The history of this project dates back to the early 80s. At the experimental machine-building plant named after V. M. Myasishchev, design and search work was carried out to develop the concept of a new heavy-duty aviation transport system.
In the early 80s of the last century, similar work was carried out in several aviation design bureaus and, of course, in the TsAGI National Aviation Research Center.
The concept of a heavy transport aircraft developed at TsAGI is quite well known in aviation circles, the author of the development was Yu. P. Zhurikhin, head of design research.
The demonstration model of the TsAGI transport system has been repeatedly demonstrated at international aviation exhibitions.
Design developments of EMZ them. V. M. Myasishchev were held within the framework of the topic, which received the index "52". They were carried out under the guidance of the chief designer of the EMZ V.A. Fedotov, the leader of the topic at the initial stage was the deputy chief designer R.A. Izmailov. The lead designer on the topic and, in fact, the author of the concept was V. F. Spivak.
The concept of the project "52" provided for the creation of a unified transport aircraft with unique transport capabilities. The main task The project was to provide an air launch of a reusable aerospace rapid response aircraft. It would be economically inexpedient to create such a unique aircraft with a takeoff weight of 800 tons for only one task. Therefore, from the very beginning, the concept of the "52" project provided for the use of this aircraft for unique transport operations, including transportation military equipment and military formations, industrial cargo in excess of large sizes and weights.
The design concept of "52" was based on the principle of "load outside". Only this principle allows you to place loads that are completely heterogeneous in their shapes and dimensions. In this case, the aircraft fuselage practically degenerates as a means of placing the load, therefore, by maintaining the minimum required size of the fuselage, it would be possible to significantly reduce the mass of the aircraft structure due to this. That's all, it would seem very simple idea upon which the entire project is based.
In this article, we will not consider the project "52" in detail. those interested will be referred to the multi-volume publication “Illustrated Encyclopedia of Aircraft EMZ them. V.M. Myasishchev”, where the development of the project is described in sufficient detail.
The author of these lines had to directly participate in these works, and in this article I would like to talk about those projects, or, more correctly, ideas that were also considered in the process of developing the concept, but were not developed and were not worked out in sufficient detail.
The very idea of creating a super-heavy transport aircraft did not arise by itself. Ministry aviation industry(MAP) set a specific task of transporting bulky goods in the interests of the national economy of the country.
The USSR, with its vast territories and large industrial centers scattered throughout the country, needed to solve this problem, because it is obvious that it is more economically profitable to transport ready-made and assembled units.
Nuclear reactors, metallurgical production convectors, gas holders and distillation columns chemical production and many other cargoes, all of them, when transported as an assembly “by air”, could be put into operation quite quickly, which means shorter terms and, accordingly, lower costs.
Any transport operation "on the ground" is a whole event for many transport services. Detailed study of the route, demolition of bridges and flyovers, power lines if they interfere with transportation, and so on ... These are the timing, these are costs, in some cases this is simply an unsolvable problem.
Cargoes weighing from 200 to 500 tons were intended for transportation, with overall dimensions from 3 to 8 m in diameter, from 12 m to 50 m in length. It is clear that, of course, not all of the proposed cargo could be transported by air, however, the project "52" could transport most of the cargo if it were implemented.
So the idea arose not just to reduce the size of the fuselage to the minimum possible, but to abandon it altogether. Why not make the transported cargo “work”? This idea was prompted by the fact that many cargoes intended for transportation looked like elongated cylindrical bodies, that is, they looked like a fragment of the fuselage.
Of course, the cargo itself, the material from which it was made and its design had to satisfy the conditions of strength when it was installed on an aircraft. The inclusion of cargo in the power circuit of the aircraft promised a significant gain in the weight return of the aircraft and, accordingly, increased its transport efficiency.
How can the transported cargo itself be included in the power circuit of a transport aircraft? Very simple, you need to make the transported cargo winged! There is such an aerodynamic scheme of the aircraft called "tandem". In this scheme, the carrier system of the aircraft consists of a pair of wings arranged in tandem one after the other with a longitudinal spacing. The transported cargo is located between the wings just in the center of gravity of the entire aircraft carrier system, everything is very simple, although it is well known what a big problem the solution of the problem of centering a heavy load is.
The tandem scheme has a somewhat larger area of the aircraft carrier system compared to the classical scheme, however, this scheme is the most suitable for cargo transportation tasks.
Both wings create lift without losing lift due to the longitudinal balancing inherent in the classical aircraft layout. The optimal profile of both wings and the degradation of their installation angles make it possible to minimize the negative effect of wing interference and, therefore, reduce aerodynamic losses.
One of the variants of the tandem aircraft consisted of two independent sections with a full-fledged wing with mechanization of the leading and trailing edges. The wing of the front section is made according to a low-wing scheme to reduce the effect of the flow bevel on the rear wing. On top of the wing of the front section on vertical pylons, the engines of the power plant are installed. The pylon engine suspension is considered to be quite versatile, allowing the required number of engines to be varied during the development process.
The location of the engines above the upper surface of the wing made it possible to use the effect of increasing the lift of the wing due to the jet blowing of the engines (the Coanda effect). Due to the greater loading of the front wing, the front wing was made in a slightly smaller area compared to the rear wing.
The front section is equipped with its own chassis - the main one, consisting of two four-wheeled main supports and two two-wheeled underwing supports. The spacing of the main and underwing landing gear along the longitudinal axis of the aircraft ensured the longitudinal stability of the front section at the airfield in the undocked position.
On top of the front section behind the cockpit, there is a back-facing glazing of the load operator's cabin, who monitor the state of the load and the load securing systems during the flight.
The rear section of the tandem aircraft is similar to the front. The wing of the rear section is upper, slightly larger in scope. Vertical tail washers are installed on the rear wing. Due to the small effective shoulder, the vertical tail unit is made of a large area, two-keeled.
The rear section of the tandem aircraft has no engines, the landing gear is similar to the front section. Due to the high location of the wing on the rear section, the underwing landing gear is attached to the vertical tail washers.
An important feature of the "tandem" scheme is also that when the aircraft takes off from the runway, the aircraft takes off flat-parallel, with virtually no pitch angle, this feature of the "tandem" is the best suited for transporting long loads, since the aircraft is blown up on takeoff cargo on an external sling for a classic aircraft becomes problematic.
For fastening various loads, transitional ring trusses were provided, adapted to a specific load.
In order to increase the transport efficiency of the tandem aircraft, it was also planned to use a passenger module, which is closed between the front and rear sections of the aircraft.
The open circuit of the tandem aircraft made it possible to adapt the aircraft to a load of various lengths, this made the aircraft efficient vehicle. In the case of an empty flight of the aircraft, both sections were docked by means of docking ring trusses.
The scheme of a tandem aircraft with a truss fuselage looked less radical.
In principle, the idea of the concept remained the same, but the fuselage was still preserved, albeit in a somewhat exotic form - two fuselage beams in the form of spatial trusses. A feature of this tandem aircraft scheme was that the rear wing with its landing gear and cargo attachment points could move along the trusses to the desired position, depending on the size of the cargo being transported and its centering. In all other respects, the concept repeated the first scheme. The shortcomings of this scheme were clearly visible, but the only positive thing was that the search for further productive ideas lay through these schemes.
The "tandem" scheme has not yet exhausted itself, perhaps it will find a worthy application in the very near future, we'll wait and see.
A source. V. Pogodin Valery Pogodin. Tandem - a new word in aviation? Wings of the Motherland 5/2004
: forward control planes without a rear tail.
Advantages
Also, various varieties of the "duck" scheme are used for many guided missiles.
see also
Write a review on the article "Duck (aerodynamic design)"
Literature
- Aircraft flight tests, Moscow, Mashinostroenie, 1996 (K. K. Vasilchenko, V. A. Leonov, I. M. Pashkovsky, B. K. Poplavsky)
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An excerpt characterizing the Duck (aerodynamic scheme)
The horses were given. Denisov was angry with the Cossack because the girths were weak, and, having scolded him, sat down. Petya took up the stirrup. The horse, out of habit, wanted to bite his leg, but Petya, not feeling his weight, quickly jumped into the saddle and, looking back at the hussars moving behind in the darkness, rode up to Denisov.- Vasily Fyodorovich, will you entrust me with something? Please… for God's sake…” he said. Denisov seemed to have forgotten about the existence of Petya. He looked back at him.
“I’ll tell you about one thing,” he said sternly, “obey me and not meddle anywhere.
During the entire journey, Denisov did not say a word to Petya and rode in silence. When we arrived at the edge of the forest, the field was noticeably brighter. Denisov said something in a whisper to the esaul, and the Cossacks began to drive past Petya and Denisov. When they had all passed, Denisov touched his horse and rode downhill. Sitting on their haunches and gliding, the horses descended with their riders into the hollow. Petya rode next to Denisov. The trembling in his whole body grew stronger. It was getting lighter and lighter, only the fog hid distant objects. Driving down and looking back, Denisov nodded his head to the Cossack who was standing beside him.
- Signal! he said.
The Cossack raised his hand, a shot rang out. And at the same moment there was heard the clatter of galloping horses in front, shouts from different directions, and more shots.
At the same moment as the first sounds of trampling and screaming were heard, Petya, kicking his horse and releasing the reins, not listening to Denisov, who shouted at him, galloped forward. It seemed to Petya that it suddenly dawned brightly, like the middle of the day, at the moment a shot was heard. He jumped to the bridge. Cossacks galloped ahead along the road. On the bridge, he ran into a straggler Cossack and galloped on. There were some people in front—they must have been Frenchmen—running from the right side of the road to the left. One fell into the mud under the feet of Petya's horse.
Cossacks crowded around one hut, doing something. A terrible cry was heard from the middle of the crowd. Petya galloped up to this crowd, and the first thing he saw was the pale face of a Frenchman with a trembling lower jaw, holding on to the shaft of a pike pointed at him.
“Hurrah!.. Guys…ours…” Petya shouted and, giving the reins to the excited horse, galloped forward down the street.
Shots were heard ahead. Cossacks, hussars, and ragged Russian prisoners, who fled from both sides of the road, all shouted something loudly and incoherently. A young man, without a hat, with a red frown on his face, a Frenchman in a blue greatcoat fought off the hussars with a bayonet. When Petya jumped up, the Frenchman had already fallen. Late again, Petya flashed through his head, and he galloped to where frequent shots were heard. Shots were heard in the courtyard of the manor house where he had been last night with Dolokhov. The French sat there behind the wattle fence in a dense garden overgrown with bushes and fired at the Cossacks crowded at the gate. Approaching the gate, Petya, in the powder smoke, saw Dolokhov with a pale, greenish face, shouting something to people. "On the detour! Wait for the infantry!” he shouted as Petya rode up to him.
“Wait?.. Hurrah!” Petya shouted and, without a single minute's hesitation, galloped to the place where the shots were heard and where the powder smoke was thicker. A volley was heard, empty and slapped bullets screeched. The Cossacks and Dolokhov jumped after Petya through the gates of the house. The French, in the swaying thick smoke, some threw down their weapons and ran out of the bushes towards the Cossacks, others ran downhill to the pond. Petya galloped along the manor's yard on his horse and, instead of holding the reins, waved both hands strangely and quickly, and kept falling further and further from the saddle to one side. The horse, having run into a fire smoldering in the morning light, rested, and Petya fell heavily to the wet ground. The Cossacks saw how quickly his arms and legs twitched, despite the fact that his head did not move. The bullet pierced his head.
After talking with a senior French officer, who came out from behind the house with a handkerchief on a sword and announced that they were surrendering, Dolokhov got off his horse and went up to Petya, motionless, with his arms outstretched.
“Ready,” he said, frowning, and went through the gate to meet Denisov, who was coming towards him.
- Killed?! exclaimed Denisov, seeing from a distance that familiar to him, undoubtedly lifeless position, in which Petya's body lay.
“Ready,” repeated Dolokhov, as if pronouncing this word gave him pleasure, and quickly went to the prisoners, who were surrounded by dismounted Cossacks. - We won't take it! he shouted to Denisov.
Denisov did not answer; he rode up to Petya, dismounted from his horse, and with trembling hands turned towards him Petya's already pale face, stained with blood and mud.
“I'm used to anything sweet. Excellent raisins, take them all,” he remembered. And the Cossacks looked back with surprise at the sounds, similar to the barking of a dog, with which Denisov quickly turned away, went up to the wattle fence and grabbed it.
Among the Russian prisoners recaptured by Denisov and Dolokhov was Pierre Bezukhov.
About the party of prisoners in which Pierre was, during his entire movement from Moscow, there was no new order from the French authorities. On October 22, this party was no longer with the troops and convoys with which it left Moscow. Half of the convoy with breadcrumbs, which followed them for the first transitions, was beaten off by the Cossacks, the other half went ahead; the foot cavalrymen who went ahead, there was not one more; they all disappeared. The artillery, which the first crossings could be seen ahead of, was now replaced by the huge convoy of Marshal Junot, escorted by the Westphalians. Behind the prisoners was a convoy of cavalry things.
From Vyazma, the French troops, who had previously marched in three columns, now marched in one heap. Those signs of disorder that Pierre noticed on the first halt from Moscow have now reached the last degree.
How to avoid balancing losses? The answer is simple: the aerodynamic configuration of a statically stable aircraft should exclude balancing with negative lift on the horizontal tail. In principle, this can be achieved on the classical scheme, but the simplest solution is the layout of the aircraft according to the "canard" scheme, which provides pitch control without loss of lift for balancing (Fig. 3). Nevertheless, "ducks" are practically not used in transport aviation, and, by the way, quite rightly so. Let's explain why.
As theory and practice show, aircraft of the "duck" scheme have one serious drawback - a small range of flight speeds. The canard pattern is selected for an aircraft that must have more high speed flight compared to an aircraft configured according to the classical scheme, provided that the power power plants these aircraft are equal. This effect is achieved due to the fact that on the “duck” it is possible to reduce the air friction resistance to the limit by reducing the area of the aircraft surface being washed.
On the other hand, when landing, the "duck" does not realize the maximum coefficient of lift of its wing. This is explained by the fact that in comparison with the classical aerodynamic scheme with the same interfocal distances of the wing and GO, the relative area of the GO, as well as with equal absolute values of the longitudinal static stability margins, the canard scheme has a smaller balancing arm of the GO. It is this circumstance that does not allow the "duck" to compete with the classical aerodynamic scheme in takeoff and landing modes.
There is one way to solve this problem: to increase the maximum lift coefficient of the CPG ( ) to values that ensure the balancing of the "duck" at the landing speeds of classic aircraft. Modern aerodynamics has already given the “ducks” high-bearing profiles with values Su max = 2, which made it possible to create a PGO with
. But, despite this, all modern "ducks" have higher landing speeds compared to the classic layouts.
The disruptive characteristics of the "ducks" also do not stand up to criticism. When landing in conditions of high thermal activity, turbulence or wind shear, a PGO that provides trim at the maximum allowable Su aircraft, may have . Under these conditions, with a sudden increase in the angle of attack of the aircraft, the PGO will enter a supercritical flow around it, which will lead to a drop in its lift, and the angle of attack of the aircraft will begin to decrease. The resulting deep stall with the PGO introduces the aircraft into a sharp uncontrolled dive, which in most cases leads to a disaster. This behavior of the "ducks" at critical angles of attack does not allow the use of this aerodynamic scheme in ultralight and transport aviation.
I belong to the category of modellers who are interested in designing and building an airplane themselves, and then having fun flying it. But the main pleasure is from the result of creative search.
After flying off for several seasons on a homemade Diamant with OS MAX 50, it became a little boring. It was clear what the plane could do and what I could do. Of course, it was possible to work on honing the skills of 3D aerobatics, but the soul asked for something unusual. I wanted to build an aircraft that no one else has, and which would have unique, inherent only to it, aerobatic capabilities.
Attempt 1
I looked at how the radio fighters fly, the idea came up to build a "flying wing" fanfly. No sooner said than done. A drawing has been drawn, the layout has been worked out, and now the plane is ready.
- Span: 1450 mm
- Length: 1000 mm
- Weight: 2000 g
- Engine: OS MAX 50
I leave for the field and understand that I have not built anything interesting. Yes, it flies, yes, it twists some figures. But nothing interesting, everything is as usual, even a little boring.
After analyzing the situation, I understand that it should have been so ... The classical scheme and the "flying wing" scheme have been worked out to the smallest detail, and they cannot offer anything new. Creativity has begun...
Being in a crisis, I leaf through old magazines and stumble upon a model of the "Duck" scheme. This is getting interesting.
Idea
The duck scheme has one interesting feature. Control surfaces are located in front of and behind the center of gravity. Accordingly, if you mix the elevator with the ailerons and do it as in a cord pilotage, then the turning moment from the elevators will be applied in front and behind the center of gravity. This, in turn, will allow you to perform loops of very small radius. It was also known from large aviation that this scheme behaves very stably in stall modes. That's just the pusher screw located at the back did not contribute to the implementation of 3D aerobatics.
The conclusion suggested itself, the engine should be put in front, but then there were problems with centering. Since the main wing is located at the rear (unlike the classical scheme, where the stabilizer does not carry the weight of the aircraft, it creates lift in the canard scheme), and the center of gravity is within 10-20% of the MAR, it was not possible to balance this design. Again, a dead end ... Scrolling further through the magazines, I find an old issue of "Wings of the Motherland", which tells about aircraft of special schemes, and among them the "Tandem" scheme is given. And the most interesting thing is that there are formulas for calculating the position of the center of gravity. I am quoting from this article.
An excerpt from an article in the magazine "Wings of the Motherland" for February 1989.
When flying at high angles of attack before stalling, the stall should occur primarily on the front wing. Otherwise, the aircraft will sharply lift its nose during a stall, and go into a tailspin. This phenomenon is called "pickup" and is considered completely unacceptable. A way to combat the "pickup" on the "duck" and "tandem" was found long ago: it is necessary to increase the angle of installation of the front wing in relation to the rear, and the difference in installation angles should be 2-3 degrees.
A properly designed aircraft automatically lowers its nose, shifts to lower angles of attack and picks up speed, thereby realizing the idea of creating a non-stallable aircraft. For a "standard canard" (horizontal tail area 15-20% of the wing area and tail arm equal to 2.5-3 MAR), the center of gravity should be in the range from 10 to 20% MAR. For a tandem, the center of gravity should be within 15-20% Eq (chords of an equivalent wing), see figure. The equivalent wing chord is defined as follows:
In equiv \u003d (S p + S s) / (l p 2 + l s 2) 1/2
In this case, the distance to the nose of the equivalent chord is:
X eq = L / (1 + S p / S c * K) - (S p + S c) / (4 * (l p 2 + l c 2) 1/2)
Where K is a coefficient that takes into account the difference in the angles of installation of the wings, bevels and deceleration of the flow behind the front wing, equals:
K \u003d (1 + 0.07 * Q) / ((0.9 + 0.2 * (H / L)) * (1-0.02 * (S p / S s)))
In the above formulas:
- S p - area of the front wing.
- S c - area of the hind wing.
- L - tandem aerodynamic arm.
- l p - span of the front wing.
- l c - span of the hind wing.
- Q - the excess of the installation angle of the front wing over the rear.
- H is the distance in height between the axis of the front and rear wings.
final version
Now the general idea has been formed. We put the engine in front, make the wings the same, and move the receiver and battery to the tail of the aircraft.
The drive of the ailerons on the front and rear wings is separate. In total, 6 steering machines are used.
It was scary to build a plane for the 50th engine right away. A whole range of questions remained incomprehensible: on which wing to make ailerons, and on which elevator, or on both; what angles of attack should be at the wings; how far the wings should be apart from each other; And, in general, will it fly?
But the creative itch took over the mind, and all doubts were cast aside. I am building a "Tandem" for the 25th engine. On it and check how it flies ...
Attempt 2
The model is drawn, drawn and built. It turned out the following.
- Both wingspan: 1000 mm
- Length: 1150 mm
- Wing chord with aileron: 220 mm
- Distance between wings: 200 mm
The front wing was placed 20 mm below the engine axis, the rear wing 20 mm higher. The wings were exactly the same and mutually interchangeable, only ailerons were made on one wing, and the elevator on the other.
Flight
The first flight only added confidence in the correct direction of the search. The model was absolutely predictable and adequate in the air, stable at low speeds and did not spontaneously fall into a tailspin. The layout with the elevator on the front wing showed its best side in relation to the scheme when the elevator was on the rear wing. This is due to the fact that at low speeds it served as flaps, increasing the lift on the front wing.
Decided! I study the behavior of this model in the air and start building a model for 61 motors. While a large plane is being built, we fly a small one. During the flight, we find another interesting feature of the model. She could stop and stand in the air against the wind. When pulling the handle towards itself at low gas, she showed a tendency to parachute.
It turned out the following:
- Span: 1400 mm
- Length: 1570 mm
- Chord with aileron: 300 mm
- Distance between wings: 275 mm
The first flight is carried out with the ailerons on the rear wing and the elevator in front.
Impressions:
Stable, stable at all speeds, very predictable. However, in the flight of a large model, one feature was discovered. The aircraft is very sensitive to the elevator. That is, I brought it into level flight, trimmed it on medium gas - it flies smoothly and steadily, but as soon as you touch the altitude control, it changes the direction of flight sharply, but at a small angle. Not that it was annoying or dangerous, just keep in mind that the model is very sensitive to the elevator.
Of course, this is unacceptable for a training aircraft, but we have a FAN designed for an advanced pilot.
Now I'm trying to mix the elevator and ailerons. That is, when I pull the handle towards myself on the front wing, both ailerons go down, and on the back wing up. But when I roll, the ailerons work in parallel on both wings.
The unstable behavior of the model in level flight was most likely due to incorrect wing angles. Unfortunately, it was not possible to change them without significant alteration.
The model is finally set up, trying what it can in the air.
- I turn off the gas. I pull the handle towards myself (squeezed expenses). The model slows down almost to a stop, then smoothly nods, accelerates and repeats the same thing. No tendency to spin. That is, if you do not specifically disrupt the flow from the wing, then the stall occurs very smoothly and is immediately restored with a set speed.
- I turn off the gas. I pull the handle towards myself (full expenses). The model stops in the air and, maintaining a horizontal position, begins to descend like a parachute. Figure "parachute". I give the handle away from me - it turns over on its back and continues its descent vertically down (just some kind of plague). The figure "reversed". That is, the model is capable of being controlled by rudders in the mode of 100% stall from the bearing planes!
- Spending on the maximum - twist the loop. True, it cannot be called a loop. Rather, it is a classic "waterfall" from a 3D complex. The model rotates around the lantern, while slowly descending. Moreover, it is not required to work with gas. And it is very easy to change the direction of rotation when shifting the rudders. Shaker figure.
- I make a "parachute" and deflect the rudder. I get a very slow flat corkscrew - a "dry leaf" figure.
- Such a figure as "harier" goes into the category of children.
- The "square loop" turns out to be exactly square, since the turning radii at the corners are almost unreadable.
You can still describe the figures for a very long time. I will only say one thing. This aircraft can do more than I can, and is able to teach an advanced pilot a few more new maneuvers that are not available on conventional aircraft. And I would especially like to note the predictability and stability of the aircraft, no matter what you do with it.
Looks like I got what I WANTED!
Attempt 4
Although the second and third aircraft showed excellent flight data, one more very important question: what are the optimal angles of attack for the wings? To solve this problem, it was decided to build a model for the 50th engine, with the ability to change the angle of attack of the wings on the ground. In addition, model number 3 was broken due to equipment failure.
It was also decided to put the front fender above the engine axis, and the rear fender below (on the previous model it was the other way around, I just wanted to check - I’ll say right away that I didn’t notice any changes in the behavior of the model.) and make a slight bevel along the leading edge, the front fender received implicitly pronounced positive "V", and the rear negative "V". This was supposed to give stability at low speeds in forward and reverse aerobatics, respectively.
I will not dwell on the description of the design and the manufacturing process. It is no different from the usual Fanfly and is clear from the photographs.
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AIRCRAFT SCHEME "DUCK"
Since the first heavier-than-air aircraft to take off, the Wright brothers' Flyer (1903), was built according to the scheme that is today known as the "duck", it seems logical to start the story of aircraft of unconventional schemes with aircraft of this class.
WRONG TERM
First, the term "duck" is a misnomer. Under the "duck" in aviation, it is generally accepted to understand an aircraft whose horizontal stabilizer and elevators are located in front of the wing, and not behind it. The term can just as well be applied to airships and gliders. In particular, early models of rigid Zeppelin airships were equipped with forward horizontal control surfaces in addition to the traditional tail ones.
Usually, the term "canard" implies the location in the front of the aircraft of the main, rather than auxiliary means of aerodynamic control.
This term appeared for the first time in France; its origin is probably due to the fact that the wing of a flying duck is closer to its tail than to its head, and not at all because this bird controls its flight with the help of a special organ located in front of the wing. Aircrafts This scheme has become quite widespread.
Many canard aircraft can be thought of as tandem wing aircraft with relatively small forward wings. In this case, the front horizontal tail (PGO), usually consisting of fixed (stabilizers) and movable (elevator) surfaces, bears a significant part of the aerodynamic load.
In recent years, the term "canard" has come to be used to describe aircraft equipped with auxiliary aerodynamic control surfaces mounted on the nose, generally speaking fairly conventional aircraft (and some delta wing aircraft), to balance the aircraft or to control the flow around it. flow, and not for the implementation of the main control or the creation of part of the total lift, as is the case with the classic "duck".
WHY FRONT HORIZONTAL TANK?
Before the Wright brothers directly started building an airplane, they
Firstly, the Wright brothers perfectly understood the functions of the "horizontal rudder" in controlling the position of the aircraft in space and believed that the forward plumage would perform such functions more efficiently than the tail. In this they turned out to be right, but, of course, they did not know the shortcomings of such a technical solution.
The second main reason for their choice was the location of the first flights, which were performed from a sandy pad, and therefore there was no possibility of using wheel-type landing gear. Both the gliders created earlier and the first Flyer were equipped with a skid landing gear, in which the aircraft fuselage was located very close to the ground. At the same time, the Wright brothers understood the need for a large angle of attack during takeoff and landing. A low-sitting Flyer-type machine would certainly cling to the ground with its tail unit if it were selected; therefore, the designers abandoned such a solution. They installed a vertical keel in the tail section of their aircraft. The beams supporting the keel were equipped with hinges and, with the help of cable wiring, could deviate upwards without affecting the controllability of the aircraft, since the keel did not deviate relative to the oncoming flow.
ADVANTAGES
In the modern sense, the main advantage of the "duck" aerodynamic scheme is the increase in aircraft maneuverability, which attracts the creators of military equipment to this scheme. The higher maneuverability of aircraft of this design proved to be very useful in improving the characteristics of some of those created in Lately ultralight aircraft.
Another advantage of aircraft: the "duck" scheme is considered to be that it is almost always possible to build such an aircraft with natural anti-spin protection: the stall of the air flow on the PGO occurs earlier than on the wing, which creates most of the lift, so the nose of the aircraft in this case is slightly descends and the aircraft returns to normal flight.
LIMITATIONS
A significant disadvantage of the "duck" scheme is that the aircraft of this scheme are inherently longitudinal instability. Instead of damping the movements of the aircraft relative to the transverse axis (in pitch), as, for example, the tail of the arrow does, the effect of the air flow on the front horizontal tail enhances the corresponding perturbations.
In his notes, O. Wright noted that the stability of the "duck" in pitch is determined by the skill of the pilot. The experience of the first flights showed that in the case when a significant lift force is created on the front horizontal tail, it has a significant effect on the balance of the aircraft.
Stalling on a PGO causes about the same effect on the balance of an aircraft as, for example, folding a pair of table legs - the other two legs continue to support the opposite end, and the table falls in the direction where there is no support.
Therefore, the anti-spin advantages of the "duck" aircraft soon faded.
Aircraft of this scheme almost completely disappeared from the practice of aircraft construction until, at the beginning of the Second World War, in-depth studies of the "duck" began to be carried out, aimed at finding possible ways improving the maneuverability of aircraft.
However, even during this period of development of aviation, it was not possible to realize the advantages of this scheme. Only in recent years have several very successful canard aircraft been created, which have demonstrated the advantages of this scheme in some specific application conditions. aviation technology.
However, these aircraft have already used special means to prevent a powerful stall from the PGO. This is achieved by increasing the critical angle of attack by blowing out the airflow on the PGO, using airfoils with different load-bearing properties, or using the PGO as a balancing surface only (in this case, the PGO does not make any noticeable contribution to the lift), for example, on aircraft with a large area close to the delta wing or tailless aircraft with a straight-swept wing.
Some of the modern missiles are built in the canard configuration, but the control systems of these missiles usually work using on-board computers and automatic stability enhancers that generate and implement trim commands that prevent the build-up of disturbances in the pitch channel.
It should be noted that all aircraft of the "canard" scheme, implemented in accordance with the technical level achieved before the 1960s, became a real misfortune. As if foreseeing this, the Wright brothers already in 1909 (when they began to use a wheeled landing gear, which made it possible to lift the aircraft off the ground and ensure a set angle of attack on the takeoff) abandoned the PGO and installed elevators in the tail section of the apparatus near the rudder.
The "duck" scheme has received the widest distribution in the field of ultralight aircraft. This class of modern aircraft has made its own way back to the type of flight performed by the Wright brothers, which is characterized by a very limited speed range, limited maneuverability and a relatively small payload.
Between 1980 and 1983, probably more aircraft of this scheme were designed and built than in the entire previous history of aviation.
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