrown into the toilet sticks outside to the porthole, is only an invention of the screenwriter.
Of course, you can not and "go outside." Ordinary doors, through which the landing and disembarkation occurs, are blocked in flight. And emergency exit doors opening inwards are securely held by the pressure difference.
Management in horizontal flight, as a rule, is in charge of the autopilot. And in general, the manual piloting mode for modern aircraft is extremely uncharacteristic. However, calling it “manual” will also not be entirely accurate. The extreme (aviators do not like the word "last") Russian aircraft with this manual control was the IL-62: there mechanical thrusts of control went through the entire aircraft. Subsequently, the control became remote, using hydraulics, but the linear relationship (that is, direct proportionality) between the deflection angle of the handwheel and the deflection angle of the control planes was preserved. In this case, the pilot himself decides how much it is necessary to turn the steering wheel in order, say, to tilt the plane to one or another angle. In airplanes of the last generation there is no steering wheel as such - only a joystick, the slope of which sets the angle of deflection of the aircraft itself, and all intermediate calculations are performed by a computer.
The “Fasten your seat belts” signs light up again and the plane starts to descend. According to statistics, landing is the most dangerous stage of the flight. The lights of the airfield are already visible ... The plane slows down, in order to preserve the lifting force, elements of wing mechanization are put forward - in general, everything is just like on take-off, only in the reverse order. A low rumble, the plane begins to shake gently - this released chassis creates flow instability.
Together with the chassis, the headlights are extended and the lights are automatically lit (usually they are mounted on the landing gear). It would seem, why aircraft headlights? Aviators jokingly answer this question like this: “So that the pilot could see where to fly!” And although, of course, the headlights are used during landing and taxiing, in fact, their main task is to scare away birds. If a bird gets into the engine, the latter is likely to fail, and this may even cause the plane to fall. Therefore, birds are a serious danger: according to ICAO (International Civil Aviation Organization), bird collisions with airplanes damage about $ 1 billion annually. Therefore, an uncompromising struggle is taking place at the airfields with birds: frightening equipment is installed, special bird services are engaged in shooting, at some airports (for example, in Domodedovo) even use specially trained hunting birds. White “commas” drawn on the coca (fairing) of the engine fans serve the same purpose - they create a frightening “blinking” effect during rotation: birds take it as a predator's eye (like headlights).
In addition to headlights, the aircraft carries aeronautical lights on it - to indicate the flight path and prevent dangerous encounters with other aircraft: green on the right wing, red on the left, and white on the keel. Remembering this arrangement is simple - pilots joke that there is a mnemonic rule: "A green co-pilot sits to the right of an experienced commander." In addition, red or white flashing light beacons are located on the fuselage and wings. And recently, the airlines have begun to highlight the keel of the aircraft during the approach - firstly, the visibility improves (for other aircraft), and secondly, there is no advertising.
And finally, the wheels touch the strip. A light smoke at the first moment accompanies their transition from dormancy to rapid rotation. At this point, passengers usually applaud. However, it is too early to rejoice: the plane is still moving at a speed of about 250 km / h, and it needs to extinguish this speed before the 2–2.5 km lane ends. And in general, aviators are a superstitious people, and before the completion of the flight it is hardly appropriate to show any emotions (it is better to thank the flight attendants when leaving the aircraft). By the way, applause may be unnecessary for another reason: when landing, the pilot may not participate in the control at all! Modern airliners allow fully automatic landing at zero visibility and automatic taxiing to the terminal (at the airports of category IIIC according to ICAO standards). True, there are no such airports in Russia yet. Determining who landed the plane is quite simple. A very soft landing is a characteristic sign of manual control: the pilot gently “mills” the plane to the ground. The automatic landing is tighter because the autopilot must simply meet the maximum vertical speed tolerances.
To slow down, the plane is equipped with several systems at once. The first is air brakes - aerodynamic shields, which the plane “fluffs” to increase resistance. The second is the reverse of the engines (although, for example, it is not on the Yak-42). The third system is the wheel brakes themselves. However, there were also more exotic options: on some old aircraft (for example, the Tu-134 of the first series) even brake parachutes were used.
Wheel brakes on old passenger airplanes are shoe-type (motorists would call them drum), and on new ones they are disc ones (on the newest models even discs made of composite materials, like in Formula-1) are used, with hydraulic drive. Moreover, the chassis is necessarily equipped with anti-lock ABS. Actually, this system came from a car in aviation - for an aircraft, uneven braking is fraught with drift and derailment from the runway.